Igneous Petrology Flashcards
(179 cards)
1
Q
is molten rock material generated by partial melting of Earth’s mantle and crust
A
Magma
2
Q
magma that rises and erupts onto the surface of Earth
A
Lava
3
Q
is the liquid portion, is composed mainly of mobile ions of the eight most common elements in the crust.
A
Melt
4
Q
the gaseous components of magma, are materials that will vaporize (form a gas) at surface pressures
A
Volatiles
5
Q
called when magma loses its mobility before reaching the surface it eventually crystallizes
A
Intrusive
Plutonic
6
Q
called when igneous rocks form by solidification of lava and volcanic debris on Earth’s surface, producing rocks with small crystals and/or non-crystalline particles of various sizes.
A
Extrusive
Volcanic
7
Q
refers to the partial melting of a source rock
A
Anatexis
8
Q
The type of magma produced by partial melting and subsequent processes depends upon factors such as:
A
The composition, temperature and depth of the source rock.
The percent partial melting of the source rock.
The source rock’s previous melting history. - Diversification processes that change the composition of the magma after it leaves the source region.
9
Q
Ways of Generating Magma from solid rock
A
Increase in Temperature
Heat Transfer
Decrease in Pressure
Flux Melting
10
Q
also known as adiabatic melting , results from a decrease in pressure.
occurs where hot, solid mantle rock ascends in zones of convective upwelling, thereby moving into regions of lower pressure
A
Decompression Melting
11
Q
Crystallization along the walls of the magma chamber in which crystals preferentially form and adhere to the edges results in marginal accretion.
A
Marginal Accretion
Inward Crystallization
12
Q
includes fractionation processes that occur when crystals develop with significantly different densities than the surrounding magma.
A
Gravitational Separation
13
Q
occurs when higher density, ferromagnesian crystals settle to the base of a magma chamber relative to the lower density liquid magma
A
Crystal Settling
14
Q
can occur if early formed crystals, such as plagioclase, are less dense than the magma
A
Crystal Flotation
15
Q
occurs whereby liquids and crystals are segregated due to factors such as velocity, density or temperature.
A
Convective Flow Segregation
16
Q
process whereby a magma chamber containing a mix of crystals and liquids is compressed, squeezing out the more mobile liquid into a new chamber and leaving behind a crystal residue in the original chamber.
A
Filter Pressing
17
Q
involves the preferential diffusion of select ions within the magma in response to compositional, thermal or density gradients as well as water content.
A
Differential Diffusion
18
Q
also called liquid – liquid fractionation , occurs when magma separates into two or more distinct immiscible liquid phases
A
Liquid Immiscibility
19
Q
occurs when two or more dissimilar magmas coexist, displaying contact relations but retaining their distinctive individual magma characteristics.
A
Magma Mingling
20
Q
implies thorough mixing so that the individual magma components are no longer recognizable.
A
Magma Mixing
21
Q
record a progressive decrease in iron and magnesium with increasing SiO2 and alkali concentrations
A
Calc-alkaline Magma
22
Q
with increasing fractionation, experience iron enrichment at low to moderate SiO2 concentrations
A
Tholeiitic Magma
23
Q
are highly enriched in Na2O and/or K2O and are less common than either calc-alkaline or tholeiitic magmas or rocks
A
Alkaline Magma
24
Q
are characterized by the voluminous occurrence of silicic and basic rocks with few intermediate rocks
A
Bimodal Magma Suites
25
are defined as plutons of more or less irregular shape with surface exposures ≥ 100 km2
Batholiths
26
are plutons with surface exposures ≤ 100 km2
Stocks
27
is a tabular, concordant pluton that parallels country rock.
Sill
28
is a blister-like concordant pluton characterized by a flat floor and domed roof
Laccolith
29
are dish-shaped to funnel-shaped concordant plutons that resemble a champagne glass in cross-section view.
Lopolith
30
tabular intrusions that cross-cut country rock layers.
Dikes
31
cylindrical plutonic dikes exposed at the surface by subsequent erosion. They represent ancient conduit pipes that funneled magma upward to a volcano that has long since been removed by erosion.
Neck
| Volcanic Neck
32
carrot-shaped, cylindrical pipes that can extend to depths of 200 km. It develop via explosive intrusions that originate deep within the mantle. The explosiveness is due to the high volatile content which propels magma and xenolith fragments upward towards the surface.
Diatreme
33
Major distinctions in rock type are based on two criteria
Magma Chemical Composition
Environment of Magma Emplacement
34
Gas Content of
Mafic
Intermediate
Felsic
1-2%
3-4%
4-6%
35
Igneous rocks are classified according to (a) and (b).
(a) is determined by magma chemistry.
(b) refers to the size, shape, arrangement and degree of crystallinity of a rock's constituent
Composition
| Texture
36
The most straightforward approach to determining the mineralogy involves visually identifying the minerals and determining their percentages by volume
Modal or Mode Composition
37
systems are commonly used in aphanitic or glassy volcanic rocks, in which a rock’s modal mineral composition can not be determined
Normative Mineralogy
38
Weight percentage of Silica of;
Ultrabasic
Basic
Intermediate
Acidic
<45%
45-52%
52-66%
>66%
39
Percent of Dark Colored Minerals
Ultramafic
Mafic
Intermediate
Felsic
>90%
70-90%
40-70%
<40%
40
General description of rock color based on mineral composition
Dark greenish rocks rich in olivine; may also contain pyroxene and amphibole
Ultramafic
41
General description of rock color based on mineral composition
Light colored or red rocks rich in potassium feldspar, quartz, biotite or muscovite
Felsic
42
General description of rock color based on mineral composition
Dark colored rocks containing pyroxene, amphibole, olivine, biotite
Mafic
43
What rock is it?
Ultramafic and Aphanitic
Komatiite
44
General description of rock color based on mineral composition
grayish to salt and pepper colored rocks rich in plagioclase, amphibole, biotite, quartz
Intermediate
45
a very dark-colored rock, depleted in SiO2 and commonly enriched in the minerals pyroxene, olivine, amphibole and plagioclase.
Peridotite
46
dark-colored, SiO2-poor rocks rich in plagioclase, pyroxene and olivine
Basalt
| Gabbro
47
are gray-colored to salt and pepper-colored rocks rich in hornblende, pyroxene and plagioclase. Contain more than half to almost two-thirds SiO2.
Andesite and Diorite
48
are light-colored rocks, containing approximately two-thirds SiO2, rich in plagioclase, alkali feldspar and quartz and also containing small amounts of hornblende and biotite.
Dacite
| Granodiorite
49
are light-colored rocks containing more than two-thirds SiO2 and rich in quartz, alkali feldspar with small percentages of plagioclase and biotite
Rhyolite
| Granite
50
Magma composition of Scoria
Basaltic
51
contain complete crystal faces that are not impinged upon by other crystalss, developed under circumstances such as slow cooling of magma.
Euhedral
| Idiomorphic
52
partially complete crystal form
Subhedral
53
Magma composition of Pumice
Felsic
54
lack any observable crystal faces, they have had to take the shapes of whatever open spaces were available between the already crystallized minerals
Anhedral
| Xenomorphic
55
there is a mix of euhedral, subhedral and anhedral grains.
Hypidiomorphic-Granular Texture
56
wholly crystalline texture
Holocrystalline
57
wholly glassy textures
Holohyaline
58
partially crystalline/partially glass texture
Hypocrystalline
59
very fine-grained as a result of rapid cooling at the surface. -implies high crystal nucleation rates
Aphanitic texture
60
-grains are too small to be resolved optically but are visible with an electron microscope and can be identified by XRD.
Crypocrystalline
61
can be discerned with a petrographic microscope ; ________rocks in which elongate rectangular grains of feldspars are dominant have felty texture
Microcrystalline
62
(A) or coarse-grained mineral sizes that has crystal diameters ranging from 1to 30mm.
(B) 1mm to 3mm
(C) 3mm to 10mm
(D) 10mm to 30mm
Phaneritic
Fine grained
Medium grained
Coarse grained
63
(A) texture consist of two distinctly different size crystals. large crystals and finer grained material
(B) large crystals in the rock is called
(C) finer grained material in the is called
Porphyritic
Phenocrysts
Groundmass
64
characterized by large crystals averaging more than30 mm in diameter
Pegmatitic
65
This texture is in contrast with Pegmatitic texture, this texture refers to extremely fine grained minerals
Aplitic Texture
66
a porphyritic rock that contains scattered phenocrysts in a glassy matrix.
Vitrophyre
67
Important alteration product of divitrification
Palagonite
68
texture that is a product of devitrification; _______ are spherical to ellipsoidal clusters of radiating fibrous alkali feldspars and a polymorph of SiO2
Spherulitic Texture
69
develops by hydration of obsidian on fracture surfaces that are exposed to moisture in the atmosphere or to meteoric water (groundwater).
Perlitic texture
70
Texture in which minerals filled the cavities
Amygdaloidal Texture
71
Texture in which gas cavities filled with primary minerals
Miarolitic Texture
72
rocks formed at intermediate depth not clearly distinct from those of volcanic and plutonic rocks. They can have fabric similar to that of plutonic and volcanic rocks.
Hypabyssal Rocks
73
Temperature at which a rock will first start to melt
or
temperature in which the phase is 100% solid
Solidus
74
The main factor that determines the texture of an igneous rock is the ___________
Other factors are
a
b
c
Cooling Rate
Diffusion Rate
Rate of Nucleation
Crystal growth rate
75
the rate at which enough of the chemical constituents of a crystal can come together in one place without dissolving
Rate of Nucleation
76
the rate at which atoms or molecules can migrate through magma.
Diffusion rate
77
a measure of the increase in crystal radius over time
Crystal Growth Rate
78
Temperature at which a rock will be fully molten.
or
temperature in which crystallization starts
Liquidus
79
is an amorphous solid. Possess a disordered form, lacking an ordered crystalline structure
Glass or Vitric
80
occurs when melts of any composition come into contact with liquid water or air.
Quenching
81
formed by partial crystallization of magma that contains scattered phenocrysts in a glassy matrix.
Vitrophyre
82
produced by fragmenting processes that creates broken pieces of volcanic rock and/or mineral grains
Volcaniclastic
| Pyroclastic
83
texture contains spherical to ellipsoidal void spaces.
- develop due to exsolution and entrapment of gas bubbles in lava as it cools and solidifies.
Vesicular texture
84
8 most abundant elements in the earth's crust by weight percent
```
O-47%
Si-28%
Al-8%
Fe-5%
Ca-3.5%
Na-3%
K-2.5%
Mg-2%
```
85
Shand Classification base %DCM
DCM- dark colored minerals
<30% Leucocratic
30-60% Mesocratic
60-90% Melanocratic
>90% Hypermelanic
86
Is it saturated, oversaturated or undersaturated?
1. Qtz + feldspars and/or Mg orthopyroxene
2. Forsterite, Nepheline, Leucite and other feldspathoids + feldspar and/or orthopyroxene minerals
3. felds and/or Mg orthopyroxene only
Oversaturated
Undersaturated
Saturated
87
Ellis Classification of % DCM
```
<10% Holofelsic
10-40% Felsic
40-70% Mafelsic
70-90% Mafic
>90% Ultramafic
```
88
Aluminum abundance
1) Al2O3 > CaO + Na2O + K2O
2) Al2O3 < Na2O + K2O
3) Al2O3 = Na2O + K2O
4) Na2O + K2O < Al2O3 < CaO + Na2O + K2O
1. Peraluminous
2. Peralkaline
3. Subaluminous
4. Metaluminous
89
are suites of rocks that form in response to similar geological conditions.
Petrotectonic Association
90
Oceanic lithospheres’s four distinct layers;
This Layer contains well - stratified marine pelagic sediments and sedimentary rocks that accumulate on the ocean floor.
Layer 1 - Sediment
91
Oceanic lithospheres’s four distinct layers;
This layer contains mantle peridotite is marked by high temperature, solid state strain fabric (metamorphosed) and represents the lowest layer of the oceanic lithosphere.
Layer 4 - Peridotite
92
Oceanic lithospheres’s four distinct layers;
This layer can be subdivided into two basaltic rock layers.
a) __________
b) __________
Layer 2
a) Pillow basalt
b) Basalt dikes
93
Mid-ocean ridge basalts can be subdivided:
a)
b)
N-MORB
| E-MORB
94
Mid-ocean ridge basalts
represent 20-30% partial melting of a well-mixed, depleted mantle source
N-MORB
95
Mid-ocean ridge basalts
- have higher incompatible elements
- represent smaller degrees (10-15%) of partial melting of residual mantle rock so that the incompatible elements are more highly concentrated
E-MORB
96
```
Chemically diverse igneous assemblages erupt in the convergent margins widely distributed in
a)
b)
c)
d)
```
Pacific Ocean
Eastern Indian Ocean
Carribean
Scotia Sea
97
Oceanic lithospheres’s four distinct layers:
This layer contains massive gabbro in the upper section, layered gabbro in a middle section, and increasing amounts of layered peridotite towards the bottom of the section, marking the base of ocean crust.
Layer 3
98
Plutonic rocks at convergent margins (7)
```
Diorite
Granodiorite
Quartz Diorite
Granite
Gabbro
Tonalite
Trondhjemite
```
99
Convergent Plate Boundaries
| Variables in which can diversify magma composition.
5
1) Composition and thickness of overlying plate
2) Composition of rock experiencing anatexis
3) Flux Melting
4) Diversification Processes
a) Fractionation
b) Assimilation
c) Magma Mixing
d) Metamorphic Reactions
5) Dip angle of the subduction zone
100
is the signature volcanic rock suite of convergent margins and constitutes one of the most voluminous rock assemblages on Earth, second only to MORB.
BADR
| Basalt, Andesite, Dacite, Rhyolite
101
contain 45 – 52% SiO2 and can be subdivided into a number of different varieties based upon major and minor element concentrations
Basalt
102
Basalts common in convergent margins
Aphanitic & Aphanitic-Porphyritic varieties of Tholeiites
Calc-alkaline Basalts
103
Basalt with higher concentrations of Al2O3, typically in concentrations greater than 16 wt %.
Arc tholeiites
104
Basalt with higher alkali concentrations and not displaying iron enrichment typical of tholeiitic fractionation trends.
Calc-alkaline Basalts
105
Rock with 52 – 63% SiO2.
Andesite
106
Andesite with
1) > 52 – 57% SiO2
2) > 57 – 63% SiO2
1) Basaltic Andesite
| 2) Silicic Andesite
107
Rock with 63 – 68% SiO 2, that extends to 77%
Dacite
108
Rock with 66 – 69% SiO 2, although the lower TAS limit begins at 57% SiO 2
Trachyandesite also called as
Latite
Shoshonite
109
Rock with >69% SiO2
Rhyolite
110
Rock with 68 – 73% SiO2 - are associated with explosive silicic eruptions producing fragmental, glassy and aphanitic to aphantic – porphyritic textures
Rhyodacite
111
develop on the overlying ocean lithosphere plate, above the subduction zone.
are underlain by intermediate to mafic plutonic suites dominated by diorite, quartz diorite, granodiorite, tonalite and even gabbro.
Island Arc
112
High magnesium intermediate volcanic rocks that contain a SiO2 - saturated (52 – 68% SiO 2) groundmass
named from ______ of ________
Boninite
Bonin Island
Western Pacific Ocean
113
This rock is silica-saturated ( >56% SiO 2 ) rocks with high Sr/Y and La/Yb ratios and low HFS (such as Nb and Ta) concentrations
This rock is named from ____ Islands of the ____
Adakites
Adak Island
Aleutian Island Chain
114
How does backarc extension occur?
“Trench pull” forces move the volcanic arc towards the subduction zone resulting in the seaward movement of the trench and volcanic arc.
115
are dark-colored, potassium - rich trachyandesites, commonly containing olivine and augite phenocrysts with a groundmass of labradorite plagioclase, alkali feldspar, olivine, augite and leucite.
Shoshonite
116
Also called as Plagiogranite
Trondhjemite
117
are fault - bounded, deformed rock sequences that mark the site of present or former convergent margins
Alpine Orogenic Complexes
118
Zone in which the lower continental lithosphere does not subduct to great depths but essentially breaks off and underplates the overlying continental lithosphere plate producing a doubly thick lithosphere.
Continent-Continent Collision Zone
119
is an intensely sheared, heterogeneous rock assemblage embbedded within a highly deformed mud matrix.
Tectonic Melange
120
Magma body that consist of concentrically layered (zoned) plutons formed in convergent margin settings
Alaskan type intrusion
121
Refers to magma generation and igneous rock suites generated within lithospheric plates
can be initiated by
Hotspot
Continental Rifts
Overthickened Continental Lithosphere
Intraplate Magmatism
122
are volcanic landforms that rise upward above sea level
Ocean island
123
are volcanically produced peaks below sea level
Seamount
124
are broad flat-topped areas that result from massive outpourings of lava flowing laterally from source vents
Oceanic Plateau
125
3 largest flood basalt events
Permo–Triassic Siberian traps
Triassic–Early Jurassic Central Atlantic Magmatic Province
Cretaceous–Tertiary Deccan traps
126
Consist predominantly of tholeiitic basalt flows tens to a few hundreds of meters thick with minor trachyandesites, nephelinites, picrites, volcanic agglomerates and tuffs
- recognized as one of the greatest known outpourings of lava when the ___________ basalt province was discovered
- analogous to burying half of the contiguous United States in lava
Siberian Flood Basalts
127
Formed during the early Jurassic
-rocks consist of tholeiitic to andesitic basalts, with rare alkaline and silicic rocks.
CAMP
| Central Atlantic Magmatic Province
128
dominated by tholeiitic basalts with minor amounts of alkalic basalts
- famous for the beds of fossils that have been found between layers of lava
Deccan Trap
129
What is the driving force behind the lithospheric extension that leads to the development of continental rifts?
Upwelling of hot plumes
Partial melting at great depths
Subduction of ocean spreading ridges
130
3 of the largest layered intrusions on Earth
Bushveld Complex in South Africa
Skaergaard Intrusion in Greenland
Stillwater Complex in Montana
131
world’s largest layered igneous intrusion
Bushveld Complex
132
Bushveld Complex consists of four main zones
```
Upper Zone
-Gabbro & Norite
Main Zone
-Gabbro & Anorthosite
Critical Zone
-Anorthosite, Norite, Pyroxenite
Basal Zone
-Orthopxn, Harzburgite, Dunite, Peridotite
```
133
Intraplate volcanics and Shallow intrusives
```
Komatiites
Kimberlites
Carbonatites
Lamprophyres
Lamproites
Anorogenic (A-type) granites
```
134
are ultrabasic volcanic rocks found almost exclusively in Archean ( > 2.5 Ga) greenstone belts
- High in magnesium ( > 18% MgO), olivine - rich volcanic rocks, depleted in titanium and LREE.
Komatiite
135
Texture that commonly occurs in the upper parts of komatiite flows or in the chilled margins of sills and dikes where rapid quenching produced skeletal, acicular crystals
Spinifex texture
136
are brecciated, magnesium - rich, ultrabasic rocks that rapidly rise to Earth ’s surface via cylindrical diatremes from deep within the mantle
Kimberlite
137
are 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 fluorite.
Carbonatite
138
are magnesium rich, volatile - rich, porphyritic rocks containing mafic phenocrysts such as biotite, phlogopite, amphibole, clinopyroxene and melilite.
Lamprophyre
139
are potassium - rich, peralkaline rocks containing minerals such as leucite, sanidine, phlogopite, richterite, diopside and olivine
Lamproite
140
are silicic plutonic rocks that are not associated with convergent margin tectonism
A-type granite
| Anorogenic Granite
141
texture refers to sodium plagioclase overgrowths on pre existing orthoclase crystals
Rapakivi
142
A naturally occurring landform produced where lava erupts onto Earth’s surface.
Volcano
143
Types of Lava
Aa
| Pahoehoe
144
Types of Volcano
| according to morphology
Shield
Stratovolcano
Cinder Cone
145
Produced by the accumulation of fluid basaltic lavas and exhibit the shape of a broad , slightly domed structured that resembles a warrior’s shield
- Gently sloping, 15° or less
Shield
146
Also called scoria cones, built from layers of volcanic cinders (ash, glassy fragments) that often start as small fissures that rapidly grow
- Steeply sloping, 30° to 40°
Cinder Cone
147
Also called ______ volcanoes, built from interlayered tephra and lava flows, generally products of gas-rich andesitic magma
- Gradually sloping
- Most dangerous and eruptive
Stratovolocano
| Composite Volcano
148
Types of Volcano
| according to activity
Active
Potentially Active
Inactive
149
Had at least one eruption during the past 10,000 years. - Locally, a volcano is active if it had a recorded eruption for the past 600 years, and has datable material since 10,000 years ago
Active Volcano
150
Has not had an eruption for at least 10,000 years, and is not expected to erupt again in a comparable time scale of the future
Inactive Volcano
151
Geomorphologically young volcano that is currently not erupting, but is supposed to erupt again
Potentially Active Volcano
152
A systematic classification of volcanic eruptions based on observations during an eruption
```
Tephra volume (m3)
Column height
Eruption type
Description
Duration
```
VEI
| Volcanic Explosivity Index
153
Calmest eruption type with steady lava fountaining and the production of thin lava flows
Hawaiian
154
Occur as a series of discrete, canon-like explosions that are short-lived, lasting for only minutes to a few hours, often with high-velocity ejections of bombs and blocks – a process of “throat clearing”
Vulcanian
155
Large, explosive eruptions involving high-viscosity magmas of andesitic to rhyolitic composition.
These eruptive columns produce widespread dispersals of tephra which cover large areas with an even thickness of pumice and ash
Plinian
156
The eruption of heated water and steam without magma
Often associated with hot springs, geysers, and fumaroles or solfataras
Phreatic
157
Also called Surtseyan, produced by the interaction of magma with groundwater or surface water
Much more explosive – as the water is heated, it flashes to steam and expands explosively
Phreatomagmatic
158
A volcanic landform that resulted from the collapse of the summit of a volcano following an explosive silica-rich eruption
Caldera
159
Dome-shaped mass produced from squeezed-out thick lava from volcanic vents
Lava Dome
160
Low relief volcanic craters that form by shallow explosive phreatomagmatic eruptions
Maar
161
Broken rock particles with varying sizes produced from volcanic eruptions
Pyroclasts
162
rock consisting of unreworked solid material of various sizes ejected from a volcanic vent
Pyroclastic Rock
163
or tephra, are volcanic materials with varying sizes produced by volcanic eruptions
Pyroclastic Material
164
solid or liquid ejecta with sizes greater than 64mm
Block and Bomb
165
rock fragments with grain sizes ranging from 264mm formed from droplets of lava
Lapilli
166
tephra that is usually glass having grain sizes lesser than 2mm
Ash
167
a fractured surface texture formed when bombs cool
Breadcrust texture
168
Pyroclastic fragments that fall to the ground due to gravity. Identified by having a good sorting of angular juvenile clasts.
Pyroclastic Fall
169
Moves at speeds up to 300m/s and can reach over to a 1000°C.
Can generate Nuee Ardentes , or “glowing cloud”
Developed with poorly sorted beds with rounded clasts that can produce block - and ash flows.
Pyroclastic Flow
170
Have low concentrations of particles mixed with gases that travels at high velocity and horizontally from the eruption site
Usually associated with phreatic and phreatomagmatic eruptions
Identified by having a “pinch and swelling” beds with moderate sorting of moderately rounded clasts
Pyroclastic Surge
171
It is a very fluid mudflow that occurs when volcanic debris becomes saturated with water and rapidly moves down steep volcanic slopes, generally following gullies and stream valleys
Lahar
172
these are derived directly from magma involved in the volcanic activity
Juvenile or Cognate Clasts
173
these are rock inclusions from the vent walls or brought from the surface by lava or pyroclastic walls
Accidental Clasts
174
It is the explosive ejection and aerial dispersal of pyroclasts of rock and magma from a volcanic vent
Pyroclastic process
175
a result of breaking up the cooler and rigid exterior of the lava as it continuously moves that can include block-sized autoclasts
Autoclastic process
176
It is brought by the weathering and disentigration of volcanic rocks
Epiclastic process
177
It is group of clasts with interstitial fluid that interact and move together
Massive Flow Transport
178
called whenclasts behaving independently in moving interstitial fluids
Traction
179
called when fully suspended clasts in interstitial fluid
Suspension
