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SU EAR 105 - Metamorphic Rocks

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EAR 105 1st Edition Lecture 7 Outline of Last Lecture I. Basaltic MagmaII. Silicate-Rich MagmaIII. Introduction to VolcanoesOutline of Current Lecture IV. Review of Rock CycleV. Introduction to Metamorphic RocksVI. Foliation & Non-FoliationCurrent LectureIV. Review of Rock Cycle- Rock Cycle: Be able to draw and label the rock cycle with correct geological termso Igneous: Cools from rock melt, crystallizes, rocks categorized by texture and compositiono Sedimentary: Results from weathering (two types) of igneous rocks, followed by compaction and cementation. The more compaction, the more the water is squeezed out. Peat rock form plant materials compacted together while minerals are inorganic, rocks can contain some organic material Soft coal, slightly more compacted than peat, aka bituminous coal Occurs at Earth’s surfaceo Metamorphic: anthracite is fully metamorphosed coal. The harder the coal, the more efficient. Metamorphic rock forms from increased heat and pressure, which ultimately alters the composition (mineralogy and texture) of the original rock.- Agents of change include temperature, pressure, chemically active fluids- Involves solid rock—cannot be hot enough to melt **volcanism occurs at plate boundariesV. Introduction to Metamorphic Rocks Two types of metamorphism: regional & contact- Contact metamorphism: relates to heat and pressure without volcanismThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o Magma (sans volcanic activity) heats surrounded rock, resulting in the production of intrusive igneous rock as well as baked  altered metamorphic rocko Magma heats and eventually fractures surrounding rock, creating new avenues for the transport of chemical fluids, rich in minerals, which leads to the formation of metamorphic rocks through chemically active fluids- Regional metamorphism: relates to tectonic plate collision; folding; involves lots of heat and pressureo occurs at points of subduction (convergent plate boundaries), resulting in the melting of implicated rocko ex. Andes Mountains- The volcanic activity leads to increasing heat and pressure, andthe changing of the rocks involved.VI. Foliation & Non-Foliationo Metamorphic Rock Texture: Can be foliated or non-foliated  Foliation is the preferred alignment of platy minerals- can be described as slaty, shistositic foliation, gneissic banding- ex. shale can get buried, exposed to increased heat and pressure. Micas make it to the surface, undergo recrystallization, and become slate.o Increased pressure causes materials to become more dense, as a general rule- Slaty cleavage describes cleavage that breaks off in relatively dense, compacted layers. Some rocks are non-foliated (the non-preferred alignment)- Ex. calcite- made of shells, becomes coquina limestone. Higherheat and pressure metamorphoses this to become marbleo The pieces of shells become interlocking crystals of calcite (compaction from the conglomeration of shells)o Ex. quartz- sand particles can recrystallize, undergo compaction and become quartzite, which consists of sand particles pressurized together.- Pressure and compaction= confining pressure- Plate collision results in folding—if the confining pressure is not equal on all sides, the plates can become deformed, in thiscase, folded. (This process relates to mountain building.) In foliation, the mineral grains, originally having a random orientation,align themselves in a way that indicates the direction of the pressure under which the metamorphosed rock formed. The mineral grains become platy and elongated Different grades of metamorphism from low to high- ex. low grade: shale  slate (low temps and pressure- ex. high grade: granodiorite  folded geniss (syrong compressional forces, high temps and pressures)- quartz form lighter colored folds, micas form darker ones Shale (dull)  slate (slightly less dull)  phylite (intermediate)  schist (shiny)- Shine relates to the density and increasing crystal size of the micas in the rockso Metamorphism is essential to the formation, availability, and further placement of natural resources Coal: the more metamorphosed coal, the more efficient it is.- Coal metamorphoses along areas involved in mountain building- Coal starts as peat, which forms at the bottom of lakes as a sedimentary


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