Earth Mat Flashcards - Ch 17

Question 1

equal diameters in all directions and assume forms approximated by spheres or cubes.

Answer 1

Equant

Question 2

one direction in which the grain diameter is not equal to the other grain diameters

Answer 2

Inequant

Question 3

A1 < A2,A3
What shape

Answer 3

Tabular

Question 4

A1 > A2=/A3
What shape

Answer 4

Bladed

Question 5

A1 > A2=A3
What shape

Answer 5

Acicular

Question 6

What divides aphanitic and phaneritic

Answer 6

Aphanitic < 1mm > Phaneritic

Question 7

are large relict grains from the protolith that have experienced deformation but have retained their original composition.

Answer 7

Porphyroclasts

Question 8

In gneiss porhyroclasts, Felds and Qtz are

Answer 8

Augen and Flaser

Question 9

are large grains that have experienced neocrystallization and growth in response to favorable temperature and pressure conditions during metamorphism.

Answer 9

Porphyroblasts

Question 10

no orientation of inequant grain = no foliation

Answer 10

Random grain orientation

Question 11

sub-parrallel inequant grain = foliations and lineations

Answer 11

Preferred grain orientation

Question 12

On the basis of grain orientation, metamorphic rocks can be divided into two major groups:

Answer 12

Rocks with non - foliated textures
Rocks with foliated textures

Question 13

commonly produced by dynamic metamorphism, contact metamorphism or burial metamorphism

Answer 13

Non-foliated metamorphic rocks

Question 14

texture is a fine-grained (<1.0 mm diameter), non-foliated fabric that develops by contact metamorphism, producing a rock called hornfels

Answer 14

Hornfelsic

Question 15

Hornfels develops in

Answer 15

metamorphic aureoles, adjacent to igneous intrusions.

Question 16

textures are characterized by large (> 1.0 mm diameter) equant grains or large inequant crystals that lack preferred orientation

Answer 16

Granoblastic

Question 17

textures occur in granulites, associated with

Answer 17

deep burial (high PT)

Question 18

common rocks with granoblastic textures

Answer 18

Metaquartzite, marbles

Question 19

contain > 90% quartz and are derived from quartz - rich sandstone or chert protoliths

Answer 19

Metaquartzites

Question 20

are granoblastic metamorphic rocks rich in calcite and/or dolomite.

Answer 20

Marbles

Question 21

recrystallization of limestone or dolostone protoliths via

Answer 21

dynamothermal, deep burial or contact metamorphism

Question 22

are granoblastic calc - silicate rocks formed by contact metamorphism of carbonate country rocks such as limestone or dolostone.

Answer 22

Skarns , also known as tactites,

Question 23

Metamorphic rocks with ____________are composed of fractured, angular particles that form in response to the brittle crushing of grains during deformation in upper crustal fault zones

Answer 23

cataclastic textures

Question 24

Cataclastic rocks that lack cohesions are either _____(<2mm) or _____(>2mm)

Answer 24

Breccia, Gouge

Question 25

are derived from metamorphism of sedimentary or igneous breccias

Answer 25

Metabreccias

Question 26

10-50% matrix cataclasite

Answer 26

Protocataclasite

Question 27

50-90% matrix cataclasite

Answer 27

Cataclasite

Question 28

90-100% matrix cataclasite

Answer 28

Ultracataclasite

Question 29

Fault reactivations can be caused by

Answer 29

cataclasites rupturing more easily than the host rock

Question 30

are glassy rocks produced by high strain rates generating localized melting in fault zones

Answer 30

Pseudotachylites

Question 31

are high strain rate cataclastic rocks created by the tremendous short - term stresses associated with extraterrestrial rock bodies impacting Earth

Answer 31

Impactites

Question 32

that form as rocks locally melted from impact and showers down like droplets as it cools

Answer 32

Glassy spherules called tektites

Question 33

that form due to the intense stresses that deform crystal structures

Answer 33

Deformation lamellae

Question 34

Coesite first discovered at

Answer 34

Meteor crater, AZ

Question 35

are non-crystalline, high grade coals that form by heating, compressing and chemically altering bituminous coal.

Answer 35

Anthracites

Question 36

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

Answer 36

Metaconglomerates

Question 37

form by the metamorphism of conglomerates and/or breccias in response to strong non - uniform stress during dynamothermal or dynamic metamorphism.

Answer 37

Stretched pebble metaconglomerates

Question 38

Metamophosed pebbles/cobbles are

Answer 38

short/flattened at Z strain, elongated at X strain direction

Question 39

are serpentine-rich metamorphic rocks that occur in non - foliated or foliated forms.

Answer 39

Serpentinites

Question 40

Serpentinization is the where

Answer 40

ol and px are hydrated to form serpentines

Question 41

are fine - 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 fluids.

Answer 41

Soapstones

Question 42

are green - colored rocks rich in silicate minerals that commonly include chlorite, epidote, prehnite, pumpellyite, talc, serpentine, actinolite and albite.

Answer 42

Greenstones

Question 43

Many __________(sodium - rich basalt) and _____________(sodium - rich andesite) occur in greenstones.

Answer 43

spilites; keratophyres

Question 44

Greenstone sequence (basal to surface)

Answer 44

Metavolcanics (komatiites) and metabasalts -> inter/silicic metavolcaninc and metavolcaniclastic -> graywackes and chert.

Question 45

Greenstone belts commonly parallel _____________ containing rocks of granitic to dioritic composition metamorphosed at high temperatures and pressures

Answer 45

granulite belts c

Question 46

Greenstone belts; Extensive km wide, Archean and Proterozoic cratons Ex.

Answer 46

Barberton Belt, S. Africa Eastern Goldfields, W. Aus Superior & Slave Cratons, NA Sao Francisco Craton, Brazil

Question 47

Greenstone belt formed by

Answer 47

Formed from H2O + CO2 metasomatism of B and UB rocks

Question 48

Why are greenstone belts uncommon in the Phanerozoic Eon?

Answer 48

related to lower geothermal gradients in the Phanerozoic as well as changes in plate tectonics Precambrian metamorphism = high grade in shallow depths; prevention of deep subduction

Question 49

are dark - colored rocks composed largely of amphiboles, such as hornblende, and plagioclase

Answer 49

Amphibolites

Question 50

Amphibolite from basic Igni protolith

Answer 50

Ortho-Amphibolites

Question 51

Amphibolite from sedimentary protolith

Answer 51

Para-amphibolites

Question 52

metamorphism in granulites

Answer 52

(>800°C) and high pressure (> 10 kbar; ~ 33 km depth) metamorphism

Question 53

High density of ___________ may drive subduction (slab-pull effect)

Answer 53

eclogite

Question 54

are very high pressure, high temperaturerocks that develop principally from basalt/gabbro protoliths.

Answer 54

Eclogites

Question 55

are fine - grained, aluminum - rich, pelitic rocks that possess fl at, planar cleavage.

Answer 55

Slates

Question 56

________ ° C, slates are transformed to Phyllite

Answer 56

250

Question 57

In the case of slates, which minerals are stable in low temps? in high temps

Answer 57

kao, smec, zeo; illite, chl, mica

Question 58

In anoxic envi: oragnics recrystallize to

Answer 58

graphite

Question 59

display phyllitic cleavage, characterized by larger crystals and more wavy surfaces than slaty cleavage

Answer 59

Phyllites

Question 60

At 250 - 300°C smec and illite transforms to

Answer 60

seri, musc, talc, chl

Question 61

_____ phyllites are transformed gradationally into schist

Answer 61

~300 ° C,

Question 62

is a very common foliation defined by the sub - parallel arrangement of macroscopic platy minerals such as phyllosilicates in closely spaced metamorphic layers.

Answer 62

Schistosity

Question 63

Schists are produced by _metamorphism at convergent plate boundaries with temperatures >300 ° C

Answer 63

dynamothermal

Question 64

are characterized by gneissic layering, a foliation characterized by the arrangement of minerals into distinct color bands.

Answer 64

Gneisses

Question 65

Gneisses that develop from an igneous protoliths are called

Answer 65

orthogneiss

Question 66

gneiss from sedimentary protoliths are called

Answer 66

paragneiss

Question 67

which refers to the thin, sill - like intrusion of magma into parallel country rock layers

Answer 67

“ Lit par lit intrusion ” ,

Question 68

Gneisses form in dynamothermal settings at temperatures that commonly exceed

Answer 68

~ 600 ° C.

Question 69

processes have been suggested for the development of gneissic banding:

Answer 69

Originate by layer transposition. Lit Par Lit Anatexis

Question 70

Layer transposition process

Answer 70

Transposition results from the pulling apart of earlier folded layers resulting in the separation of hinges and limbs Insoluble phyllosilicates in fold limbs and soluble qts/felds in hinge, tightly compressed forming alternating bands

Question 71

are “ mixed ” rocks that possess textural and structural characteristics of both igneous and metamorphic rocks

Answer 71

Migmatites

Question 72

are silica - and iron - rich rocks that formed primarily in the Early Proterozoic and Archean.

Answer 72

Ironstones

Question 73

are metaquartzites that contain 20 – 30% iron and are also commonly banded

Answer 73

Taconites; found largely in lake superior

Question 74

Metamorphic ______ are pervasively deformed rocks so that their original composition and texture are largely obliterated.

Answer 74

tectonites

Question 75

tectonites are Classified by solid state flow fabric from deformation what are they

Answer 75

S tectonites = Foliated L tectonites = lineation, no foliation L-S tectonites = Foliation, Lineation

Question 76

are rock structures or textural elements that provide information concerning the relative sense of displacement of rock components within fault zones or shear zone

Answer 76

Shear sense indicators

Question 77

indicate the sense of displacement in shear zones and may also provide information on displacement distance.

Answer 77

Offset markers

Question 78

allows displacement distance to be measured; intersections by linear features and planar faults/shear zones

Answer 78

Piercing Points

Question 79

are asymmetrical porphyroclasts or poryphyroblasts with mineral tails that “ point ” in the direction of shear.

Answer 79

Grain tail complexes

Question 80

Mineral tails may form by a combination of:

Answer 80

Plastic flattening of pre-existing grains Pressure soln from grain center Dynamic. recryst. at the rim of the grain Neocryst in pressure shadows around grain

Question 81

____________ grain tail complexes consist of wedge - shaped tails that do not cross the reference plane of shear slow grain rotation; fast tail growth Tail growth at minimum compressive stress (45° to ref plane) during rotation

Answer 81

Sigma (σ)

Question 82

_________ tail complexes are produced by relatively rapid grain rotation relative to tail growth rate Fast grain rotation = bending of inner portion of the tail, crosses reference plane

Answer 82

Delta (δ) grain

Question 83

fractures oriented at shear direction <45° inclination from foilation

Answer 83

Synthetic Fractures

Question 84

fractures oriented against shear direction >45° inclination from foilation

Answer 84

Anti-synthetic Fractures

Question 85

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

Answer 85

S - C foliations

Question 86

in S-C The letter S represents __________ and the letter C is for ____________, a French term for shear direction, which lies in the C plane

Answer 86

Schistosity; cisaillement