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GLE 2024 (Day 2) > METAMORPHIC PETROLOGY (METAMORPHISM TYPES) > Flashcards

METAMORPHIC PETROLOGY (METAMORPHISM TYPES) Flashcards

1
Q

Differentiate local and regional met based on scale

A

local met : < 100 sqkm
Regional met : > 100 sq km

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2
Q

Tectonic or geologic settinsg where local met occurs?

A

1)Impact craters (Impact Met)
2) Fault and Shear Zones (Dynamic Met) and
3) Igneous contact with country rocks (Contact Met)

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3
Q

Tectonic or geologc setttings where regional met occurs?

A

Covergent or divrgent plate boundaries

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4
Q

What is impact metamorphism?

A

Metamorphism which occurs via explosive volcanic eruptions or relatively rare collisions of extraterrestrial objects wiith earth

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5
Q

What are the products of high strain rate w/in impact met?

A

Breccias,
shocked quartz lamellae,
pseudotachylites

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6
Q

Ultrahigh pressure silica polymorphs?

A

Coesite and Stishovite

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7
Q

Rocks produced by meteorite impacts?

A

Impactites

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8
Q

The age which is said to be dominated by meteorite bombardement

A

4.3 Ga (Pliocene)

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9
Q

A meteorite impact crater under the Yucatan Peninsula in Mexico which is said to be responsible for the extinction of dinosaurs

A

Chicxulub crater (65Ma)

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10
Q

impact crater located in arizona desert of SW USA which was tought to be a volcanic crater and is the site where astronauts trained for their moon walk in the 1960s

A

Meteor Crater/ Barringer Crater (25K-50K years)

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11
Q

A layered intrusive igneous complex recognizes to be a meteorite impact structuer

A

Subdury Complex (1.85 Ga)

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12
Q

What is dynamic metamorphism?

A

Metamorphism induce by non uniform stress in fault zones and shear zones which is usually of local extent but can also occur in regional scale in areas of large fault or shear zones

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13
Q

Rocks which are fragmented angular with finer grained matrix formed by dynamic metamorphism at depths of 5km of the upper crust in which there is relatively cold rocks low earth pressure

A

Cataclasites

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14
Q

This is a type of cataclasite with coarser clasts (>2mm) making up at least 30% of the rock

A

Fault Breccia

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15
Q

Another term for fault breccia

A

Melange

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16
Q

cataclasite with matrix <50% of the rock vol

A

PROTOcataclasite

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17
Q

cataclasite with matrix 50-90% of the rock vol

A

MESOcataclasite

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18
Q

cataclasite with matriz >90% of the rock vol

A

ULTRAcataclasite

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19
Q

These are partially melted rocks formed by quenching under high strain rates in shear zone fractures w/in 5-10 km depth. These rocks are characterized by ultrafine-grained vitreous material usually black or flinty that occurs in dilation fractures of the host rocks in the form of planar veins, injection veins or matrix

A

Pseudotachylites

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20
Q

What drives partial melting to form pseudotachlites?

A

Frictional Heat and geothermal gradient

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21
Q

These are rocks fromed by grain size reduction via microscopic cataclasis, plastic stretching and thinning associated with narrrow ductile shear zones at depths greater than 10-15 km

A

Mylonites

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22
Q

These are rocks associated with wide ductile shear zones

A

Striped Gneiss

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23
Q

These are local metamorphism which develop where hot magmas intrudes relatively colder upper crustal country rocks at depths less than 10km. (Variable temp and low P)

A

Contact Metamorphism

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24
Q

What dictates temperature in contact met zones?

A

Size, temp of pluston and distance from the intrusion

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25
This is produced by the heat around an igneous intrusion which ranges from cm to hundred of meters in diamter chracterized by difference in mineral assemblages caused by alteration
Metamorphic aureole
26
A general term for fine-grain, contact metemorphic rock rich in silcates
Hornfels
27
protolith of hornfels
Mudstones
28
These rocks are formed by contact metemophism of quartz arenite
Metaquartzites
29
This develop when igneous rocks intrude carbonate rocks
Skarns
30
How do skarns form?
When chemical reactions with magmatic fluids result in enrichment of carbonate rocks with SiO2
31
This type of met. is associaed with hydrothermal altertaion at oceanic spreading ridges.
Ocean floor metamorphism
32
How does extensional fractures and normal faults serve as two way conduits?
It serves as vents for hot magma which result in extensive metal sulfide deposits in basic ign rocks at the same time, cold oygenated seawater descends through fissures and reacts with the basaltic crust enriching it in Na and Mg.
33
IN which environments will Oli and pyx alter to magnetite and hematite?
Shallow oxidizing envi
34
What variety of olivine and pyx alter to serpentinite?
Mg-rich varieties (Forsterite and Enstatite)
35
How does spilitization occur?
Exchange of Na from Sewater and Ca from ca-plag in basalts result in conversion to na-plag such as albite
36
Na-rich basalt
Spilites
37
Where does spilite usually form?
Oceanic ridges and volcanic arcs
38
where does it occur in the surface?
Precambrian greenstone belts and ophiolites
39
minerals associated with spilitic basalt
Chlorite, Epidote, Actinolite (Propylitic Minerals)
40
This results from increase in lithostatic stress induced by deep burial of rock and produces non-foliated textures which usually affects regional subsiding basins that accumulate sequences of sediments and volcanic debris (low grade Met via increase in T and P)
Burial Met
41
Tectonic settings in which burial met can occur?
Rifts, Foreland Basins, Passive Marine Basins, Contental margings, Forearc and Backarc basins and pull apart basins
42
Temperature ranges of burial met
150-350 deg cel
43
Low temp mineral assemblages of burial met
Zeolite, Prehnite, Pumpellyite, Chlorite and Micas
44
Modern day example of burial met?
Bay of Bengal and Gulf of Mexico
45
A regional met induced by varying increase both in pressure via non-uniform stress and temp which usually produced foliated rocks and is the most aerially extensive met type on Earth
Dynamothermal Met
46
Where does dynamothermal met dominate?
Covergents margins associated with fold and thrust felds
47
These are the most volumetrically and economically important types of met?
Ocean Floor and Dynamothermals
48
Results when heat transfer is dominant agent especially near pluton?
Thermal Met
49
Occurs when stress results to deformation and recyrstallization
Dynamic Met
50
Results when both temp and stresses are combined
Dynamothermal
51
Results when fluid enhanced infiltration and alteratiion
Metasomatism
52
Regional vs local
regional ? area of wide extent ? affecting large volume of rock ? large scale tectonic processes (Seafloor spreading, crustal thickening, and deep basin subsidence) while local are those with ?limited volume extent (Magmatic intrusion, faulting or meteorite impact)
53
Met types falling under regional classification?
Orogenic and Burial
54
Diff orogenic and burial
Orogenic is associated with various phase of mountain building including both compressional and extensional regimes while burial is a lowgrade met in sed basins due to burial
55
Met types falling under Regional-Local Classificaion?
Ocean-Floor and hydrothermal Met
56
What is ocean floor met?
related to steep geothermal gradient occuring near spreading centers what causes incomplete recrystallization assoc with cicrulaiong hot aqeous fluid
57
What is hydrothermal met?
Met associated with hot H2O rich fluids
58
What are met types under local met? (6)
1) Contact, 2) Dislocation, 3) Impact, 4) hot Slabs, 5) Combustion and 6) Lightning met
59
Met occuring adjacent to ign intrusions as a result of thermal and metasomatic effects of mgma
Contact Met
60
Met rocks from in the surroundng country rocks
Contact aureole - Ito mismo ung met rocks
61
Assoc with fault or shear zones inducing grain reduction in rocks
Dislocation Met
62
Caused by passage of shock waves due to impact of extraterrestrial body which involves melting and vaporiztaion
Impact Met
63
This met occurs beneath an emplaced hot tectonic body where thermal gradient is steep and inverted
Hot Slab Met
64
Metamorphism cause by spontaneous combustion of naturally occuring substances such as bituminous rock, coal or oil
Combustion Met
65
Met due to strlke of lightning which produces rocks that are almost entirely glass
Lighting met
66
Rocks that is produced from lightnin strike
Fulgurite

GLE 2024 (Day 2) (41 decks)

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