Metamorphic rocks are produced when preexisting rocks are altered by heat, pressure and the chemical action of pore fluids.
-remain solid while readjusting to new environ.
-minerals commonly have preferred orientation
-crust largely metamorphic to depth of 20 km
-must study metamorphism indirectly

Study Meta Rx:
a) mineral assemblage -- T and P of formation
b) texture and structure -- history of deformation in crust

Type of Meta Extent
Principal Agent(s) of Change
*Contact =local T
*Regional =lg. scale T, P and deformation
Shear =local deformation
Rift Zone =lg. scale T
Burial =lg. scale T and P
Shock =local T and P

Agents of Metamorphism:
t, hydrostatic P, directed P and pore fluids

Classification:
texture (foliated or non-foliated) vs. composition

Original Intensity of Metamorphism -- Rock low grade --> high grade
Shale ->slate -> phyllite -> schist -> gniess
foliated Granite schist -> gneiss (planar texture)
Basalt schist -> amphibolite
Limestone -> marble
non-foliated Sandstone ->quartzite (granular texture)
slaty cleavage + planar texture= schistosity
gneissic =layering

How do geologists determine relative intensity of metamorphism?
-metamorphic facies
-metamorphic zones
a) index minerals
b) isograds

Laboratory calibration is required in order to quantitatively determine intensity of metamorphism.

1. What are metamorphic "zones" and how are they used to establish the relative intensity of metamorphism.
2. Describe the environment (areal extent, pressure, temperature, role of deformation & pore fluids) in which regionally metamorphosed rocks are formed.
3. Explain the difference between confining or hydrostatic pressure and directed pressure. Use a labeled diagram to assist you in explaining how foliation is developed in schist.
4. What is contact metamorphism and how does it differ from regional metamorphism?
5. Outline the changes (textural and mineralogical) which a shale undergoes as it is progressively buried deeper in the crust and metamorphosed.

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