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GLE 2024 (Day 2) > METAMORPHIC PETROLOGY (PLATE TECTONICS) > Flashcards

METAMORPHIC PETROLOGY (PLATE TECTONICS) Flashcards

1
Q

Sites or environments of Regional Metamorphism

A
  1. Divergent PB
  2. Convergent PB
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2
Q

Divergent Plate boundaries are associated with these processes

A

1.Continental Rifts and Oceanic Rifting
2. Sea Floor Sprading
3. Hydrothermal Processes

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3
Q

Convergent Plate boundaries are associated with

A
  1. Subduction
  2. Formation of Magmatic Arcs
  3. Continental Collissions
    (Dynamothermal Processes)
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4
Q

Metamorphism in Continental Rifts

A

1) Contact Met from intrusions of shallow dikes, sills and flood basalts
2) Hyrothermal alteration associated with hot volatile fluids
3) Dynamic Metamorphism due to brittle exensional faulting in the Upper crust and Ductile shearing in the lower crust
4) Burial Met due to deposition of thick, non-marine detrital seds sequqnce in rift basins

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5
Q

Facies associated with Burial Met

A

Zeolite
Prehnite-Pumpellyite

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6
Q

What kind of Metamorphism is related to Ocean Spreading Centers or Oceanic Ridges

A

Hydrothermal Metamorphism

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7
Q

Hydrothermal Met of Oceanic Ridges (Upper levels of oceanic crust) composed of Basalt, Gabbro and Peridotite results to what facies

A

Albite-Epidote Hfels Series
Zeolite
Prehnite-Pumpellyite

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8
Q

At deeper levels of the oceanic crust gabbro and peridotite forms what facies

A

Hornblende hfels facies

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9
Q

Why is foliations and high P garnet not formed by hyrothermal metamorphism of the sea floor

A

Because there is a minimal compressive stress and low confining pressures

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10
Q

This reaction adds Na, Cl, Br, CO3, SO4, and O2 to the oceanic crust

A

Metasomatism via the reaction of cold seawater infiltrating into fractured oceanic lithosphere

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11
Q

Result of extensive hyrdrothermal alteration of the oceanic crust

A

Spilitic Basalt (Na-Rich)

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12
Q

What forms due to leaching of magma adnd precipitate onto the sea floor via black smokers

A

VHMS or VMS

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13
Q

Outer Met Belt

A

Subduction zone

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14
Q

Inner Met Belt

A

Magmatic Arc

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15
Q

The outer Met belt which occurs on the ocean or trench isde is composed of these facies series

A

1) Sanbagawa
2) Franciscan

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16
Q

What chracterized the 2 facies series associated with Outer Subductions

A

Lowe Thermal Gradients
High P/T to very high P/T

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17
Q

this favors the development of very high P/T ratios that characterizes the Fraciscan Series

A

Rapid Steep Subduction Zones

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18
Q

What favors the development of moderate to high P/T ratios that characterizebs Sanbagawa Facies Series

A

Slower Shallower Subduction

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19
Q

What happens to the facies formed by ocean ridge alrteration as they approach a subduction zone?

A

Overprinted by
Greenschists and high P Blueschists and Eclogite facies due to burial in subduction zones

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20
Q

what is notably absent in the outer met belt?

A

High T Amphibolite and Granulite Facies

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21
Q

facies sereis related to the inner met belt in continent or arc side of a subduction zone

A

Buchan
Barrovian

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22
Q

What Characterizes the 2 facies associated with Inner belt of subduction

A

Md to High Temp gradient
Low to Mod P/T

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23
Q

Whats facies occurs in the inner met belt and formed by arc magmatism and compressive stress?

A

Hfels
Zeolite
Prehnite Pumpellyite
Greenschists
Amphibolite
Granulite

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24
Q

What facies are absent in the inner met belt?

A

High Pressure
Blueschists and Eclogite

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25
Deep linear throughs in ocean basins thatmark the surface expressions of inclined subduction zones
Trenches
26
At what depths do high P/T Sanbagawa and Fraciscan Facies series form?
700km subduction of cold lithosphere
27
this region is located on the overriding plate between the trench and the volcanic arc
Forearc Regions
28
What comprises the forearc region of subduction zones?
1) Accretionary Wedge (Prism) 2) Forearc Basin 3) Forearc Basement
29
a tectonically thickened wedge on the landward sie of some trenches which contains a diverse assemblage of deformed rocks that are tectonically dismembered through faulting, folding and shearing
Accretionary Wedge
30
What are the diverse suites of rocks incorporated into the Accretionary Prism?
1) Mafic and Umafic from the oceanic lithosphere, plateaus, islands and guyots 2) Limestone and Chert from pelagic seds accumulated on the sea floor 3)Muds,mudrocks and coarser volcanodetrital seds derived from the arc landward 4)Int. to silicic volcanic and plutonic rocks deried from adhacent volcanic arc complex of from far traveled arcs that have migrated towards the subduction zone 5) Met suites or rocks highly variable i composition orgin and facies (Inner Met Belt Facies) 6)High P/T Blueschists and sometimes Eclogite derived from subd zones
31
Formation of tectonically deformed rocked material coming from the offscraping, underplating, folding and shearing of subducting lithosphere situated within the forearc accretironary prism
Tectonic Melange
32
Meaning of French "Melange"
Chaotic Mixture
33
Petrologic composition of Melange
Lithic Fragments Mafic and Umafic Chert, Limestone, Sandstone Serpentinite, Phyllite (Zeolite-Eclogite Rock Frags)
34
What is the characteristics of the matrix of melange and its implication?
Scaly mudrock expulsion of pore fluids due to further compression
35
High faulted ophiolite complexes that commonly occur in accretionary wedges
Supra subduction Zone Ophiolites
36
The process of emplacement of oceanic/arc lithosphere fragments onto the overriding hanging wall plate
Obduction
37
Diagnostic Facies of Phanerozoic Subduction Zones
Blueschists Facies
38
this deveops in between the high P/T accretionary prism and Low P/T paired metamorphic belts of the magmatic Arc
Forearc Basin
39
What metamorphism usually occurs in the forearc Basin
Burial due to deposition of volcaniclastics
40
assemblages usually form in the forearc basin
Zeolite Prehnite-Ppumpellyite
41
consists of overriding plate rocks which existed prior to subduction as well as younger volcanic-magmatic arc material that formed after subduction
Forearc Basement
42
Metamorphism at Forearc Basement
Burial due to thick sed overlying deposits in the basin and or Dynamothermal Met
43
What are the possible products of Dynamothermal Met
1) High P/T facies assoc with the underlying subduction 2)mod P/T facie due to adjacent magmatic arc
44
This consists of Intermediate to silicic plutons overlain by composite volcanoes
Magmatic Arc Complex
45
whats the geothermal gradient in a magmatic arc complex
>/= 40degcel/km
46
What facies Series develop in Magmatic Arc Complexes?
1) Contact 2) Buchan and sometimes 3) Barrovian
47
Formed by extensions in an ocean-ocean convergent margin that are actively spreading and can eventually evolve into marginal seas
Back Arc Basin
48
What type of metamorphism forms on Back Arc Basins?
Like in the ridge Metasomatism and Hydrothermal Met
49
What series are formed in Back Arc Basin
Zeolite Prehnite-Ppumpellyite Hornfels at shallow depths Greenschists at greater depths
50
Formed as a result of transtenstional stress in oblique-slio basins or along bends I faults
Pull Apart Basins
51
What metamorphism occurs in Pull apart basins?
Burial
52
What series are associate with pull apart basins?
zeolite Prehnite-pumpellyite
53
What are the tectonic features created in Ocean-Continent Convergence?
Fold Thrust Belts Foreland Basins
54
What processes induce metamorphism in Ocean-Continent Convergence?
Intense Compression Thickening of Lithosphere Late Silicic Intrusion
55
Facies Series formed in O-C Convergence
Buchan to Barrovian
56
The isostatically depressed lithosphere infront of the fold and thrust belt
Foreland Basin
57
Deep basin filling of Marine deposits forming alteranating Shale, Sandstone, Chert and Carbonate Layers (Finegrained)
Flysch Deposit (Finegrained)
58
Overlying sandstones and conglomerates in the foreland deposit overlying the finegrained flysch deposit
Molasse Deposit (Coarse Grained)
59
Facies series associated with suture zones
Barrovian Facies Series
60
What facies reflect the geothermal gradients from 20-40 deg cel of the barrovian facies series
Greenschists Amphibolite Granulite

GLE 2024 (Day 2) (41 decks)

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