Popular in Geology 1610
Popular in Geology
This 3 page Class Notes was uploaded by Ashley Barry on Tuesday February 16, 2016. The Class Notes belongs to 1610 at University of North Texas taught by Byers in Fall 2016. Since its upload, it has received 5 views. For similar materials see Geology 1610 in Geology at University of North Texas.
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Date Created: 02/16/16
Metamorphism Sir Charles Lyell :from the latin word metamorphis- to change the transformation of pre existing rock from igneous,sedimentary,or metamorphic origins through a continuum of change three primary agents of metamorphism are: heat,pressure,chemical/ﬂuids ultimate source of heat energy are the earths interior and stress from plate tectonics 2 scales of metamorphism:regional and contact major settings of metamorphism regional - large scale contact or thermal fault zones impact hydrothermal burial tishimingo granite intruded by magic dike-sharp contact metamorphism fault metamorphism-2 plates moving past each other (san andreas fault) echelon fault-low grade metamorphism impact metamorphism meteor crater (arizona,aka barring crater) barring crater 50000 years old created by impact of 150 ft diameter piece of space material moving around 26000 miles per hour 92 percent ion 7 percent nickel and 1 percent trace elements 5 impact craters in texas hydrothermal minerals sphalerite-zinc galena-lead chalcopyrite-copper bornite-copper magnetite-iron talc-talc graphite-lead agents of metamorphism heat increases 20-50 degrees celsius per km depth starts about 300 degrees celsius pressure most metamorphose at depth of 10-30 km .3-.4 bars per km of depth 1 bar approx. one earth atmosphere ﬂuids accelerate chemical reactions dissolving atoms and ions dissolved in ﬂuid can mir=grate through a rock and react with solids to form new minerals texture terms for metamorphic rock 2 major groupings: foliated and non foliated textural terms slaty phyllitic schistose gneissic polymorph kyanite- al2sio5 andalusite- al2sio5 silimanite-al2sio5 index minerals used to estimate the degree of metamorphism quartz (sio2) ans feldspar groups (k,al,si3o8)is found in metamorphic rocks but doesnt make a good index mineral shale formed by consolidation of clay,silt,or mud characterized by ﬁnely laminated structures (ﬁssility) slate chlorite starting to grow exhibits rock cleavage harder than shale more sheen no fossils denser than shale phyllite mica starting to grow has more sheen than slate microscopic crenelations platy material (mica) larger than in shale but not visible schist schistose visible mica index minerals schistose texture gneiss seperation of light and darm minerals augen=eyes migmatite partially melted minerals that melt at low temps liquify ﬁrst and will ﬂow or pool if majority of rock melts and refreezes it becomes igneous non foliated or granoblastic foliation is absent crystals grow in equant shapes such as cubs or spheres these metamorphic rocks are deﬁned by their composition rather than their texture massive in appearance parent metamorphosed product foliated : shale,sandstone=slate,phyllite,schist,gneiss non foliated: quartz rich sand=quartzite limestone=marble basalt=greenstone