Metamorphic Rocks
Metamorphic Rocks
Metamorphism – The transformation of pre-existing rocks into new
types by the action of heat and pressure changes.
Photos by C.C. Plummer
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Metamorphic Rocks
Metamorphism – The transformation of pre-existing rocks into new
types by the action of heat and pressure changes.
Heat – from magma intrusion, compression, or decay of radioactive
elements. Generally, at depths of about 35 km, temps are high enough
to begin melting rocks.
Metamorphic Rocks
Metamorphism – The transformation of pre-existing rocks into new
types by the action of heat and pressure changes.
Pressure – generates heat, and
along points of contact can melt
rocks. Also generates the
development of banded and foliated
textures. Increasing pr4essure
conditions force grains closer
together and eliminates pore space.
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Metamorphic Rocks
Metamorphism – The transformation of pre-existing rocks into new
types by the action of heat and pressure changes.
Chemically active fluids – chemical exchange of elements generate
different mineral compositions.
Metamorphic Rocks
Two different types of metamorphism:
1. Contact
metamorphism –
occurs upon
contact of hot
igneous rocks and
surrounding
country rocks. As
distance from
intrusion increases
degree of
metamorphism
decreases.
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Metamorphic Rocks
Two different types of metamorphism:
1. Regional metamorphism –
occurs upon contact of hot
igneous rocks and
surrounding country rocks.
As distance from intrusion
increases degree of
metamorphism decreases.
Metamorphic Rocks
Identifying metamorphic rocks using
texture.
Foliation – parallel arrangement of
minerals
Photos by C.C. Plummer
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Metamorphic Rocks
Identifying metamorphic rocks using
texture.
Foliated rocks:
Slate – metamorphosed clayey rocks
(shale). Sheety appearance
Photo by C.C. Plummer
Photo by P.D. Rowley, USGS
Metamorphic Rocks
Identifying metamorphic rocks using
texture.
Foliated rocks:
Schist
Photo by C.C. Plummer
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Metamorphic Rocks
Identifying metamorphic rocks using
texture.
Foliated rocks:
Gneiss
Metamorphic Rocks
Identifying metamorphic rocks using
texture.
Foliated rocks:
Gneiss
Photo by C.C. Plummer
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Metamorphic Rocks
Identifying metamorphic rocks using
texture.
Nonfoliated rocks:
Marble
Quartzite
Photo by C.C. Plummer
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