Metamorphic Rocks Definitions • Metamorphic Rock - "Meta"= "Meta"= Change Change (Grk) - "Morph"= form (Grk) a rock that has been changed from its original form ( parent ) by heat , pressure , and fluid activity into a new rock ( daughter ) Heat Sources Sources Include Include Magma •• Magma - temperature of of magma magma temperature composition of of magma magma composition Geothermal gradient gradient •• Geothermal - temperature increases increases with with depth depth of of burial burial temperature core of of Earth Earth is is warmer warmer than than outer outer crust crust core Uniform Pressure vs Directed Pressure Uniform Pressure Lithostatic •• Lithostatic "Lithos"= rock, rock, static= static= unchanged unchanged (pressure) (pressure) "Lithos"= uniform (aka (aka non-directed) non-directed) uniform equal intensity intensity from from all all directions directions by by rocks rocks equal Directed Pressure one direction of squeezing is much stronger than the others Minerals align themselves to reduce stress Types of Metamorphism Contact •• Contact caused by by igneous igneous activity activity caused Dynamic •• Dynamic aka cataclastic cataclastic aka associated with with faults faults & & earthquake earthquake zones zones -associated Regional •• Regional caused by by tremendous tremendous pressures pressures caused associated with with tectonic tectonic plate plate activity activity associated Contact Metamorphism Igneous Intrusions Intrusions •• Igneous - size and and type type of of magma magma important important size >> mafic magma magma hotter hotter than than felsic felsic mafic heat decreases decreases away away from from magma magma heat >> forms aa zone zone of of altered altered country country rocks rocks called called forms Aureoles Aureoles Sometimes creates a metamorphic rock called a hornfels -in essence a “cooked” rock Dynamic Metamorphism aka Cataclastic Cataclastic Metamorphism Metamorphism •• aka associated with with Fault Fault Zones Zones •• associated -Places where where the the Earth's Earth's crust crust ruptured ruptured Places Rock Rock pulverized pulverized >> heat and and pressure pressure come come from from movement movement along along the the heat Fault Fault Mylonite resultant rock rock is is known known as as aa Mylonite •• resultant Regional Metamorphism Most common common form form of of metamorphism metamorphism •• Most caused by by large large scale scale forces forces •• caused lithospheric plate plate collision collision lithospheric covers very very large large areas areas •• covers - metamorphic belts belts or or zones zones metamorphic Zones are are characterized characterized by by Zones >> >> Index Minerals Minerals Index form under under specific specific temperatures temperatures and and pressures pressures form metamorphic facies facies metamorphic commonly associated associated with with •• commonly shields: areas ofareas crystalline rocks rocks Shields andstable Mountains: of crystalline Shields of the World Metamorphic Textures Foliated •• Foliated Folios == page page or or leaf-like leaf-like Folios rock has has distinct distinct banding banding or or layering layering rock >> often not not smooth smooth like like in in sedimentary sedimentary rocks rocks often formed under under directed directed pressure pressure formed Non-foliated •• Non-foliated no distinct distinct layering layering character character no often aa massive massive crystalline crystalline texture texture often formed under under uniform uniform pressures pressures formed Foliated Texture Foliated Textures Slatey •• Slatey - Schistose •• Schistose looks like like blackboard blackboard looks dull surface surface >> dull smooth, thin thin layering layering smooth, breaks into into flat flat slabs slabs breaks >> referred to to as as slatey slatey cleavage cleavage referred no mineral mineral grains grains visible visible no Phyllitic •• Phyllitic >> garnets, staurolites staurolites garnets, >> due to to mica mica minerals minerals due may may have have shiny shiny appearance Gneissic •• Gneissic looks like like waxed waxed surface surface looks has aa "sheen" "sheen" to to itit >> has may have have little little "waves" "waves" on on may surface surface referred to to as as >> referred -distinct bands of minerals visible visiblegrains mineral grains crenulations crenulations some small small grains grains visible visible some larger larger grains grains -may look look like like igneous igneous rock rock may may may have have crude crude banding banding >> intensely distorted distorted intensely different minerals minerals than than different schistose schistose Foliated MM Rocks slate phyllite schist gneiss MM MM Rocks Rocks that that could could form form as as aa shale shale (sedimentary) (sedimentary) parent parent rock rock is is exposed to increasing directed pressure and temperature Non-foliated Rocks • Marble: - Quartzite: •• Quartzite: metamorphosed metamorphosed quartz sandstone sandstone quartz metamorphosed limestone Environment of Formation- EOF look for specific minerals Map out where those minerals are found reconstruct T & P for given minerals Find a modern setting that has similar T & P using Uniformitarianism Metamorphic Zones Metamorphic Zones-Map Zones-Map Metamorphic Metamorphic Facies distinctive metamorphic metamorphic lithologies lithologies that that occur occur in in well well •• distinctive defined areas areas and and named named after after the the key key rocks rocks found found defined Metamorphic Zones • Metamorphism is common along most plate boundaries like this [...]... look like like igneous igneous rock rock may may may have have crude crude banding banding >> intensely distorted distorted intensely different minerals minerals than than different schistose schistose Foliated MM Rocks slate phyllite schist gneiss MM MM Rocks Rocks that that could could form form as as aa shale shale (sedimentary) (sedimentary) parent parent rock rock is is exposed to increasing.. .Metamorphic Textures Foliated •• Foliated Folios == page page or or leaf-like leaf-like Folios rock has has distinct distinct banding banding or or layering layering rock >> often not not smooth smooth like like in in sedimentary sedimentary rocks rocks often formed under under directed directed pressure pressure formed Non-foliated... Non-foliated Rocks • Marble: - Quartzite: •• Quartzite: metamorphosed metamorphosed quartz sandstone sandstone quartz metamorphosed limestone Environment of Formation- EOF look for specific minerals Map out where those minerals are found reconstruct T & P for given minerals Find a modern setting that has similar T & P using Uniformitarianism Metamorphic Zones Metamorphic Zones-Map Zones-Map Metamorphic Metamorphic... Uniformitarianism Metamorphic Zones Metamorphic Zones-Map Zones-Map Metamorphic Metamorphic Facies distinctive metamorphic metamorphic lithologies lithologies that that occur occur in in well well •• distinctive defined areas areas and and named named after after the the key key rocks rocks found found defined Metamorphic Zones • Metamorphism is common along most plate boundaries like this