Geo Lab 5 (Metamorphic Rock)

Metamorphic Rock

crystalline rocks that form from other rocks

Metamorphism

takes place at varying depths within the Earth’s crust where both temp and pressure are higher than at the surface

water

____ allows ions to move about more readily, thereby speeding up the chemical reactions that enable growth of a mineral

1. regional

2. contact

Two types of metamorphism:
1.
2.

regional metamorphism

____ _____ occurs over areas of hundreds or thousands of square kilometers

contact metamorphism

heat from an intruding body of magma causes ____ ______ of the surrounding rocks

1. recrystallization

2. development of new minerals

3. deformation and reorientation of existing minerals

Important changes that may take place during metamorphism:
1.
2.
3.

grade

intensity of metamorphism

high grade

____ ___ metamorphic rocks are the most intensely metamorphic rocks

low grade

__ _____ metamorphic rocks are the least intensely metamorphosed

directed pressure

pressure that is greater in one direction than others

lithostatic pressure

pressure felt equally in all directions

1. nonfoliated

2. foliated

Two main textural subgroups:
1.
2.

foliation

the arrangement of platy mineral crystals or flattened rock fragments in parallel or nearly parallel planes

nonfoliated metamorphic

these rocks generally lack obvious flat or elongate mineral crystals with parallel alignment

foliated metamorphic

these rocks contain minerals that are aligned in parallel planes

foliated texture

____ _____ commonly results from the parallelism of micas

migmatite

a mixed igneous-metamorphic rock with zones of light colored igneous looking quartz and feldspar with dark colored foliated zones

hornfels

general name used for contact metamorphic rocks that are nonfoliated and too fine grained for individual minerals

index minerals

characteristics of metamorphic rocks formed under a certain range of temperature and pressure

isograds

when lines approximate the same metamorphic grade, they are called ____

1. shale vs slate

2. quartz sandstone vs quartzite

3. limestone/dolostone vs marble

4. graywacke vs basalt

Problem rocks
1.
2.
3.
4.