Exploring Planet Earth
Exploring Planet Earth GEOL 101
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This 21 page Class Notes was uploaded by Thad Will on Sunday October 25, 2015. The Class Notes belongs to GEOL 101 at University of Nevada - Las Vegas taught by Staff in Fall. Since its upload, it has received 33 views. For similar materials see /class/228638/geol-101-university-of-nevada-las-vegas in Geology at University of Nevada - Las Vegas.
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Date Created: 10/25/15
UNLV GEOL101 Lecture Outline Fall 2009 12109 I Mineral deposits A ore 1 metallic mineral 2 can be profitably mined and processed 3 definition of an ore changes with a price of the metal b technology mining cost goes down B in addition to ores we also extract 1 industrial minerals a used in industrial or chemical processing 2 gems a sapphire diamond etc some minerals are both gem and industrial 1 diamond sapphire 2 depends on usage quality size 3 building materials a sand and gravel b stone C distribution of elements on earth 1 98 of the crust is composed of about 8 elements a O Si Al Fe Ca Mg Na K 2 concentration of the rest is pretty small D for an ore to exist 1 a geologic process must concentrate desired minerals 2 some possible processes a magmatic separation b hydrothermal alteration c weathering d precipitation e placer ll magmatic segregation A occurs during cooling of an intrusive igneous body B requires a large intrusive cools very slowly heavy minerals crystallize early a chromium b platinum 2 settle to the bottom of the melt 3 lighter minerals float to the top a can form large crystals called pegmatites 1 muscovite 2 feldspar 3 gem minerals 4 rare earth minerals b pegmatite crystals can be huge 1 North Carolina 2 feldspar crystals size of telephone poles 3 used in ceramics industry lll hydrothermal deposits A occurs in the final stages in cooling an igneous intrusion B fluid at the top of the chamber contains light elements 1 significant water and volatile gasses 112509 UNLV GEOL101 Lecture Outline Fall 2009 2 silicon oxygen and metallic ions fluids may be driven out of the magma 1 move through pores fractures 2 can travel long distances 10 s of miles D in fractures 1 forms vein deposits a silver copper gold or mercury Keewenaw Tristate districts 2 metal is often big enough to be seen with the naked eye 3 usually mined with underground techniques E in small pores 1 alters the host rock 2 leaves minute traces of the metal 3 called disseminated deposits a Comstock Lode and central Nevada 4 amenable to surface mining F in limestone 1 metamorphoses the rock 2 leaving ores of lead copper zinc or iron 3 Tristate district IV weathering deposits A weathering can concentrate minor amounts of ore minerals B undesirable minerals are preferentially weathered 1 removed 2 leaving behind the desirable minerals C aluminum was once more expensive than gold is found everywhere strongly bound to other elements economically viable concentrations are relatively rare aluminum in silicate minerals has a high extraction cost in rainy tropical environments a other minerals are leached from the soil b aluminum does not leach out easily c weathering can leave 1 hydrated aluminum oxide bauxite 2 bauxite yields pure aluminum a Reynolds process b lots of electricity V precipitation deposits A desirable minerals may also be precipitated B copper and silver 1 hydrothermal fluids deposit a copper silver b also deposit pyrite weathering of pyrite forms sulfuric acid sulfuric acid mobilizes copper and silver move downward with the groundwater groundwater dilutes acid metals are precipitated at groundwater table porphyry copper deposits a Arizona b Utah QWPQN NQ SJ PFJ N 112509 UNLV GEOL101 Lecture Outline Fall 2009 C Uranium 1 mobilizes in an oxidizing environment a groundwater containing 0 C02 2 precipitates in a reducing environment a oxygen decreases b chemical or biologic activity D Utah and Wyoming 1 uranium laden groundwater in buried stream channels 2 dead logs created local reducing environments 3 uranium compounds precipitated in the dead logs VI placer deposits A streams transport the products of erosion and weathering B some minerals are especially resistant to weathering 1 gold platinum diamonds tin C these minerals are denser than rest of transported load 1 silicate minerals are lighter 2 sand gravel D particles settle out by weight plaoer minerals will settle with larger silicates E placer deposits are mined on the basis of density differences placer deposits have to have a source 1 it may be possible to trace the placer upstream 2 find the original source rock California s Mother Lode Vll Building materials A commonly available in most locales 1 low intrinsic value 2 value is added by processin 3 price is often determined by the haulage distance B aggregate 1 crushed stone a different rocks fit different needs b granite for railroad ballast 1 stable 2 heavy 2 sand a stream deposits b glacial outwash 3 gravel C gypsum 1 plaster 2 drywall 3 deposited as an evaporite 4 mined by surface excavation or solution D clay 1 bricks 2 steel manufacture 3 waste disposal 4 kitty litter E concrete 1 shale 2 limestone 3 aggregate Vlll Industrial minerals 112509 UNLV GEOL101 Lecture Outline Fall 2009 A minerals used in agricultural or industrial processes B fertilizer 1 potassium a a common evaporite b mined by surface excavation or solution c western US and Michigan basin 2 phosphate a aviary deposits b calcium phosphate Florida C halite 1 evaporite mineral a mined by underground or solution b evaporation of sea water 1 arid regions 2 California 2 used for a table salt b road salt c industrial processing d food processing D pegmatites 1 mined for feldspar ceramics 2 mica electrical manufacturing 112509 UNLV GEOL101 Lecture Outline Fall 2009 1 12409 Natural resources A definition of a natural resource 1 naturally occurring material 2 can be put to beneficial use B renewable resources 1 can be replenished in a reasonable amount of time 2 examples solar energy wind energy plant matter C nonrenewable resources 1 cannot be replenished at all or 2 renews slowly with respect to the human life span 3 examples oil gas D ground water 1 can be placed in both categories a some groundwater is replaced quickly b in other places groundwater is gt 10000 years old 2 climate change effects replenishment of ground water E resources and reserves 1 these are quantifiable terms that describe how much is there 2 resource is the total amount of a given material that exists a obviously we don39t know for sure b this is an estimate 3 reserves are what we obtain economically a reserves are always less than resources 1 increases when new sources are found 2 can also decrease if an estimate was bad b reserves changes with price technology and legal climate ll Energy sources A nonrenewable 1 uranium 2 fossil fuels 3 geothermal B renewable solar wind biomass hydroelectric geothermal fusion lll Fossil Fuels A definition 1 combustible hydrocarbon compounds a coal QWPWN b oil and natural gas 0 oil shale tar sands peat other less useful forms 2 formed from ancient life B formation 1 thick layers of organic matter were buried 2 burial prevented significant decay oxidation 3 stored solar energy remains available 4 energy can be released through combustion oxidation 112509 UNLV GEOL101 Lecture Outline Fall 2009 C importance 1 90 of total energy consumption in the US 2 much is imported 3 consumption is exceeding new discoveries 4 discovery of major new reserves is unlikely D air pollution major source of urban air pollution 2 contributor to global warming a burning produces C02 gas b CO2 is a greenhouse gas c allows solar radiation to pass through d reflects thermal energy back to the planet IV Coal A definition 1 altered plant matter 2 coal is a rock but not a mineral a mineral must be inorganic b mineral must have definite chemical composition B formation 1 thick layers of dead plants are buried 2 requires lush vegetation stagnant water a tropical swamps b sinking ground surface subsiding basin c extremely lush plant growth 1 plants unlike what we see today 2 possibly high CO2 in the atmosphere 3 pressure and temperature metamorphose materials a water and gases driven off 1 CO2 CH4 methane b becomes progressively harder more valuable 1 peat lignite bituminous anthracite 2 lignite ignites easily lots of smoke 3 anthracite is hard to light almost no smoke C location of deposits 1 Pennsylvania Germany England Wyoming 2 these regions were once close to the equator a plate tectonics moved them b large basins that were later folded D usage 1 primarily for electric generation 2 currently provides about 20 of US energy needs a percentage is likely to increase b we have more coal than oil E environmental problems 1 air pollution a coal deposits commonly contain sulfur b burning coal produces sulfur oxides SOx c atmospheric SOx combines with water vapor 1 forms sulfuric acid 2 acid rain d sulfur emissions can be reduced 1 process is called scrubbing 2 adds significantly to the cost of power 112509 UNLV GEOL101 Lecture Outline Fall 2009 3 produces residue that must be disposed 2 extraction a surface mining of shallow deposits 1 also known as strip mining 2 most profitable way to extract coal 3 shallow coal usually has lots of sulfur b surface mining 1 the old way a strip off the overburden b dig out the coal c leave d has damaged large amounts of land i huge open pits e acid mine drainage 2 the new way a steps 1 and 2 above b put chat and overburden back c restore landscape d leave e better but not perfect c underground mining 1 expensive dangerous 2 usually for better grade coal 3 or cheap coal is not locally available V Oil and Natural Gas A definition 1 liquid hydrocarbons a complex molecules b based on carbon and hydrogen 2 oil is fluid at surface pressure 3 natural gas is gaseous at surface pressure 4 formed from plant and animal remains 5 following burial in a marine environment B we don39t really understand how petroleum forms 1 biologic matter is buried in a marine environment 2 the burial process must prevent decay a most marine environments are oxygen rich b decay is prevented by rapid burial 1 inorganic sediments clay 3 at great depth heat and pressure effect a change C we do understand how petroleum migrates 1 after formation oil and gas are in shale a both are lighter than water 2 density causes them to migrate upwards a this is really fortunate b shale doesn39t transmit fluids easily c we couldn39t extract oil from deep shale 3 to form a deposit geology has to stop upward flow a feature called a trap 1 gas lighter at the top 2 oil below the gas 3 water brine below the oil b without a trap 112509 UNLV GEOL101 Lecture Outline Fall 2009 1 oil and gas will migrate right to the surface 2 seep out of the ground 3 this how it was discovered c hydrocarbons within a trap are under pressure 1 they will migrate to a drill hole 2 flow upward towards the surface 4 geologists look for traps a oil doesn39t form everywhere 1 traps are deeply buried 2 data a drill holes b geophysical exploration c surface geology d intuition D future of petroleum 1 US is utterly dependent on imported oil and gas 2 worldwide usage is increasing quickly a particularly in Asia 3 we are unlikely to find major new deposits a have looked most everywhere in the world b smaller deposits will be found 4 oil will become increasing expensive a electrical generation will move towards coal 5 in terms of gasoline maybe 4050 years left VI Tar sands A earth materials saturated with a sticky type of hydrocarbon 1 hydrocarbon is called bitumen 2 very much like road tar 3 sand is a common host hence tar sand 4 can also be found in sand shale limestone etc B reserves 1 biggest are the Athabasca tar sands in Alberta Canada 2 Russia Venezuela also have lots of this 3 reserves are greater than oil just more expensive to get C extraction and processing are expensive 1 tar doesn39t flow like oil 2 tar sands may be mined like coal 3 can also be heated underground till it flows 4 tar is not as potent as oil requires more processing 5 marginally profitable in Canada where oil is expensive Vll Oil shale A definition 1 fine grained sedimentary rock shale 2 contains a hydrocarbon called kerogen a similar to oil and gas b nature hasn39t completed the transformation B locations 1 US has most of the worlds known reserves 2 oil shale are located in Colorado Utah and Wyoming C extraction 1 fluids don39t flow well through shale a almost impermeable b very small open spaces 112509 UNLV GEOL101 Lecture Outline Fall 2009 2 rock must be mined to produce oil a 10 gallons per ton of rock b this is expensive c not economically feasible d also produces lots of waste rock to dispose of e lots of bizarre schemes have been tried 1 underground fires 2 using waste rock for construction 3 we will use this in the future 4 reserves are greater than oil technical problems exist Vlll Nuclear Energy A definition 1 energy produced through nuclear fission 2 the controlled chain reaction splitting of Uranium235 3 resulting heat produces steam for electric generation B availability 1 uranium is pretty common 2 U235 makes up less than 1 of all uranium 3 3 U235 necessary for nuclear fission a pure uranium must be enriched 4 uranium ores a often placed by groundwater b large reserves in Wyoming and Alberta Canada C meltdown 1 nuclear plants will not explode like a bomb 2 the potential exists for release of radioactive dust a extremely hazardous D future 1 nuclear power is currently out of favor a cost 1 building plants 2 operation within safety regulations 3 disposal of residue nuclear waste b unpopularity 2 fusion a energy from combining instead of splitting atoms 1 this is how the sun works b benefits 1 unlimited raw material hydrogen oxygen 2 nice waste products water c problem 1 we can39t do it 3 breeder reactors a fission reactors make their own nuclear fuel b benefits 1 eat their own waste 2 greatly reduce disposal problems c problems 1 less stable that conventional system 2 can produce weapons grade material IX Solar energy A conversion of solar energy to power 1 obviously the sun has to shine for this to work 112509 UNLV GEOL101 Lecture Outline Fall 2009 2 amount of solar energy varies by a 39 1 New Mexico 360 days 2 Seattle 60 days 3 nearer the equator gets more sun b season c time of day 3 for optimum efficiency devices have to follow the sun 4 two types of solar energy systems a collectors 1 active 2 passive b photovoltaic B collectors 1 passive a means direct heating by the sun b windows facing east are a good example c common in western US 1 east facing glass wall 2 light shines on a stone or concrete floor a heats up during the day b radiates heat during the night 2 active a move solar energy from one place to another b solar water heaters are a good example 1 common in western 2 essentially radiators that sit on the roof a black panels facing sun b antifreeze trickles through panels i use yearround c carries heat to a conventional water heater C photovoltaic systems 1 directly turn solar energy into electricity 2 manufacturing cost per ampere is extremely high 3 good for a number of specialized uses a remote locations 1 village medical clinic 2 data collection locations b intermittent use 1 boat battery charger X Wind energy A historic uses of wind energy 1 move ships 2 pump water a windmills b shallow aquifers less than 40 feet deep 3 generate electricity B electric generation process a wind turns a propeller b propeller turns a generator c propellers can be a variety of shapes 1 size matters 112509 UNLV GEOL101 Lecture Outline Fall 2009 a more blade area more power 39 big b ades ii lots of small ones 2 hard to balance large conventional props 2 requires a steady winds of at least 10 miles per hour b direction must be constant 3 relatively few locations meet this criteria 4 mountain passes near oceans are good locations a steady onshore winds b valleys channel the wind C wind farms 1 large scale installations 2 may have several thousand wind turbines 3 provide electricity free of emissions 4 downside a ugl 1 by nature these occupy scenic locations 2 outside San Francisco Bay area b nois c dangerous to migratory birds XI Hydroelectric energy A water is heavy 1 work is required to lift water 2 mechanical energy is released when it falls a historically water drove mechanical devices 1 grist mill 2 machine shop 3 monitor water cannon b now water drives electrical generators c amount of energy produced depends on d flow rate e height of the fall B benefits of hydroelectric dams no emissions 2 relatively low cost energy 3 side uses a recreation b water supply municipal agricultural C down side 1 dams completely change the character of a river a loss of recreational opportunities b reduce biodiversity 2 dams have a finite life span a eventually fill with sediment 3 increase evaporative losses a big reservoirs have lots of surface area b especially bad in desert areas D examples 1 salmon runs on the US Pacific coast a irreparably damaged by dams b salmon migrate from ocean to spawn in rivers 1 upstream passage is blocked by dams 112509 UNLV GEOL101 Lecture Outline Fall 2009 2 downstream a reservoirs our simply to big b reservoirs harbor competitive fish c salmon was an important renewable food source d salmon used to be cheaper than hamburger 2 Nile river in Egypt a Aswan high dam built by Russia US declined to help said it was a bad idea 2 president Nasser wanted this real bad 3 use the power to modernize Egypt b completely environmental screwu 1 destroyed hundreds of historic sites 2 the Nile floods used to a wash salts out to the ocean b bring nutrients to the soil 3 now farmers a have salinity problems b must maintain irrigation systems c must add fertilizer 4 fisheries a lake has provided new opportunity b also decimated ocean sardines 5 schistomatosis a parasitic organism b gruesome disease i often fatal ii not a fast death c carried by river snails 39 used to get washed out to sea ii love the lake and canals 6 the reservoir they don39t get the expected power i it leaks badly b is filling quickly with sediment i upstream desertification ii over farming three gorges dam in China 3 E future of dam construction 1 2 3 F stored 1 2 big hydroelectric dams are not being built in the US a most of the good sites have been used b environmental concerns c expense small hydroelectric sites are still being developed source of clean electricity for specific situations hydroelectric power used to provide a buffer during peak usage periods generators work best when run at constant output a increases efficient and reliability b reduces management maintenance costs during off peak hours a excess electricity is used to pump water uphill b placed in a storage reservoir during peak hours a stored water is used to generate electricity 112509 UNLV GEOL101 Lecture Outline Fall 2009 b a lot of energy is lost in this process maybe half c it works in some situations SF Bay Area G tidal energy 1 special type of hydroelectric energy 2 dam is placed across a narrow inlet estuary or fjord 3 must have significant tidal fluctuations 4 headaches a a limited number of suitable locations b estuaries are extremely productive environments c significant resistance to developing such sites Xll Geothermal energ A requires hot rocks near the earth39s surface 1 cooling magma bodies 2 can provide a significant amount of heat B electric generation water in the hot rock may be superheated a flashes to steam when brought to surface b great to spin generators 2 problems a sources of energy are highly localized b have a finite life span 1 existing water has been pumped out 2 replacing water has not worked well c water tends to be highly mineralized 1 corrosive and deposits scale a high initial cost for equipment b high maintenance costs c disposal problems C other means of geothermal energy production downhole heat exchange a can also be used for cooling b needs a significant temperature difference c requires shallow groundwater d porous rock e Reno NV 2 direct heating of buildings and greenhouses a warm but not superheated b has been very successful where applicable 1 Iceland Xlll Biomass A consists of 1 firewood 2 animal dung 3 other processed fuels a methanol B accounts for approximately 14 of world usage 1 most usage in under developed countries 2 fossil fuels are expensive 112509 UNLV GEOL101 Lecture Outline Fall 2009 92909 Weathering A surface of the earth is a dynamic environment 1 mountain building uplifts portions of the crust 2 other processes work to level the earth s surface a mass wasting b erosion c weathering B mass wasting 1 transfer of rock andor soil down slope through the direct action of ravity 2 essentially landslides C erosion 1 removal andor transport of earth materials through the action of moving water wind or ice 2 covered elsewhere D weathering 1 decomposition of rock at or near the earth s surface 2 results from mechanical or chemical action 3 occurs because rocks are not at equilibrium a rocks are initially formed at depth b surface conditions are different 1 temperature a much cooler at the surface b temperature changes in cycles 2 pressure is lower at the surface 3 weatheratmosphere E weathering mass wasting and erosion work together 1 weathering weakens and fragments intact rock 2 it can be moved by mass wasting or erosion 3 movement exposes new rock to weathering ll Chemical weathering A fundamentals 1 chemical decomposition of rock 2 forms components more stable at the earth s surface 3 water plays a leading role in chemical weathering a most reactions occur in solution b lack of water severely retards chemical weathering 4 principal processes a dissolution b oxidation c hydrolysis B dissolution 1 occurs when the mineral is soluble in water a simply dissolves into flowing water b most minerals are insoluble in pure water c small amounts of acid dramatically can increase solubility 2 normal acidification of rain water a absorb C02 from the atmosphere b forms weak carbonic aci 3 further acidification of groundwater a additional CO2 in soil gas adds to acidity 10109 UNLV GEOL101 Lecture Outline Fall 2009 b decay of organic matter produces humic acids 4 other sources of acid a oxidation of sulfide minerals particularly pyrite b forms sulfuric acid 5 calcite a primary mineral in limestone b highly susceptible to acidic water c dissolution of calcite 1 puts the Ca ion in solution hard water 2 releases CO2 gas d caverns form when acidic water dissolves limestone e used to neutralize acidic waters C hydrolysis 1 hydrogen from water replaoes an element in the mineral structure to form a new and more stable mineral 2 the atom that is freed becomes mobile 3 hydrolysis of feldspars a forms clay minerals b releases silica and metallic ions 4 quartz itself is pretty insoluble so is left behind 5 acidic water helps hydrolysis 6 acid rain on igneous rocks can be a serious problem releases metals eg Al Cu Zn D oxidation 1 chemical reaction in which an element gives up electrons to and joins with oxygen atoms 2 4Fe 302 gt 2Fe203 hematite rust 3 important weathering mechanism a strongly affects FeMg minerals and sulfides b usually occurs in conjunction with hydrolysis 4 acid mine drainage a mining exposes lots of fresh surfaces for weathering b oxidation of sulfide minerals also yields sulfuric acid Iquot Mechanical weathering A fundamentals 1 fragmenting of intact rock into smaller pieces a process is purely mechanical b pieces retain chemical properties of the original rock 2 frees particles for transport 3 increases surface area a chemical action occurs on exposed surfaces b fragmentation enhances chemical weathering B principal types of mechanical weathering 1 frost wedging 2 unloading expansion 3 thermal expansion 4 organic activity 5 erosion a performed by moving wind water or ice b we ll cover erosion separately C frost wedging 1 water expands by about 9 when it freezes 2 applies considerable pressure 10109 UNLV GEOL101 Lecture Outline Fall 2009 3 water seeps into small cracks in rocks a macroscopicfractures b microscopic fractures along crystal boundaries 4 expansion during freezing enlarges the crack 5 daily cycle in mountainous midlatitude regions 6 frost wedging often leads to formation of a talus slope D unloading 1 rock strength a rocks are very strong when compressed b relatively weak under tension 2 lithostatic pressure a most rocks form deep in the earth b weight of the material above applies force 1 confining pressure 3 exhumation a occurs when overlying material is removed 1 erosion 2 excavation b confining pressure is removed c rock tries to expand d produces tensile stress e most rocks don t respond well to tension 1 crack during unloading 2 particularly true for plutonic igneous rocks f same process occurs in mines and quarries 1 often occurs suddenly rock burst 4 unloading fractures a usually parallel to ground surface b plutonic rocks can form rounded structures 1 called exfoliation domes 2 somewhat like an onion skin E thermal expansion 1 daily surface temperatures in deserts can change gt30 C 2 minerals may have different expansion rates 3 cracking occurs from differential expansion 4 field evidence implies that this happens but laboratory tests have not successfully recreated the phenomenon F organic activity 1 plant roots invade small cracks 2 root growth enlarges the cracks 3 burrowing animals remove loose matter a open up pathways for other processes G general effects of rock fractures not all rock fractures result from unloading 2 cooling and tectonic activity are also important a occur prior to exposure of the rock mass 3 in addition to fragmenting a rock mass fractures provide pathways for water and opportunities for other weathering mechanisms IV Rate of Weathering A controls on rate of weathering 1 minerals present 2 weather 10109 UNLV GEOL101 Lecture Outline Fall 2009 3 shape and surface area B mineralog 1 weather follows Bowen s reaction series a high temperature minerals olivine weather easiest 1 form at high temperatures and pressures 2 environment is very different from the surface b low temperature quartz are more durable form in an environment more similar to the earth s surface 2 hence it is more stable there C climate 1 tropics have the fastest weathering arctic the slowest 2 warm temperature speeds chemical activity 3 most reactions won t occur without water 4 organic growth produces humic acids 5 topography slope plays a role a organic growt b amount of water c solar heating D shapesurface area 1 bigger the surface area the more reactions can occur 2 sharp corners have lots of surface area a weather quickl b called spheroidal weathering V Metamorphism A definition 1 alteration of existing rock to form another type of rock a occurs in response to specific agents 1 heat 2 pressure 3 chemical activity b weathering is decomposition not metamorphism 2 rock is formed under a given set of conditions a agents change conditions b rock is no longer at equilibrium c minerals react to equilibrate with new conditions 3 can be a simple transformation shale to slate 4 can be so complex that it is impossible to determine what the original rock was VI Heat A probably the most significant metamorphic agent B heat energy is necessary to recrystallize existing minerals 1 for example clay is unstable at elevated temperature 2 clay minerals tend to form mica 3 mica becomes unstable at ye higher temperatures C sources of heat deep burial of surface rocks a results from tectonic activity mountain building b T goes up 2030 C per kilometer of depth 2 rising magma body D contact metamorphism 1 most apparent when magma rises nearly to the surface 2 produces an extreme temperature difference 10109 UNLV GEOL101 Lecture Outline Fall 2009 a near surface country rock is cool b temperature gradient creates a thin altered zone c it is also likely that plenty of water is available 1 assists in chemical reactions 2 transfers heat rapidly Vll Pressure A sources of pressure 1 burial in a subsiding basin a weight of the overlying material 2 tectonic burial a mountain building thickens the Earth39s crust 3 directional pressure a induced through tectonic gneous activity B effects of pressure 1 compacts mineral grains 2 recrystallization at contact points 3 mineral grains become elongated 4 rotate to become parallel 5 remember that hot rocks under pressure are much more pliable than what we see at the surface Vlll Chemical activit A fluids can react with minerals in the rock to form new minerals 1 mostly water 2 carry ions in solution 3 my be acidic or caustic 4 hot water is more reactive than oold a carries ions easier than cold water b higher energy levels B water comes from 1 dehydration of minerals clays 2 pore spaces between mineral grains 3 seafloor spreading zones 4 released from magma with other fluids and gases IX Metamorphic effects on texture A texture reflects the degree of metamorphism 1 directed pressure leads to alignment of mineral grains a elongate perpendicular to primary stress b creates a banded structure referred to as foliation 2 pressure and temperature cause recrystallization a bigger crystals b grow perpendicular to primary stress B slaty cleavage slate forms from shale under lowgrade metamorphism a relatively mild pressures and temperatures b clay minerals change to tiny mica crystals 1 too small to see oriented perpendicular to principal stress 2 slate breaks parallel to the mica crystals a called slaty cleavage b different than mineral cleavage C schistosity 1 increased pressure and temperature 2 forms larger visible mica crystals 10109 UNLV GEOL101 Lecture Outline Fall 2009 3 gives the rock a scaly appearance 4 rocks are often deformed wavy D gneissic texture 1 occurs at highest temperatures less than partial melting 2 minerals segregate 3 form light and dark bands within the rock 4 foliated but will not split along the foliations E nonfoliated texture 1 crystals are of similar size in all directions 2 usually occurs when a single mineral is present a minor impurities can add color and form bands b limestone metamorphoses into marble c impurities can make spectacular patterns X Metamorphic effects on mineralogy A minerals change during metamorphism 1 original ones not stable in the new environment 2 form stable minerals for the changed environment B two basic categories of mineralogic changes new minerals form from existing minerals and in situ water a some elementscompounds may leave eg C02 2 new ions are added by hydrothermal fluids a fluids released from a cooling magma b sea water percolating near spreading sites 1 metal rich fluids gush from undersea springs 2 cold water leads to rapid precipitation C diagnostic index minerals indicative of particular environments 2 can be used as diagnostic tools 3 examples of index minerals a chlorite low temperature and pressure b garnet high temperature XI Categories of metamorphic processes A regional metamorphism 1 burial places pressure on large regions 2 temperature is elevated B contact metamorphism magma bakes or boils the surrounding rocks 2 surrounds batholiths dikes sills C fault metamorphism blocks of solid rock slide past each other 2 creates a highly deformed or pulverized zone 3 relatively rare occurrence D partial melting 1 this is rarely a metamorphic process 2 partial melting often forms new magma a this is an igneous process not metamorphic b key factor is that the molten rock migrates 3 occasionally the molten rock stays in lace a some but not all minerals melt then solidify b this forms a metamorphic rock E combinations of the above Xll Foliated metamorphic rocks A slate 10109 UNLV GEOL101 Lecture Outline Fall 2009 very fine grained rock composed mainly of small mica flakes results from low grade metamorphosis of shale usually red black green a green comes from ironsilicate minerals b red is hematite stain iron oxide c black implies high organic content petroleum 5 foliation a cannot be seen b known to exist from strong cleavage c results from alignment of mica flakes PF ONT B phyllite 1 midway between schist and slate 2 looks like slate except the cleavage surfaces have a sheen 3 often green in color with bright mica flakes strongly foliated rocks formed by regional metamorphism mountain building individual mineral grains are visible platy rock can be split into flakes or slabs foliations are often deformed schist refers to the texture mineralogic descriptors are added eg garnetmica schist often contain accessory minerals a such as garnet staurolite b embedded within the platy structure NQP PP NT D gneiss 1 banded metamorphic rocks a alternating lightdark bands b bands consist of elongated mineral grains rather than the platy mineral grains found in slate and schist c banded structure can display intricate folding 2 results from high grade metamorphism 3 gneiss refers to the texture 4 mineralogic descriptors are added eg granite gneiss E migmatites 1 transition between igneous and metamorphic rocks 2 low temperature minerals actually melt a silicates such as quartz potassium feldspar b melted portion stays in place and recrystallizes in the banded form F mylonite 1 mineral grains are highly deformed and elongated 2 forms from shear stress in fault zones Xlll Nonfoliated metamorphic rocks A quartzite 1 high grade metamorphism of sandstone 2 quartz grains fuse to form a very hard rock B marble 1 coarse grained crystalline rock 2 formed from the carbonate rocks limestone dolostone 3 pure white marble is prized by sculptors 4 impurities within marble can impart colors and patterns 10109 UNLV GEOL101 Lecture Outline Fall 2009 10109
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