Exam Overview: Earth Materials - Weathering, Soils, and Metamorphism, Study notes of Geology

Download Exam Overview: Earth Materials - Weathering, Soils, and Metamorphism and more Study notes Geology in PDF only on Docsity! GLY 26/526 - Earth Materials - Final Exam Overview - 2013 Here is an overview of what we have covered during the second half semester. Weathering and Soils the sedimentary cycle weathering, transport, deposition, compaction, cementation Weathering climate control on the balance of chemical vs. mechanical weathering difference between weathering and erosion mechanical weathering unloading, frost wedging, root wedging, salt crystal growth, sand blasting, stream abrasion, glacial abrasion, wetting & drying of swelling clays (smectites) spheroidal weathering chemical weathering controls: mineralogy, climate, biological agents, water chem., topography acidification of water: meaning of acid, pH, dissociation of carbonic acid dissolution reactions (e.g., CaCO3) leaving no solid byproduct hydrolysis of silicate minerals (e.g., feldspars) producing clays and ions effect of chelating agents oxidation & hydration (esp. of iron) resistance of minerals to chemical weathering - Goldich stability series hi silica framework silicates most stable against chemical weathering lo silica isolated tetrahedra silicates least stable because…(metal cations vs. silica; ionic vs. covalent bonding) Si-O, Al-O, metal-O bond strengths products of weathering solids: gravel, sand, silt, clay-size particles, clay minerals dissolved ions: metal cations, silica, bicarbonate clay minerals structure & characteristics two-layer & three-layer clays swelling clays Understand, in detail, how rocks are weathered (especially chemical weathering) and the materials produced by weathering. Docsity.com Soils soil-forming processes weathering (changing bedrock/parent material into sediments) incorporation of organic matter into upper portion of developing soil downward leaching of ions & translocation of clays soil profile characteristics of O, A, B, C horizons zones of eluviation and illuviation E horizons K horizons textural classification of soils percentage of sand vs. silt vs. clay characteristics of soils by climate tropical-equatorial: very deep, rich in insoluble residues (Al & Fe hydroxides) arid-desert: poorly developed horizons temperate mid-latitude: well developed horizons polar/tundra: poorly developed horizons, mostly mechanical weathering Understand, in detail, the processes that make soil from bedrock and the characteristics of soil horizons and differences in soils in different climates. Metamorphism recrystallization in the solid state to minerals stable under changed P-T conditions metamorphic agents elevated pressure ! confining pressure ! differential stress (responsible for foliation) temperature ! typical geothermal gradient ~25-30 °C per km ! meta beginning ~150-200 °C ! up to onset of partial melting (anatexis) ~600-800 °C hydrothermal fluids ! juvenile, seawater, meteoric water, connate fluid, fluid from meta. of minerals ! hydrothermal reactions -> volatile-rich mins, veins, fluid inclusions ! fluids from the rocks themselves -> deuteric reactions ! fluids from outside source -> metasomatism time ! solid state recrystallization is very slow ! (except in impacts and sudden fault movement) prograde & retrograde metamorphism Docsity.com very high pressure facies - subduction zones, lower crust, upper mantle blueschist facies eclogite facies ultra-high pressure minerals (someday a new facies) be able to estimate the T-P conditions the rocks experienced according to the metamorphic facies, or given the T-P, identify the metamorphic facies - using the metamorphic facies T-P chart (e.g., Fig. 18.2) additionally, using the appropriate mineral assemblages tables (Tables 18.1-18.13) be able to identify if a given mineral might be found in a metamorphic rock given the protolith and P-T conditions and vice versa, given an assemblage of minerals, what were the P-T conditions and likely protolith retrograde metamorphism of very high pressure minerals metamorphism to lower P-T minerals not common b/c exceedingly slow b/c of lower temp & lacking volatiles Al2SiO5 polymorphs andalusite, kyanite, silimanite be able to identify from a P-T diagram which of the three is stable ! or given that one of these is found in a metamorphic rock ! be able to constrain the P-T metamorphic facies series contact facies series - increasing temp. ! contact metamorphism, shallow depths Bucan facies series - increasing temp. & moderately increasing pressure ! volcanic arcs (generally high heat flow, moderate pressure in the mountains) Barrovian facies series - increasing pressure & temp. ! orogenic belts; deepest burial = highest temperature Sanbagawa facies series - high pressure -moderate temperature ! 10-20 °C per km geothermal gradient ! compressional subduction complex (some foliation) Franciscan facies series - very high pressure - low temperature ! subduction zones ! < 10 °C per km geothermal gradient (subducting slab is cool) ! accretionary melange! paired metamorphic belts high pressure facies series (Sanbagawa or Franciscan) ! parallel to high temperature, low to moderate pressure facies series (Contact or Buchan) subduction zone and adjacent volcanic arc given information on metamorphic minerals or metamorphic facies found in rocks across an area be able to identify the metamorphic facies series and tectonic environment alternatively, given the tectonic environment in which a suite of rocks were metamorphosed, be able to identify the peak T-P that may have resulted, the metamorphic facies that should be found, and where in the suite a given characteristic mineral might be found Docsity.com hydrous minerals from midocean ridge to subduction zone hydrothermal metamorphism at midocean ridge serpentine and many other hydrous minerals form in ocean crust metamorphic dewatering of subducting ocean crust flux melting of ultramafic mantle rocks and formation of mafic primary magma be able to recognize minerals that would likely metamorphose releasing water in a subduction zone Magma know how primary magmas are formed: be able to explain decompression melting at midocean ridges & hotspots flux melting at subduction zones understand partial melting be able to explain using Bowenʼs Reaction Series be able to tell which minerals in the mantle will melt and why be able to explain why the resulting partial melt is mafic know the composition of primary melts (partial melts of mantle rock) mafic magma from partial melting of ultramafic mantle rock magmatic differentiation know how primary basaltic magmas may be differentiated into all other magmas by various forms of fractional crystallization, assimilation, magma mingling... 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