UNIVERSITY OF SOUTH ALABAMA Last Time GY 111 Physical Geology Metamorphism 1 A Agents of Metamorphism B Types of metamorphism C Hydrothermal fluids webnotes only Lecture 26 Regional Metamorphism Metamorphism Metamorphism a solid state change recrystallization of a parent rock by physical agents using operating deep within the interior of the Earth Metamorphism 1 Agents of Metamorphism Heat 25 C to 800 C up to the point of melting 2 3 Pressure 1 bar to 12 kbars Chemically active fluids AKA hot water http news service stanford edu news 2005 Shale Parent Rock Slate Metamorphic Rock Types of Metamorphism zRegional heat and pressure Types of Metamorphism z Contact heat only Associated with convergent plate boundaries Metamorphic aureole Metamorphic aureoles http www indiana edu geol105 images gaia chapter 5 regmeta jpg 1 Types of Metamorphism z Today s Agenda Cataclastic pressure only Regional Metamorphism Mylonites Shear zones A Foliated rocks B Non foliated rocks Web notes 26 http www cliffshade com colorado homestake hsz01 jpg Regional Metamorphism Involves both heat and pressure Regional Metamorphism Pressure causes certain minerals clays to deform and change their orientation in the original parent rock e g shale sedimentary Kaolinite a clay Regional Metamorphism Regional Metamorphism Pressure causes certain minerals clays to deform and change their orientation in the original parent rock The most stable configuration for platy minerals like clays and micas is perpendicular to the stress direction e g shale sedimentary e g shale sedimentary 2 Regional Metamorphism Regional Metamorphism The most stable configuration for platy minerals like clays and micas is perpendicular to the stress direction Foliated Rocks This is a low grade form of metamorphism and does not impose great changes in the rock e g color stays the same Foliated Rocks But it can develop rock cleavage e g slate metamorphic Foliated Rocks Foliated Rocks As metamorphic grade increases especially pressure minerals begin to alter and new minerals start to grow Higher P T causes minerals to grow large enough to be visible Metamorphic minerals include garnet talc graphite chlorite kyanite staurolite etc e g Kaolinite is unstable at all but Low P T and turns into micas Low Shale Medium slate phyllite Low Shale Medium slate phyllite Med High schist 3 Foliated Rocks Foliated Rocks Higher P T causes minerals to grow large enough to be visible Metamorphic minerals include garnet talc graphite chlorite kyanite staurolite etc Low Medium slate phyllite Med High schist Foliated Rocks Slate High gneiss Terminology Hell Rock cleavage foliation schistosity gneissosity sp Low Medium slate phyllite Med High schist High gneiss Foliated Rocks Phyllite http www fdltcc edu geology PAGES MetamorphicKit images M phyllite jpg Foliated Rocks Garnet Mica schist Foliated Rocks Kyanite schist http www pitt edu cejones GeoImages 1Minerals 3MetamorphicMineralz Kyanite KyaniteSchist jpg 4 Foliated Rocks Non foliated Rocks Foliations can only develop during metamorphism if there was mica and or clay in the original parent rocks But what about clean limestones Gneiss Chalk Board Non foliated Rocks Foliations can only develop during metamorphism if there was mica and or clay in the original parent rocks Non foliated Rocks Quartz arenite sandstones also produce non foliated rocks when subjected to high grade metamorphism Marble non foliated Non foliated Rocks Today s Homework 1 Start defrosting a turkey Warning marble can look exactly the same as quartzite Next Time 1 Marble non foliated Contact metamorphism Quartzite non foliated 5
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