Chapter 4- Metamorphism

Question 1

isochemical

Answer 1

no elements are added or removed

Question 2

granoblastic

Answer 2

texture of metamorphic rocks that contain interlocking equidimensional crystals

Question 3

foliation

Answer 3

texture found in metamorphic rocks, formed by preferred alignment of flat, platy minerals

Question 4

slaty cleavage

Answer 4

texture in fine grained rocks formed by low grade regional metamorphism. Platy crystals recrystalise perpendicular to direction of stress so the rock splits into thin sheets

Question 5

cataclasis

Answer 5

brittle fracturing and grinding down of existing rock, usually in fault zones

Question 6

Porphyroblasts

Answer 6

large crystals that have grown during recrystalisation in a metamorphic rocks and are surrounded by a finer grained crystal groundmass

Question 7

Schistosity

Answer 7

the texture in medium and coarse grained metamorphic rocks formed by the preferred alignment of flat/tabular minerals. alignment is perpendicular to direction of stress and no traces of the original bedding remains

Question 8

gneissose banding

Answer 8

seperation of light and dark coloured minerals into layers/bands, mm-cm thick. light band is typically granoblastic and the dark band normally shows schistosity

Question 9

Contact Metamorphism

Answer 9

Metamorphism due to heat but not pressure, occurring adjacent to igneous intrusions, no foliation but change to chemical composition

Question 10

Dynamic Metamorphism

Answer 10

occurs in fault zones, directional stress leads to recrystalisation

Question 11

Regional metamorphism

Answer 11

occurs over large areas with high/low temps/pressures, at convergent plate margins. minerals show preferred alignment

Question 12

mylonite

Answer 12

forms at depth where ductile deformation oeads to recrystalisation producing a fine grained and highly deformed rock

Question 13

Metamorphic rock produced by limestone

Answer 13

marble

Question 14

metamorphic rock produced by sandstones high in quartz content/orthoquartzite

Answer 14

metaquartzite

Question 15

Metamorphic rock produced by shale

Answer 15

slate, phyllite, schist, gneiss

Question 16

Metamorphic grade

Answer 16

measure of the intensity of metamorphism

Question 17

country rock

Answer 17

the rock into which an igneous rock has been intruded

Question 18

metamorphic aureole

Answer 18

region surrounded an igneous intrusion in which the country rock has recrystalised and changed by the heat from the intrusion

Question 19

spotted rock

Answer 19

formed by low grade metamorphism in the outer part of the metamorphic aureole

Question 20

index minerals

Answer 20

metamorphic minerals which are stable under specific temperature and pressure conditions, indicating the metamorphic grade

Question 21

hydrous minerals

Answer 21

minerals containing h2o in their crystal structure, ie clay minerals and chlorite, found in low grade metamorphic rocks

Question 22

anhydrous minerals

Answer 22

minerals lacking h2o, ie garnet, found in high grade metamorphic rocks

Question 23

hydrous mineral found in high grade metamorphic rocks

Answer 23

biotite