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100 Cards in this Set
- Front
- Back
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What is meant by the crystallization of magma
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it is the process is which magma changes into a solid rock
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what are the five groups of chemical elements tha occur in magma
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1. big 8 (O Si Al Fe Ca Na K Mg)
2. elements that crystallize at temps higher than the big 8 (Cr) 3. elements whose ionic radius & charge allow them to substitute for memebers of the big 8 (Ga Ge) 4. elements whose ionic radius and charge do not allow them to substitute for big 8 (Li Be B F U Th W) 5. elements that dissolve in magmas water and later precipitate in the host rock (Pb Zn Sb) |
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What is pyroxene?
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pyroxene is a family of silicate minerals in which AUGITE is the most abundant member
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What is amphibole?
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amphibole is a family of silicaate minerals in which HORNBLENDE is the most abundant member
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what is meant by magmatic segregation?
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magmatic segregation is a concentratin of mienrals that crystallize at the highest temps at the bottom of the magma chamber
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which igneous minerals are typically removed form the magma by magmatic segregation
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minerals that accumulate by magmatic segregation include: chromite, olivine, ca feld, augite, pyrite, magnetite, ilmenite, chalcopyyrite, pyrrhotite, pentlandite, arsenopyrite
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what is hydroxide
how does it form why is it part of many ionically bonded minerals |
1. hydroxite is 1 oxygen atom ionically bonded to 1 hydrogen atom (OH)
2. it forms when a molecule of water (H2O) loses one of its hydrogen atoms 3. because it carries a -1 charge, which causes it to act as an anion (-) and is therefore attracted to cations(+) to form ionically bonded minerals |
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why is there unlimited ionic substituion between anorthite (ca feld) and albite (na feld)
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there is unlimited substitution because calcium and sodium ions are nearly equal in size and their charges are within one of eachother (ca+2/Na+1)
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under what circumstance is there limited solid solution between na feld and k feld?
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limited:only in magma at temps above 1220F
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why is there no solid solution between na feld and k feld at surface temps
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b/c temps below 1220F, the atomic structure contracts so much that the large K cations are squeezed out of the structure, thus destroying the solid solution
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what is exsolution
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the process in which a solid solution (2 minerals homogenously mixed as one) physically separate to form two chemically different minerals (perthite)
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what is perthite
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a rock made of na felds and k felds, formerly a solid solution
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what causes exsolution of na felds and k felds
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occurs when the temperature of their solid solution drops below 1220F causing the atomich structure to contract thus forcing out the large K ions
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what is pegmatite
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an extremely course textured igneous rock
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what specific type of geologic structure do most pegmatites form
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most occur as dikes
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what are 2 most obvious visible differences between a simple pegmatite and complex pegmatite
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1. simple pegs contain only quartz, muscovite, k or na felds and complex pegs contain exotic minerals in addition to those
2.simple peg minerals are arranged at random in a dike, complex peg minerals are zones within a dike |
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what minerals are charactristic of simple peg
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quartz (smoky, rose, milky), muscovite and Na or K felds (microcline)
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what minerals are typical of complex pegs
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in addition to simple peg minerals, complex peg also contains: lepidolite, spodumene, amblygonite, beryl, chrysoberyl, tourmaline, cassiterite, comumbite, cryolite, topaz, monazite, moylbdenite etc
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which polymorph of kfeld is most typical of pegmatite
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microcline
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why do nonmembers of the big 8 (such as nickel, gallium, manganese, vanadium, germanium, and others) commonly engaged in ionic substitution for members of the big 8?
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b.c a combination of their ionic radius and magnitude of charge renders them suitable for ionic substitution for the big 8
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2 reasons why Li Sn Be B Nb W U Mo NEVER engage in ionic substitution with the big eight
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1. their ionic radius or magnitutde of charge renders them unsuitable for ionic sub with the big 8
2. some are exceptionally l8ight weight (Li Be B)and therefore reside on the top of teh mabma chamber placing htem in an inaccecssible location for ionic substition |
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name a 6 minerals that occur only in pegmatites
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lepidolite, beryl, chrysoberyl, spodumene, amblygonite, cryolite, monazite, columbite, cassiterite, scheelite, betafite
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what is meant by an essential igneous mineral: examples
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is one of that must be in a particular rock in order for that rock to be what it is. Example: quartz is essential for granite because the rock cannot be granite without the presence of quartz
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what is meant by an assessory igneous mineral
metallic example: non metallic example: |
one that need not be present in a particular rock but occurs with fairly frequent regularity. Quartz is an assesory to diorite, it's not required but it occurs often
metallic:magnetite, ilmenite, pyrite, chalcopyrite, pyrrhotite, pentlandite, rutile nonmetallic: sphene, fluorite, apatite |
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what is meant by undersaturated magma
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one with less than average amount of silicon >28%
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What is the most common mineral that crystalizes from undersat magma
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nephaline
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under what unusual circumstance would corundum crystallize from magma
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corundum crystallizes from undersat magma that runs out of silicon but still contains aluminum and oxygen
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what gives RUBY its color
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impurities of chromium (Cr) give corundum it's ruby red color
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what gives saphire its blue color
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impurities of iron and titanium give corundum it's saphire blue color
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what is a hydrothermal mineral
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a mineral the precipitates from hot water beneath the earths surface
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what is the chief source of water for hydrothermal solutions
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water derived from magma
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what metals are typically dissolved in hydrothermal solutions
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Metals:lead, zinc, copper, gold, silver, mercury, antimony, arsenic, barium, strontium, cobalt, boron, calcium and magnesium
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what non metals are typically dissolved in hydrothermal waters?
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non metals:fluorine, chlorine and sulphur
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name 10 minerals that precpitate form hydrothermal waters
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copper, silver, gold, pyrite, chalcopyrite, galena, sphalerite, cinnabar, stibnite, celestite, strontianite, barite, millerite and quartz
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what gasses are typically dissolved in hydrothermal solutions
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fluorine, chlorine, carbon dioxide, ammonia
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why do many hydrothermal deposits consist of large well formed crystals
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because the openings through which hydrothermal waters flow are often very large, which allows the development of large well deveoloped crystals
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why are hydrothermal solutions highly acidic (low pH)
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the dissolved gasses they carry in solution turn the water acidic (Cl dissolved in water makes hydrocloric acid (HCI), F dissolved inw ater makes hydrofluoric acid (HF))
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what is the diff between hypothermal, mesothermal and epithermal deposits?
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hypothermal deposit is one that precipitates with water between 600 and 1000F at a relatively great depth
mesothermal is one that precips from water between 400 and 600F at mod depth epithermal precipitates from water between 100 and 400 at a shallow depth |
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State 2 mechanisms that trigger the precipittion of minerals from hydrothermal solution that are purely PHYSICAL in nature
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1. decrease in water temp
2. decrease in water pressure |
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state 2 mechanisms that trigger precipitation of minerals from hydrothermal solution that are CHEMICAL in nature
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1. decrease in acidity of the solution
2.metal exchange (Ion exchange) |
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what commonly causes a sudden decrease in acidity (increase in pH) of an ascending hydrothermal solution
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an encounter with limestone, marble or dolostone host rock
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why do many hydrothermal deposits occur in limestone or marble host rocks
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because limestone and marble neutralizes the acidic nature of a hydrothermal solution, causing minerals tthat remain dissolved only in acidic water to precipitate
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explain the process of metal exchange also know as ion exchange
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when a metal in solution encounters a metal in the host rock that is MORE soluable than it, the two metals exchange places (this assumes that the requirements of ionic size and magnitude of charge are met)
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what does a hydrothermal solution become when it reaches the surface of the earth
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hot spring
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for what 2 reasons is the mineral content of a hot spring relatively low
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1. by the time a hydrothermal solution reaches the surface, most of what it has in solution has already precipitated
2. as it approaches the surfaces it mixes with normal ground water and surfaces water and becomes diluted |
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what three minerals are most characteristic of hot spring deposit
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opal, aragonite, and cinnabar
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what is a precipitate
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a precipitate is a mineral that precipitates from surface water without the necessity of excessive sea water evaporation
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5 minerals most common form as precipitates
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calcite, aragonite, chalcedony, glauconite, phosphorite (apatite)
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what is the dolomite problem
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an unsettled issue, some clame dolomite precipitates from sea water, others claim it forms from the addition of magnesium to preexisting limestone
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what is an evaporite
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a mineral that precipitates from sea water ONLY AFTER excessive evaporation (80% evap required)
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what is always the first mineral to form in a body of evaporting sea water
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anhydrite
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what causes anhydrite to change to gypsum
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anhydrite changes to gypsum when water is added to the atomic structure
CaSO4 + H2O = CaSO4'H2O |
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what causes gypsum to change to anhydrite
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water is removed from gypsum
CaSO4'H2O - H2O = CaSO4 |
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what is the second evaporite to form in a body of evaporating sea water
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halite
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at what stage of hte game does sylvite precipitate from water
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sylvite precpitates after 98% has evaporated
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what is the origin of glauconite
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only precipitates from sea water in the presence of undecayed fecal matter on the sea floor
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what minearls are most associated with LAKE precipiation?
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kernite, boraz, soda-niter?, colemanite, ulexite
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of what importance are lake evaporites
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lake evaporites provide most of the worlds supply of boron, nitrogen, and the relatively heavy halide elements such as bromine and iodine
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what is a resistate
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a mineral that once formed never chemically weathers to form another mineral
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name 4 metallic and 4 nonmetallic resistates
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metallic:magnetite ilmenite rutile cassiterite columbite and gold
nonmetallic:quartz chert zircon andalusite topaz hematite and limonite |
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what are 2 major agents of chemical weathering?
what is hydrolysis? |
water and oxygen
hydrolysis is a form of chemical weathering in which surface water changes a mineral into a diff mineral |
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what 4 chemical elements occur in all memebers of hte clay family
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aluminum, silicon, oxygen, and hydrogen
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what specific minerals weather to form kaolinite
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k felds and na felds
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what 2 mineral families are the most susceptible to hydrolysis
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feldspars and feldspathoids
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what specific minerals weathers to form montmorillonite
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ca felds
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what 2 factors most control what specific minerals form during chemical weathering
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1.chemical composistion ofthe mineral being weathered
2. the specific chemical weathering process (hydrolysis, oxidation, reduction) |
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what very unique property is possessed by all member of the clay family
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they all have the ability to absorb large quantities of water thus sweling several times their original dry volume
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what is montmorillonites claim to fame
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can absorb several hundred times more water than its original dry volume
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what is laterization
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complete removal by solution of silicon from a member of the clay family
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what member of the big 8 is absolutely most resistant to solution in water
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aluminum
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what specific mineral forms from laterization
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bauxite and diaspore
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under what climatic conditions does laterization occur
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extremly hot and humid conditions
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what is oxidation
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oxidation is a form of chemical weathering in which oxygen in the air alters the composition of a mineral
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what 3 groups of minerals are particularly susceptible to oxidation
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Fe bearing, Mn bearing, and the sulphides
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name 4 minerals that form exclusively from oxidation
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hemtite, goethite, limonite, pyrolusite, manganite
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whatis hydration and dehydration of a mineral
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hydration is hte addition of water to the chemical composition of a mineral, dehydration is the removal of water from teh chemical composition of a minearl
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what is the zone of oxy0enrichment and what minerals form there
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the zone in which dissolved metals from teh zone of leaching (?) are reprecipitated in the presence of oxygen (above the water table)
cuprite, malachite, azurite,, chrysocola, turquois, cerrusite, smithsonite |
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what is the zone of supergene enrichment and what minerals form there
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the zone in which dissolved metals from the zone of leaching are reprecipitated in the absense of oxygen, below the water table
chalcopyrite, bornite, covellite, chalcocite, native copper |
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what mineral forms when copper bearing solutions react with:
pyrite below the water table? |
chalcopyrite
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what mineral forms when copper bearing solutions react with:
chalcopyrite below the water table |
bornite
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what mineral forms when copper bearing solutions react with:
bornite below the table |
covellite
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what mineral forms when copper bearing solutions react with:
covellite below the table |
chalcocite
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what mineral forms when copper bearing solutions react with:
chalcocite below the table |
native copper
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what always happens to the percentage of a chemical element in a mineral that forms by supergene enrichment?
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it always increases
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why does metamorphism occur
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because most rocks and minerals respond to a change in their environment. This change often results in formation of one or more new minerals that are more stable in the new environment.
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name FIFTEEN minerals that form from either exclusively or almost exclusively by metamorphism
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sillimanite andalusite kayanite talc staurolite tremolite actinolite epidote diopside wollastonite serpentine glaucophane clorite forsterite graphite the garnets the zeolites
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name 4 factors that control what minerals form during metamorphism
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1. the minerals in the parent rock
2. the agent of metamorphism 3. the intensity of metamorphism 4. the presence or absence of water |
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what are three agents of metamorphism
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1. direct pressure
2 heat 3. hydrothermal solutions, known in physical as "hot water" |
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in what two ways are high grade metamorphic minerals different from low to med grade minerals?
what is the reason for these 2 differences? |
1. they do not contain HYDROXIDES (which is derived from water)
2. they consist of relatively few chemical elements Water is driven out of the high grade zone due to the high heat and energy environment associated with high grade metamorphism. As the water leaves, it dissolves soluble cations and removes them from the HIGH GRADE zone, leaving fewer different chemical elements |
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what is meant by retrograde metamorphism?
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is a type of metamorphism in which rocks and minerals formed during a particular metamorphic event are remetamorphosed to a lower grade during a subsequent metamorphic event
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what is the only way to know FOR SURE that a rock or mineral underwent retrograde metamorphism?
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the rock contains psuedomorphs
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for what 2 reasons do HIGH GRADE metamorphic minerals NOT revert back to their original parents as they become exposed to low pressuers and temps at the earths surface?
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1. chemical elements that were driven out of the parent during metamorphism are usually NOT put back into hte rock when it becomes exposed at the surface
2. the high-energy needed for bond-breaking (necessary so old minerals can be converted to new ones) is not availible at the surfaces. Thus, high grade metamorphic minerals are usually preserved. |
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what is contact metamorphism?
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contact metamorphism is the heat-induced changes that occur in the host near a body of hot magma. Hornfels forms from contact metamorphism.
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although not visible to the eye, what is most often the predominant mineral in the metamorphic rock HORNFELS when shale is the parent rock?
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ANDALUSITE typically fromed in low pressure HIGH TEMPERATURE environment, as is hornfels
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what is regional metamorphism
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is a metamorphic event htat effects a significantly large region of continent. Regional metamorphism occurs most often along convergent plate boundries. Foliated metamorphic rocks form from regional metamorphism
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what family of minerals typically forms in low temp low pressure environment of subduction zone? how?
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the zeolites. They form from a hot water metamorphism of the feldspars.
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what one unique mineral forms in the very strange high pressure but low temp environment
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glaucophane
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since subduction is a natural part of the plate tectonic process, why is hte mineral referred to in the previous question not more common
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because glaucophane continues to subduct and goes deeper it moves into a high temp environment whcich changes glaucophane to hornblende
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why does the subduction process make lots of serpentine
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serpentine forms from hot water metamorphism of olivine aboce a subduction zone because teh hot water released from subducted ocean floor ascends into the overriding place, much of which is made of olivine rick rock peridotite
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what happens during metamorphism to cause forsterite to form
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during the hot water metamorphism of olivine (MgFe)2SiO4, water completely dissolves the iron leaving only forsterite Mg2SiO4
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