Metamorphic

Question 1

Process of change undergone by an existing rock (protolith) in solid state to another rock

Answer 1

Metamorphism

Question 2

Agents of metamorphism

Answer 2

Heat, pressure, deviatoric stress, chemically active fluids

Question 3

Source of heat

Answer 3

Geothermal gradient (20-30 C per km)
Intrusive bodies
Radioactive decay

Question 4

Pressure

Confining pressure vs deviatoric stress

Answer 4

Equal force in all directions

There us a dominant axis

Question 5

Chemically active fluids must be

Answer 5

Hot

1. Fluids in pore spaces of original rock
2. Fluids from dehydration of hydrated minerals (crystalline)
3. Water from magmatic bodies

Question 6

Type of metamorphism

- area or volume affected

Answer 6

Local metamorphism: small volume (<300 km3)

Regional metamorphism: thousands of km

Question 7

Type of metamorphism

Chemical processes

Answer 7

Isochemical - no change in the bulk chemistry of the rock

Allochemical - there is change

Question 8

Dominant metamorphic agent

1. Contact
2. Dynamic
3. Static
4. Metasomatism

Answer 8

1. Contact - heat ( magma chamber)
2. Dynamic - deviatoric stress
3. Static - pressure
4. Metasomatism - chemically active fluids
5. Dynamothermal - T and P combined

Question 9

Classification of metamorphic rock

Answer 9

Texture - size, shape and relationships of constituent minerals
Protolith - original rock that was transformed by metamorphism
Mineralogy - mineral assemblage present

Question 10

Based on texture

Answer 10

Foliated - parallel alignment of minerals

Nonfoliated - no preferred mineral alignment (metamorphism – transformation of one mineral to another)

Question 11

Why is parent rock important?

Answer 11

1. Chemical composition of metamorphic rocks rocks = parent rock (besides metamorphism)
   Chemical makeup of parent rock determines the degree of change a metamorphic agent will cause (e.g. granite may be metamorphosed by basaltic magma but gabbro will not)

Question 12

Other metamorphic rocks in Philippines

1. *– foliated amphiboles + plagioclases
2. *– hydrothermally alteration of peridotites
3. *– hybrid (quartz and feldspar)

Answer 12

Amphibolite
serpentine
migmatite

Question 13

Other metamorphic rocks in Philippines

1. Amphibolite – * amphiboles + *
2. serpentine – *alteration of *
3. migmatite – hybrid (*)

Answer 13

foliated, plagioclases
hydrothermally, peridotites
quartz and feldspar