Metamorophic Rock Chapter 6 Section 3

Recognizing Metamorphic Rock Metamorphosed rocks have been changed Heat and pressure turn rocks to magma Rocks that don’t reach their melting point Texture changes Mineral composition changes Chemical composition changes

Recognizing Metamorphic Rock During Metamorphism rocks change while they are still solid Heat required for metamorphic rock to form Deep within Earth Near intrusions Pressure also needed Deep burial Compression during mountain building

Metamorphic Minerals Foliated Nonfoliated Layers and bands High pressure during metamorphism causes flat or needlelike crystals Perpendicular to pressure Parallel alignment of minerals creates the layers in foliated metamorphic rocks. Form in blocky shapes Examples: Quartzite and marble

Grades of Metamorphism Different combinations of heat and pressure result in different grades. Low grade Low temperature and low pressures High grade High temperature and high pressure Intermediate grade In between high and low grade metamorphism

Types of metamorphism Regional Metamorphism High temperatures and pressure affect large regions Range in grade from low to high Results include Changes in minerals Changes in rock type Folding and deforming of rock layers

Types of metamorphism Contact Metamorphism Molten material (an intrusion) come in contact with solid rock Local effect High temperature to moderate/low pressure Temperature decreases with distance from an intrusion, metamorphic effects decrease with distance.

Types of Metamorphism Hydrothermal Metamorphism Very hot water reacts with rock Alters chemical and mineral composition Hot fluids migrate in and out of roc changing the mineral composition and texture. Valuable ore formed this way Gold, copper, zinc, tungsten and lead

Economic importance Salt Gold, silver, copper and lead Fossil fuels

Metallic mineral resources Occur mostly as metal ores Many are precipitated from hydrothermal solutions In veins- gold Spread through the rock mass In intrusions or in contact metamorphic zones

Non-metallic mineral resources Metamorphism of ultrabasic igneous rocks Talc and asbestos

Rock cycle The continuous changing and remaking of rocks.