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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.
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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 • Form in blocky shapes • Examples: • Quartzite and marble • 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.
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.