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Petrology > Metamorphic Rocks (Part 1 - Metamorphism and Metamorphic Textures) > Flashcards

Metamorphic Rocks (Part 1 - Metamorphism and Metamorphic Textures) Flashcards

1
Q

The process of change or transformation of a pre-existing rock, in the solid state, into another rock due to heat, pressure and chemically active fluids.

A

Metamorphism

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2
Q

A form of metamorphism due to hydrothermal fluids exchanging constituents with an external source.

A

Metasomatism

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3
Q

Increase in temperature and pressure

A

Prograde Metamorphism

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4
Q

Decrease in temperature and pressure

A

Retrogade Metamorphism

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5
Q

Metamorphism that affects areas with less than 100km²

A

Local Metamorphism

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6
Q

Metamorphism that affects areas greater than 100km² and is commonly associated with convergent and divergent plate boundaries.

A

Regional Metamorphism

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7
Q

Also known as Protoliths

A

Parent Rocks

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8
Q

The original rocks from where the produced metamorphic rocks transformed from.

A

Protoliths

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9
Q

3 Agents of Metamorphism

A

Heat
Pressure
Chemically Active Fluids

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10
Q

Provides energy for chemical reactions and recrystallization of minerals.

A

Heat

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11
Q

Provides stress in equal directions or varying amounts in different directions.

A

Pressure

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12
Q

Provides and enhances mobility of ions present.

A

Chemically Active Fluids

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13
Q

Low Temperature Range and Pressure Range

A

200-300°C , 300-600 MPa; 0-6 km depth

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14
Q

Intermediate Temperature Range and Pressure Range

A

300-500°C, 600-1000 MPa; 2-20 km depth

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15
Q

High Temperature Range and Pressure Range

A

> 500°C, >1000 MPa; >20 km depth

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16
Q

2 Types of Pressure

A

Hydrostatic Pressure
Lithostatic Stress

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17
Q

also called as confining pressure

A

Hydrostatic Pressure

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18
Q

A uniform or isotropic form of pressure, where pressure is equal in all directions, which usually produces equant grains and non-foliated texture of metamorphic rocks.

A

Hydrostatic Pressure

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19
Q

also called as burying pressure

A

Lithostatic Stress

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20
Q

A non-uniform or anisotropic form of pressure, where pressure is unequal in all directions, which usually produces inequant grains and foliated texture of metamorphic rocks.

A

Lithostatic Stress

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21
Q

6 Types of Metamorphism

A

(CHDBID)
Contact Metamorphism
Hydrothermal Metamorphism
Dynamothermal Metamorphism
Burial Metamorphism
Impact Metamorphism
Dynamic Metamorphism

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22
Q

A variable temperature, low pressure metamorphism that develops locally where hot magma intrudes relatively cold, upper crustal country rock. (give a product)

A

Contact Metamorphism (Hornfels, Metaquartzite, Skarn)

23
Q

Chemical alteration from circulating fluids within cracks and fissures. Pervasive at ocean spreading ridges
that experience tension, thinning and uplift, causes metasomatism. (give a product)

A

Hydrothermal Metamorphism (Alteration Products, Metallic ore deposits)

24
Q

Name all major types of Hydrothermal Alteration

A

(AAACPPPSSSSZ)
Albitic - Albite
Alunitic - Alunite
Argillic - Kaolinite, Smectite, Illite
Carbonatization - Carbonate Minerals (Calcite, etc.)
Phyllic - Sericite, Quartz, Pyrite
Potassic - Biotite, Potassium Feldspar
Propylitic - Chlorite, Epidote, Actinolite, Tremolite
Sericitic - Sericite
Serpentinization - Serpentine
Silication - Quartz, Chert
Spilitization - Albite
Zeolitic - Zeolite Minerals

25
Q

A regional metamorphism induced by increase in pressure and temperature with non-uniform stress which produces foliated textures, mostly aerially extensive, and dominates convergent margins and associated fold and thrust belts. (give a product)

A

Dynamothermal Metamorphism (Greenschist, amphibolite, granulite, blueschist, eclogite)

26
Q

Metamorphism that results from increase in lithostatic stress caused by deep burial of rocks and produces non-foliated textures, affects regional subsiding basins that accumulate thick sequences of sediments and volcanic debris, and usually starts at temperatures 150 °C to 300 °C and gradational with diagenesis at depths of about 8 km. (give a product)

A

Burial Metamorphism (Non-foliated rocks with low temp. mineral assemblages)

27
Q

A local form of metamorphism generated by explosive volcanic eruptions or relatively rare collisions of extraterrestrial objects with Earth, causing a high strain rate. (give a product)

A

Impact Metamorphism (Impactites)

28
Q

Induced primarily by non-uniform stress in fault zones and shear zones, where the high strain rate is mostly local but extend to a regional scale in large faults or shear zones, and most likely recur in the same fault or shear zone. (Give a product)

A

Dynamic Metamorphism (Cataclasites, pseudotachylites, mylonites)

29
Q

A low temperature, brittle grain-fracturing process that involves grain size reduction through the mechanical grinding, rotation and crushing of rock.

A

Cataclasis

30
Q

A fine-trained, non-foliated, clastic metamorphic rock produced by cataclastic processes.

A

Cataclasite

31
Q

A ductile grain reduction process that produces oriented grains of smaller diameter.

A

Mylonitization

32
Q

A product of mylonitization characterized by grain size reduction via macroscopic scale cataclisis, plastic stretching and thinning associated with ductile deformation.

A

Mylonite

33
Q

Occurs in metamorphic rocks where individual atoms or molecules can migrate in gaseous, liquid or solid phases from one location in a rock body to a new location.

A

Diffusion

34
Q

Involves the dissolution of solid grains under high compressive stress conditions.

A

Pressolution

35
Q

An insoluble seam that accumulates as soluble minerals dissolve.

A

Stylolite

36
Q

Occurs when existing minerals are transformed under higher temperature and/or pressure conditions, without experiencing a significant change in chemical composition.

A

Recrystallization

37
Q

The nucleation and growth of new minerals as pre-existing minerals become unstable due to temperature or pressure changes.

A

Neocrystallization

38
Q

Newly formed minerals that are distinctly larger than the minerals in the surrounding matrix.

A

Porphyroblasts

39
Q

The segregation of minerals in an initially homogenous rock due to different physical or chemical characteristics such as solubility, ductility, mineral growth or crystallization temperature.

A

Differentiation

40
Q

Partially melted rocks that form by quenching under high strain rates in shear zone fractures.

A

Pseudotachylites

41
Q

A metamorphic halo in the contact zone that surrounds it, produced from the heat of the igneous intrusion, and
can range from centimeters to hundreds of qmeters in diameter.

A

Aureole

42
Q

The size, shape, orientation and intergranular relationships of metamorphic rocks’ constituents that were influenced by temperature and pressure conditions or relict textures.

A

Metamorphic Textures

43
Q

Metamorphic textures based on the sizes of the notable grains in metamorphic rocks.

A

According to Grain Size

44
Q

Metamorphic textures based on the orientation of the grains in a metamorphic rock.

A

According to Grain Orientation

45
Q

Texture defined by large relict grains

A

Porphyroclasts

46
Q

Texture defined by large relict grains from the protolith that have experienced deformation but retained its composition.

A

Porphyroclastic

47
Q

Oval-shaped feldspar porphyroclasts that are particularly common in gneiss.

A

Augen

48
Q

Oval shaped quartz porphyroclasts that are particularly common in gneiss.

A

Flaser

49
Q

Texture defined by large grains

A

Porphyroblasts

50
Q

Texture defined by large grains that experienced neocrystallization and growth in response to favorable temperature and pressure conditions due to metamorphism.

A

Porphyroblastic

51
Q

A texture of metamorphic rocks that exhibit planar
arrangement of mineral grains or structural features of a rock.

A

Foliated

52
Q

A texture of metamorphic rocks that exhibit linear arrangement of mineral grains or structural features of a rock.

A

Lineation

53
Q

A texture of metamorphic rocks that lack the planar arrangement of mineral grains or structural features of a rock.

A

Non-Foliated

Petrology (16 decks)

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