METAMORPHIC ROCKS

Question 1

Formation

Answer 1

Crustal plates collide. One pushed under other. Rocks high preassure and temperature.

Minerals and rocks become unstable. They group into new stable minerals adapted to new conditions: metamorphosis

Question 2

Temperature

Answer 2

Process occurs on solid rocks: tempeature lower than melting points of minerlas (otherwise become magma and then igneous)

Question 3

New mineral formation

Answer 3

All rocks can undergo metamorphosis.
Which new minerals depends on original mineralogical compositions of rocks.

Clay minerals –> micas

Question 4

Micas

Answer 4

Minerals
Clay minerals metamorphosed: they are both silicate minerals consisting of thin stacked plates.

Plates of mica all grow in same direction:Flat side perpendicular to direction of preassure

Very fragile in direction parallel to plates: rocks containing micas easily split in one diretion: schistosity

Question 5

Degree of metamorphosis

Answer 5

Can vary from weak to strong.
Micas: weak to moderated strong metamorphosis
Strong metamorphosis: feldspars and dark minerals start from micas: banded pattern due to preassure, no schistosity: GNEISS

Question 6

Gneiss

Answer 6

Coming from feldspars, quartz and micas.
Banded patterns.
Strong metamorphosis

Question 7

Classification

Answer 7

Minerals oriented parallel(schistosity and mineral banding)

No oriented minerals

Question 8

Schistosity

Answer 8

If parent rock has no clay or micas minerals-> metamorphic rock has no schistosity

Question 9

Quartzite

Answer 9

Metamorphosed quartz sandstone.
Hard, glassy.
Has only grains of mineral quartz.
No schistosity. Massive clevege. Breaks irregularly.
Under influence of high pressure and temperature in this dense solid mass.

Question 10

Marble

Answer 10

Metamorphosed limestone.
Mainly calcium carbonate crystals: calcite.  Newly formed calcite crystals  visible.
Massif
Some clevege.
Not schistose: fractures randomnly. 
Softer than quartzite

Question 11

sandstone

Answer 11

poorly or well cemented with for example silica

Question 12

Sand

Answer 12

unconsolidated loose grains, pores ar filled with with air or water. no cementation

Question 13

Slate

Answer 13

Microscopic micas, all oriented in sam direction.
Perfecly flat clevage, schistosity.
Weak metamorphosis

Question 14

Schist

Answer 14

Clearly visible micas oriented in the same direction.
Smooth ondulating clevege , schistosity
Moderate metamorphosis