METAMORPHIC ROCKS METAMORPHIC ROCKS What is Metamorphism What

METAMORPHIC ROCKS

METAMORPHIC ROCKS • What is Metamorphism? • What Drives Metamorphism? • Metamorphic Textures • Common Metamorphic Rocks

Metamorphic Rocks What Is Metamorphism?

PSCI 131: Metamorphic Rocks WHAT IS METAMORPHISM? • “meta” = change; “morph” = shape • Change of one rock type into another – Heat and (usually) pressure • Parent rock – Rock that gets metamorphosed into something else – ANY rock type can be a parent rock, including a metamorphic rock

Metamorphic Rocks What Drives Metamorphism?

PSCI 131: Metamorphic Rocks: What Drives Metamorphism? Three Metamorphic Agents • Heat: most critical • Pressure • Chemically active fluids

PSCI 131: Metamorphic Rocks: What Drives Metamorphism? Heat • A form of energy • Vibration of atoms and molecules • Hotter = faster vibration

PSCI 131: Metamorphic Rocks: What Drives Metamorphism? Role of Heat in Metamorphism • Provides energy for chemical reactions • Weakens atomic bonds in mineral crystals

PSCI 131: Metamorphic Rocks: What Drives Metamorphism? Pressure • Confining pressure • Differential stress

PSCI 131: Metamorphic Rocks: What Drives Metamorphism? Confining Pressure • Equal in all directions • Deep burial

PSCI 131: Metamorphic Rocks: What Drives Metamorphism? Differential Stress • Higher pressure from sides • Converging tectonic plates Zone of intense differential stress

PSCI 131: Metamorphic Rocks: What Drives Metamorphism? Chemically Active Fluids • Some minerals are hydrated – E. g. gypsum Ca. SO 4 + 2 H 20 • Water driven out of these minerals by heat • Circulating water promotes transport of atoms

Metamorphic Rocks Metamorphic Textures

PSCI 131: Metamorphic Rocks: Textures Foliation • Created by differential stress • Preferred orientation of elongated minerals

PSCI 131: Metamorphic Rocks: Textures Foliated Textures Slaty cleavage Schistosity Gneissic texture

PSCI 131: Metamorphic Rocks: Textures Nonfoliated Textures • Interlocking grains • Confining pressure or absence of pressure

PSCI 131: Metamorphic Rocks: Textures Nonfoliated Textures Marble, made of interlocking calcite grains. Limestone metamorphoses into the nonfoliated rock marble.

Metamorphic Rocks Common Metamorphic Rocks

PSCI 131: Metamorphic Rocks: Common Types Common Foliated Rocks • • Slate Phyllite Schist Gneiss From: radford. edu

PSCI 131: Metamorphic Rocks: Common Types Common Nonfoliated Rocks Marble Parent: limestone Quartzite Parent: sandstone Anthracite Parent: coal

End of Metamorphic Rocks