earth mat Flashcards by Unknown Unknown

marks the path of the subducted plate as it descrnds into the asthenosphere

inclined seismic wadati benioff zone

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3 devastating earthquakes along inclined seismic zones

chile 1909
alaska 1964
sumatra 2004

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produced the banda aceh tsunami killed 300k in indian ocean region

sumatra 2004

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which convergence occured thqt brought the closing of tethys ocean

convergence of india and asia

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when did eurasia and india formed himalayan

40Ma

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what is the limestone on top of mt.everest

chomolungma

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which ocean was the limestone of mt.everesy priginated?

tethys ocean

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how many elements were fiscovered

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what is h1
h2
h3

protium
deutrium
tritium

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varieties of garnet

almandine
andradite
grossularite
pyrope
spessartine
uvarovite

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abdundant in pelitic metamorphic rocks including schists gneisses and granulites occurs ib laumbium rich pegmatites

almandine

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metamorphosed carbonate rocks and skarns

andradite
grossularite

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ultrabasic rocks inclusing mantle peridotes and kimberlites

pyrope

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scarcer mineral in skarns

spessartine

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scarce mineral in chrominum enriched ultrabasic rocks

uvarovite

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haracterized by aggregates of sheaves of radiated
microscopic silica crystals that are often water
bearing

chalcedony

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Stable at relatively low temperatures and
pressures; widespread in igneous,
metamorphic and sedimentary rocks

Alpha quartz

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Stable at elevated temperatures and relatively
low pressures; occurs primarily in volcanic
rocks

Beta quartz

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Stable at high temperatures and low pressures;
occurs in silica - rich volcanic rocks

Cristobalite

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Stable at relatively high temperatures and low
pressures; occurs in silica - rich volcanic rocks

Tridymite

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Stable at high pressures; occurs in meteorite
impactites, kimberlites and ultra high
pressure metamorphic rocks produced at
great depths

Coesite

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Stable at very high pressures; occurs in
meteorite impactites and is theorized to be
an important constituent of the deep mantle

Stishovite

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Stable at low pressures and fairly low
temperatures; forms around hot springs, in
soils and in ocean basins, especially as
accumulations of diatoms and radiolaria

opal

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felsic utonice igneous to ks and pegmatites and meanirphic schists common variety is bright green amazonite tricilinc stubby crystals

microline

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felsic plutonic igneous tovks metamorphic schists and gneisses monoclincic prismatic with evident symmetry

orthoclase

high temp kfels more transparent than others monoclinic

sanidine

what does IYGS stands for

international unuion of gelogical science

hydrous from secondary mineral 100-250

zeolite

By alteration of nepheline in silica - undersaturated, feldpathoidal igneous rocks Hexagonal; prismatic; rare

Cancrinite

Scarce mineral in metamorphosed limestones/skarns Isometric; equant; rare

Lazurite

In silica - undersaturated, potassium - rich volcanic rocks Hexagonal; stubby prismatic;

Leucite

In silica - undersaturated, feldpathoidal igneous rocks .Hexagonal; prismatic; rare

Nepheline

In medium – high grade metamorphic carbonates/ skarns and pelitic schists, gneisses Tetragonal; prismatic; square sections

Scapolite *

In silica - undersaturated, feldpathoidal igneous rocks. Isometric; equant; rare

Sodalite

ZEOLITE GROUP Isometric; equant; trapezohedra

Analcime

Trigonal; equant; pseudocubic rhombohedra

Chabazite

Monoclinic; platy – capillary; scaly – fi brous

Clinoptilolite

Monoclinic; prismatic – platy

Heulandite

Monoclinic; prismatic

Laumontite

Orthorhombic; prismatic – acicular; radiated – fi brous

Natrolite

Monoclinic; tabular – platy; close radiated, sheaf - like groups

Stilbite

what are the zeolites?

analcime chabazite clinoptilolite heulandite laumontite natrolite stilbite

feldspathoids group

cancrinite lazurite leucite nepheline scapolite sodalite

what are granitic dikes

aplites

when melt of any composition comes in contact with water or air

quenching

eounded masses of radiating crystals

spherulites

cristobalite seed crystals grow into white snowflake forms

snowflake obsidian

glassy Si92 rich volcanic rocks higher water contents than obsidian

perlites

cloudy appearance and curved or subspherical cooling cracks

perlitic tecture

rocks contianing5-30% vesiclez

named by a modifier Vesidular basalt

rocks less than 5% of vesicles

vesicle bearing basalt

cilicon and oxygen percent on earth

75% weight 94.7 by volume

the obly anion in the abundant elements of the eart

oxygen

what are the 4 common vcanic rocks?

rhyolite dacite andesite basalt

what are the percents of volcanic rocks

>66% 63-66% 52-63% 45-52%

what are under the feldspar group

calcite potassium felds sodium

sio2 concentrations tend to be enrich with minor elements suchc as

li be and ba

examples of minor elements

chromium manganese hydrogen titanium phosphorus

remaining after melt remov has a different chemical co position than ghe original parent rock id enriched in compatible elements and depted in incompatible elements

residual rock or restite

what are the incompatible elements

k rb sr and ba

enumerte the LREE

lanthanium la cesium ce praseodymium pr beodymium Nd samarium Sm

enumerate HREE

europium eu gadolinium Gd terbium Tb dysprosium Dy holmium Ho erbium Er thulium Tm ytterbuum Yb lutetium Lu

elements chsrwc as having a relatively high ionci charge guven raidus immobile tend to remain on restite

high field strength

valence charge trsce elements with a ratio of greater than 0.2 sre

large ion lithophile LIL elements

mobile in partial melts and useful in determining the role of hydrous fluid interaction and the parental osurce of the partial melt

large ion lithophile LIL

faure calculate the mean of this to distinguish between different magmatic environments such as ocean floor ocean islands and island arcs

Sr87/Sr86

mullen used this to identify the five basalts

MnO2 TiO2 and P2O5

minor elements to use the distungusihed the mod ocean eidge basalt and ocean island basalt

Rb sr Y nb

percent of minerals felsic intermediate mafic ultramfic

<40% Dark colored mineral 40-70% 70-90% >90%

IUGS COLOR INDEX

<35% DCM leucocratic 35-65% mesocratic >65% melanocratic

indirect scheme using data derived from chemical analysis of a rock samole first norm classification was deviae dby cross iddings pirsson and washington referred to as CIPW used in apahanitic or glassy volcanic rocks in modal cqnnot be determined

Normative mienralogy

rocks are charac by minerals with unusually high Al2O3 contents

peraluminous

rocks contain normative or modal minerals with unusually high K2O and/ or Na2O contents

peralkaline

rocks contain mafic minerals with average aluminum contents

metaluminous

rocks contain madic minerals with low alumnium concentrations

subaluminous

who was ghr skeme iniated the rock nomenclature in 1960 for IUGS

albert streckeisen

in the QAPF diagram what does plagioclase invludes

scapolite

feldspathoids included in QAPF

nepheline sodalite cancrinite leucite analcite nosean hauyne and kalsilite

less than 2% and 0.5 % Co2 and only the Na2O +K2O are plotted in the vertical

TAS

partial melting of rock magmas and lavas that solidify to produce igneous tocks in crust are formed by it produce liquid melt fracrion enriched in lower temperature constituents and a residual rock component enriched in higher temperature refactory elements

anatexis

implies that solids and melt separate into isolated fractions that do not continue to react together during the melting process

fracrional melting

geothermal gradueng of upper 10km

~25C/km

geothermal gradient in old continental lithosphere

5-10C/km

geothermal gradient at hotspots ocean sprrqding ridges and volcanic arcs

30-50C

also known as adiabatic melting wc results a decrease in pressure and is related to rock depth whereby 10km depth corresponds approx 3.3 kbars

Decompression melting

agent that reduces the melting temperatureof a substance

flux

father of modern petrology

bowen

closed system diversification original nelt rvolves jnto one or more melts with different composition

differentiation

early formed crystals are segregated from the remaining melt early proponeyn of fractional crystallization

fractional crystallization

bowen studied in what university

carnegie institute of washington in 1910

studied rocks from a shallow igneous intrusion named situated in New Jersey west of new york ~2"" mys intrusion that consists largely of basuc rocks including basalt, diabase (coarse grained basalt) and gabbro

palisades sill

evidence for crystal settling and convective flow

Tertiary age Skaergaard Inteusion

tertiary age in greenland contains sedimentary like features such as cumulate layering graded bedding cross bedding and slump structures

skaergaard

one parent magma fractionated to profuce geo or more distinctly different daughter magmas with different composition

liquid fractionation

involves the preferential diffusion of select ions within the magma in response to compositional thermal or debsity gradients as well as water content plays a huge role in transport and concentration of metallic ores deposits in plutonic systems

differential diffusion

liquid liquid fractionation occurs when magma separates i to two or more distinct immiscible liquid phase

liquid immiscibility

liquid immiscibility was seen in

deccan traps triassic jurassic rattlesnake hill basaly of connecticutr

gorceful injection of magma fractures the surrounding wall

stoping

country rocks that fall

stope and xenoliths r thw results

foreign crystals bot generated by crystallization of the sureoubding magma

xenocrysts

liemstones and schists xenoliths stoped into a granitic magma

thorr region of donegal, ireland

suites of rocks that form in response to similar geological conditions

pectrotectonic associations

sudden flood burst of glacial lake water or water contained within glaciet

jokulkhlaups

named for south america andes mountains wc overlie the peru chile trench by far the most common calc alkaline volcnaic ro k froming at convergent margins

andesite

high aluminum basalts

tholeiitic arc

qrz -phytic volcanic rocks intermediate between andesite and rhyolite tas 77%

dacite

also known as latites and shoshoniteslower TAS 57% SiO2 contain phenocrysts of andesine to oligoclasw pmagioclase feldspar amidst groundmass of orhoclase and augite

trachyandesites

>69 % sio2 ~68-73% SiO2 assoc with explosive silicic wruptions producing fragmental glassy and aphanitic to aphanitic porphyritic textures

rhyolites rhyodacites

contian >20% qtz and plag metaluminous

grabodiorites

known as plagiogranites are granodioritic rocks in wc sodium plagioclase representd half to two thirds of the total feldspar components

trondhjemites

young island arc produce

tholeiite basalts which are doung in oceanward side of volcanic arc newrest the rench boninites adakites

high Mg untermediated 52-68% groundmass contin phenocrysts of opx lack plag pehnocrysts encriched in chromium nickel volatile elements lree deelted in hree and hfs occur proximal to the trench bear geochemical signatureprodyct of subduction related arc systems high temp loe pressure remelting

boninites

silica srayrated >56% high lree low hfs derived by slab melting of eclogitw and garnet amohibolite from the deacending ocean lithosphere knly form where young think hot ocean kithosphere subducted beneath island arc lithosphere known to form at contiennt continetn colkision sites as a result of shallow slab subduction plutonic equivalent is trondhjemites and tonalites

adakites

an px bearing suite of rocks of generally granitic composition occur in ttg

charnockites

ttg aasoc oxcur in archean rocks

pilbara craton of australia and the bear-tooth and big horn mountains of wyoming

dark colored potassium rich trachyandesitws containing olivine and augute phenocrysts with a groundmass of labradorite leucite thickened lithospeherw fartehst from the trench rwgion in continent continent collisions in backarc basins

stoshonites

plutonic equivalent of rhyodacite and rhyolite

granitoids

used for silica oversaturated plutonic rocks that contain essential potassium feldspars and quartz form at mayyrw convergent margins tend to be peraluminous to metaluminous

granitoid

form by partial melting of basic to intermediate igneous rocks i namor above yhe subduction zone at ocean ocean or ocean continent convergent margins

i type granites

peraluminoud potassium rich s type granites and granodiorites are prticulary common at continent continent collisions

s type

detived from phyllosilicates minerals in graywackes and mudstones of the continental crust and accretionary wedge. peoduce two mica granites containing biotite and muscovite

perlauminous sedimentary

20-60% and 35-90% alkali to plagioclase feldspars assoc with precambrian cratons and convergent margins

granite

mantle derived larental magmas low Sr87/Sr86 rations <0.704 assoc with calc alkaline tonalites qtz diorites and gabbroic rocks degelop in island arc settings copper and gold mineralizations

m type granites

melting of an ig wous protolith from wither the downgoing oceanic lithosphere or the overlying mantle wedge enriched in Na2O and Ca2O and contain lower Al2O3 concentrations less than 0.708 derived from a mantle source enriched in mafic minerlas porphyry copper tubgsten and molybdenum prevalent along the mesozoic cenozoic andes mountains

i type granites

sedimentary crustal rocks in collision zones depleted in Na2O but enriched in Al2O3 peraluminous. >7.08 earlier se cycle. also known mica granites contain both muscovite and biotite rich in phyllosilicate mienrals tin deposists assoc with

s type granites

anorigenic produced by activitws that do not involve the subduction and collision of lithospheric plates enriched in akaline elements depelted in Mg Ca Al Cr Ni mote enriched ib LIL elemenyd and depelted in refractory elements peralkaline alkali rich

a type granites

fault bounded mark the site of present or former convergent margins been transporrted far from thwir site of irigin by thrust faulting and shearing dismembered into fault blocks and junbled together in a haphazard fashion contain disrupted pelagic sediment layers basalt cumulate basic and ultrabsic layers and assoc with tectonic melanges

alpine orogenic complex

sheared heterogeneousrock assemblage embedded within a highly deforemed mud matrix form at subduction zones miced withcrocks formwd in forearc settings slices of eclogite peridoite and blueschist

tectonic mélanges

alpine presefved in orogenic belts serpentizied in the alps known as steinmann trinity types consist pelagic chert serpentinite hydrothermally altered peridotite and spilites (altered pillow basalts)

ophiolites

develop due to the extensional tectonics result in backarc spreading or forearc spreading chromium petrotecronic

suprasubduction zone SSZ ophiolites

pricess by which epiclastic sediment transportation is initiated by erosion is

entrainment

occurs when mienrals such as clays and micas expand when wetted

slacking

rwsult from changes from daily seasonal in rock temperature

insolation

zone of accumulation, is characterized by enrichment in some of the constituents leached from the A - horizon. The process by which materials are translocated downward to be added to the lower part of a soil is known as illuviation.

B - horizon

The process by which materials are translocated downward to be added to the lower part of a soil

zone of illuviation

commonly gives the B - horizon a distinctly reddish or yellowish

humid climates, reprecipitation of amorphous or crystalline iron oxides (e.g., hematite = Fe 2 O 3) or hydroxides (e.g., limonite ≈ FeOOH)

In humid climates, where chemical decomposition is thorough,

clay minerals and bauxite are also concentrated in the B - horizons to form aluminum - rich horizons.

n dryer climates, calcium carbonate (CaCO 3) precipitates, producing B k soil horizons. In many cases, mineral precipitation in the B - horizon binds soil particles together into hard, nodular zones or into completely indurated sub - horizons called

duricrusts.

most common examples of duricrusts are the calcium carbonate

calcrete or petrocalcic

arid, desert climates. Similar hard sub - horizons of silica and gypsum

( silcrete ) ( petrogypsic

are partially cemented clods of soil particles of various sizes that give the soil a crumbly lump appearance.

Peds

hich are concentrations of illuviated material such as clays or iron oxides that occur as layers or that envelope less - altered cores.

Cutans,

which are prolate to equant hard lumps formed by mineral precipitation and include concretions and nodules of all sizes.

Glaebules

called the soil mantle , represents moderately to minimally weathered, slightly altered materials that are transitional to the underlying, unaltered parent material. Where soils are developed over bedrock, the largely unweathered bedrock constitutes the so - called R - horizon or regolith horizon.

C - horizon,

has organized soils into 12 major orders, which are fairly easy to learn (Figure 12.20 ). Each order is subdivided into as many as seven suborders of which there are a total of 64. The suborders are subdivided into more than 300 great groups, which are subdivided into some 2400 subgroups, which are further subdivided into families and lastly into soil series. Some 19,000 different soil series have been mapped in the United States alone

e USDA - NRCS (1999)

was developed with the endorsement of the International Union of Soil Scientists (IUSS) and the Food and Agricultural Organization (FAO) of the United Nations. It divides soils into 25 orders and 98 groups based on the physical characteristics of the soil Unlike the USDA - NRSC classifi cation scheme, climate is not considered in the WRB. The long - range goal of these efforts is to promulgate adherence to a single standard worldwide soil classifi cation scheme.

1998 a world reference base (WRB) for soil sciences

Most geotechnical and engineering personnel in the United States use th soils are given names and symbols according to their particle size distributions, notably the proportions of gravel, sand, silt and expansive clays, and to the content of non - expansive clays and organic materials in the soils. Engineering defi nitions of gravel, sand, silt and clay do not correspond exactly to those used by geologists, who employ the Wentworth – Udden grade scale (W - U scale)

Unifi ed Soil Classifi cation System

where particle diameters exceed 4.0 mm (as compared with 2.0 mm in the W - U scale).

Gravel (G),

where particles range from 0.074 to 4.0 mm (as compared with 0.0625 – 2.0 mm in the W - U scale

Sand (S),

where particles range from 0.004 to 0.074 mm (as compared with 0.004 – 0.0625 in the W - U scale).

Silt (M),

which are defi ned in the same way in both systems as particles smaller than 0.004 mm (4 μm). The USDA - NRCS classifi cation system, however, defi nes clays as particles smaller than 2 μ m.

Clays (C),

Gray to brown A - horizon epipedon; B sub - horizons rich in clays with reasonably high concentrations of bases such as Ca, Na, Mg; reasonably high moisture content Relatively humid areas with sparse forest or savannah cover; base and water content yield fertile soils

Alfisols

Weak horizon development; rich in disordered clays and Al – humus complexes; high phosphorous retention; good moisture capacity and cation exchange capacity Form in a wide range of non - arid climates; mostly on volcaniclastic materials; tend to be quite fertile

Andisols

Sparse organic material in A - horizon epipedon; well - developed B - horizons, often rich in Ca - carbonates, even gypsum; low moisture content for long periods of time Dominate in arid regions with sparse rainfall and vegetative cover; suitable for agriculture only if irrigated

ardisols

Lack signifi cant soil horizon development; soils only because they have the capability to support rooted plants; often sand rich Occur in any climate or setting; mostly on young surfaces; also in chemically inert parent materials or on slopes where erosion occurs

entisols

Permafrost soils and soil features; patterned ground, broken horizons and incorporation of organic matter in lower horizons produced by frost heaving and churning In high latitude and/or high elevation areas where soils freeze for long periods

gelisols

Mostly very organic rich O - horizon; deeper horizons tend to be poorly developed, if at all Mostly peat and muck from partially decomposed plant debris in swamps or bogs or water - saturated soils in areas of poor drainage

histosols

Weak horizon development; less clay concentration in B - horizon than alfi sols; carbonate and silica - rich B - horizons may occur; reasonably high moisture content Form in a range of non - arid regions from subpolar to tropical; often with forest cover; less suitable for agriculture than alfi sols

inceptisols

Very dark, thick, organic - rich O and A epipedon; high base content, especially calcium; clays with high cation exchange potential Common under grasslands in semi - arid plains and steppes with seasonal moisture defi cits; some under forest cover; great for grain production

mollisols

Weak horizon development; extreme decomposition and base depletion; clays, mostly kaolinite, with low cation exchange capacity; bauxite under extreme conditions; quartz and iron oxides Develop over long periods of time in tropical/subtropical settings with high rainfall and thick vegetative cover; generally infertile

oxisols

Thick O - horizon; well - leached A - horizon with low Fe, Al, Ca; well - developed B - horizons with clays, reddish iron oxides or black humic material; good cation exchange Dominate under coniferous forests; in areas with reasonable rainfall; generally suitable for agriculture

spodosols

Well - leached A - horizon with some organics; clay - rich B - horizons with generally low base contents as Ca, Na and K are largely removed which distinguishes them from alfi sols Humid climates; low base content; soils unsuitable for sustained agriculture unless fertilized with Na and K

ultisols

High expansive clay content; large changes in volume associated with wetting and drying; cracks when dry and other evidence of soil movement; may have horizons Poor soil for structures given the volume changes and tendency for strength and plasticity to change during wetting and drying c

vertisols

<5% fi nes; continuous size variation over a range Well - graded gravel GW

Clean gravel

<5% fi nes; mostly one size or polymodal Poorly graded gravel GP

Clean gravel

>12% fi nes; mostly silt Silty gravel GM >12% fi nes; mostly clay Clayey gravel GC

Dirty gravel

<5% fi nes; continuous size variation over a range Well - graded sand SW C>5% fi nes; mostly one size or polymodal Poorly graded sand SP

lean sand

>12% fi nes; mostly silt Silty sand SM

Dirty sand

re those that contain more than total 50% sand and gravel by weight. Gravels contain more gravel than sand, whereas sands contain more sand than gravel. Coarse - grained soils are further subdivided according to the percentage of fi ne - grained components (clays + silts).

Coarse - grained soils

contain less than 5% fi nes

Clean soils

contain more than 12% fi nes

dirty soils

contain more than 50% silt plus clay. Silts are defi ned as soils with more silt than clay, whereas clays contain more clay than silt. Fine - grained soils are further subdivided according to their mica content, organic content and their degree of plasticity. Highly organic soils are prone to compaction, dehydration and decomposition resulting in volume loss, which makes these soils unsuitable for construction. Soil plasticity is largely determined by the soil ’ s ability to absorb water and therefore by their smectite (expandable lattice) clay content. As will be seen in the following section, plasticity is an extremely important measure of the mechanical properties of soils and allows one to predict how they will react in different circumstances. The “ L ”in the group symbols stands for loam, a soil that contains appreciable amounts of both silt and clay in the fi ne fraction.

Fine - grained soils

is the amount of stress a soil can bear without failing by rupture or plastic fl ow. It is an expression of the ability of a soil to resist irreversible deformation such as inelastic changes in shape, volume and position. Strong soils are quite resistant to stress and, along with many kinds of bedrock, generally provide excellent substrates for buildings. Weak soils are subject to compression, collapse or fl ow when stressed and therefore provide poor substrates for structures

Soil strength Problems for engineers arise because soil strength can change, especially in response to changes in water content (Box 12.3 ), so that formerly strong soils loose strength and become weak soils that fail by rupture, fl ow plastically or even fl ow like a liquid.

The measure of a soil ’ s tendency to change strength is expressed by measure of the change in soil strength that results from changes in water content and various kinds of disturbances such as vibrations, excavations and loading that stress soils. Soil sensitivity in response to water content, easily determined in the lab, is commonly expressed by Atterberg limits that permit the subdivision of fi ne - grained soils into four classes on the basis of how they behave as their moisture content changes (Figure 12.21 ).

soil sensitivity

soils, (3) plastic soils, and (4) liquid soils. The boundary between brittle solids and semi - solid soils is which is the water content below which soils do not shrink as additional moisture is lost during drying

shrinkage limit (SL Above the shrinkage limit, semi - solid soils shrink and crack as they lose moisture and become progressively more stiff and brittle. Soils that remain brittle or semi - solid under all conditions of potential moisture content tend to be strong and provide excellent substrates for most construction projects so long as they are not loaded beyond their rupture strength. Solid bedrock is even better

eparates semi - solid soils from plastic soils and is the water content at which soil deformation changes from rupture to plastic fl ow (Figure 12.21 ). Plastic substances change shape and/or volume in response to stress or pressure but do not rupture visibly. Because they retain cohesive strength, they do not fl ow like a liquid. Plastic soils are moisture sensitive in that their strength decreases and they deform more easily as they become progressively less cohesive with increasing moisture content. This helps to explain the many slope failure incidents that occur following heavy rainfall and the concurrent infi ltration of groundwater into soils.

plastic limit (PL

of a soil is a measure of its cohesiveness, which is sensed as a sticky, cohesive feel to the touch. It generally increases with clay content (especially expandable smectites) and water content. Soils with low clay content tend to be relatively non - cohesive and therefore possess relatively low plastic limits. Soils with high clay content tend to be much more cohesive and to possess signifi - cantly higher plastic limits. Because plastic soils deform when loaded, they do not make good substrates for major construction projects

plasticity

separates plastic soils from liquid soils (Figure 12.21 ). It is the water content at which soils lose their shear strength and begin to fl ow. When a suffi cient amount of moisture has been added to a soil, it may begin to behave as a liquid; that is, it will loose cohesive strength and begin to fl ow under its own weight. This can have disastrous consequences for the structures placed such soils. The liquid limit tends to be rela-

e liquid limit (LL)

contain less than 30% gravel in their detrital fraction and contain mroe sand

sands and sandstones

epiclastic sediments contain 5-30% gravel in ghe epiclastic fractuon

gravelly sands or gravelly muddy sandstones

if a sandstone contains less than 5% gravel and has a sand:mud ratio greater than 9:1

pure sand (arenites)

they pxcupy the four sectiond in the bottom left portion of folks GSM diagram

mudrocks

less than 5% gravel

sandy muds and sandy mudrocks with san mu ratio >1:9

this prefix can be sued if any gravel occurs in the muds or mudrocks

gravel bearing

they occupy the six sectors in the bottom right portion of GSM

sands and sandstones

an attmeot to represent the thpical particle size in the population and detrital grain populations can be described by 3 lf this

central measure

which a best fit line is plotted for similar data

frequency curve

most anudnant particle size easily determiend when size data are plotted in a historgram

mode

particle size such that half the population is larger and half is smaller

median

large meteor that explodes in space

bolides

areas where bolides collided with earthes surfaces producing inpactitites

breccia

A well-sorted, matrix-free conglomerate, which forms where the sediment transported and deposited comprises only pebble and gravel grades.

sieve deposits

fault collapse and rockfall breccias are oligomictic composition:

mature, quartz rich conglomerates

produced by barious combinations of sedimentary and tectonic processesthat mic several rock types and tectonic prcosses that mix seceral rock types are

melanges gravelstones

this decompose less rapidly and are more common preserved in gravelstones derived from magmatic atc and i tracratonic rift

Granitoid rock dragmentd

generic term for a diverse category of coarse-grained igneous rocks that consist predominantly of quartz, plagioclase, and alkali feldspar. Granitoids range from plagioclase-rich tonalites to alkali-rich syenites and from quartz-poor monzonites to quartz-rich quartzolites.

granitoids

ise dto documeny strike slip on the san grabriel fauly in southern california

ridge basin breccia

part kf major transfom plate australia and pacific plate

alpine fault

recognized unusual clasts derived from ultramafic rocks and greenschist amohibolite grade schists in pliocene conglomerates deposited i cascade valley

sutherland

minimum eight lateral slip on the alpine since 3.6 Ma has been 27km/Ma up to

35km/Ma

detived from caples and toesse terranes wc are now lcoated 420 mn to the southwest of the

maruia basin

abergae dectral slip on the alpine fault is

37km/Ma

sandstone stuat contain 75-95 quartz and have more feldspar then lithic feagments

sub arkoses

less than 75% Q plit in one of the four sectors in the bottom portion

submature to immature arkose

those with neglible mud matrix and in boundary at 5%mud

arenites

uplofted recycled accretionary complexes

subduction complexes

exposed in orogenic belts some distances from convergent plate boundaries

foreland uplifts

consists of stable cratonuc areas that are divided into shields and platforms

continental block source areas

consist primarily of precambrian plutonic and high grade metamorphic rocks such as granitoids gneisses and grnaulitws

shields

charac bt a relatively thin veneer of largely mature detrital sedimentary rovks and or carbonate sedimentary rocks that overlie sgield rocks

platforms

sediments are derived from pre existing mature and sed rocks overly plutonic basement rocks in a stable platform setting with very low reloef

craton interior

both platform sed rocks and plutonic basement shod rocks are exposed as soruce rock thpes in settings of low to moderate relief

transitional cratons

basement of plutonic igenoud and metamorphic rocks are exposed in an area of high relief resilting drom uplift along dailts in contintental aetting

uplifted basement

produced by the minimal decomposition of ferromagnesian mienrals and commonly from in alkaline soils with impeded drainage high latitutdes where precipitation and temperatures arw low

chlorites

product kf the weathering kf ferromagnesian minerals plud plag favored impeded drainage alkaline conditions and semi arod climates

smectites

common products of weathering of feldspars k felds most common in temperated region soils with near neutral pH

illites

common in mod latitudes semi arid to temperate soils witj slightly alkaline pH

mixed layer illite-smectite clays

warm humid acidis soul common i nsubtropics cations tend to be leached from inetrlayer sites gives rise to degraded illites and kandites such as

kaolinite

wam humit high acidity low pH intense deomposition allows silica to sissolve readily giving rise to

gibbsite and ohter minerals of the bauzite suite

comkon at high latitudes

chlorites

common at low latitutdws

kaolinite

common in younger tertiary rocks

smectite clays and smectite illite older rocks dominated by illite

potassium iron rich illite produced in marine envi dome generated in slow precipitation oxidizing envi also forms by relacement of fecal pellets under marine conditiond are reducing its sand grains occur as disseminated grains in sands in areas ate detrital influx large indicateor of of marin sedimentation

glauconite

colmonly form around decomposing organic matter that reduces iron enabling it to he removed in wolution

redcutipn spots

smectite rich claystones for ed by the alteration of colabic ash deposits generated by explosive eruptions popcorn liek

bentonites

used for organic rich mudstones and claystones

sapropel

oil cam be extracted by rhe process of

pyrolysis

bituminous oragnic material in mudrocks buried and heated to 100-140 ac is converted into petroleum and when heated into petroleum and when heated over 160 converted into natural gas

kerogen

where is sapropel in jurassic found

connecticut

later deeper diagenesis

mesodiagenesis

shallow diagenesis that lccurs as sedimentary rocks approach the sirface due toverosion

telodiagenesis

creation of this can reduce the porosity of lithic sanatones and conglomerates making them less efficient storwrs and transmitters of fuids

psuedomatrix

most common between grains i quartz sands and gravs with little or no plastic mateix and occurs less frequently in feldspathic sands and gravels occurs ober a range of depths and causes significant decreases in porosity

pressure solution or pressolution

one phase is more soluble than the other

concavo convex

what are the major cements in detrital sedimentafy rocks?

silica minerals cl carbonate minerals iron oxides and hydroxides feldsprs and clay minerals

quartz occurs chiefly in the form overgrowths in which the silica that lrecipitatws drom pore solutiond i itially nucleates on a pre existing detrital quartz grain

syntaxial quartz

morw soluble in alkqline waters than in mildly acidic waters common cement in volcanoclastic sediments a decrease in pH can cause cement precipitaiton but an increse can cause dissolution

opal

bladed commonly a radiating to divergent havit when observed under a petrogrpahic microscope

chalcedony

any lrocess that removws carbo dioxide from subsurface waters raises the pH making them more

alkaline

composed of one or more calcitw crystals that occupy small pore spaces bwteen settital grains

blocky cement

composed of si gle large calcite crystals that nucleates and grows to fill multiple pore spaces so tht it completely envelops several detra grians which appear as inclusions within a si gle calcite

poikiloptic cement

common in sedime ts deposited in failry arid terrestrial environemnts such as alluvvial fans braided streams and meandering stream channels and flood plains and deserts

hematite

occurs as stacks of platy layers called books preciipitate fairly shallow depths feom low potassium acidic pore waters during eodiagenesis and telodiagenesis acidic pore waters are common in continental settings

kaolinite cement

forms at higher temperatures and deths from high potassium alkaline pore waters especially in marine settings form mostly during late eodiagenesis and mesodiagenesis

illite cement

when k felds is altered and this is the fine grained mica related to nuscovite

sericite

at higher tenepratures both calcium and potassium deldspars are altered to

albite

volcanic fragements during progressive burial and diagenesis alter to

zeolite minerals

become unstable and are transformed into mixed layer clayes above 100C

smectite

converted into illite or chlorite above 150C

kaolinite

mixed layers clays transformed into more ordered illite above

200

all clay minerals are transformed into these above 300C

chlorite or micas such as muscovite

zeolite minerlas stable at 100 and stable from 100-200 and 200 above

analcime and heulandite laumonite phrenite and pumpelyite

transitional between diagenesis and low grade metamorphic process very low grade ascribed to this

zeolite or prehnitr punpellyite facies

form by the precipitation of material around a nucleation surfac esuchas fossil sand grain or shale chip wether outcrops as cannon ball like structures precipitation of kienral cmeent such as linonite or hematite siderite purite marcasite form under reducing conditions and calcite is common formed under the ozidizing reducing conditions

concretions

similar to contetions but lack a well defined nucluse and generally lack concentric growth ringd

nodules

increasingly soluble as pH decreases and acidity increases

limestones

charac by mienral filled cracks whose origin remains unknown

septarian nodules

this orginate as nodules or concretiond of calcite or anhydrite and in acidic the exteriors are replaced by chalcedony

geodes

common in detrital sed rocks in carbonate iron rich cmenetd mimic stratification secondary features often truncated against promintent joint surfaces form by lrecipitation of various iron oxide minerlas moving througj bodies of rock separated by fractures

liesegang bands

fluids moving into such bodies of rcok from the outside in often produce ring like parterns of bands

liesegang rings

less than 4% mg

low magnesium calcite

more than 4% mg

hogh magnesium calcite

carions of substitute for calcium

strontium

most unstable during diagenesis especially in meteoric water whereas low mg is stable t

aragonite that's why aragonite and high mg calcite is not lresent in older rocks

in solid solution with ankerite and abudnanc ein increase with age in ancient carboante sed rocks especially in precambrian

dolomite

carbonate mineral

siderite!! 😭

mor ebaundant in ancient than in modern carboante sequences

Low Mg calcite

more abudnant in modent tuan in ancient

high mg calcite

more abudnant in mdoenr than in ancient carbonate sequences

aragonite

mroe ahundant in ancient than in mosent carbonate sequnces

dolomite

cabroante shells begin dissolution becomes significant ata dpeth becomes complete where bottom waters are sufficiently cold and acidic below depth all caco3 is dissolved

lysocline

tropics occurs @ 4000-5000 m

carbonate compensation depth CCD

of the amount of detrital sediment flowing into an area exceeds carboante production and preservation

carbonate bearing detrital sediment fossil bearing sandstone will form instead of wottle or no detrital sediment cotnent

sand pr gravel size clastic particles called grains or

allochemical constituentd allochems

mud sized particles called mud or

micrite

prginacally bound accumulations of carbonate called

boundstoe s or biolithites

clasts of carbonate sediment

limeclasts

soherical concentrically laminated sand sized particles possess a nucleus form by accretion of calcium carbonate laminae about a particle such as a shell fragment or sand grain that acts as a nucleus for precipitation can radial calcium cavornate structures involve in endolithic bacteria such as cyanophyted indication of shallow amrine wave or tidal cureent agitated wnvi of deosition in tropical or subtropical setting

ooids

gravel sized clasts of cohesive carbonate sediment produced when clasts of cohesive carbonate sediments or sed rocks are eroded most are derived nearby coeval deposits of cohesive deposition derived intraclasts

limeclasts

erosion of older source rockd outside the area of deposition are called

lithoclasts or extraclasts

are produced when partially demented grain clusters are eroded during storms encrusted in cyanophyted carbonate laminae may form transforms to botryoidal graisn

grapestone

resemble ellipsoidal fecal pelleted excreted by many organisms

peloids

coarser carbonate mud particles are called

macrospar

large modern carbonate mud is produced by thid

calcareous green algae tusy secrete fine needles of aragonite upon decomposition needles are release generating carboante mud

micro boring activity of blue green cyanophyte bacteria and algae accom by precipitation of carbonate in micropores converts original carbonate materail into micrite

micritization

who introdurc rudite lutite arenite

Grabau

emphasizes the tecture of carbonate rocks utilizing rarher simple terminology

dunham's classification

less than 10% grains

mudstone

more than 10% grains

wackestone

contain interstitial diagenetic mienral cements rhat bind the grains together

grianstone

no depositional texture is recognizable

crystalline carbonate

produ ed by organisms that build rigid organic structures such as reefs by secreting the calcium carbonate

framestone

produced by organisms that build organic strutures sich as stromatolites and reefs by binding and encrusting pre-existing carbonate material

bindstone

generated bu organisms that trap carbonate sediment by acting as baffles that hinder its movement across the bed causing it to be trapped process in reefs and bioherms

bafflestone

carbonate bearing rocks with a matrix supported framework

floatstone

precipitated in the pore spaces between allochems during diagrnesis

sparry cements

25% intraclasts in allochem population are given

intra

if the interstices between intraclasts are largely filled with diagenetic cement the rock is

intrasparite

if filled with mud

intramicrite

fewer than 25% intravlasts occur the rock contains more than 25% ooids the bames are

oosparite and oomicrite

if neither intraclasts nor ooids exceed 25% of the allochems then

fossils and pellets or peloids dominate

micrites that contain small spar filled voids produced during diagenesis

dismicrite

in situ carbonate accumulations roughly equivalenh to Dunhams boundstones

biolithite

rocks with at leadt one third of both spar and micrite between allochems

poorly washed sparites

<1% allochems

allochemical micrite

1-10% allochems

sparse allochemical micrite

>50% allochems

packed allochemical micrite

aimplest distribution of carbonate depositional envi occurs on where the idela model the bottom slopes gently seaward over fistances develop on the margins of shallow subtropical seas environments occupy roughly shore parallel bands charac by warer depths gradually increase seaward

carbonate ramps

ideal carbonate ramps

supratidal intertidal subtidal avove normal wave base subtidal above storm wave base subtidal below wave base

where do carbonate found

low relief intracratonic platforms or passive margins or in oceanic environments far from land

develop newr shelf or platform margins where nutrient rich waters upwelling from depth encourage the development of carbonate buildups (wc creates a queit water lagoon on the landward side) such as reefs and sand shoals

rimmed platforms

what is the ideal landward to seaward sequence of environments

supratidal intertidal lagoonsl reef or subtidal sho/island with local tidal channel reef flank/platform slope deepeater mass flow l/pelagic

develop during sea level high stans when oceans flood dissolution of grains composed of aragonite or high magnesium calcite produces form of ooids and fossils is preseved as a cavity of similar shape

moldoc porosity

cements that nicleate on grains grow at similar rates to produce coatings if nearly constant thickness

isophacous rim cements

composed of low magnesium calcite

meteoric cements

involves the nucleation on host grains of multiple crystals that grow outward into pore spaces to produce a fri he of crystals with striagjt boundaries whose size increases away from the host grains

drusy calcite

involve the precipitation of low mg calcite that nucleates in optical continuity with a low mg calcite grain

syntaxial calcite

consists of a si gle crystal large enougj to incorporate multiple grains during its growth

poikiloptic calcite

continued lrecipitation on grain bottoms leads to the development of that hang downward from the grain

pendant cements

carbonate rocks new crystals form and it become larger the neomorphism is called

aggrading neomorphism

neomorhic sparry calcite and can be recognized where neomorphism is incomplete because patches of dusty micrite and microspar remain can often be inferred because grains formerly supported by mud matrix are separated and seem to flot unsupported in sparry calcite

psudospar

formed during sea level high stands such as ordovician-devonian and jurqssic cret and precmabrian

dolomite

examples of large evapotrite sequences deposited in shallow subsideing cratonuc basins

paleozoic williston basin centered in north dakota and silurian mcihigan

large evaporites deosited in foreland basins

silurian salina group of new york pennsylvanian in the taconic foreland basin pennsylvanian-permian paradox group in the foreland basin of the ancestral rocky mountains

deposited in rift basin

hulf coast basin proto atlantic ocean basin of jurassic to cretaceous age

deposited in deep basins assoc with the irregular closing of ocean basins at convergent plate boundaries

permian delaware basin in west texas

BIF range in 3.8-1.8 with a peak abindance between?

2.5-2.2 Ga

when did BIF hiatus?

1.0 Ga

BIF late proterozoic rocks formed from

0.8-5.5 Ga

dominate archean iron rich sed rocks fromed bwteen 3.8-2.6 Ga occur as fairly thin <10-100m elongate lenses of linited lateral extent occur within archean greenstone belts assoc with submarine ultramafic mafiic volcanic rocks mudrocks and sparse volcanoclastic greywacke sandstonesform in dee water marine forearc or backarc basin or advanced intracratonic rift settings minimal influx of detrital sediments

algoma type BIF ontario california

iron rich bands are composed almost exclusively extremely fine grained rocks

femicrites

dominate proterozoic iron rich sed rocks 2.6-1.8 Ga and again from 0.8-0.5 Gamuch larger than algoma 100-1000m occur in borad belts contain fermicrites and GRANULAR IRON FORMATIONS with ooids pisoliths intraclasts and pelltes similar to those in shallow water carbonate sequences

superior type BIF

the slope of the stress – strain line is referred s a constant of proportionality that describes the slope of the line. The slope steepness of line E is a measure of resistance to elastic distortion. The E slope is dependent upon the stiffness or rigidity of the material. A rigid, stiff rock (high E) such as granite requires greater stress to achieve a given strain than a soft, pliable shale (low E

Young ’ s modulus of elasticity (

which mesoscopic ductile behavior is facilitated by microscopic fracturing and frictional sliding. Cataclastic fl ow occurs at low lithostatic pressures in the shallow crust.

Cataclastic fl ow

high pressure diffusional mass transfer process grain boundaries are compressed and dissolved resulting in the generation of a fl uid phase (Figure 16.14 ). As each mineral has different dissolution tendencies, pressure solution results in mineral differentiation whereby more soluble minerals are removed and less soluble minerals are concentrated can involve substantial volume loss and is particularly important in marble, metaquartzite, slate, limestone, dolostone, shale and quartz sandstone. clay - rich rocks produces cleavage in slates, as well as embayed grains and grain overgrowths in quartz - rich rocks such as sandstone and metaquartzite.

Pressure solution

also known as grain boundary or volume diffusion is a high temperature and high pressure process by which solid particles experience translation within a mineral. Crystal lattice vacancies migrate to sites of greatest stress and atoms relocate to sites of minimal stress.

Solid state diffusion

e commonly black –due to enrichment in carbon and iron oxides –and have the appearance of wound sutures stitched together which are jagged seams of insoluble mineral residue that accumulate and concentrate along a dissolution seam

Stylolite

common in calcite and feldspar minerals.

Mechanical twinning

common in micas and other platy minerals such as clays.

Kinking

ability to fl ow at shallow depths results in unusual qualities that make rock salt highly suitable for the storage of oil as part of the strategic petroleum reserve of the US government uitable rock for a nuclear waste repository

Rock salt ’ s ability to fl ow

p crustal and mantle processes within Earth. Factors such as depth, temperature, stress conditions, mineral composition, rock texture, rock competency and strain rate

rheology

refers to the rate at which a rock is pulled apart, compressed or sheared

Strain rate

are useful geothermometers because these common minerals change strain behavior with increasing temperatures

minerals such as quartz, feldspars, amphiboles, garnet and biotite

Approximate temperatures at which some major minerals change from brittle to ductile behavior

Biotite ∼ 250 ° C Quartz ∼ 300 ° C Feldspar ∼ 400 ° C Amphibole ∼ 650 – 700 ° C Garnet 600 – 800 ° C

s produce undulose extinction, deformation lamellae and recrystallization

Ductile processes

describes the resistance of rocks to fl ow. Rocks that fl ow easily are less competent, or incompetent. competency increases with higher pressure but decreases with higher temperature

Competency

rocks commonly display ductile behavior and include rock salt, shale, siltstone, slate, phyllite and schist. These rocks contain clays, micas, evaporates, talc, chlorite and other relatively soft minerals with Mohr ’ s hardness < 3.

Incompetent

ocks commonly display brittle behavior and include metaquartzite, granite, gneiss, quartz sandstone, basalt, gabbro and diorite. These rocks contain minerals with Mohr ’ s hardness > 3 such as quartz, feldspars and ferromagnesian minerals.

Competent

The rupture of competent layers produces “ French bread ”or sausage - shaped structures called are isolated remnants of competent rock that once formed a continuous bed surrounded by less competent rocks

boudins

r commonly occurs at depths less than 10 km because of upper crustal low temperature/low lithostatic pressure conditions, which allows for the development of fractures

Brittle behavior

e fractures through which fl uids fl ow, producing one or more secondary minerals that precipitate from solution. Common secondary vein minerals include quartz, calcite, zeolite and chlorite originate due to tensile or shear stresses.

Veins

produced by high strain rate events that blast rock apart due to high pressures. Igneous intrusions with high volatile contents are capable of hydrofracturing rock producing random breakage. Rare meteorite impacts are also high strain events that produce massive disruption of rock. High strain rates can produce stockwork veins, which are a cluster of irregularly shaped veins of variable orientation that occur in a pervasively fractured rock body

Non - systematic vein arrays

onsist of veins that display orientations suggesting a common origin in response to directed stress metaquartzite beds bounded by phyllite layers. In response to nearly vertical compressive stress, the metaquartzite experiences horizontal tension, resulting in brittle fracturing and the generation of extensional joints. Quartz fl uids precipitate in the joints creating tension veins parallel to the maximum compressive stress direction.

Systematic vein arrays

a series of offset, parallel veins that formed in response to sinistral shear within metaquartzite.

en echelon quartz vein array

minerals are equant and may display euhedral crystal faces indicating growth within an unimpeded open space

Blocky or sparry

displays a linear, acicular character (Figure 16.26 ) suggesting that vein growth was incremental in response to fracture width increase develop by repeated cycles of a “ crack and seal ”mechanism whereby elevated fl uid pore pressures crack a vein, followed by sealing from mineralized solution provides information regarding displacement sense as well as progressive vein growth in both brittle and ductile environments.

Fibrous veins

an imaginary plane connecting a series of hinge lines

axial surface (axial plane)

the point at which the sense of curvature changes from one fold to another

inflection point

a convex - upward structure are called

antiforms

concave - upward shapes are referred

s synforms

consist of two limbs that dip towards the hinge. Synclines contain young rock in the hinge and progressively older rock away from the hinge

Synclines

consist of two limbs that dip away from the hinge. Anticlines contain old rocks in the hinge and progressively younger rock further away from the hinge.

Anticlines

younger fold structures are superimposed upon earlier fold structures, refolded folds are referred to as

superposed folds or superimposed folds

consist of folds in which the limbs and hinges have been pulled apart due to extension ( occur with multiple fold generations, involving the replacement of an earlier tectonic fabric (S 1) by a more recent tectonic fabric (S 2) by ductile mechanisms such as recrystallization and pressure solution. e associated with high temperature and high pressure metamorphism

Transposed folds

be used in the analysis of a map - scale antiform. Geologists can determine position within a map - scale fold structure by looking down the plunge direction of the

parasitic folds.

essentially ductile fault zones that accommodate displacement develop in ductile lower crustal rocks. commonly occur in tectonic m é langes mylonites and pseudotachylites

Shear z ones

consists of larger rock blocks encased within a scaly, clay - rich matrix.

. M é lange

also known as texture, refers to the geometric arrangement of grains within a rock.

fabric

Parasitic folds produce

Z (clockwise rotation), M (symmetrical form) or S (counterclockwise rotation) shapes indicating shear sense.

produced by deformation processes after the initial lithifi cation of the rock. Metamorphic rocks are dominated by tectonic fabrics although some primary fabrics

tectonic fabric

no undeformed parts of the rock remain

continuous fabric

both deformed and undeformed parts of the rock are visible.

spaced fabric

sheet - like structures that include joints, veins, faults, axial surfaces of folds, shear zones and cleavage

Planar features

commonly develops in response to compressive stresses associated with dynamic or dynamothermal metamorphism.

celavage

consists of parallel foliations oriented nearly perpendicular to the maximum compressive stress, and converging towards the inner arc of the fold hinge area. is steeper than the bedding angle in upright folds.

Axial planar cleavage

contain one long axis and two short axes, producing needle - like structures. intersection lineations, form lineations, crenulation lineations, stretching lineations and surface or slip lineations

Linear structures contain one long axis and two short axes, p

commonly forms due to the intersection of two fracture sets or a fracture set and bedding are ∼ 5 – 10 cm long and generally less than 2 cm in width and height s facilitated by the internal alignment of inequant clay minerals. e develops in weakly deformed shales or mudstone and is an early stage in the development of slaty cleavage

Pencil cleavage

inear features produced by geological structures.

Form lineations

linear features that occur as a result of a secondary cleavage imposed upon a fi ne - grained rock (slate or phyllite) that experienced an earlier cleavage represent hinge lines formed by the intersection of two planar surfaces

Crenulation lineations

refer to vein mineral fi bers that precipitate on rock surfaces via crack – seal processes. Slickenlines produced during displacement in faults and shear zones (

Slip or fi ber lineations

derived from igneous rocks include volcanic fl ow contacts, intrusive contacts, vesicles, phenocrysts and other features that survive the temperatures and pressures of metamorphism.

Relict features

disc - shaped (pancake or paper - like) grains in which one axis is signifi cantly shorter than the other two axes

Tabular,

(prismatic) grains in which one axis is signifi cantly longer than the other two axes, which are not equal to one another.

Bladed

prolate (cigar - shaped) grains in which one axis is signifi cantly longer than the other two axes, which are of equal length.

Acicular (needle - like)

large relict grains from the protolith that have experienced deformation but have retained their original composition. Their large size relative to surrounding minerals is due to signifi cant crushing or stretching of the surrounding minerals and/or the growth of new, smaller crystals. minerals include quartz and feldspars

Porphyroclasts

composed of quartz.

flaser

large grains that have experienced neocrystallization and growth in response to favorable temperature and pressure conditions during metamorphism minerals include garnet, staurolite and cordierite

Porphyroblasts

occurs when inequant grains are oriented sub - parallel to one another and can produce lineations and foliations

Preferred grain orientation

line - like features similar to pencils all pointing in a common direction. Preferred orientation of tabular grains, especially phyllosilicate minerals, with sub - parallel long axes produces foliations.

Lineations

exist between weakly foliated and non - foliated textures.

Gradations

a fi ne - grained ( < 1.0 mm diameter), non - foliated fabric that develops by contact metamorphism, producing a rock derived from fi ne - grained protolith rocks such as shale, mudstone, tuff or basalt equant edvelops in metamorphic aureoles, adjacent to igneous intrusions.

Hornfelsic texture . Recrystallization causes hornfels to be somewhat harder and more brittle than the mudstone

characterized by large ( > 1.0 mm diameter) equant grains or large inequant crystals that lack preferred orientation occur in high grade rocks known as granulites, that form at elevated temperature and pressure conditions associated with deep burial. develop during metamorphism of a wide range of protoliths under uniform stress conditions display anhedral, sutured boundaries that refl ect a combination of pressure solution, recrystallization and annealing characterizes many non - foliated rocks such as metaquartzite and marble and contact metamorphosed skarn deposits commonly develop with minerals such as quartz, feldspar and calcite that have low euhedral form potentia

Granoblastic textures

contain >90% quartz and are derived from quartz - rich sandstone or chert protoliths Because the quartz grains interlock, rupture occurs through grains, rather than around grain boundaries gives this mineral a smooth, glazed appearance as opposed to the granular appearance

Metaquartzites

granoblastic metamorphic rocks rich in calcite and/or dolomite via dynamothermal, deep burial or contact metamorphism. accessory minerals include graphite and calcium -and/ or magnesium - bearing minerals such as brucite, diopside, forsterite, wollastonite epidote, serpentine, idocrase (vesuvianite), tremolite and grossular garnet. Accessory minerals provide distinctive hues that allow marble to assume a wide variety of colors Venus de Milo and Michelangelo ’ s David, sculptured from Gre

Marble

also known as tactites, are granoblastic calc - silicate rocks formed by contact metamorphism of carbonate country rocks such as limestone or dolostone. The release of silica and volatiles from the magma results in extensive metasomatism, generating calc - silicate mineral assemblages and/or metallic ore deposits contain carbonate minerals such as calcite, dolomite and ankerite and silica group minerals such as quartz minerals (calcium – magnesium silicates) include wollastonite, tremolite, diopside, talc, epidote, grossular garnet, phlogopite and idocrase (vesuvianite associated ore minerals such as gold, silver, tungsten, molybdenum or iron.

Skarn

develop during dynamic metamorphism in a wide variety of rocks within 15 km of Earth ’ s surface

Cataclastic texture

Cataclastic rocks that lack cohesion are

breccia if they contain coarse ( > 2 mm diameter), angular fragment

if they are composed of fi ner sized fragments.

gouge

develop during dynamic or dynamothermal metamorphism develop during dynamic or dynamothermal metamorphism

Metabreccias

cohesive rocks with cataclastic textures produced by brittle deformation form under low temperature, high strain, dynamic metamorphic conditions such as upper crustal fault zones. non - foliated; but phyllosilicate rich can be

cataclasites

are glassy rocks produced by high strain rates generating localized melting in fault zones Near instantaneous solidifi cation of melts produced by pressure release during fracturing produces very dark - colored, vitreous to fl inty rocks commonly occur as vein material in cataclastic rocks such as fault breccias and cataclasites.

Pseudotachylites

Cataclasite series rock terms

10 – 50 Protocataclasite 50 – 90 Cataclasite 90 – 100 Ultracataclasite

Glassy spherules called t form as rocks are locally melted due to impact. The impact of extraterrestrial rock bodies produces showers of droplets that cool very rapidly as

tektites

high pressure mineral coesite was fi rst discovered in the fi eld at

Meteor Crater

can occur with non - foliated or foliated textures

metaconglomerates, serpentinites, soapstones, greenstones, granulites, eclogites and amphibolites

derived from conglomerate protoliths and contain sub - rounded to rounded relict clasts with diameters > 2 mm

metaconglomerates

form by the metamorphism of conglomerates and/or breccias in response to strong non - uniform stress during dynamothermal or dynamic metamorphism. During metamorphism, pebbles and cobbles are shortened and/or fl attened parallel to the Z - strain direction and relatively elongated parallel to the X - strain direction Pebble alignment may defi ne a metamorphic foliation or lineation fabric examples of lineations occur in Pennsylvanian Purgatory Formation metaconglomerate in the Narraganset Basin, Rhode Island where stretched pebbles are arranged parallel to one another like loaves of French bread

Stretched pebble metaconglomerates

forms by hydrothermal alteration of ultrabasic rocks at temperatures below ∼ 500 ° C group minerals (Chapter 5 ) include lizardite [Mg 3 Si 2 O 5 (OH) 4], chrysotile [Mg 3 Si 2 O 5 (OH) 4 ] and antigorite [(Mg,Fe) 3 Si 2 O 5 (OH) 4]. Lizardite and chrysotile are low temperature minerals and antigorite is the higher temperature mineral.

Serpentinites

fi ne - grained rocks that form through the alteration of ultrabasic rocks, or magnesium - rich sedimentary rocks such as dolostone, by low temperature and low pressure hydrothermal fl uids These minerals impart a low hardness and white to green color low porosity prevents staining or seepage

Soapstone

green - colored rocks rich in silicate minerals that commonly include chlorite, epidote, prehnite, pumpellyite, talc, serpentine, actinolite and albite. orm by low to moderate (200 – 500 ° C) temperature alteration of basic and, to a lesser extent, ultrabasic igneous rocks. During metamorphism, plagioclase and primary ferromagnesian silicates such as olivine, pyroxene and amphibole are converted into this miberal commonly produced by hydrothermal metamorphism of basalts and gabbros in oceanic crust near divergent plate boundaries later be incorporated into m é langes and orogenic belts along convergent plate boundaries occur on a very large scale in greenstone belts, which are abundant in Precambrian rocks

Greenstones

(sodium - rich basalt) that occrus in greenstones

spilites

(sodium - rich andesite) that occrus in greenstones

keratophyres

occur in large synclinal structures ultrabasic metavolcanic rocks ( komatiites) and metabasalt form the basal layers and are overlain successively by intermediate and silicic metavolcanic and metavolcaniclastic sequences, which are in turn capped by graywackes and chert commonly parallel granulite belts containing rocks of granitic to dioritic composition metamorphosed at high temperatures and pressures yield valuable metallic ore deposits containing copper, gold, silver, nickel, zinc and lead

Greenstone belts Phanerozoic greenstone belts are rare. best known greenstone localities include the Barberton belt in South Africa, the eastern goldfi elds of Western Australia, the Superior and Slave Provinces in North America, and the Sao Francisco Craton in Brazil.

dominate the history of continents in the Archean and Early Proterozoic Eons green - colored minerals such as actinolite, chlorite, epidote, prehnite, pumpellyite, serpentine and talc. belts are synclinal to tabular rock assemblages that contain peridotite and gabbroic intrusive rocks and ultrabasic to basic volcanic rocks called komatiites. occur in association with granitic gneisses in Precambrian cratons

Greenstone belts

formed by extensive metasomatic alteration of basic and ultrabasic rocks through chemical reactions with H 2O and CO 2

actinolite, chlorite, epidote, prehnite, pumpellyite, serpentine and talc

overlain successively by basalt and rhyolite layers.

Komatiites

Amphibolites derived from basic igneous rocks such as basalt and gabbro are called

ortho - amphibolites

s amphibolites produced from sedimentary protoliths are called p

para - amphibolites

are medium -to coarse - grained rocks that contain granoblastic to foliated texture by high temperature ( > 800 ° C) and high pressure ( > 10 kbar; ∼ 33 km depth) metamorphism High temperature: s trigger dehydration reactions resulting in the transformation of hydrous amphibole and mica minerals into anhydrous minerals such as pyroxene, potassium feldspar, kyanite and garnet. The high pressure and very low water content prevents melting, and preserves the rock ’ s metamorphic fabric Saxony, Germany minerals include orthopyroxene, clinopyroxene, potassium plagioclase, garnet and quartz. orm in high temperature and high pressure conditions of the lower continental crust, upper mantle and as a result of subduction of crust at convergent margins. common in Precambrian greenstone belts and in association with eclogites.

Granulites

s are very high pressure, high temperature rocks that develop principally from basalt/gabbro protoliths major rock type in Earth ’ s lower crust because they are stable at temperatures that exceed 400 ° C and pressures that exceed 1.2 GPa commonly red and green because they contain green jadeite pyroxene, omphacite (sodium/calcium pyroxene) and red garnet as major minerals. can form by a number of processes, which include (1) high pressure recrystallization of deep continental crustal rocks during thickening at continent – continent collisions, (2) partial melting of the mantle followed by deep crystallization as high pressure eclogite, or (3) high pressure metamorphism of subducted oceanic lithosphere deep within Earth high density (3.5 – 4.0 g/cm 3 ) may be one of the driving forces for plate motion. The slab - pull effect generated by

eclogite

fi ne - grained, aluminum - rich, pelitic rocks that possess fl at, planar cleavage. layering is defi ned by the sub - parallel orientation of microscopic phyllosilicate mineral grain develops during metamorphism under non - uniform stress at relatively low temperatures ( ∼ 150 – 250 ° C) and low pressures

Slate

haracterized by larger crystals and more wavy surfaces than slaty cleavage silky or glossy sheen commonly develop by the recrystallization of slate and therefore from the same protoliths as slate t temperatures of ∼ 250 300 ° C, smectite and illite clays metamorphose to slightly coarser grained minerals such as sericite, muscovite, talc and chlorite that align parallel to each other and defi ne foliations. develops in response to non - uniform stresses at temperatures and pressures that exceed those that produce slaty cleavage display a crenulation cleavage that cross - cuts an earlier generation of cleavage

Phyllites

very common foliation defi ned by the sub - parallel arrangement of macroscopic platy minerals such as phyllosilicates in closely spaced metamorphic layers. This foliation is commonly less regular than that of either slates or phyllites. Light - refl ecting, macroscopic crystals generally impart a high sheen or sparkle to the like slates and phyllites, can develop from pelitic (shale, mudstone, graywacke) or altered tuff protoliths produced by dynamothermal metamorphism at convergent plate boundaries with temperatures > 300 ° C

schist or schistosity

alternating light - colored quartz and/or feldspar - rich layers and dark - colored layers rich in biotite, amphibole and –at increasing temperatures –pyroxenes. develop from lower grade metamorphic rocks as well as from a variety of protoliths including granites, diorites, gabbros, mudrocks, tuffs and graywackes. The protolith dictates the mineral components in gnei evelop due to extensive layer transposition, recrystallization and neocrystallization processes that result in the segregation of minerals into separate layers Gneisses form in dynamothermal settings at temperatures that commonly exceed ∼ 600 ° C

Gneiss

Gneisses that develop from an igneous protoliths are called

orthogneiss

The vast majority of gneissic bands originate by results from the pulling apart of earlier folded layers resulting in the separation of hinges and limbs

Transposition

which refers to the thin, sill - like intrusion of magma into parallel country rock layers occur to a limited extent when granitic magma intrudes mafi c country rock producing alternating light and dark color bands.

“ Lit par lit intrusion

possess textural and structural characteristics of both igneous and metamorphic roc commonly display an irregular, swirling mix of colors contain zones of rock with the outward appearance of granitoid igneous rocks mixed with zones of rock that resemble typical gneiss. Light - colored segments consist of quartz and feldspars; dark - colored components are enriched in pyroxene. With additional melting, migmatites melt suffi ciently so as to produce magma. under high temperature ( > 800 ° C) conditions in the lower crust dynamothermal metamorphism at convergent plate boundaries by a number of processes that involve some combination of (1) partial melting (anatexis), (2) magma injection, and/or (3) ductile deformation and plastic fl ow of rocks in the lower crust.

Migmatite

silica -and iron - rich rocks that formed primarily in the Early Proterozoic and Archean alternating hematite, magnetite and chert layers form red and black color band Deposits in the Lake Superior region of North America and in Western Australia are among the riches this deposit

Ironstone

Mylonite series as defi ned by Sibson

10 – 50 Protomylonite 50 – 90 Mylonite 90 – 100 Ultramylonite

metaquartzites that contain 20 – 30% iron and are also commonly banded. Ironstones have been major sources of iron ore since the mid 1800s considered waste rocks because of their lower iron content, are now the principal ore rocks mined in the Lake Superior region due to depletion of richer ore deposits.

Taconites

provide important information regarding the sense of displacement in shear zones

Mylonites

are pervasively deformed rocks so that their original composition and texture are largely obliterated defi ned by their solid state fl ow fabric generated through intense ductile or brittle – ductile deformation

Tectonite

Foliated tectonites are called

S tectonites.

s. Tectonites with a pronounced lineation, but no foliation, are called

L tectonites.

Tectonites with both foliation and a lineation are referred to a

L - S tectonites

s indicate the sense of displacement in shear zones and may also provide information on displacement distance. Linear features (e.g., fold axes) cut by planar faults or shear zones provide “ piercing points

Offset marker

re asymmetrical porphyroclasts or poryphyroblasts with mineral tails that “ point ”in the direction of shear. Tail complexes form commonly about minerals such as feldspars and quartz well developed in schists, gneisses and mylonitic rocks

Grain t ail c omplexes

consist of wedge - shaped tails that do not cross the reference plane of shear

Sigma ( σ) grain tail complexes c

are produced by relatively rapid grain rotation relative to tail growth rate. Rapid grain rotation results in a signifi cant bending of the earlier formed parts of the tail so that it crosses the reference plane.

Delta ( δ) grain tail complexes

preferentially oriented in the direction of shear. The fractures are inclined at low angles ( < 45 ° ) to foliations. show displacement consistent with the overall sense of shear

Synthetic fractures

are preferentially oriented in a direction opposite to the sense of shear. Antithetic fractures are inclined at high angles ( > 45 ° ) to the foliation plane and display an opposite sense of movement to overall sense of shear

Antithetic fractures

develop in mylonitic, schistose and gneissic rocks subjected to ductile shear.

S - C foliations e letter S represents schistosity (foliation) and the letter C is for “ cisaillement ” , a French term for shear direction, which lies in the C plane phyllosilicates form the schistosity and dissolution seams occur within the cisaillment zone

low temperature

e ( ∼ 150 – 400 ° C),

moderate temperature

(400 – 600 ° C)

high temperature

( > 600 ° C) conditions

atmospheric pressure ranges

low pressure (0 – 2 kbar ≈ 0 – 6 km depth), moderate pressure (2 – 6 kbar) or high pressure ( > 6 kbar ≈ > 20 km depth)

into the second half of the 20th century, metamorphic petrologists considered the highest metamorphic pressures to be

∼ 15 kbar

3.3 kbar corresponds to

∼ 10 km

ultra - high pressure xenoliths are derived from depth

400 km

minerals form within a more limited temperature and/or pressure range. These minerals, referred to rovide critical information because they effectively indicate the temperature/pressure conditions of metamorphism.

index minerals,

lines drawn on geological maps that mark the fi rst appearance of a particular index mineral.

chlorite isograd marks the fi rst appearance of chlorite and the biotite isograd marks the fi rst appearance of biotite.

e consists of the region bounded by two isograd lines

metamorphic zone biotite isograd marks the transition to the higher grade biotite zone

six metamorphic zones based on the six index mineral isograds are progressive metamorphism whereby progressively higher grades of metamorphic minerals and rocks are produced with increasing temperature in an evolving orogenic belt

Barrovian zones

bounded by the chlorite and biotite isograds chlorite - bearing slate, chlorite - sericite phyllite and chlorite - sericite schist. quartz, muscovite, albite (sodium plagioclase) and pyrophyllitebecomes unstable and begins to be replaced by biotite at the high temperature limit of this zone

chlorite zone

marking the fi rst appearance of biotite –and the almandine (garnet) isograd. Common rocks in the biotite zone include sericite - biotite phyllite and biotite schist. forms by chemical reactions that involve minerals such as chlorite, muscovite, quartz, magnetite and rutile

Biotite z one

is bounded by the almandine garnet isograd –marking the fi rst appearance of almandine garnet –and the staurolite isograd include garnet schist or garnet - mica schist Other minerals common in pelitic rocks of the almandine zone include biotite, muscovite, magnetite, quartz and sodium plagioclase minerals such as albite or oligoclase forms through the chemical transformation of chlorite and magnetite

almandine zone

lies between the staurolite isograd –marking the fi rst appearance of the higher temperature mineral staurolite –and the kyanite isograd quartz, almandine, potassium feldspar, biotite and muscovite. Potassium feldspar forms through the breakdown of muscovite staurolite exists only within the staurolite zone

Staurolite z one

occurs between the kyanite and sillimanite isograds that mark the fi rst appearances of kyanite and sillimanite, Common rock types include kyanite schist and kyanite - mica schist commonly occurring in pelitic rocks of the kyanite zone include biotite, muscovite, almandine garnet, cordierite and quartz.

Kyanite z one

occurs inside the sillimanite isograd and marks the highest temperature zone sillimanite schist, sillimanite gneiss and cordierite gneiss e biotite, muscovite, cordierite, quartz, oligoclase and orthoclase. Sillimanite and potassium feldspar can also develop by dehydration of muscovite in the presence of quartz, as in the reaction

Sillimanite z one

introduced the concept of metamorphic facies –a more comprehensive approach to assessing the conditionsrecorded by metamorphic rocks . Metamorphic facies are defi ned by a group or assemblage of critical minerals, rather than a single index mineral as used for Barrovian zones

Eskola

)initially identifi ed fi ve metamorphic facies

sanidinite, hornfels, greenschist, amphibolite and eclogite.

original hornfels facies proposed by Eskola

: (1) albite - epidote hornfels, (2) hornblende hornfels, (3) pyroxene hornfels, and (4) sanidinite hornfels

Chlorite, muscovite, quartz, pyrophyllite, albite, graphite Calcite, albite, biotite, zoisite, quartz Chlorite, albite, epidote, sphene, calcite, actinolit

Chlorite

Biotite, muscovite, chlorite, quartz

Biotite

Almandine, biotite, magnetite, muscovite, quartz Garnet, andesine, zoisite, biotite

Almandine

Sillimanite Sillimanite, biotite, cordierite, muscovite, almandine, quartz, oligoclase, orthoclase Bytownite, anorthite, diopside, garnet

Sillimanite

include non - foliated, fi ne - grained hornfels rocks and coarser grained rocks with granoblastic textures heat - induced metamorphism in aureoles surrounding igneous intrusions. T metamorphic aureoles are localized around the intrusion, commonly having widths of 100 m or less. Ocean spreading centers represent regionally extensive zones of hydrothermal metamorphism that produce hornfels facies rocks on a large scale, effectively altering entire ocean basins.

Hornfels facies

Chloritoid, albite, epidote, muscovite, chlorite, biotite, andalusite, quartz Hornfels

Pelitic

Epidote, albite, chlorite, actinolite, biotite, talc, sphene Hornfels

Basic

Antigorite (serpentine), actinolite, tremolite, talc, chlorite, biotite, albite, magnesite, brucite, dolomite Hornfels

Ultrabasic

Albite, epidote, quartz, microcline, muscovite, biotite Hornfels, metaquartzite

Quartz - feldspathic

Calcite, dolomite, epidote, tremolite, idocrase (vesuvianite), magnesite, brucite Marble, skarn

Calcareous

low temperature hornfels facies, with temperatures generally < 450 ° C and pressures < 2 kbar (depth < 6 km). develop in the outer fringes of many metamorphic aureoles. The characteristic minerals of this assemblage are albite and epidote, which most commonly occur in basaltic tuffs and lavas thermally metamorphosed at ocean ridges, hotspots and in volcanic – magmatic arcs roughly the low pressure equivalent of the greenschist facies

Albite - e pidote h ornfels f acies

compose the bulk of many metamorphic aureoles, forming at temperatures generally between 450 and 600 ° C and at pressures < 2.5 kbar ( < 8 km). Chlorite, albite, epidote and actinolite –common in albite - epidote hornfels facies –are notable by their absence in the hornblende hornfels assemblage. At temperatures above 450 ° C, dolomite is replaced by diopside via the following chemical reaction low pressure equivalent of the amphibolite facies,

Hornblende h ornfels facies

less common than the lower temperature hornfels facies commonly adjacent to higher temperature basic intrusions, pyroxene hornfels facies rocks evelop at temperatures of 600 – 800 ° C and at pressures < 2.5 kbar ( < 8 km). the higher temperatures at which pyroxene hornfels form, dehydration reactions produce a largely anhydrous suite of minerals

Pyroxene h ornfels f acies

are very rare, forming in very high temperature ( > 800 ° C) and low pressure ( < 2.5 kbar ≈ < 8 km) conditions in association with basic and ultrabasic intrusions develop where the country rock is in contact with the intrusion or in country rock inclusions (xenoliths) within the intrusion Contact metamorphic facies provide a means to place hydrothermal metamorphic rocks and ocean ridge alterations into the facies concept

Sanidinite hornfels facies

as a low grade metamorphic facies produced by temperatures between ∼150 and 300 ° C and pressures less than 5 kbar ( ∼ 15 km depth) hydrous sodium and calcium aluminum tectosilicate mineral group formed by diagenetic or low temperature metamorphic reactions coexist with quartz, include analcime, laumontite, heulandite and wairakite. Accessory minerals in the zeolite facies may include albite, kaolinite, vermiculite, adularia, pumpellyite, sphene, epidote, prehnite, montmorillonite, smectite, muscovite, chlorite and calcite originate from the hydrothermal alteration of volcanic protoliths such as basalt and andesite, the devitrifi cation of basaltic glass and tuff, and the reaction of pelites and graywackes with saline waters occur in isolated vesicles and veins or as pervasively disseminated minerals within the metamorphic rock. develops by hydrothermal alteration at divergent margins, hotspots and convergent margins or during burial metamorphism at depths less than 5 km. Laumontite and heulandite are particularly common peratures approaching 250 ° C and depths of 3 – 5 km, zeolite facies minerals begin to alter to prehnite and pumpellyite facies minerals, which occur in the upper zeolite facies but are the dominant minerals in the prehnite - pumpellyite facies, discussed below

Zeolite facies

Kaolinite, zeolite, quartz, montmorillonite, vermiculite, phengite, epidote, muscovite Metapelite, argillite, slate

Pelitic

Zeolite, albite, quartz, phengite, sphene, epidote, chlorite, prehnite, pumpellyite Metabasite or greenstone

Basic

Lizardite serpentine, talc, olivine, chlorite, prehnite, pumpellyite Serpentinite or greenstone

Ultrabasic

Quartz, zeolite, albite, sphene, epidote, quartz, muscovite Metaquartzite or metagraywacke

Quartz - feldspathic

Zeolite, calcite, quartz, epidote, dolomite, lawsonite, talc, muscovite Marble

Calcareous

zeolite minerals

natrolite stilbite chabazite heulandite thompsonite analcime laumonite wairakite

produced by hydrothermal alteration and burial metamorphism at temperatures and pressures that exceed zeolite facies conditions. based on metasedimentary basin deposits in New Zealand. widespread at oceanic ridges and therefore affect substantial portions of the oceanic crust generated at spreading ridges protoliths include basalt, graywackes and mudstones (pelites). generally forms under low temperature (250 – 350 ° C) and fairly low pressure ( < 6 kbar, ∼ 20 km depth) conditions minerals include quartz, albite, chlorite, muscovite, illite, phengite, smectite, sphene, titanite, epidote, lawsonite and stilpnomelane.

prehnite - pumpellyite facies

higher temperature assemblage containing pumpellyite and actinolite has been called

transitional pumpellyite - actinolite facies

generally form under medium temperature (350 – 550 ° C) and pressure (3 – 10 kbar ≈ 10 – 30 km depth) conditions associated with dynamothermal metamorphism at convergent plate boundaries. At these higher temperature and pressure conditions, pervasive recrystallization and/or neocrystallization commonly results in the obliteration of relict text epidote, chlorite and actinolite abundant in orogenic fold and thrust belts, where they record regional, moderate temperature/pressure metamorphic conditions at convergent plate boundaries. extensively exposed in orogenic belts such as the Appalachians, the Alps and the Otago fold and thrust belt of southern New Zealand.

Greenschist f acies

orresponds to lower greenschist facies conditions with minerals such as chlorite, dolomite, stilpnomelane and calcite.

chlorite zone

corresponds to upper greenschist facies conditions and contains biotite and tremolit

biotite zone

corresponds to the uppermost greenschist to epidote - amphibolite facies

lower part of the almandine garnet

As pressures decrease, the low pressure fi eld of greenschist metamorphism grades into the

albite - epidote hornfels facies

As progressively higher temperature conditions develop within orogenic belts, the greenschist facies transforms into higher grade

amphibolite facies metamorphism

form at high temperatures ( ∼ 550 – 750 ° C) and moderate to high pressures (4 – 12 kbar ≈ 12 – 40 km depth) in regional orogenic belts at convergent margins marks the appearance of staurolite in pelitic rocks, where staurolite may occur with kyanite. increasing temperature, include the upper part of the almandine zone, all of the staurolite and the lower part of the sillimanite zone.

Amphibolite f acies transition from greenschist to amphibolite facies is marked by an increase in hornblende, garnet and anthophyllite and a decrease in actinolite, chlorite, biotite and talc in basic and ultrabasic rocks.

Barrovian zones Almandine Staurolite Sillimanite Mineral species Albite Albite-oligoclase Oligoclase-andesine Andesine Epidote Actinolite Hornblende Chlorite

Metabasite

Chlorite Muscovite Biotite Almandine Staurolite Andalusite Sillimanite Plagioclase Quartz

Metapelite

The low temperature part of the amphibolite facies that corresponds with the almandine zone is also known as the

epidote - amphibolite facies ( “ transitional ”facies)

With decreasing pressure, the lowest pressure fi eld of the amphibolite facies metamorphism grades into

hornblende hornfels fi eld

As temperatures increase, the amphibolite facies grades into the higher temperature

granulite facies

consists of high temperature ( ∼ 700 – 900 ° C) and moderate to high pressure (3 – 15 kbar ≈ 10 – 50 km depth) mineral assemblages minerals are predominantly anhydrous (Table 18.11 ), due to dehydration reactions at high temperatures. Hydrous minerals hornblende and biotite, but not muscovite,

granulite facies Foliated granulite rocks are less common because many of the inequant, hydrous phyllosilicate minerals

Hydrous minerals hornblende and biotite, but not muscovite, can occur in the lower part of the granulite facies, sometimes referred

granulite I

The upper part of the granulite facies, sometimes referred to as haracterized entirely by anhydrous minerals

granulite II

Amphibole minerals (tremolite, anthophyllite, hornblende) dehydrate to

pyroxene minerals (enstatite, diopside, hypersthene), and phyllosilicate minerals (such as muscovite) dehydrate to anhydrous minerals (orthoclase) in response to high temperatures.

occurs as surface waters percolate downward, in so doing leaching near surface metals and concentrating them at deeper levels within Earth ’ s crust epigenetic process that commonly develops in oxidizing zones above the water table

Supergene enrichment

a primary or syngenetic process that occurs as deep, upwelling magmatic fl uids concentrate ore synchronous with rock development

Hypogene enrichmen

ore bodies are considered to be veins or layered, stratiform bodies. Tabular ore bodies commonly form along fracture systems, igneous layers, metamorphic foliations or sedimentary beds

Tabular

ore bodies, appropriately referred to as pipes or chimneys, commonly form in response to ore - enriched magma or hydrothermal solutions that rise buoyantly towards Earth ’ s surface.

Cylindrical

e. Lensoid ore deposits are referred to as meaning that they have a foot - like shape.

podiform

broadly disseminated ore deposits typically develop in close proximity to large igneous intrusions in which ore - bearing fl uids infi ltrate –and in many cases locally metamorphose –surrounding rock. Intense forces associated with igneous intrusions result in elevated fl uid pressures. These fl uid pressures are directed outward into the rock body resulting in extensive hydrofracturing of the surrounding country or host rock.

Irregular

(VMS) deposits are copper – zinc – lead sulfi de deposits concentrated on the ocean fl oor at divergent and convergent plate boundaries ores include silver, gold, cobalt, nickel, iron, tin, selenium, manganese, cadmium, bismuth, germanium, gallium, indium and tellurium upwelling plumes of black, metal - laden “ smoke ”from ocean ridge vents release hydrothermal fl uids. The chimney - like structures produced by > 360 ° C black smokers are enriched in chalcopyrite, sphalerite, pyrite and anhydrite. Metasomatic mixing of seawater and black smoker hydrothermal fl uids also produce “ white smokers ” , erupting < 300 ° C plumes that precipitate quartz, calcite, anhydrite, pyrite and barite on the sea fl oor. accumulate by the growth and subsequent collapse of black smoker chimneys resulting in layered (stratiform) or lens - shaped (podiform) metal deposits and collapse breccias overlying stockwork sulphide – silicate dike structure

Volcanogenic m assive s ulfi de d eposits

produce mounds and nodules enriched in manganese, zinc, iron, cobalt, copper and nickel. Beneath the overlying mound, hydrothermal fl uid fl ow and steeply inclined chemical and thermal gradients commonly produce cylindrical pipe zones with a higher temperature, chalcopyrite - rich inner core and lower temperature, sphalerite – galena - rich outer zones

black smoker environments

Named after the Troodos ophiolite (Cyprus) in the Mediterranean Sea. Cyprus - type VMS are basalt - dominated deposits associated with ophiolites and enriched in copper, zinc, nickel, chromium and manganese and with minor amounts of silver and gold

Cyprus type

Juvenile, nascent volcanic arc

Besshi type

Form in ocean ridge (East Pacifi c Rise) or backarc basin

Cyprus type

Named after mature convergent margin deposits in the Japanese convergent arc system. Kuroko - type VMS are dominated by silicic rocks such as rhyolite. Kuroko deposits are enriched in copper, zinc and lead and may also contain substantial gold and silver

Kuroko type

Named after the Besshi copper mine in Japan. Besshi - type VMS are early formed convergent margin deposits containing basalt, rhyolite and greywacke rocks. Besshi deposits are notable for their ore concentrations of copper and cobalt and only minor concentrations of zinc

Besshi type

Mature volcanic arc or backarc basin (Okinawa Trough)

Kuroko type

ores are leached from their igneous host rocks and concentrated in overlying sedimentary rocks.

Rift d eposits

most famous example of a rift basin deposit ron – copper – nickel deposits represent two important rift deposits involving sedimentary deposits bearing ore minerals derived from underlying rift basalts. represents a 1.1 Ga continental rift that formed synchronous with the Grenville Orogeny in eastern North America underlain by the Duluth gabbro complex, which formed from basaltic magma that crystallized at deeper levels within Earth ’ s interior. As magma fractures and intrudes the pre - existing host rock, dissolved metal ions infi ltrate, cool and precipitate via magmatic crystallization processes or magma segregation processes.

Keweenaw Basin in the Lake Superior region of Michigan

represent two important rift deposits involving sedimentary deposits bearing ore minerals derived from underlying rift basalts.

Bethlehem, Pennsylvania iron deposits and the Keweenaw, Michigan (USA

formed from basaltic magma that crystallized at deeper levels within Earth ’ s interior. s recognized as an important platinum group element ore deposit yet to be mined.

e Duluth gabbro complex

liquids separate from metal - rich, silicate magma n in silicate magma results in the concentration of metallic sulfi de deposits containing copper, iron, nickel, chromium, vanadium, palladium and platinum. Common ore minerals include chalcocite, bornite, chalcopyrite, chromite, pentlandite, nickelline, magnetite and hematite.

Immiscible s ulfi de d eposits and l ayered i gneous i ntrusions

Exceptional examples of ore - bearing layered igneous intrusions include

the Sudbury Mine in Ontario (Canada), the Duluth Complex and Stillwater Mine in Montana (USA), the Skaergaard Intrusion of Greenland and the Bushveld Complex of South Africa

principal source of copper –form as silica - rich magma intrudes and fractures the host rock and subsequently crystallizes. Forces associated with magma injection, coupled with hydrothermal fl uid pressures, result in the diffuse infi ltration of ore - bearing fl uids into complex network of fractures and pore spaces of the surrounding rock at temperatures > 500 ° C. Cooling and crystallization results in massive, low concentration ( <2%) deposits of copper, molybdenum, gold, zinc, mercury, silver, lead, lithium and tin disseminated throughout a zone of alteration within the host rock and in more concentrated veins surrounding the intrusion ccur in association with silicic to intermediate intrusions, such as granite or granodiorite, at convergent plate boundaries.

Porphyry deposits

world ’ s largest open - pit porphyry copper mine, producing 12 million tons of copper since open - pit operations began in 1906

0.8 km deep and 4 km wide Bingham Mine in Utah (USA

Cordilleran fold belt extending from Alaska southwards through the Andes Mountains. Similar deposits also occur in Indonesia and throughout the Alpine – Himalayan belt

Porphyry deposits of copper

associated with magma intrusions due to extensional hydrofractures that develop as hydrothermal fl uids escape upward from the magma, and later cool and precipitate as vein deposits. Vein deposits occur at plate boundaries as well as intraplate settings.

Vein deposits

Because of the high concentration of metals, vein deposits are referred to as can contain gold, silver, copper or metal sulfi des that occur in association with gangue minerals such as quartz or calcite

lode deposits

Familiar examples are the lode veins famous gold vein deposits originated as vein - fi lling fractures produced by granitic intrusions at convergent margin systems.

1849 California gold rush and the Klondike gold rush of Canada

coarse - grained igneous textures that develop in plutons of granitic composition containing quartz, feldspars, amphiboles and micas as major minerals –occur within continental plates and at convergent plate boundaries important sources of tin, molybdenum, gold and silver and the primary source for beryllium, lithium, tantalum, niobium and rare Earth element ores

Pegmatite deposits

promote ion diffusion and the development of large crysta

OH, fl uorine, boron and H 2O

concentrate metallic elements into ore deposits through solid state changes as well as hydrothermal fl uid reactions. Hydrothermal fl uids are critically important in driving metamorphic reactions and in concentrating ore metals

Metamorphic o re - f orming e nvironments

e hydrothermally altered assemblages that contain thick sequences of volcanic suites and interbedded sedimentary layers contain among the world ’ s greatest concentrations of copper, chromium, nickel, gold, cobalt and silver deposits. consist of down - warped basinal deposits in which peridotite rocks are overlain successively by basaltic layers, silicic igneous rocks and marine sediments derived from develop due to slow cooling of a low viscosity magma characterized by high volatile content. Volatiles such as OH, fl uorine, boron and H 2O promote ion diffusion and the development of large crystals (Chapter 8 ). Pegmatite deposits are closely associated with the vein deposits described above. Granitic pegmatites –containing quartz, feldspars, amphiboles and micas as major minerals –occur within continental plates and at convergent plate boundaries. Minor and accessory minerals in pegmatites include beryl, apatite, lepidolite, spodumene, cassiterite, wulfenite, molybdenite, scheelite, tourmaline, topaz, uraninite, lithiophillite, columbite, tantalite, gold and silver. Pegmatites are important sources of tin, molybdenum, gold and silver and the primary source for beryllium, lithium, tantalum, niobium and rare Earth element ores. Figure 19.10illustrates a beryl - bearing granite pegmatite from the Black Hills of South Dakota (USA). Let us now briefl y consider metamorphic processes that occur in regions surrounding igneous intrusions. 19.1.2 Metamorphic o re - f orming e nvironments Metamorphic processes concentrate metallic elements into ore deposits through solid state changes as well as hydrothermal fl uid reactions. Hydrothermal fl uids are critically important in driving metamorphic reactions and in concentrating ore metals. When we think of hydrothermal processes, Yellowstone or Iceland may come to mind where hot magma reacts with subsurface fl uids to create geysers or hot springs. In fact, hydrothermal deposits are formed by a number of different means that may originate as meteoric (surface) waters, seawater, groundwater, formation pore fl uids or deep magmatic fl uids. Greenstone b elts Greenstone belts (Chapter 18 ) are hydrothermally altered assemblages that contain thick sequences of volcanic suites and interbedded sedimentary layers. They are called greenstones because of green - colored metamorphic minerals such as chlorite, epidote and serpentine. Greenstone belts are particularly abundant in Precambrian cratonic belts where they Figure 19.10 Granite pegmatite from the Black Hills of South Dakota containing large crystals of beryl, quartz and feldspar. Gold deposits are associated with the Black Hills pegmatite. (Photo by Kevin Hefferan.) (For color version, see Plate 19.10, between pp. 408 and 409.) Figure 19.11 Cobalt mine in the greenstone belt in Bou Azzer, Morocco. (Photo by Kevin Hefferan.) MINERAL RESOURCES AND HAZARDS 551 altered komatiite, basalt and peridotite rocks (Chapter 10 ) that form at very high temperatures ( > 1400 ° C) near the base of the greenstone assemblage.

Greenstone belts

contact metamorphosed rocks enriched in calc - silicate minerals high temperature alteration of country rocks, usually carbonate rocks, by the intrusion of silicate magmas. Hot magma intruding carbonate rock produces ion exchange via hydrothermal solutions. Minerals such as calcite and dolomite release CO 2 and obtain SiO 2 from the magma; as a result, a distinctive suite of calc - silicate minerals form that include calcium pyroxenoid (e.g., wollastonite), calcium amphibole

Skarns

skarns that develop in any sedimentary country rock

Exoskarns

occur in igneous country rock

endoskarns

form in geothermal systems, hot springs, hydrothermal vents on the sea fl oor and at convergent and divergent plate boundaries. In these environments, skarns are commonly associated with porphyry, pegmatite, vein and VMS deposits

Modern skarns

formed as a result of chemical precipitation in shallow marine environments 1.8 – 2.5 billion years ago. These deposits are well developed in the Lake Superior region of North America, where they have represented over 80% of US production since 1900, and are referred to as Superior - type deposits. Similar massive deposits also occur in the Hamersley Basin of Australia, the Minas Gerais deposits of Brazil and the Kursk region of Russia

Banded i ron d eposits

consist of alternating iron - rich and silica - rich layers. The iron - rich layers contain both ferrous and ferric iron. Ferrous iron minerals include magnetite and siderite, whereas ferric minerals include hematite and goethite

Superior - type banded iron formations (BIF)

contain iron ore concentrations that occur in metasedimentary deposits, most of which are Archean contain hematite and magnetite interbedded with volcanic rocks, graywackes, turbidites and pelagic sedimentary rocks. form in deep abyssal basins heated by submarine volcanic activity concentrated iron - rich layers ∼ 30 – 100 m thick and extending a few square kilometers in area

Algoma - type d eposits

Tin Tungsten Bismuth Copper

Granitic plutons in continental crust

Copper Zinc Gold Chromium

Backarc

Copper Gold Silver Tin Lead Mercury Molybdenum

Magmatic arc

Lead Zinc Copper Chromium

Forearc basin

Copper Zinc Manganese Cobalt Nickel

Oceanic ridge

similar to Algoma - type deposits in that hydrothermal fl uids leach and concentrate metallic ore. contain lead – zinc – iron sulfi des precipitated by submarine hot springs. Hydrothermal fl uids containing dissolved metals rise upward and are “ exhaled ”into clastic sedimentary basins releasing metal - rich brine solutions into the surrounding country rock

Sedimentary e xhalative d eposits

form from warm ( < 300 ° C) saline solutions that fl ow in the pore spaces within permeable carbonate or sandstone rocks in deep sedimentary basins. MVT deposits precipitate lead and zinc in thick limestone, dolostone or sandstone deposits (Figure 19.17 ). These deposits most commonly occur in distal foreland basins where brine fl ow produces secondary, epigenetic deposits. In addition to lead and zinc minerals such as galena and sphalerite, the brine formation waters precipitate halite, sylvite, gypsum, calcium chloride, barite and minor amounts of gold, silver, copper, mercury and molybdenum

Mississippi V alley - type d eposits

uranium occurs in placer deposits

Athabasca Basin) Canada and Australia are the two largest uranium exporters in the world

erosional surfaces representing time gaps between depositional cycles. In Precambrian ( > 1 Ga) cratons consisting of gneisses and granites, 100 – 300 ° C hydrothermal fl uids leach metals from underlying rocks and deposit them as ores in tabular vein deposits along unconformity surfaces

Unconformity d eposits

Major unconformity - derived deposits of uranium were discovered in

Canada ’ s Rabbit Lake deposit in 1968 and in Australia ’ s East Alligator River fi eld in 1970

Sedimentary deposits of uranium occur in tongue - shaped form in fl uvial sandstones as dissolved uranium is transported in stream channels. The uranium is derived from granitic rocks and silicic tuffs. In the presence of oxygen, uranium is soluble and moves downstream as a dissolved phase. Under reducing conditions, uranium precipitates within the pores of sandstone. Variations in oxygen concentrations result in cycles of dissolution and precipitation producing irregular, tongue - shaped deposits.

Roll - front d eposits

Laterite soils enriched in aluminum hydroxide minerals are collectively referred to as is the primary source of aluminum, is produced by the intense leaching of granitic rocks containing aluminum - rich feldspar minerals and, in some cases, gold ore.

. Bauxite,

derived from the breakdown of igneous rocks such as gabbro, pyroxenite or peridotite

Laterites

Laterites are extensively mined in countries such as

China, Guyana, Australia, Jamaica, New Caledonia, Brazil, India and Surinam.

precious metals, (2) light metals, and (3) base metals.

Non - ferrous metals

alloyed with other elements –such as manganese, cobalt, nickel, chromium, silicon, molybdenum and tungsten –to make steel

Ferrous metals

occur largely in their native state and include platinum, palladium, rhodium, ruthenium, iridium and osmium. PGE have similar chemical characteristics, serving primarily as catalysts in chemical reactions. Platinum and palladium are the “ most abundant ”of the rare PGE, occurring in concentrations of ∼ 5 ppb in Earth ’ s crust. PGE are obtained primarily from layered gabbroic intrusion widely used as the catalysts in automotive catalytic converters, in oil refi ning and in converting hydrogen and oxygen to electricity in fuel cells. I

Platinum group elements (PGE)

PGE are obtained primarily from layered gabbroic intrusions (Chapter 10 ) such as the

Bushveld Complex in South Africa and the Stillwater and Duluth Complexes in the USA where PGE occur with chromite and nickel deposits.

gold bondin gwith silver equals?

electrum

gold bonding with tellurium to form telluride minerals such as

calaverite

silver base metals in sulfi de mineral

argentite, tennantite and tetrahedrite

originate via magmatic processes and concentrate through hydrothermal reactions in a number of igneous environ r found in placer deposits typically originate via granitic intrusions, Precambrian greenstone belts, deep turbidite sedimentary basins (Chapter 11 ) and as fi nely disseminated grains within porphyry copper deposits and VMS deposits. P

Gold and silver

largest gold deposits on Earth occur in Archean age ( > 2.5 Ga) placer deposits that formed by weathering granite source rocks and depositing high density gold and uranium in a clastic sedimentary basin. discovered in 1886 and mining continues to this day. Notable gold rushes in the 19th century, which included the California and Klondike gold rushes, also involved placer deposits in which high specifi c gravity gold fl akes and nuggets weathered from vein deposits, settled to the base of streams and were later extracted by panning techniques

Witwatersrand deposits of South Africa

produce signifi cant tonnage of both gold and silver

Utah ’ s Bingham copper mine and the Grasberg copper mine in Indonesia

consist of low density elements such as magnesium (1.7 g/cm 3 ), beryllium (1.85 g/cm 3 ), aluminum (2.7 g/cm 3 ) and titanium (4.5 g/cm 3

Light metals

are alloyed with scandium and cored with light - weight materials such as graphite.

Aluminum baseball

constitutes ∼8% of Earth ’ s crust by weight, it is a diffi cult metal to obtain and process. is obtained primarily from laterite soils that have experienced extreme leaching in tropical environments. Laterite soils derived from the weathering of granitic or clay - rich rocks commonly contain the bauxite group minerals diaspore, gibbsite and boehmite. Although bauxite is the only commercial source of aluminum, this light metal could be processed from clay or feldspar group minerals at a signifi cantly higher cost. Whether derived from bauxite, clay or feldspars, aluminum production requires an enormous amount of energy.

Aluminum

very expensive, relatively rare element that occurs in the minerals beryl and beryllonite. Ore deposits of these minerals occur in silicic pegmatite intrusions and in related hydrothermal veins alloyed with copper to increase hardness and is widely used in computer, telecommunications, aerospace, military and automotive electronics industries due to its high conductivity, light weight, stability at high temperature and resistance to corrosionis a known carcinogen and inhalation of this dust is particularly lethal,

Beryllium

about 1% by weight of Earth ’ s crust and occurs in ore minerals such as ilmenite, rutile and anatase. occurs in layered gabbroic intrusions and in coastal placer deposits derived from the weathering of gabbroic intrusions light - weight metal with a very high melting temperature (1678 ° C) and is widely used in aircraft engines and high speed turbines. reports that titanium represent 30% of modern aircraft weight. Ocean research submersibles such as the Alvin also consist largely of titanium. used for joint replacements and prostheses in the medical industry.

Titanium

non - ferrous metals that oxidize easily include copper, zinc, lead, tin, lithium, uranium, mercury, arsenic, cadmium, antimony, germanium, rhenium, tantalum, zirconium, hafnium, inidium, selenium, bismuth, tellurium and thallium.

Base metals

ccurs in the native state as well as in sulfi de, oxide, hydroxide and carbonate minerals.

copper

Zinc oxide minerals zincite and franklinite were exclusively mined

terling Mine in Franklin, New Jersey, which ceased operations in the 1980s.

occurs primarily in the sulfi de mineral galena. Minor minerals include anglesite, cerussite and crocoite. As noted previously, lead occurs with zinc in MVT and sedex environments. used since ancient times in lead crystal glassware, lead glass and as a sweetener for wine. Physical and mental debilitation due to ingestion of lead has been cited as one of the possible causes for the fall of the Roman Empire.

lead

derived primarily from the mineral cassiterite and is associated with silicic igneous intrusions in sedimentary rock. closely associated with tungsten and molybdenum ore deposits in granite plutons and associated hydrothermal vein networks in continental crust overlying subduction zones. Tin also occurs in VMS, MVT and placer deposits.

Tin

obtained from oxide and phosphate minerals such as uraninite and carnotite in unconformity and placer deposits derived by weathering granite source rocks. primary fuel for nuclear reactors and is a major energy source. While the production of nuclear energy does not emit the contaminants or greenhouse gases associated with fossil fuels, the mining and disposal of uranium material poses major environmental problems

Uranium

associated with a high lung cancer incidence due to inhalation of radioactive radon gas, produced as a breakdown product of uranium

Uranium mining

another uranium daughter product, is a major contaminant of groundwater. chemically similar to calcium, it is readily absorbed into bones causing cancer.

Radium

had been proposed as a permanent nuclear waste repository but its future use as of this writing is uncertain

Yucca Mountain, Nevada

include scandium, yttrium and the 15 lanthanide elements found in minerals such as monazite, which occurs in granite pegmatites, hydrothermal veins and placer depositsused as catalysts in oil refi ning, in chemical synthesis, as catalytic converters in automobiles, as glass additives, in glass polishing, in fi ber optic lasers, phosphors for fl uorescent lighting, in color televisions, cell phones, electronic thermometers and X - ray screens, and as pigments, superconductors, dopants and more

Rare Earth metals

exhibits the phenomenon of phosphorescence and is utilized in electrical equipment such as fl uorescent lights and cathode ray tubes

phosphor

is an impurity that alters the optical and electrical properties of semiconductors.

dopant

Fire - retardant materials, batteries, ceramics and glass. While antimony use and production is declining, China, Bolivia, Mexico, Russia, South Africa, Tajikistan and Guatemala continue to mine antimony in association with Pb, Zn, Ag, Sn and Wo

Antimony: in stibnite, tetrahedrite and jamesonite

Hydrothermal veins with Cu, Ni, Ag and Au and in Cu porphyry deposits

Arsenic: in realgar, orpiment, enargite, arsenopyrite and tennantite

Byproduct of Wo, Mo and Pb mining in porphyry deposits

Bismuth: in bismuthinit

Hydrothermal vein deposits, MVT deposits and Kuroko - type VMS deposits

Antimony: in stibnite, tetrahedrite and jamesonite

Toxic aspect used in copper chromate arsenic (CCA) wood preservatives, herbicides, insecticides and ammunition. Arsenic use continues to decline due to adverse health effects that include breathing and heart rhythm problems and increased risk of bladder, lung and skin cancer. Producers include China, Chile,

Arsenic: in realgar, orpiment, enargite, arsenopyrite and tennantite

Over - the - counter stomach remedies (Pepto - Bismol), foundry equipment and pigments. As a non - toxic replacement for lead, Bi is increasingly being used in plumbing, fi shing weights, ammunition, lubricating grease and soldering alloys. Because of its low melting temperature, Bi is used as an impermeable low temperature coating on fi re sprinklers. Bi is mined in China, Peru, Mexico, Canada, Kazakhstan and Bolivia

Bismuth: in bismuthinite

NiCd rechargeable batteries for alarm systems, cordless power tools, medical equipment, electric cars and semiconductor industry, and steel and PVC pipes for corrosion resistance and durability. Previously used as a yellow, orange, red and maroon pigment. Unfortunately Cd interferes with Ca, Cu and Fe metabolism resulting in softening of the bones and vitamin D defi ciency. Because of adverse health effects, Cd use is declining. Producers include China, Canada, South Korea, Kazakhstan, Mexico, the United States, Russia, Germany, India, Australia and Peru

Cadmium: in greenockite; primarily derived from sphalerite

Byproduct of Zn mining in VMS and MVT - type deposits

Cadmium: in greenockite; primarily derived from sphalerite

Fiberoptic cables, where it has replaced Cu in wireless communication, solar panels, semiconductors, microscope lenses and infrared devices for night - vision applications in luxury cars, military security and surveillance equipment. Gm is also used as a catalyst in the production of polyethylene terephthalate (PET) plastic containers and has potential for killing harmful bacteria. The USA is the leading producer of Gm

Germanium: rarely forms its own mineral but occurs with Zn and Cu

Byproduct from MVT deposits and in Cu ore deposits

Germanium: rarely forms its own mineral but occurs with Zn and Cu

Used in the construction of nuclear rods because Hf does not transmit neutrons. Major producers of zirconium and hafnium include Australia and South Africa

Hafnium: in ilmenite and rutile

Placer deposits

Hafnium: in ilmenite and rutile

Indium – tin oxide (ITO) is used in the production of fl at panel displays and other LCD products. ITO is also used in windshield glass, semiconductors, breathalyzers and dental crowns. Major producers of indium include China, Canada, Belgium and Russia

Indium is in sphalerite, cassiterite and wolframite

VMS, MVT and hydrothermal veins with Sn, Wo and Zn

Indium is in sphalerite, cassiterite and wolframite

Used in glass, ceramics, greases and batteries. Because of the adverse health issues associated with Cd and Pb, Li batteries are increasingly being used in power tools, calculators, cameras, computers, electronic games, cellphones, watches and other electronic devices. The primary producers include Chile, Australia, Russia, China, Argentina and Canada

Lithium: in spodumene, lepidolite and lithiophilite

Granite pegmatites and alkali brines from playa basins

Lithium: in spodumene, lepidolite and lithiophilite

Only metal that is liquid at room temperature for which it is commonly referred to as quicksilver. Previously used for automotive switches, cosmetics, pigments, gold processing and hat making. Hg is highly soluble and readily enters the bloodstream where it attacks the nervous system causing psychotic behavior ( “ mad as a hatter ” ), irritability, tremors and can lead to death. Hg continues to be used in thermometers, batteries, electrical fi xtures and dental amalgam fi llings and is used as a catalyst in paper production. Hg use in these and other capacities will continue to decline because of its adverse health effects. Hg is obtained from mines in China or Kyrgyzstan or obtained as a secondary ore in copper, zinc, lead and gold mines throughout the world

Mercury: in cinnabar

Low temperature ( < 200 ° C) hydrothermal vein deposits

Mercury: in cinnabar

Used with Pt as a catalyst in oil refi ning and the generation of high octane, lead - free gasoline. Re is a superalloy used in high temperature turbine engine components, crucibles, electrical contacts, electromagnets, electron tubes and targets, heating elements, ionization gauges, mass spectrographs, semiconductors, thermocouples, vacuum tubes and other uses. Producers of Re include Chile, the United States, Kazakhstan, Peru, Canada, Russia and Armenia

Rhenium substitutes for molybdenum: in molybdenite

Cu porphyry deposits

Rhenium substitutes for molybdenum: in molybdenit

Decolorized green tints are caused by iron impurities in glass; reduces solar heat transmission in architectural plate glass. Together with Cd, Se is used to generate ruby red colors in traffi c lights, plastics, ceramics and glass. Selenium ’ s photoelectrical properties were used as photoreceptors in replacement drums for older plain paper photocopiers. In the digital age, Se enables the conversion of X - ray data to digital form. Se serves as a catalyst in oxidation reactions, and is used in blasting caps, rubber compounds, brass alloys and in dandruff shampoos. Se is also used in fertilizers and as a dietary supplement for livestock. Se has both positive and negative health aspects: defi ciencies increase the incidence of stroke while excess selenium is related to deformities. Major producers of Se include Japan, Canada and Belgium

Selenium: in selenite gypsum; more commonly occurs with sulfi de minerals such as FeS and CuS minerals

Byproduct of Cu ore deposits

Selenium: in selenite gypsum; more commonly occurs with sulfi de minerals such as FeS and CuS minerals

Used in electrical capacitors, automotive electronics, pagers, personal computers and cell phones. Major producers of Ta include Australia, Brazil, Mozambique, Canada, Ethiopia, Congo (Kinshasa) and Rwanda

Tantalum: in microlite, pyrochlore and tantalite

Pegmatites, hydrothermal veins and placer deposits

Tantalum: in microlite, pyrochlore and tantalite

Used as a semiconductor and as a metal alloy for ductility and strength. Te is among the rarest elements in Earth ’ s crust

Tellurium: in calaverite

Pegmatites, veins.

Tellurium: in calaverite

Previously used in rat and ant poison until its toxicity to humans became apparent. Tl interferes with the metabolism of K and can cause death. Tl - 201, a radioactive isotope, is used in the medical industry for cardiovascular imaging. Tl is also used an activator in gamma radiation detection equipment, infrared detectors and in high temperature superconductors used for wireless communication. Major producers include Canada, European countries and the USA

Thallium: in association with sphalerite

VMS and MVT deposits

Thallium: in association with sphalerite

Used as a fuel in nuclear reactors due to the ease with which it transmits neutrons; also used in ceramics and as an abrasive, metal alloy and refractory material due to its very high melting temperature (2550 ° C). Major producers include Australia and South Africa

Zirconium: in rutile and ilmenite

Placer deposits

Zirconium: in rutile and ilmenite

Polishing compounds, radiation shield, glass, ammonia synthesis

Cerium

Permanent magnets

Dysprosium

Fiber optic amplifi er, glass additive

Erbium

Phosphors in cathode ray tubes

Europium

Phosphor and laser crystals

Gadolinium

Dopant in laser crystals

Holmiun

Catalyst in petroleum refi ning, glass additive, rechargeable batteries

Lanthanum

Phosphor

Lutetium

Permanent magnets, glass additive, dopant in laser crystals

Neodynium

Yellow pigment in ceramics

Praseodymium

Fluorescent lighting starter

Promethium

Permanent magnets

Samarium

Metal halide lamps

Scandium

Phosphors

Terbium

Isotope used in medicine

Thulium

X - ray source, glass and laser additives

Ytterbium

Phosphor, synthetic gems, superalloy

Yttrium

consist of primary nutrients such as nitrogen, phosphorous and potassium, and secondary nutrients such as calcium, magnesium and sulfur

Fertilizers

Approximately 95% of world phosphate production is used

as fertilizer and ∼5% is used in products such as detergents, fi re retardants and toothpaste

Light - weight and high strength metal. Major producers include Australia, Papua New Guinea, Jamaica, Brazil and India Bauxite in laterite deposits derived from weathering silicic igneous rocks

Aluminum: diaspore, boehmite, gibbsite

Granite pegmatites, hydrothermal veins around silicic igneous rocks Light - weight metal stable with high temperature strength. Major producers include the USA, China and Mozambique

Beryllium: beryl

Organic or inorganic sources Alloyed for hardness. Producers are widespread globally

Carbon: graphite

Layered gabbroic intrusions, ophiolites, VMS, laterites, placer deposits Corrosion resistance; important alloy in “ stainless steel ” . Major producers include South Africa, Kazakhstan and India

Chromium: chromite

Layered gabbroic intrusions, hydrothermal veins, evaporite brines in desert basins Corrosion and abrasion resistance; used in industrial and gas turbine engines. Major producers include Congo (Kinshasa), Zambia, Australia, Russia, Canada, Cuba, Morocco, New Caledonia and Brazil

Cobalt: cobaltite

Marine carbonate rocks and layered igneous intrusions. Hardens Al and corrosion resistance. Magnesium producers are widespread globally

Magnesium: magnesite, olivine

Supergene weathering of Mn rich rocks in laterites; Mn nodules in VMS; marine limestones and shales Corrosion resistance in Al; alloyed with Cu for strength; replaced lead in fuel. Major producers include South Africa, Gabon, Australia, Brazil and China

Manganese: pyrolusite, psilomelane, rhodonite, rhodochrosite

Porphyry type deposits and granite pegmatites Hardness; corrosion resistance, high temperature strength. Producers include the USA, Chile, China and Peru

Molybdenum: molybdenite

Layered gabbroic intrusions ophiolites, komatiites and laterites derived from ultrabasic rocks High temperature strength; corrosion resistance; used in jet engines and turbines. Major producers include Russia, Canada, Australia, Indonesia, New Caledonia, Columbia and Brazil

Nickel: nickelline, pentlandite, millerite

Clastic sedimentary rocks, pegmatites and hydrothermal veins Deoxidant in steel; increases strength and corrosion resistance. Silicon producers are widespread globally

Silicon: quartz

Placer sand deposits (beach dunes) or from layered gabbroic igneous intrusions Light weight and strong; strategic mineral with limited reserves; six times stronger than steel; aircraft commonly contain one - third Ti. Producers include South Africa, Australia, China and India

Titanium: ilmenite, rutile

Pegmatites and hydrothermal veins derived from granitic intrusions. Also skarns, hot springs High temperature strength; high speed drills, armor plating, light fi laments. Major producers are China, Russia, Kazakhstan, Austria, Portugal and Canada

Tungsten: scheelite, wolframit

Pegmatites, veins, layered igneous intrusions, phosphate sedimentary rock. High strength, ductility, toughness; used in high rises, oil platforms. Major producers are South Africa, China and Russia

Vanadium: vanadinite, uraninite

MS or MVT Corrosion resistance. Major producers include China, Peru, Australia and Ireland

Zinc: sphalerite, zincite

forms by bacterial reduction of gypsum and other sulfate minerals and by sublimation from volcanic gases around vents.

sulfur

consists of rocks such as limestone, marble, sandstone, granite, gneiss and slate. Dimension stone has been used since at least the construction of the pyramids over 4000 years ago and, until recently, dimension stone remained the

Dimension stone

used marble quarried locally in Carrara, Italy. Vermont slate was the rock of choice for sidewalks, blackboards and roof tiles in the eastern United States; slate from Wales provided an equal service in Wales and England. Homes in Ireland and England were largely constructed of limestone.

Michelangelo

consists of sand, gravel and crushed stone. derived from unconsolidated sedimentary layers deposited in beaches, deltas, deserts and stream systems or by glaciers. In the absence of available sand and gravel, roduced by mechanically crushing rock. The equipment and energy required to crush rock makes this a more expensive operation. Due to their low hardness and abundance, limestone and dolostone are rocks of choice for crushed quality is lowered by the presence of pyrite, which oxidizes to produce rust, and shale, which weathers easily. Concrete, developed by the Romans

Aggregate

developed by the Romans 2000 years ago, is the dominant construction material used in world today

Concrete

is made by heating limestone and clay in a kiln to produce clinker. Clinker is then ground to a powder and mixed with gypsum most common hydraulic cement, meaning that it hardens with water. In many construction projects cement has replaced dimension stone because of its ease of transport, workability and the ability to create forms to fi t site - specifi c construction projects. Cement quality is affected by the presence of chert (promotes cracks in concrete), magnesium content (MgO must be <5%) and pyrite concentration (produces SO 2 gas).

Portland cement

an evaporite mineral that commonly forms in sabkhas or intertidal fl ats of marine systems. In addition to its use in cement used in plaster and wallboard (sheetrock) for building construction

Gypsum

s produced by heating and dehydrating gypsum at temperatures of ∼ 150 ° C

Plaster of Pari

used to increase soil aeration and retain moisture and chemicals in agricultural soils.

Vermiculite

tilize clays and other minerals such as feldspars, hematite, bauxite, bentonite, pyrophyllite, borax, wollastonite, barite, lepidolite and spodumene. Clay forms the basis of pottery and other ceramic materials. Feldspars, borax and wollastonite are used to produce ceramic glazes on pottery that increase hardness, provide a vitreous luster and preserve color. Hematite serves as a pigment. Barite hardens ceramics and serves to preserve pigments. Bauxite and pyrophyllite provide high temperature strength. Lithium minerals lepidolite and spodumene are added to ceramics to prevent volume change with temperature variations.

Ceramic

promote eutrophication of water bodies by deteriorating water quality due to excessive nutrient input.

Phosphates

inert, inexpensive materials that extend the volume of material at low cost include barite and phyllosilicate minerals such as kaolinite, smectite, mica, talc and pyrophyllite

Fillers

used as a light - weight fi ller in cement, concrete and plaster

vermiculite

used as a fi ller in chocolate

Barite

e is used as a fi ller in ice creams and shakes.

kaolinite

is a siliceous rock composed of microscopic marine organisms called

diatoms

breaks chemical bonds, thereby lowering the melting temperature of materials

fl ux

Common insulating materials include

asbestos, micas, silica and vermiculite

commonly contains amphibole (tremolite) asbestos which is a known carcinogen as well as a known contributor to mesothelomia and asbestosis

vermiculite

used in jet engines, turbines and high speed drills that generate extremely high temperatures. heat - resistant materials that have very high melting temperatures and are chemically resistant to breakdown.

Refractory minerals

(Fe, Al, Sn, Zr, Cr).

High quality quartz sand, such as from used in glass making, as foundry sand for making metal molds, and as an abravise

St Peters sandstone,

Limonite, goethite, spinel, orpiment cadmium, uranium

pigment Yellow

Azurite, lazurite, zircon, spinel, cobalt

Blue

Malachite, glauconite, epidote, celadonite, atacamite [Cu 2 Cl(OH) 3], barite, chromium

Green

Hematite, cinnabar, iron, mercury, strontium

Red

Realgar

Orange

Azurite, chrysocolla, turquoise

Turquoise

Malachite, dioptase, gaspeite [(Ni,Mg)CO 3], copper

Copper

Vivianite [Fe 3 (PO 4 ) 2 8(H 2O)], aegerine

Blue gray

Hematite, pyrolusite, cuprite, purpurite (Mn 3 PO 4 )

Purple

Lazurite [(Na,Ca) 8 (AlSiO 4 ) 6 (SO 4 ,S,Cl) 2 ]

Lapis lazuli

Montmorillonite, lepidolite, rhodonite, rhodochrosite, titanium, manganese

Pink

Graphite, magnetite, pyrolusite

Gray – black

is non - crystalline and organic, forming the tusks of large animals slaughtered for these gem materials.

Ivory

One well - known synthetic gem is the isometric zirconium oxide crystal called

cubic zirconia

costume jewelry

imitaion gems

is soft and fl exible, with a hardness of 4 – 4.5. Platinum hardness increases substantially when alloyed with 5 – 10% iridium

Pure platinum

lloyed with silver and copper, becomes progressively lighter in color with increasing silver to copper ratio and

becomes darker in color with increasing copper to silver content

produced by alloying 18 karat gold with nickel, copper and zinc.

White gold

generated by alloying 18 karat gold with silver, nickel and copper.

Green gold

refers to a thin veneer of gold overlying a base meta

Rolled gold or gold plated

another soft, fl exible precious metal with a hardness of 2.5

Silver

Silver must be alloyed with 7.5 – 10% copper to produce a harder

“ sterling silver ”or “ coin silver ”

refers to the saturation or purity of a color.

Intensity

is a function of the frequency of light and is described as red, orange, yellow, blue, green, indigo and violet

Hue

refers to the ratio between the velocity of light through air and the velocity of light through a mineral substance. Minerals with a high refractive index (diamond RI = ∼2.4) tend to be more brilliant than minerals with lower refractive indices (quartz RI = ∼1.5)

refractive index (RI)

a play of color characterized by an intermingled rainbow - like assortment of green, yellow, orange and blue

Gems such as pearls and opals display a “ mother of pearl ”opalescence

helliodore (yellow)

beryl

(green by day, red by night

Alexandrite

(yellow – green – brown

cat ’ s ey

Demantroid (andradite garnet: green – yellow), hessonite (grossular garnet: green – yellow), uvarovite (chromium – green), almandine, pyrope, spessartine (red)

Garnet

Amazonite

Microcline

Nephrite jade (amphibole)

Tremolite - actinolite

Zircon (diamond like)

Zircon

Tanzanite (violet blue)

Zoisite

enriched in red wavelengths of light and is relatively depleted in blue – green wavelengths.

Incandescent light

whereby colors change under different lighting conditions;

photochroism

Ruby, emerald, pyrope, grossular, uvarovite, tourmaline (GEMS)

Chromium

Dioptase, malachite, azurite

Copper

Sapphire, aquamarine, olivine, almandine garnet, amethyst quartz

Iron

Morganite, pink tourmaline, spessartite garnet

Manganese

Green beryl, blue zoisite, garnet

Vanadium

Blue sapphire

Titanium

e resistance to breakage

Toughness ,

features a smooth, rounded top and a fl at base, resembling the form of a contact lens

cabochon cut

which is highly prized in diamonds, consists of fl at, polished, planar surfaces (facets) bounded by sharp angles that result in a sparkling, radiating, adamantine luster.

A faceted cut

The upper fl at surface is called the

top, bezel or crown with a fl at tab in the center of the crown

base of the faceted cut is referred to as

pavilion or back

constitutes those faces between the crown and the base.

girdle

vary in size from microscopic grains to over 3000 karats in weight. 75% e of lower quality industrial grade and the remaining 25% are gem - quality stones

Diamonds

Gem - quality diamonds are rated and sold according to the four Cs:

carat (karat), color, clarity and cut.

Refers to the weight of the diamond. One karat is equivalent to 200 mg. s defi ned of consisting of “ 100 points ”so that a 300 mg diamond is 1.5 karats or 150 points

Karat

is measured from a D (perfectly colorless) to Z (markedly colored) scale where the following ranges exist:

Color

colorless range; these are area and extremely expensive

D – F:

nearly colorless, wherein color is only detected under magnifi cation

G – J:

faintly yellow, wherein slight yellow hues can be noted by the unaided eye.

K – M:

very light yellow, where a light yellow color is obvious.

N – R:

light yellow, where a yellow tinge is distinctly visible.

S – Z:

football - shaped cut with a length : width ratio of ∼ 2 : 1

marquise cu

cut is a rectangular form with beveled corner edges

emerald

cuts resemble the forms for which they are named

pear, oval and heart

buying a diamond

affordable karat size (0.5 – 1 karat) and select a nearly colorless G – J color range and slightly fl awed S 1 clarity rang

controls ∼75% of the global diamond market.

cartel

uranium, radium, radon, polonium and thorium arsenic, mercury, cadmium and chromium

carcinogen

Aluminum, arsenic, beryllium, cadmium, copper, indium, lead, lithium, manganese, mercury, molybdenum, selenium, tellurium, thallium, zinc

Teratogenic

Radium, radon, thorium, uranium

Radioactive

involves the excavation of holes several kilometers wide and over 1 km deep.

Open pit mining

bones and teeth composed of hydroxyapatite [Ca 5 (PO 4 ) 3 (OH)], cryptocrystalline fl uorapatite [Ca 5 (PO 4 ) 3 (F)] and amorphous collophane are minor components of many sedimentary rocks. Much rarer are phosphate - rich rocks called phosphorites that contain more than 50% phosphate minerals and/or 20% phosphate by weight. or occurrence of phosphorites is in the form of laminae and beds of cryptocrystalline fl uorapatite and amorphous collophane interlayered with carbonates, siliceous sediments and detrital mudrocks strata appear nearly black in outcrop;

Phosphatic materials, ccumulate in areas where the infl ux of detrital sediment is minimal, thus ensuring that phosphate content is high. Modern examples of such phosphorites occur mostly as crusts near the sediment – water interface, in fairly shallow (30 – 500 m) tropical to subtropical waters (latitude < 40 ° ), beneath areas of upwelling

is medium to dark brown and isotropic in thin section

collophane

indicated by the average amounts of carbonaceous material in sandstones (0.05%), limestones (0.3%) and mudrocks (2.0%), preservation of organic matter occur when large quantities of organic matter are produced in surface environments that are depleted in oxygen so that bacterial decomposition is inhibited

CARBON - RICH SEDIMENTARY ROCKS AND MATERIALS

organic soils such as

histosols

Anoxic swamps typically develop

in paralic shoreline environments, especially in parts of deltaic systems bypassed by distributary channels

woody plants did not inhabit terrestrial environments until the middle Devonian, coal deposits do not occur in rocks older than Devonian and do not become abundant until the

Carboniferous

Coals are commonly associated with

(1) soils, especially vertisols and histosols, (2) mudrocks such as tonsteins and bentonites and (3) a variety of marine – terrestrial transitional and lacustrine facies.

soft, somewhat porous, and possesses a brownish color and rather dull luster (Figure 14.30 ). Carbon content in the organic fraction is relatively low (50 – 70%) and volatile content (including moisture) is high (45 – 55%) water (H 2O), carbon dioxide (CO 2), hydrogen (H 2 ) and methane (CH 4)

Lignite

burial and heating of lignite, which increases carbon content, drives off volatile components and transforms some vitrintie less porous and slightly more refl ective than lignite

Sub - bituminous coal

half of the available coal reserves worldwide and are used primarily as fuel in electric power - generating stations when burned they have an especially large potential to produce signifi cant amounts of airborne pollutants contributors to acid rain and global warming

Sub - bituminous coallow rank coals soft coals.

organic molecules that contain hydrogen and carbon as essential constituents.

hydrocarbons

consists of very light molecules, dominated by chain - structured alkanes such as methane (CH 4), ethane (C 2 H 6) and propane (C 3 H 8) with the general formula C n H 2n+2

Dry gas

consists of somewhat heavier molecules, including alkanes such as butane (C 4 H 10) and ring - structured cycloalkanes such as cyclobutane (C 4 H 6) and cyclohexane (C 6 H 12) with the general formula C n H n.

Wet gas

temperatures less than 50 ° C, bacteria convert some of the sapropels to methane while increases in temperature produce thermocatalytic conversion of sapropels to important constituents of oil shales

kerogens, which are composed of very heavy, insoluble organic molecules.

begins to convert kerogens into crude oil and natural @100C

catagenesis

Conversion of petroleum to wet gas reaches a maximum near 125 ° C and dry gas conversion peaks near

150 ° C

organic material is cooked to temperatures of 60 – 120 ° C, the ∼ 2.0 – 4.5 km, At lower and higher temperatures, only kerogens and natural gas are produced and, at still higher temperatures ( > 200 ° C), very few hydrocarbons remain.

oil window

The rocks in which crude oil and natural gas eventually accumulate are called

reservoir rocks

impermeable rocks, typically mudrocks or evaporites, overly the oil trap or reservoir and keep oil from rising toward the surface, they ar

cap rocks

Petroleum traps that involve geological structures produced by deformation such as folds and faults are c

structural traps ;

e produced by depositional patterns that trap petroleum in reservoir rocks are

stratigraphic traps

results from increasing temperature and/or pressure conditions over time.

Prograde metamorphism

occur due to processes such as recrystallization, neocrystallization and other processes induced by increasing pressure and/or temperature

Mineral replacement and transformation

decreasing temperature and/or pressure so that lower temperature/pressure mineral assemblages develop that overprint earlier peak temperature/pressure mineral assemblages. Volatile components serve as catalysts

Retrograde metamorphism

use of mineral assemblages or deformation characteristics of specifi c minerals to infer peak temperature and/or pressure conditions of metamorphism

Geothermobarometry

onset of metamorphism begins at

∼ 150 – 200 ° C

The higher temperature/pressure range of diagenesis marks the transition to low grade metamorphism (Figure 15.1 a). Progressively higher temperatures and/or pressures result in higher grades of metamorphism

∼ 600 – 800 ° C

fl uids derived from magma, principally at ocean spreading ridges, magmatic arcs and over hotspots.

“ Juvenile ”

Fluids and vapors containing serve as catalysts in metamorphic reactions.

H 2O, CO 2 , CH 4, K, Na, B, S and Cl

bulk composition of rocks changes as a result of chemical reactions with hot fl uids of variable origin occurs via deuteric reactions and metasomatic reactions.

Hydrothermal a lteration

known as formation pore fl uids, stored in spaces between grains or crystals

Connate fl uids,

involve reactions in which igneous rocks are “ stewing in their own juices ” . Hot, vapor - rich fl uids are commonly associated with igneous intrusions that provide the heat, fl uid and corrosive compounds to chemically alter minerals. Minerals produced by deuteric reactions include albite, calcite, epidote, sericite, chlorite, serpentine and talc

Deuteric reactions

involves changes in solid rock composition resulting from hydrothermal fl uids exchanging constituents with an outside source involve leaching, whereby elements are removed from the rock, as well as precipitation, whereby elements are introduced by hydrothermal fl uids into the rock from an outside source important process in submarine volcanic settings such as the oceanic ridge system where basaltic magma interacts with seawater

Metasomatism

Magma containing calcic plagioclase (e.g., laboradorite) reacts with sodium - rich seawater; ionic exchanges occur that convert the calcic plagioclase into sodic plagioclase (e.g., albite) in a process

spilitization

aluminum - rich rocks such as shale, mudstone and altered volcanic tuff (bentonite)

Pelite

commonly include minerals enriched in SiO 2 , Al 2 O 3 and K 2O. With increasing temperature and pressure, clay minerals such as kaolinite, smectite and illite become unstable and are transformed into the aluminosilicate minerals

pelitic metamorphic rocks

e US Occupational Safety and Health Administration (OSHA) defi nes minerals as fi liform minerals with lengths greater than 5 μm, diameters less than 5 μm and length : width ratios > 3 : 1. These minerals are considered fi brous if their length : width ratio is greater than 10 : 1

Asbestos

oft, curly, fl exible fi bers and constitutes ∼95% of all the asbestos used in industry.

Chrysotile

hard and brittle. represent <5% of all asbestos used in industry.

amphibole

lung tissue encapsulates asbestos particles. weakens the heart and destroys the lungs.

Asbestosis:

lining of the lung and stomach caused by asbestos.

35 – 40 - year

whereby individual atoms or molecules can migrate in gaseous, liquid or solid phases from one location in a rock body to a new location high viscosity inhibits migration whereas low viscosity enhances molecule migration

Diffusion

s small, angular grains that infi ll between larger grains as in cement mortar produce a mortar texture . high strain rate fault zones within the upper crust as well as in rare meteorite impacts.

Cataclasis

dissolution of solid grains under high compressive stress conditions. High, localized compressive stress regimes result in alterations to the crystal lattice structure so that an aqueous phase is produced at high stress sites.

Pressure solution

one grain impinges upon another grain, initiating a soluble phase in the indented grain

Dissolution occurs

As soluble minerals dissolve, insoluble minerals (iron oxides, micas, graphite) accumulate as an insoluble seam called a

stylolite

nucleation and growth of new minerals as pre - existing Diffusion enhances the nucleation and growth of new minerals

Neocrystallization

now known to predate the Cretaceous – Tertiary extinction by 300,000 years

Chicxulub meteorite

also known as Barringer Crater –is now thought to have formed 25,000 – 50,000 year ago by ~50 m diameter of the southwestern USA, is ∼ 1.2 km in diameter and 180 m deep rim has been uplifted 30 – 60 m due to debris

Meteor Crater ’ s

long considered a layered intrusive igneous complex, is now also recognized as a meteorite impact structure

1.85 Ga Sudbury Complex of Ontario

non - uniform stress in fault zones and shear zones

Dynamic m etamorphism

Within the upper 5 km of Earth ’ s surface, the brittle crushing and grinding of rocks produces

s fault breccia or a m é lange

partially melted rocks that form by quenching under high strain rates in shear zone fractures

Pseudotachylites

heat from the igneous intrusion produces a metamorphic

aureole

occurs when magnesium - rich olivine or pyroxene minerals are altered to serpentinite by seawater - derived hydrothermal fl uids.

Serpentinization

a result of the exchange of sodium from seawater for calcium in plagioclase, which converts the plagioclase into albite.

Spilitization

ame for sodium - rich basalts that form along ocean ridges and volcanic arcs. occur in Precambrian greenstone belts and in ophiolite

spilites

Notable modern - day examples of burial metamorphism

Bay of Bengal and the Gulf of Mexico and pull - apart basins in southern California

regional metamorphism induced by increases in both pressure and temperature. dominates convergent margins and associated fold and thrust belts. combines a complex set of processes that involve crustal shortening due to the convergence of two lithospheric plates All of the great mountain belts –Himalayas, Alps, Atlas, Urals, Pyrenees, Carpathian, Cordilleran, Zagros, Andes, Appalachians –formed as a result of crustal shortening and igneous activity and are the sites of intense

dynamothermal metamorphism

ng normal forces of equal (uniform) or unequal (non - uniform) magnitude that intersect a principal plane at right angles

principal stress axes

parallel to two principal stress axes and normal (perpendicular) to the third stress axis.

principal planes

playground analogy

refers to the uniform compressive force directed radially inward by the surrounding mass of water

Hydrostatic stress

refers to a uniform compressive force exerted radially inward due to the mass of surrounding rock. Rock stresses are commonly expressed in kilobars (kbar), megapascals (MPa) or gigapascals (GPa). Most rocks have a density of ∼ 2.6 g/cm

Lithostatic stress

displacement , means that an object has moved from one point to another point

Translation

development from an initial to a fi nal state study describes a series of strain events resulting in a fi nal strain state.

e kinematic strain

refers to one or more intermediate strain steps describing separate strain conditions

Incremental strain

that no rotation of the incremental strain axes occurred from an initial to fi nal strain state

Coaxial strain

how materials respond to stress

Rheology

a linear relationship exists between stress and strain so that the strain is proportional to the amount of stress

Hooke ’ s law, elastic behavior

a measure of the angular changes to linear features. Rigidity (G), also known as shear modulus, is a measure of resistance to change in shape. For elas

Shear strain

is a measure of resistance to change in shape

Rigidity (G), also known as shear modulus,

described in terms of length change (translation), shape change (strain or distortion) and volume change (dilation). Length change, represented by the symbol e, refers to elongation of a linear feature

Elastic behavior

measure of the resistance to a change in shape incompressibility

e bulk modulus

measure of material “ fattening ”compared to its “ lengthening ”i change in object diameter divided by change in object length. ange from 0 to 0.5, which means that all Earth materials increase in diameter and decrease in length in response to compressive stres

Poisson ’ s ratio

e slope of the stress – strain line elasticity is a constant of proportionality that describes the slope of the line.

Young ’ s modulus of elasticity

marked by the appearance of wollastonite and the absence of hydrous minerals such as phlogopite

Calcareous rocks

are hypersthene - bearing granitic gneisses

Charnockites

occurs in the highest temperature dynamothermal metamorphism region at (1) convergent plate boundaries, (2) at the base of thick continental crust, and (3) in the uppermost part of the mantle corresponds with the upper parts of the Barrovian sillimanite zone and –at still higher temperature –the cordierite - garnet zone.

Granulite facies metamorphism

low pressure fi eld of granulite facies metamorphism grades into the

pyroxene and sanidinite hornfels facies

higher temperature granulite

migmatites of the granulite facies are produced.

moderate to high pressure (4 – 20 kbar ≈ 13 – 66 km depth), low temperature (150 – 500 ° C) minerals include magnesio - riebeckite, lawsonite, jadeite pyroxene, aegirine, crossite and kyanite form in subduction zones where oceanic lithosphere is forced downward to great depths at geologically rapid rates

blueschist facies

e serves as a proverbial icicle in Earth ’ s interior

Subduction of oceanic lithosphere

With increasing temperature and pressures exceeding 12 kbar, blueschist facies converts to the

eclogite facies.

develops at high temperatures (400 – 900 ° C) and very high pressures (12 – 25 kbar ≈ 40 – 82 km chemically similar to a silica - undersaturated, anhydrous basalt and generally develop from basic protoliths. commonly with reddish brown garnet porphyroblasts conditions include pyrope, majorite, and to a lesser degree, grossular

Eclogite facies

Eclogite facies rocks occur in three major environments:

In the lower continental crust and mantle ( > 40 km depth) and later exposed on Earth ’ s surface in deeply eroded fold and thrust belts. 2 At convergent margins in ophiolite complexes and subduction zone m é langes. 3 As xenoliths in diamond - bearing kimberlite pipe

youngest documented eclogites in the world, produced along the oblique subduction zone. Oblique subduction involves components of both thrusting and strike - slip faulting

Papua New Guinea

minerals occur within the eclogite facies at pressures > 25 kbar ( > 80 km depth) and temperatures > 600 ° C. U

Ultra - high pressure (UHP)

high pressure minera

Majorite

fi rst dynamothermally produced coesite in

Alpine rocks.

distributed along continent – continent collision zones such as in the Alpine – Himalayan belt, the Ural Mountains, the Western Gneiss region of Norway and in pan - African belt rocks

UHP

two low pressure and high temperature facies series are recognized: (1) the very low P/T contact facies series, and (2) the somewhat higher P/T Buchan facies series. T

Low P/T series group:

the high P/T group includes the Sanbagawa facies series and Franciscan facies series, represented by zone C i

High P/T series group

consists of relatively low pressure ( < 2.5 kbar ≈ 8 km depth) but moderate to high temperature mineral assemblage recorded by the series of hornfels facies; each of the individual facies is defi ned based on a low pressure assemblage of minerals stable at specifi c temperature ranges

Contact facies series

With increasing temperature the contact facies series progresses through the sequence

(1) zeolite facies, (2) albite - epidote hornfels facies, (3) hornblende hornfels facies, (4) the rarer pyroxene hornfels facies, and (5) at very high temperatures, sanidinite hornfels facies

record high geothermal gradients ranging from 40 to 80 ° C/km northeastern Scotland also known as the Abukuma facies series individual facies efi ned by low to moderate P/T mineral assemblages. efl ects higher temperatures, but only moderate increases in pressure. develop by regional metamorphism and magmatic arc activity at convergent margins.

Buchan f acies s eries

Buchan facies series progresses, with increasing temperature and pressure,

(1) zeolite, (2) prehnite - pumpellyite, (3) greenschist, (4) amphibolite, to (5) the high temperature, moderate pressure granulite facies

develop in response to geothermal gradients of ∼ 20 – 40 ° C/km, refl ecting the progressive increase in both temperature and pressure during regional metamorphism

Barrovian facies series

are produced under geothermal gradients in the range of 10 to 20 ° C/km refl ects the rapid increase of pressure relative to temperature during progressive regional metamorphism at convergent plate boundaries slightly higher temperatures. This may result from (1) slower subduction giving the rocks more time to heat up as pressures increase, or (2) higher geothermal gradients during subduction.

Sanbagawa facies

The Sanbagawa facies series progression includes (

zeolite, (2) prehnite - pumpellyite, (3) blueschist facies, followed in some cases by (4) greenschist, and/or (5) amphibolite facies.

develop where geothermal gradients are < 10 ° C/km. Franciscan facies rocks are characterized by unusually high P/T ratios during progressive metamorphism. rapid increase in pressure relative to slow increases in tem e high pressure minerals jadeite, glaucophane and lawsonite are particularly important indicators of the high pressure, low temperature conditions. Kyanite, the high pressure polymorph of aluminum silicate, and phengite are common in pelitic rocks

Franciscan facies series

The Franciscan facies series progresses from

(1) zeolite, (2) prehnite - pumpellyite, (3) blueschist, possibly to (4) the eclogite facies

a means by which petrologists predict equilibrium assemblages of minerals in many systems, including both igneous and metamorphic rocks

phase diagram

. Such equilibrium mineral reaction and assemblage diagrams are referred to as

petrogenetic or paragenetic grids refers to the conditions under which the rock originated, whereas the term paragenesis refers to the formation sequence of an equilibrium set of minerals that formed at different times, e.g., along a metamorphic temperature – pressure trajectory.

is based on the molecular amounts of three components, ACF, where A = (Al 2 O 3 + Fe 2 O 3 ) − (Na 2 O + K 2O), C = (CaO –3.33P 2 O 5 ) and F = FeO + MgO + MnO. used to depict average compositional differences between the fi ve major compositional groups of metamorphic rocks: (1) aluminum - rich pelitic rocks, (2) calcium/magnesium - rich, aluminum - poor calcareous rocks, (3) magnesium/iron - rich ultrabasic rocks, (4) iron/magnesium/calcium - rich basic rocks, and (5) quartz feldspathic rocks that contain on average similar amounts of all three components

ACF ternary diagram

is used to discriminate equilibrium mineral assemblages derived from pelitic and quartzo - feldspathic protoliths with excess Al 2 O 3 and SiO he three apices indicate the following: A ′ = (Al 2 O 3 + Fe 2 O 3 ) − (K 2 O + CaO + Na 2O), K = K 2O and F = (FeO + MgO).

A′KF diagram

for metamorphic rocks where A = Al 2 O 3, F = FeO and M = MgO useful in discriminating mineral compositions in ferromagnesian - rich basic and ultrabasic rocks as well as many pelitic rocks.

AFM diagram

have also been developed for calcareous rocks as illustrated i are CaO, MgO and SiO 2.has powerful applications in the depiction of mineral assemblages in calc - silicate rocks (containing minerals such as calcite, dolomite, wollastonite and diopside) and

CMS ternary diagrams

drawn on ternary diagrams between equilibrium minerals that coexist under specifi c temperature and pressure conditions.

Tie lines

used as a predictive model for mineral assemblages in rocks. In the real world, where the number of components is generally more than three, mineral assemblages are more complex than the simple diagrams presented above

Ternary diagrams

extensive hydrothermal metamorphism of basalt, gabbro and peridotite occurs at ocean ridges resulting in

albite - epidote hornfels, zeolite and prehnite - pumpellyite facies mineral assemblages

At deeper levels within the oceanic crust and upper mantle, gabbro and peridotite are altered to higher temperature

hornblende hornfels facies assemblages

occurs on the ocean or trench side and consists of Sanbagawa or Franciscan facies series rocks, characterized lower thermal gradients and high P/T to very high P/T mineral assemblages Rapid, steep subduction favors the development of very high P/T ratios that characterize the Franciscan facies series, whereas slower, shallower subduction favors the development of the moderate to high P/T ratios that characterize the Sanbagawa facies series

The outer metamorphic belt

contains hornfels, zeolite and prehnite - pumpellyite facies metamorphism from early ocean ridge alteration. However, these rocks are commonly overprinted by more recent greenschist facies and high pressure assemblages such as blueschist and eclogite facies rocks due to burial in the subduction zone. exposed in subduction zone complexes, accretionary wedges and m é langes

outer metamorphic belt

occurs on the continent or arc side and consists of Buchan or Barrovian facies series rocks, characterized by moderate to high temperature gradients and by moderate P/T to low P/T mineral assemblages marked by the occurrence of hornfels, zeolite, prehnite - pumpellyite, greenschist, amphibolite and granulite metamorphic facies produced by arc magmatism and compressive stresses. Notably absent are high pressure assemblages of the blueschist and eclogite facies. The inner metamorphic belt occurs along the magmatic arc complex

inner metamorphic belt

The subduction of relatively cold lithosphere to depths as great as 700 km produ

high P/T Sanbagawa and Franciscan facies that occur only in association with ocean plate subduction. ater be incorporated into forearc accretionary wedges and m é langes, discussed below.

ocated on the overriding plate between the trench and the volcanic arc, include the accretionary wedge (prism), forearc basin and forearc basement

Forearc a ccretionary w edges and m é langes

produced within the forearc accretionary prism chaotic mixture, commonly contains fragments of rocks that include basalt, gabbro, peridotite, chert, limestone, sandstone, serpentinite, phyllite, zeolite, prehnite - pumpellyite, greenschist, amphibolite, blueschist and eclogite rock fragments encased in a scaly mudrock matrix.

Tectonic m é langes

enriched in pore fl uids that are expelled upon further compression to produce a scaley matrix

accretionary m é lange matrix

Highly faulted ophiolite complexes commonly occur in accretionary wedges. Because of their location above subduction zones form by the offscraping and offslicing of oceanic and/or arc lithosphere resulting in the emplacement of oceanic/arc lithosphere fragments onto the overriding hanging wall plate

supra - subduction zone (SSZ) ophiolites.

mineral assemblages, the diagnostic facies of Phanerozoic subduction zones, are exposed in subduction m é langes within the accretionary wedge of most young convergent margins. The subduction m é lange is characterized by a diverse suite of metamorphic facies including high P/T blueschist and eclogite assemblages of the Franciscan and/or Sanbagawa metamorphic facies series (

Blueschist facies

develop between the uplifted accretionary wedge/ subduction zone complex and the volcanic arc occur between the high P/T rocks of the accretionary prism and the low P/T paired metamorphic belts of the magmatic a ommonly affected by burial metamorphism due to deposition of volcaniclastic sediment derived from the adjacent volcanic arc. Total basin - fi ll thicknesses can exceed 10 km, resulting in zeolite to prehnite - pumpellyite facies assemblages underlain by forearc basement, which consists of overriding plate rocks that existed prior to subduction as well as younger volcanic – magmatic arc material that formed after subduction began

Forearc b asins and b asements

consists of deep intermediate to silicic plutons that are overlain by the composite volcanoes of the volcanic arc uration and aerial extent of igneous activity leads to long - term, intense heating of rocks in the overlying plate. This heating creates higher than normal geothermal gradients ( ≥ 40 ° C/km) generating contact, Buchan and, to a less degree, Barrovian facies series assemblages

Magmatic a rc c omplexes

Progressive Buchan facies series metamorphism generates regionally developed

zeolite, greenschist, amphibolite and granulite facies

moderate to low P/T Buchan and Barrovian facies series rocks are well developed throughout the world, including the

Pacifi c rim, eastern Indian Ocean, Caribbean and Scotia region. Ancient examples occur in the Caledonian, Appalachian, Ural and Alpine – Himalayan fold and thrust belts

develop in response to tensional stresses within the arc complex extension in an ocean – ocean convergent margin, such as in the western Pacifi c Ocean, results in the generation of actively spreading marine backarc basins that can eventually evolve into marginal seas also form in ocean – continent convergent margins, as for example in the Tyrrhenian Sea. Zeolite and prehnite - pumpellyite facies as well as hornfels facies metamorphism occur at relatively shallow depths. Greenschist facies temperatures can be attained at greater depths.

Backarc b asins

form as a result of trans - tensional stress in oblique - slip environments or along bends in faults Local extension produces a down - dropped block which infi lls with sediments with thicknesses capable of producing burial metamorphism occur in transform, divergent or convergent plate boundaries as well as within plate settings. ubjected to sub - greenschist conditions in the zeolite and prehnite - pumpellyite facies. California ’ s San Andreas Fault.

Pull - apart basins

in the overlying plates of many convergent margins. Formerly gently dipping to horizontal continental slope and continental shelf sedimentary rocks –such as shales, limestones, dolostones and sandstones deposited in passive marine settings –are subjected to intense subhorizontal compressive stress Sevier fold and thrust belt and Rocky Mountain foreland basin (Figure 18.30 ) developed in the Mesozoic and Early Cenozoic in response to subduction activity. In the fold and thrust belt, Precambrian, Paleozoic and Mesozoic sedimentary rocks were folded and displaced eastward by thrust faults. Syn -to post - orogenic magmatism intruded the fold and thrust belt

Ocean – c ontinent c onvergence: f old and t hrust b elts and f oreland b asins

accommodated by folds and thrust faults that result in the telescoping or “ piggybacking ”of thrust slice

horizontal shortening

In the adjoining foreland basin, an initially deep basin fi lls with marine deposits producing alternating shale, sandstone, chert and carbonate layers producing what is referred t

fl ysch deposit

With continued thrusting and infi lling, fi ne - grained marine rocks are succeeded by sandstones and conglomerates in what are referred to as

molasse

important for the generation of oil and gas deposits as well as extensive lignite, bituminous and anthracite coal deposits.

Fold and thrust belts and foreland basins

develops –marking the former site of the subduction trench –within an accretionary m é lange containing intensely deformed rocks which can include ophiolite, forearc fragments, blueschist, ocean plateaus and ultra - high pressure (UHP) assemblages

suture zone

produces vertical uplift and intense lithospheric thickening accommodated by folding and thrust faulting, producing widespread classic Barrovian facies series assemblages

Continued horizontal shortening

The elevated temperatures and pressures produce This situation is well displayed in the Himalayan belt, which contains the highest mountain peaks on Ea

greenschist, amphibolite and granulite facies refl ecting geothermal gradients ranging from ∼20 to 40 ° C/km in the Barrovian facies series

contain an uplifted Tibetan Plateau, suture zone and fold and thrust belt that formed as a result of continent – continent collision.

Himalayan Mountains

Eruptions begin as fi ssures, evolving to central vent fl ows and the generation of large shield volcanoes, fi ery basaltic lava fountain eruptions, quiet lava fl ows and cinder cones Kilauea, Hawaii

Hawaiian

Persistent fi ssure eruption of low viscosity basaltic lava fl ows. Prolonged quiet eruptions may generate lava plateaus and fl ood basalts Laki, Iceland, 1783 12 km 3 of lava

Icelandic

Explosive, steam - blast eruptions with lava fl ows and pyroclastic debris. Surtseyan eruptions are named after the volcanic island of Surtsey, which rose above sea level on November 14, 1963. Within 2 months Surtsey, a newly created island south of Iceland was 1.3 km long and 174 m high (Decker and Decker, 2006 ). Surtsey continued to erupt until 1967 Surtsey, Iceland, 1963

Surtseyan (phreatomagmatic)

Periodic bursts ( “ burps ” ) of moderately explosive eruptions ( < 5 km high) with great concentrations of pyroclastic fragments and incandescent basaltic lava fl ows Stromboli, Italy

Strombolian

Explosive eruptions of basaltic to rhyolitic viscous lava and large volumes of volcanic ash plumes ( < 25 km high) and pyroclastic debris Vulcano, Italy

Explosive eruptions Vulcanian

Violent eruptions of volcanic debris ejected, scattering ash over thousands of square kilometers Mt Vesuvius, Italy

Vesuvian

Tephra eruptions emit immense ash clouds > 11 km in height into the stratosphere Krakatoa, 1883

Plinian

Violent tephra eruptions of volumes > 1 km 3 and ash cloud heights 25 – 55 km Mt Taupo, New Zealand, 181 AD

Ultraplini

consist of concentrically layered (zoned) plutons formed in convergent margin settings everal kilometers in diameter, exhibit a dunite core and pyroxenite shell, and are surrounded by massive gabbro. Late granitic zones may also occur around the perimeter of the intrusive structure. In contrast to tectonically emplaced alpine suite form in situ by intrusion of magma into the surrounding country rock commonly occur as post - orogenic intrusions in volcanic arc or accretionary m é lange terrains economically important as sources of metals, particularly platinum group elements (PGE)

Alaska - type intrusions

remains an active exploration site with economic deposits of copper, nickel, platinum and palladium

Duke Island

refers to magma generation and igneous rock suites generated within lithospheric plates, rather than at plate boundaries. Tholeiitic to alkalic basalt and related gabbros of hotspots and LIP. * Siliceous anorogenic granite and rhyolite. * Silica - undersaturated rocks. * Basic – ultrabasic suites including komatiites and kimberlites. * Carbonatites.

Intraplate magmatism

ncompassing volumes > 10 6 km 3 (Mahoney and Coffi n, 1997 ), are the greatest manifestation of intraplate magmatism on Earth basaltic in composition although silicic examples, known as SLIP (silicic large igneous provinces), such as Yellowstone, also occur. most widespread Phanerozoic intraplate magmatic features consist of massive tholeiitic fl ood basalts. These massive volcanic landforms occur as both oceanic fl ood basalts and continental fl ood basalts

Large igneous provinces (LIP),

are a geochemically distinct suite of rocks distinctly different from MORB ( OIB are more alkalic and are less depleted –and may in fact be somewhat enriched with respect to incompatible elements such as potassium, rubidium, uranium, thorium and LREE OIB were considered to perhaps represent partial melts from a deeper, undepleted mantle source. However, ocean island basalts display large variations in strontium, neodymium and lead and other isotopic ratios, suggesting the role of multiple sources and processes Small degrees of melting of a primitive mantle source. * Melting of a mantle source enriched in alkali elements. * Incorporation of subducted oceanic crust in the source region. * Entrainment of subducted sedimentary rocks in the source region t magmas were derived from non - primitive sources of variable mantle composition. For example, Rb/Sr and Nd/Sm ratios are lower than primitive mantle ratios while U/Pb, Th/ Pb and U/Th ratios are higher than primitive mantle sources display isotopic ratios indicative of an enriched mantle source, particularly their elevated incompatible element and NiO concentrations

Ocean island basalts (OIB)

Hawaiian Islands constitute the highest mountains on Earth with a relief of ∼ 10 km high; Mt Everest in contrast has an elevation of just over 9 km. Hawaiian hotspot has been active for over 80 million years, generating a chain of seamounts and islands extending for a distance of 5600 km dominated by olivine tholeiites; tholeiitic basalts comprise ∼99% of the exposed Hawaiian volcanic rocks with alkalic basalts contributing only a small fraction

Hawaiian

results from fractional crystallization of early formed, magnesium - rich olivine and pyroxene

The dominant tholeiitic iron - enrichment trend

ocated near the Solomon Islands in the western Pacifi c Ocean, is the largest oceanic fl ood basalt plateau on Earth asalts erupted either in a single massive fl ood eruption ( ∼ 122 Ma) or in a series of eruptions spread over 10 million years with the initial massive outpouring occurring ∼ 122 Ma. T Ocean Drilling Project (ODP) rock core analyses, hought to consist largely of a relatively homogeneous low potassium tholeiite that erupted as massive sheet fl ows and pillow basalts, accompanied by minor volcaniclastic and vitric tuff deposit was derived by 30% melting of a primitive, enriched, high magnesium (15 – 20 wt % MgO) mantle source.

Ontong – Java basalt

include the Deccan traps of India, Karroo basalts of Africa, Siberian fl ood basalts of Russia and the Columbia River, Snake River plain and Keweenaw fl ood basalts of the United States

Continental fl ood b asalts

The three largest fl ood basalt events –the

Permo - Triassic Siberian traps, the Triassic – Early Jurassic Central Atlantic Magmatic Province and the Cretaceous – Tertiary Deccan traps –correspond with the largest extinction events in Earth ’ s history

silicic - dominated provinces containing rhyolite caldera complexes and ignimbrites

SLIP

formed during the Early Jurassic break - up of the Pangea supercontinent, which produced rift basins and fl ood basalts in North America, South America, Europe and Africa rocks consist of tholeiitic to andesitic basalts, with rare alkaline and silicic rock

CAMP

consist predominantly of tholeiitic basalt fl ows tens to a few hundreds of meters thick with minor trachyandesites, nephelinites, picrites, volcanic agglomerates and tuffs

Siberian fl ood basalts

were already recognized as one of the greatest known outpourings of lava when, in 2002, the western Siberian Basin fl ood basalt province was discovered which effectively doubled the aerial extent of the Siberian traps to approximately 3,900,000 km 2

251 Ma Siberian fl ood

Over 1,000,000 km 3 of fl ood basalt erupted in southwestern India between 65 and 69 Ma encompass an area of 500,000 km 2 in western India elated dike swarms are interpreted to result from rifting as the Indian Plate migrated over a mantle plume dominated by tholeiitic basalts with minor amounts of alkalic basalts. Geochemical studies suggest that the Deccan basalts originated by fractional crystallization of shallow magma chambers ( ∼ 100 kPa, 1150 – 1170 ° C). The basaltic magma experienced variable degrees of contamination as it ascended and assimilated granitic crustal rocks

Deccan t raps

are among the most studied CFB on Earth. consist largely of quartz tholeiites and basaltic andesite, with 47 – 56 wt % silica The Grande Ronde Basalt, which erupted 15.5 – 17 Ma, comprises approximately 87% of the total volume of the Columbia River basalt Over 300 individual lava fl ows erupted from northwest trending fractures between 6 and 17 Ma, making this the youngest continental fl ood basalt province on Earth.

Columbia River fl ood b asalts created by multiple pulses of heterogeneous mantle - derived magmas, contaminated by continental crust during magma ascent and magma mixing

produce a wide array of rocks that include alkalic basalt as well as alkaline and silicic rocks. Alkaline rocks include phonolite, trachyte and lamproite. Silicic rocks include rhyolite and rhyodacite, which occur in lava domes or as pyroclastic fl ow and ash fall deposits. Plutonic rocks vary from syenite and alkali granite to gabbroic rocks. Upwelling of hot plumes generated by the return convective loop of downgoing oceanic lithosphere. * Partial melting at great depths of overthickened continental lithosphere following supercontinent assembly. * Subduction of ocean spreading ridges resulting in shallow sub - lithospheric melting producing backarc basin type extension within the continental lithosphere.

Continental r ifts 1.1 Ga Keweenaw rift of the Lake Superior basin (USA

The widespread occurrence of basalt and rhyolite without signifi cant andesite is referred to as occurs at continental rifts and hotspots underlying continental lithosphere. Partial melting of the mantle generates basaltic magma.

bimodal volcanism

recognized three immense rhyolitic lava deposits at Yellowstone ’ s silicic large igneous province

2.1 Ma Huckleberry Ridge Tuff, the 1.3 Ma Mesa Falls Tuff and the 640,000 - year - old Lava Creek Tuff. Together, these three tuff deposits constitute the Yellowstone Group. The Huckleberry Ridge eruption dispersed 2450 km 3 rhyolite deposits over an area of 15,500 km 2 and produced a caldera over 75 km long. The Mesa Falls eruption produced tuff deposits largely within the Huckleberry Ridge Caldera. While the Mesa Falls eruptive deposits were restricted to the pre - existing caldera, a new 16 km caldera developed along the northwest end of the Huckleberry Ridge Caldera. The youngest Lava Creek cycle of eruptive activity began around 1.2 Ma and continued for approximately 600,000 years. The Lava Creek eruption produced a large caldera and scattered rhyolitic deposits over an area of 7500 km 2 . Thus the Yellowstone Caldera is a composite caldera generated by three separate rhyolitic eruptive events. In the intervening time between each of these rhyolitic eruptions, basaltic lava also erupte

The smallest of Yellowstone ’ s three Quaternary eruptive events released fi ve times more debris than the massive

1815 Tambora (Indonesia) eruption.

are anorogenic bodies injected into stable continental cratons at moderate depths develop by differentiation of eclogite – peridotite parent magmas resulting in mineral segregation within a pluton.

Layered b asic – u ltrabasic i ntrusions As with Alaskan - type intrusions, layered basic – ultrabasc intrusions are highly valued for metal deposits, particularly platinum group elements (PGE) as well as chromium, nickel and cobalt

Three of the largest layered intrusions on Earth are the

Stillwater Complex in Montana, the Bushveld Complex in South Africa and the Skaergaard Intrusion in Greenland

Other signifi cant layered intrusions include

Muskox Intrusion of the Northwest Territories (Canada), the Keweenaw and Duluth Intrusion of Minnesota (USA) and the Great Dike of Zimbabwe.

formed during the Keweenaw rift event, is a major undeveloped PGE source. Plans are currently underway to begin mining PGE in the

Duluth Complex,

2.7 Ga a large, layered basic – ultrabasic igneous intrusion in the Beartooth Mountains of southwestern Montana. exposed along a northwesterly strike for a distance of 48 km, with observable thicknesses up to 6 km. formed when basic magma intruded metasedimentary rocks, is the fi nest exposed layered intrusion in North America and contains economic deposits of platinum group metals as well as chromium, copper and nickel sulfi des The basal zone consists of norite, harzburgite and bronzite - rich orthopyroxenite layers. The ultramafi c zone consists of dunite, harzburgite, bronzite - rich orthopyroxenite and chromite - rich peridotite layers. The basal and ultramafi c zones contain copper, chromium and nickel sulfi de ore deposits. The upper banded zone consists largely of repetitive layers of alternating norite, gabbro, anorthosite and troctolite and is enriched in copper, nickel and PGE ore deposits

Stillwater Complex

South Africa ’ s 2.06 Ga massive laccolith or domal structure, is the world ’ s largest layered igneous intrusion. Extending over 400 km in length, up to 8 km thick and underlying an area of 60,000 km 2 , this complex contains a layered sequence of basic and ultrabasic rocks, capped locally by granite. Upper zone consisting of gabbro and norite. 2 Main zone containing gabbro and anorthosite. 3 Critical zone consisting of anorthosite, norite and pyroxenite. 4 Basal zone consisting of orthopyroxenite, harzburgite, dunite and peridotite. A chromite horizon occurs at the top of the basal series hosts the largest reserves of vanadium, chromium and platinum group metals in the world. PGE are concentrated within what is referred to as the Merensky Reef within the critical zone. Anorogenic granitic rocks capping the complex contain tin, fl uorine and molybdenum formed through differentiation processes accompanied by a series of magmatic injections, resulting in a massive laccolith or domal structure

Bushveld Complex

Whereas most layered ultrabasic – basic intrusions are Precambrian in age, Greenland ’ s 55 Ma youngest of the great PGE - enriched intrusion opolith intrusion crops out along Greenland ’ s eastern shores and offers exceptionally good exposures of layering formed by differentiation and convective current structures heralded as the fi nest example on Earth of fractional crystallization, displaying layered sequences of euhedral to subhedral crystals as well as distinctive structures usually associated with sedimentary beds

Skaergaard Intrusion

ultrabasic volcanic rocks found almost exclusively in Archean ( >2.5 Ga) greenstone belts. Greenstone belts are metamorphosed assemblages of green - colored rocks that contain layers of ultrabasic and basic rocks overlain by silicic rocks and sediments elevated liquidus temperatures of 1575 – 1800 ° C

Komatiites

consists of needle - like, acicular olivine, pyroxene (augite and/or pigeonite) and chromite phenocrysts in a glassy groundmass occurs in the upper parts of komatiite fl ows or in the chilled margins of sills and dikes where rapid quenching produced skeletal, acicular crystals

Spinifex texture

The virtual absence of Phanerozoic komatiites may be attributed to lower upper mantle temperatures which precludes the extensive mantle melting required to produce ultrabasic melts. The only known Phanerozoic ( < 544 Ma) komatiites occur on

Gorgona Island, Colombia, where 88 Ma komatiites erupted as > 1500 ° C ultrabasic lava fl ows. Gorgona Island, located 80 km west of Colombia in the Pacifi c Ocean, is composed largely of gabbro and peridotite otable for the rare occurrence of ultrabasic pyroclastic tuffs which record explosive volcanism

komatiite metallic ore

e 2.7 Ga Yilgarn Craton of Western Australia, the 3.5 Ga South African Barberton region and the 2.7 Ga Canadian Shield

recciated, magnesium - rich, ultrabasic rocks that rapidly rise to Earth ’ s surface via cylindrical diatremes (Chapter 8 ) from deep within the mantle The high volatile content serves two primary purposes in that (1) it lowers the melting temperature preventing crystallization, and (2) it provides the propellant “ jet fuel ”to accelerate kimberlite magma to Earth ’ s surface. eruptions form maar craters (Chapter 9 ) thatlargely fi ll with brecciated, contain the high pressure minerals pyrope garnet, jadeite pyroxene and diamond, which are stable at mantle depths > 150 km.

Kimberlite

gneous rocks enriched in carbonate minerals such as calcite, dolomite or ankerite –are important CO 2 energy sources propelling kimberlites up from mantle depths shallow intrusive to volcanic rocks that contain >20% CO 3 minerals such as natrolite, trona, sodic calcite, magnesite and ankerite as well as other minerals such as barite and fl uorite. The origin of carbonatite was a contentious issue prior to the 1960 eruption of the Oldoinyo L ’ Engai Volcano in Tanzania. Oldoinyo L ’ Engai erupted unusually low viscosity pahoehoe carbonatite lava at temperatures of ∼ 500 ° C form in stocks, dikes and cylindrical structures primarily at continental rift

Carbonatites

magnesium - rich, volatile - rich, porphyritic rocks containing mafi c phenocrysts such as biotite, phlogopite, amphibole, clinopyroxene and melilite. associated with kimberlites and continental rift zones, but also occur as dikes intruding granodiorite plutons at convergent margin settings.

Lamprophyres

potassium - rich, peralkaline rocks containing minerals such as leucite, sanidine, phlogopite, richterite, diopside and olivine. enriched in barium ( > 5000 ppm), lanthanum ( > 200 ppm) and zirconium ( > 500 ppm). relatively poor in CO 2 ( < 0.5 wt %). occur in areas of thickened lithosphere that have experienced earlier plate convergence or rifting episodes.

Lamproites

are silicic plutonic rocks that are not associated with convergent margin tectonism include stable cratons, continental rifts, ocean islands and inactive, post - collisional continental margins. 1.1 – 1.4 Ga following the assembly of the mid - Proterozoic Columbia Supercontinent. granitic intrusions are widespread in North America, extending from Mexico to the Lake Superior Signifi cant volume occur in Precambrian cratons throughout the world. These mid - Proterozoic granitoid rocks are remarkably similar in age, composition and appearance, displaying rapakivi texture Peak Batholith in Colorado (USA), develop from the partial melting of residual silicic granulite rocks (Chapter 18 ) that had previously generated I - type granites

Anorogenic (A - type) granites

texture refers to sodium plagioclase overgrowths on pre - existing orthoclase crystals

Rapakivi