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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
Q

Deep linear throughs in ocean basins thatmark the surface expressions of inclined subduction zones

A

Trenches

26
Q

At what depths do high P/T Sanbagawa and Fraciscan Facies series form?

A

700km subduction of cold lithosphere

27
Q

this region is located on the overriding plate between the trench and the volcanic arc

A

Forearc Regions

28
Q

What comprises the forearc region of subduction zones?

A

1) Accretionary Wedge (Prism)
2) Forearc Basin
3) Forearc Basement

29
Q

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

A

Accretionary Wedge

30
Q

What are the diverse suites of rocks incorporated into the Accretionary Prism?

A

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
Q

Formation of tectonically deformed rocked material coming from the offscraping, underplating, folding and shearing of subducting lithosphere situated within the forearc accretironary prism

A

Tectonic Melange

32
Q

Meaning of French “Melange”

A

Chaotic Mixture

33
Q

Petrologic composition of Melange

A

Lithic Fragments
Mafic and Umafic
Chert, Limestone, Sandstone
Serpentinite, Phyllite
(Zeolite-Eclogite Rock Frags)

34
Q

What is the characteristics of the matrix of melange and its implication?

A

Scaly mudrock expulsion of pore fluids due to further compression

35
Q

High faulted ophiolite complexes that commonly occur in accretionary wedges

A

Supra subduction Zone Ophiolites

36
Q

The process of emplacement of oceanic/arc lithosphere fragments onto the overriding hanging wall plate

A

Obduction

37
Q

Diagnostic Facies of Phanerozoic Subduction Zones

A

Blueschists Facies

38
Q

this deveops in between the high P/T accretionary prism and Low P/T paired metamorphic belts of the magmatic Arc

A

Forearc Basin

39
Q

What metamorphism usually occurs in the forearc Basin

A

Burial due to deposition of volcaniclastics

40
Q

assemblages usually form in the forearc basin

A

Zeolite
Prehnite-Ppumpellyite

41
Q

consists of overriding plate rocks which existed prior to subduction as well as younger volcanic-magmatic arc material that formed after subduction

A

Forearc Basement

42
Q

Metamorphism at Forearc Basement

A

Burial due to thick sed overlying deposits in the basin and or
Dynamothermal Met

43
Q

What are the possible products of Dynamothermal Met

A

1) High P/T facies assoc with the underlying subduction
2)mod P/T facie due to adjacent magmatic arc

44
Q

This consists of Intermediate to silicic plutons overlain by composite volcanoes

A

Magmatic Arc Complex

45
Q

whats the geothermal gradient in a magmatic arc complex

A

> /= 40degcel/km

46
Q

What facies Series develop in Magmatic Arc Complexes?

A

1) Contact
2) Buchan and sometimes
3) Barrovian

47
Q

Formed by extensions in an ocean-ocean convergent margin that are actively spreading and can eventually evolve into marginal seas

A

Back Arc Basin

48
Q

What type of metamorphism forms on Back Arc Basins?

A

Like in the ridge
Metasomatism and Hydrothermal Met

49
Q

What series are formed in Back Arc Basin

A

Zeolite
Prehnite-Ppumpellyite
Hornfels at shallow depths
Greenschists at greater depths

50
Q

Formed as a result of transtenstional stress in oblique-slio basins or along bends I faults

A

Pull Apart Basins

51
Q

What metamorphism occurs in Pull apart basins?

A

Burial

52
Q

What series are associate with pull apart basins?

A

zeolite
Prehnite-pumpellyite

53
Q

What are the tectonic features created in Ocean-Continent Convergence?

A

Fold
Thrust Belts
Foreland Basins

54
Q

What processes induce metamorphism in Ocean-Continent Convergence?

A

Intense Compression
Thickening of Lithosphere
Late Silicic Intrusion

55
Q

Facies Series formed in O-C Convergence

A

Buchan to Barrovian

56
Q

The isostatically depressed lithosphere infront of the fold and thrust belt

A

Foreland Basin

57
Q

Deep basin filling of Marine deposits forming alteranating Shale, Sandstone, Chert and Carbonate Layers (Finegrained)

A

Flysch Deposit (Finegrained)

58
Q

Overlying sandstones and conglomerates in the foreland deposit overlying the finegrained flysch deposit

A

Molasse Deposit (Coarse Grained)

59
Q

Facies series associated with suture zones

A

Barrovian Facies Series

60
Q

What facies reflect the geothermal gradients from 20-40 deg cel of the barrovian facies series

A

Greenschists
Amphibolite
Granulite

GLE 2024 (Day 2) (41 decks)

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