Metamorphic Rocks

What is a metamorphic rock? Rocks that have changed once another rock Pressure and heat changed the rocks without melting Rock has undergone metamorphism

Temperature Heat lower limit is 150ºC, causes molecular expansion stretches and weakens the bonds in minerals crystals tend to grow larger by joining together. minerals can lose water and change minerals reactions may occur between minerals. lower limit is 150ºC, upper limit is the melting temperature

Pressure Compresses minerals Causes stress break some bonds new minerals form re-oriented minerals

Metamorphic Grade High Grade Metamorphism Low Grade Metamorphism High heat High pressure Low Grade Metamorphism Low heat Low pressure

Types Regional Contact Hydrothermal Large area Magma touches (comes in contact w/) rock Hydrothermal Hot water dissolves minerals Deposits new minerals

Regional Metamorphism widespread metamorphism often associated with mountain building

Contact Metamorphism heat and sometimes fluid intrusion of magma into the shallow crust, Contact metamorphism can also be found in the soil or rock underlying a lava flow.

Hydrothermal Metamorphism Quartz Hydrothermal solutions hot water with dissolved minerals Metallic ore deposits Can introduce new minerals Slate

Textures Foliated Nonfoliated Preferred orientation Minerals flattened Blocky crystal shape No preferred orientation

Foliation High Grade Minerals align Because of pressure Granite (top) Gneiss (bottom) Same minerals Foliation in Gneiss

Non-Foliated Low Grade Low heat/pressure Crystals can grow

Identification Texture Grain size Mineral Composition Foliated Non foliated Grain size Fine grained Coarse Grained Mineral Composition

Foliated Rocks Non-Foliated Slate Schist Gneiss Quartzite Marble

Parent rock to Metamorphic

Uses of Metamorphic Rocks Art Sculptures Marble Building material Floor tiles Counters Old Chalkboards Slate

Major Concepts Can be formed from any rock igneous, sedimentary, or existing metamorphic rocks Involves recrystallization in the solid state Little change in chemical composition Driving forces are changes in temperature, pressure, and pore fluids. Minerals and new textures are formed