Geology - Metamorphic Rocks

Question 1

What does metamorphism derive from?

Answer 1

Constant changing geologic systems such as rock, magma and fluid movement constantly occuring disrupting thermodynamic equilibirum.

Question 2

What are equilibra factors governed by?

Answer 2

Kinetic factors, depending on compositon/fabric of the parent rock, fluid composition and temperatures and pressures

Question 3

Diagenesis

Answer 3

This is the physical and chemical processes affecting sedimentary materials after depoisiton and before metamorphism and between deposiiton and weathering.

Question 4

What is onset of partial melting based on?

Answer 4

Rock composition, metamorphic regimes and heterogenous rock bodies overlapping in hundreds of degrees.

Question 5

What are the lower limit changes of metamorphic rock?

Answer 5

The distinction between metamorphism and diagenetic changes in sedimentary/volcanistic deposits.

Question 6

Metastable

Answer 6

This is a phase in which an energy barrier must be surmounted before that phase can be transformed to one of lower energy.

Question 7

Example of a metamorphic rock?

Answer 7

Migmatites formed by anatexis are generally heterogenous and preserves evidence of partial melting at micro/mcaroscopic scales.
Vitroclasts may undergo diagenesis to zeolites

Question 8

Antexis

Answer 8

This refers to partial melting of crustal rocks at the P-T fields between the solidus and liquidus

Question 9

What is metamorphism the product of?

Answer 9

Chemical equilibria of sedimentary and igneous rocks

Question 10

Example of the process of metamorphism?

Answer 10

Mudrock is a sedimentary product by mixture of quartz and clay being an accidental assemblage of mineral grains deposited in a basin.

Question 11

Widest thermal stability of any material?

Answer 11

Quaerz

Question 12

In mudrock deformation, how does change occur?

Answer 12

Clay minerals affected whilst quartz are not, where clays decompose forming one or more new minerals like mica or chlorite, or react with quartz or another material in the mudrock to generate a new metamorphic material.

Question 13

Example of temperature and pressure fluctuations produce different materials?

Answer 13

Mid-ocean ridge eruption forming basalt.

Question 14

What happens when basalt reacts with water?

Answer 14

Water acts as a catalyse, enhancing basalt to seek a new more thermodynamically facourable configuration.

Question 15

Metamorphic Facies

Answer 15

Describe mineral assemblages in metamorphic rocks formed under similar pressures and temperatures.

Question 16

What does metamorphic facies observe?

Answer 16

Mineral assemblages abundant in metamorphic rocks are limited, both within individual rocks and across spectrums of rock composition.

Question 17

What are pressure-temperature time models used for?

Answer 17

Understanding relationship of the P-T paths taken by rocks in metamorphism

Question 18

What are the four types of metamorphism?

Answer 18

Burial
Regional
Contact

Question 19

Burial Metamorphism

Answer 19

This is where sediments are buried deeply enough such that heat and pressure cause recrystallisation of the minerals allowing new minerals to grow

Question 20

Regional Metamorphism

Answer 20

This is a large-scale action of heat and pressure across and extensive area.

Question 21

QContact Metamorphism

Answer 21

This is either due to heating, with our without burial or by lying close to magma intrusions.

Question 22

What minerals are shared with metamorphic and igneous rocks?

Answer 22

Quartz, feldspars, micas and apatite.

Question 23

Orthosilicates

Answer 23

Lack sharing of tetrahedral units, like olvine and garnet

Question 24

Pyroxenes

Answer 24

This is a group of silicates of calcium, magnesium, iron and amphiboles.

Question 25

Amphiboles

Answer 25

These are complex hydrated silicates of Ca, Mg, Fe and Al

Question 26

Ferromagnetism

Answer 26

This is the containing of electrons in unfilled shells with permanent magnetic moements in absence of external fluids.

Question 27

What metamorphic rocks are othosilicates commonly found in?

Answer 27

They coexist with quartz and feldspars in recrystallised quartz like mudstones

Question 28

Examples of metamorphic chain silicates?

Answer 28

Single chain like pyroxenes and double chain like amphiboles

Question 29

Example of chain silicates?

Answer 29

Hornblende and pyroxenes

Question 30

Porphyroblasts

Answer 30

These are large mineral crystal in a metamorphic rock that has grown within the finer grained matrix

Question 31

Foliated

Answer 31

These are planar and linear fabric elements in a rock.

Question 32

What are the most commmon metamorphic rocks?

Answer 32

Mudrocks
Calcareous
Mafic/Ultramafic

Question 33

What do mudrocks develop from?

Answer 33

Recrystallization and modificaiton of clay minerals with microscopic graind sizes that form new crystal structures.