ES 100 Midterm 1
What SiO2 polymorph forms in igneous rocks?
alpha quartz comes from silicic volcanic ash
Why do many basalts have LREE enrichment?
crsyal fractionalization incompatible separte out earlier create sections of own minerals
For H2O, there is water and steam but what is H2O fluid? What is happening?
diff btwn fluid an liquid: fluid high pressure cant go to gaseoues state
Why are rhyolites hotter than their plutonic counterparts?
dry gaseous
Why does adiabatic decompression lead to mantle melting?
dry in mid ocean ridges, oi, cf basalts
Why are rhyolites hotter than granite?
dry less wet lower melting point
Which two bonds allow a high degree of electric conductivity in minerals and why? Please offer an mineral example of each.
electrons free to move throughout the structure. metallic: Zn, Fe, Cu, Au
Why do many granites have subequal amounts of quartz, alkali feldspar, and plagioclase?
eutectic in middle tetery diagram so equal composotion of each all melt at same point
What is a eutectic? peritectic?
eutectic- the lowest possible melting point of the mixture of two minerals peritectic- the point on the liquidus indicating the composition of the liquid
What causes the "play of colors" (called schiller or iridescence) in some plagioclase feldspars? Explain.
exsolution of minerals create thin layers that defract the light which creates irridence
What is a fissure eruption? Pahoehoe lava? Aa lava? Pele's hair?
fissure eruption: magma leaks out of earth through crack pahoehoe: ropey aa: blocky peles hair: glassy strings
Why is serpentinite termed the "spirit of oceans past"?
found where ancient oceans used to be before the land was destroyed through subduction
What is a nebula?
gas and dust clouds contract under gravitational forces
Why are magmas buoyant?
heating
How does H20 dissolve in magma?
high pressure
What is the Phase Rule? How many degrees of freedom occur at a eutectic or peritectic? What is the consequence of fixed pressure?
number of degrees of freedom= the variation of temp, pressure, composition. once pressure fixed everything else constant
Name a mineral that has the following property: Taste Soluble in weak HCl acid Magnetic attraction Pyro- and piezoelectricity
taste: borax, halite soluble in weak HCl acid: calcite magnetic attraction: magnetite pyro- and piezoelectricity: quartz
What governs how shallow a magma will rise?
temperature and volitiles
Why do magmas rise before melting can proceed to a large percentage?
warm magma boyant and rises loses volitailes as it rises
What is a distribution coefficient as related to crystals and melt? How can it be used to predicted element trends during fractional crystallization? What happens when D >1, D=1, and D<1
separation between 2 compositions of minerals incompatible minerals stay liquid compatible turn to solid equal composition
Why the ocean crust age symmetrical age distribution?
symmetrical age distribution to the ridge due to sea floor spreading and subduction, mapping of sea floor after WWII width of bands reveal rate of sea floor expansion average of 6cm/year
How can some minerals be used to date the origin of the earth's crust?
zircon-> contain radioactive elements like uranium to lead or potassium to argon
What is the origin of carbonatites?
The reason for this is the nature of the lava which is so rich in sodium that it has an unusually low melting temperature -- somewhere in the range of about 1000 degrees F (about half that of basaltic lava)
What is ionization potential?
The relative ability to withdraw an e-., the ease of ionization The lower the IP,the greater the ease of ionization
What controls the density or specific gravity of a mineral?
The specific gravity of a mineral is the weight of that mineral compared to the weight of the same volume of water. Specific gravity is related to the density of a mineral.
What is the nature of solid solution of olivine? Please draw a phase diagram of Fo-Fa vs. temperature. Show how it works for a given melt composition.
(Mg,Fe)2SiO4
What is the solid solution of olivine?
(Mg,Fe)2SiO4
What is the nature of continental crust? How is they can have such old crust? What mechanisms lead to continental growth? What rocks are common?
30 - 70 km thick,Dating back to 4.0 b.y., less dense than ocean crust Granitic rocks are common, 1/3 quartz, plagioclase, and K-feldspar+ hornblende, biotite, muscovite. Dual processes of continental growth: magmatism and accretion
Describe the origin of the solar system and Earth.
4.56 b.y. most of nebula formed Sun, some material in solar disc to form planets, moons, asteroids, meteorites, comets
Name two examples of metamorphosed basalt. Where do they form?
Accretion - the other half of continental growth, Fault emplacement of oceanic and continental "suspect" terranes, High pressure metamorphism. Blueschist, Serpentinite
How did the core, mantle, and crust of the earth form? What is their composition? What fueled this?
Accretion of primordial solar material, kinetic energy from material created heat, gravitational compression, meteorite impacts, radioactive decay. Energy released by sinking iron and nickel created molten core magnetic field. Mantle, lower density materials would have risen from core, convective cooling. Core: iron and nickel Mantle: silica rich Crust: solid silica material
Draw Bowens reaction series. Which part of it has the minerals in basalt? andesite? rhyolite?
Basalt- highest temp andesite- middle rhyolite- lowest temp
What is the significance of congruent melting? What is the petrogenetic significance of a thermal divide? Please give show an example.
An intermediate, congruent-melting phase creates a thermal divide that cannot be crossed except by external influences.
What are feldspathoids? How are they related to feldspars? Name an example and what rocks have these?
Anhydrous framework silicates similar to feldspars, but with lower SiO2 content. tend to form from melts rich in alkali's and poor in silica. Although they are far less common than the feldspars, the unique settings in which feldspathoids occur are often of great tectonic and economic importance. Where present in sufficient quantity and purity. leucite, nepheline, kalsilite and sodalite. Igneous rocks.
What is the rock composition of ocean crust?
Basalt and gabbro 1/2 plagioclase 1/2 Olivine, Pyroxene Melting of mantle peridotite Crust - 7 to 10 km
What are the common minerals in basalt or gabbro? andesite or diorite? rhyolite or granite?
Basalt/gabbro:(Ca)plagioclase, amphibole, pyroxene, olivine, ferromagnesium minerals andesite/diorite: (Na,Ca)plagioclase, amphibole, pyroxene, ferromagnesium minerals rhyolite/granite: quartz, orthoclase, (Na)plagioclase, mica, amphibole
What is the Van der Waal's bond? What mineral properties does it lead to. Offer two examples.
Between molecules, e.g., layers of graphite, talc Weak attraction, Very soft, High compressability, thermal expansion. Talc, Graphite
What is the nature of pyroxene solid solution? Show this in a composition phase diagram. Where is the immiscibility gap or solvus?
Ca,Fe,MgSi(1-2)O6 Bottom left of pyramid between CaMgSi2O6 and Mg2Si2)6
What causes some minerals to be colored?
Caused by the absorption, or lack of absorption, of various wavelengths of light-Some trace elements produce colors Usually transition metals
How can minerals be used to determine the pressure and temperature history before arrival at the earth's surface?
Certain minerals can only form at certain levels of temperatures and pressure levels
Offer a mass balance numerical model of assimilation.
Ch=xaca+xbcb
What is cleavage in a mineral? Offer some examples.
Cleavage - breaks along flat planes, 1 plane - mica 2 planes - feldspar,3 planes - calcite, halite,4 planes - fluorite, 6 planes - sphalerite
What are compatible and incompatible elements? How do each change with increasing silica? Why?
Compatible Elements: Mg, Ca, Fe, Al, Ti - concentrated in early minerals- decrease when silica increases Incompatible Elements: K, Na, H2O - enriched in evolved melts- increase when silica increases
What is congruent melting? Incongruent melting?
Congruent melting- the solid and liquid have the same composition Incongruent melting- melt to form a liquid of different composition
What leads to covalent bonding between atoms? What are the properties of minerals with a high degree of covalent bonding? Offer an example.
Covalent bond - atoms with high EN. when electrons are shared. Occur among identical atoms or those close together on periodic table. are the strongest type of bond, form the hardest minerals, highest melting temps. are directional, angle of the bonds in controlled by orientation of the shared orbitals. Quartz, diamond, graphite
What is the evidence for a dead planet or moon and one that is geologically alive?
Dead planet: lack of tectonic plate movement, no atmosphere, huge crater impacts geologically alive: tectonic plates, volcanic activity, magnetic field, atmosphere
What are the two processes that lead to volatile loss (boiling) and how does this effect magma composition and the nature of eruptions?
Decompression boiling (beer bottle effect) Wet vs. dry solidus. Wet magmas are cooler and are emplaced deep. Dry magmas are hotter and can rise to shallow or surface levels Crystallization boiling All magmas eventually boil due to crystallization of anhydrous minerals.
What governs magma density? viscosity?
Density- determined by composition viscosity- the higher the silica content the higher the viscosity
What amphiboles are stable at greenschist metamorphic grades? blueschist metamorphic grades? in igneous rocks?
Derived from basalt ocean crust, The blue mineral is glaucophane, a sodic amphibole. Actinolite in greenschist igneous amphibole- horneblende
Why are diamonds so hard and graphite so soft?
Diamond - SP3 covalent bond Graphite -SP2 covalent bond
What is the origin of diamond? How does it arrive into the Earth's upper crust? What drives these rapidly rising intrusions? How does this happen? Why are diamonds only found in continents?
Diamonds in kimberlites are xenocrysts, "foreign" minerals captured by the rising magma while deep in the Earth's mantle. Most are old, and date from the Archean. Kimberlites (mica peridotites) are ultrapotassic & ultramafic magmas rich in CO2.The CO2 is capable of propelling the magma explosively upward at velocities 400m/sec through a pipe-shaped structure. Diamonds are a high P polymorph of carbon. Such conditions are only found in the mantle, below 100 to 150 km.
What are galaxies? How many are there?
Dispersed matter clusters, forms gravitational force, form nebula, collapse into flat rotating disk, once big enough gravitational collapse and fusion begins to create star, residual matter creates planets, etc. 125 billion galaxies with new estimates of 2 trillion.
What is the evidence that led to the Big Bang Theory? When did it occur?
Edwin Hubble discovered that a galaxy's velocity is proportional to its distance. Doppler effect red furthest away moving away. Universe continually expanding. Big Bang about 13.7 billion years ago.
What was the Big Bang?
Essentially a huge supernova, debris from explosion hurled at high speeds, material dispersed throughout space
For mantle peridotite to be fertile, that is capable of melting to produce basalt, it needs an aluminous phase. What are these minerals and how do they change with pressure (depth)?
Fertile mantle - capable of producing alkali basalt
Forsterite olivine never coexists with quartz but fayalitic (Fe rich) can. Why is this?
For compositions where opx is stable; olivine and silica do not coexist, For iron-rich compositions, fayalite and silica are stable as intermediate opx is not.
What is the origin of ocean islands (not island arcs)? Why are they age sequenced?
Hot spots. Age sequenced as the plate moves the hot spot stays in the same spot therefore the speed of the plate can be traced
What are I-type, S-type, and A-type granites?
I- from an igneous source, often hornblende bearing S- Usually muscovite bearing, plus other aluminous minerals A- Meaning alkalic, anydrous, and anorogenic - and often red
How was the core of the Earth imaged? What is its structure and composition? What field of force is created by the core? How does this happen? Why is the inner core solid?
Inner Core: The inner core begins about 5100 km beneath the crust. The pressures are 45,000,000 pounds per square inch. Solid due to pressure. Fe-Ni alloy, plus sulfur Outer Core: The outer core is so hot that the metals in it are in the liquid state. The outer core is located about 2900 km beneath the crust and is composed of the melted iron and nickel, plus sulfur. Magnetic field created by core. created by convection of outer core
What are the two atomic structures of iron? Please make a sketch of each. Which one exists in the deepest portions of the core? What holds the atomic structure together? What property does this lead to?
Inner core: iron body centered cubic outer: face centered cubic
What is the nature of solid solution for alkali feldspars? Please draw a phase diagram for Or-Ab vs. temperature. Show how it works for a given melt composition.
KAlSi2O8 to NaAlSi2O8
What is the solid solution in biotite mica?
KMg3[AlSi3]O10(OH)2 : phlogopite KFe3[AlSi3]O10(OH)2 : annite K[Mg2Al][Al2Si2]O10(OH)2 : eastonite
What are the three polymorphs of Al2SiO5? Please draw their stability fields on a P-T diagram.
Kyanite, Andalusite, Sillimanite.
Name some varieties of luster and offer some mineral examples
Luster is the appearance of a mineral's fresh surface in reflected white light, divided into metallic and non-metallic: metallic, silky, vitreous, gumdrop. Topaz, Gypsum, apatite, magnetite, artintite
What is the significance of magnetite- vs. ilmenite-series granites? How does this relate to the composition of biotite?
Magnetite- High fO2, Mt > Ilmenite, Biotite with low Fe/Mg Ilmenite- Low fO2, Ilm >magnetite, Biotite with high Fe/Mg with > O2, biotite becomes Mg rich and oxides become dominated by magnetite
What is the source of ocean basalt?
Mid-ocean ridges. MOR Basalt - from the asthenosphere (depleted mantle)
What is a mineral? A rock?
Mineral: a naturally occurring solid, ordered atomic arrangement, definite chemical composition, formed by inorganic processes rock: a naturally occurring consolidated mixture of minerals
What is the fuel of the Sun? How did it form?
Mostly helium and hydrogen, 10,000F, H fusion. Most of material from nebula collapsed inward to form Sun
What is the nature of solid solution for plagioclase feldspars? Please draw a phase diagram for An-Ab vs. temperature. Show how it works for a given melt composition
NaAlSi3O8 to CaAlSi2O8
What are the seven silicate structures? Offer one mineral example of each.
Nesosilicates ("islands") - olivine Sorosilicates ("paired islands") - epidote Cyclosilicates (rings) - tourmaline Inosilicates (single chains) - augite Inosilicates (double chains) - amphiboles -> horneblende Phyllosilicates (sheets) - micas- > muscovite mica Tectosilicates (frameworks)- quartz
What is the origin of the following rock textures: Obsidian Vesicular tecture Pyroclastic Aphanitic Phaneritic Equigranular phaneritic Porphyritic aphanitic or phaneritic Pegmatitic Foliated Lineated
Obsidian- volcanic, silicic, and rapid quenching Vesicular tecture- gases frozen into stone during outgassing Pyroclastic- violent breakage during explosive eruption Aphanitic- volcanic or shallow intrusion Phaneritic- plutonic, slow crystallization Equigranular phaneritic- uniform crystallization Porphyritic aphanitic-early slow cooling followed by rapid crystallization; volcanic or shallow intrusion or phaneritic- Early slow cooling later more rapid in a deeply-emplaced magma Pegmatitic- large plutonic crystals, usually at water saturation Foliated- strain fabric in layers; a zone of ductile shear - termed an orthogneiss Lineated- a linear fabric; indicative of stretching
Describe how silica saturation works. What mineral exist when silica oversaturated, saturated, and undersaturated?
Over saturated - quartz present Saturated - no quartz; feldspars and pyroxene perfectly saturated Undersaturated - olivine and feldspathoids present
Explain the alumina saturation principle. What is peraluminous, metaluminous, and peralkaline? What minerals occur in rocks of each?
Peraluminous - excess Al-that alumina (Al2O3) first goes to feldspar. After feldspars, if there is an excess, aluminous minerals can form such as muscovite, garnet, and sillimanite. Metaluminous- Al deficiency, then the excess Ca can form other calcic minerals, such as hornblende, augite, and titanite (sphene). Peralkaline- Al deficiency relative to alkalis, then sodic pyroxene (aegirine) and amphibole (riebeckite) can form.
How does perthite form?
Perthite - exsolution lamellae of albite in host of orthoclase At low temperature, one phase unmixes to become two phases
What is the solid solution for alkali feldspar? Plagioclase? Show their range of composition on an An-Ab-Or diagram.
Plagioclase: Exchange: CaAl = NaSi
What leads to ionic bonding between atoms? What are the properties of minerals with a high degree of ionic bonding? Offer an example.
Positively charged cations attract negatively charged anions. Occur among atoms that are far apart on the periodic table. are weaker than covalent bonds, but stronger than metallic bonds. form mineral bonds that are soluble in water. are non-directional, anions and cations can be approximated as charged spheres that pack closely together in mineral structures. Halite
What controls the hardness of a mineral? Offer some minerals and their hardness on Mohs Scale.
Related to the atomic structure of the mineral,Minerals with strong covalent bonds are the hardest, Softest minerals have metallic or van der Waals bonds. 10-diamond, 9-corundum, 8-topaz, 7-quartz, 6-orthoclase, 5-apatite, 4-fluorite, 3-calcite, 2-gypsum, 1-talc
What is tenacity of a mineral? Offer some examples.
Resistance to breaking. Brittle - breaks and powders easily (e.g., quartz, feldspar)Malleable - can be hammered into thin sheets (e.g., gold, copper)Sectile - can be cut into thin shavings (e.g., gypsum)Ductile - can be stretched into a wire (e.g., gold, silver)Flexible - can be bent but not elastic (e.g., chlorite)Elastic - can be bent and return to original position (e.g., mica)
What are the polymorphs of K-feldspars and in what types of rocks are each found?
Sanidine, the high T polymorph, has the highest monoclinic symmetry (2/m). Occurs in rhyolites Orthoclase from Greek for "straight fracture," because its two cleavages are at right angles to each other. Monoclinic; occurs in granites Microcline is the lowest T polymorph is triclinic. The cystal face is slightly less than right angles; hence the name "microcline" from the Greek "small slope." Occurs in pegmatites and metamorphic rocks.
What are the three polymorphs of KAlSi3O8? Which on forms at the highest temperature? Lowest temperature?
Sanidine, the high T polymorph, has the highest monoclinic symmetry (2/m). Occurs in rhyolites Orthoclase from Greek for "straight fracture," because its two cleavages are at right angles to each other. Monoclinic; occurs in granites Microcline is the lowest T polymorph is triclinic. The cystal face is slightly less than right angles; hence the name "microcline" from the Greek "small slope." Occurs in pegmatites and metamorphic rocks.
How can volatile metasomatism lead to mantle melting? Where does such occur and what is the dominant volatile and its origin? What is the volcanic rock type that is produced?
Sea Water Fluxing the mantle wedge when sea water present=> andesite subduction zones
How is the heterogeneity of the mantle imaged? What is happening? What are "subduction graveyards"?
Seismic tomography reveals considerable heterogeneity in the mantle: Subduction graveyards- where plates stop, Deep plumes
How does a star form? Supernovae? What elements are formed in each ?
Star accumulation of debris that creates gravitational field high pressure and temp cause fusion of hydrogen and helium-> only light elements lithium, beryllium, boron
Which SiO2 polymorphs form in high pressure conditions, including impact craters?
Stishovite- forms at extreme pressures so great that silica tetrahedra break down and silicon assumes six-fold coordination.. The most common occurrence are meteorite craters. Coesite - formed by deep burial of crust, really deep and all due to collisional processes and meteorite impact
What are the two types of subduction? What rock is uniquely volcanic in subduction zones. What are the two melting origins of this volcanic rock? Explain.
Subduction Volcanism, Accretion. Volcanic- Andesite - melting of basalt ocean crust or the hydrated mantle wedge, Plagioclase + Hornblende + Pyroxene + Magnetite, Gaseous, viscous, and prone to explosion. Rhyolite- Melting of andesite or continental crust,The most explosive, Volcanic equivalent to granite,Sanidine, quartz, plagioclase, biotite, hornblende.
In what tectonic settings do we find tholeiitic rocks? calc-alkaline rocks? alkaline rocks?
TH: ol thol basalt, thol, qtz thol, thol andesite, dacite, rhyolite, Settings: MOR, immature IA, near-trench mature IA, CFB CA: high Al basalt, basaltic andesite, andesite, dacite, rhyolite, Settings: Mature IA (island arcs) and active continental margins ALK: nephelinite, basanite, alkali ol basalt, trachybasalt, trachyandesite, trachyte (=syenite), phonolite (=neph syenite) Settings: OI (ocean islands), CR (continental rifts), BA (back arcs)
What is electronegativity?
The ability of an atom to attract electrons Low for metals atoms, high for non metals
What is the origin of the Earth's magnetism? How does it protect the planet? How was it used to prove continental drift?
The convection in the molten metallic outer core. Diffuses UV radiation, new crust at midocean ridges has magnetic anomalies due to periodic reversals in magnetic field, anomalies are split apart, correlate age anomalies on either side
What is the D" layer? How does it form? How does it lead to mantle plumes or "hot spots"? How do the latter respond to plate tectonics?
The lower mantle contains a heterogeneous region with thickness 200-300 km, called D". Sitting atop the core-mantle boundary, this layer has been credited with a diverse array of behavior/phenomena, from scattering of seismic waves, to partial melt and the source of mantle plumes that carry heat all the way to the surface. mantle reheated in the D'' layer and rises again
What is tholeiitic vs. calc alkaline? What controls the different trends of magma evolution in a AFM diagram?
Tholeiitic rocks are characterized by low Al and iron enrichment over Mg Calc-alkaline rocks have high Al and low Fe/Mg. water content and oyxgen
What is the rock cycle and how do minerals respond as they encounter new geologic conditions, including melting, weathering, sedimentation, hydrothermal activity, and metamorphism. Name some minerals formed in each environment.
Throughout the rock cycle, chemical reactions are destroying older minerals and replacing them with new ones stable in that environment. Each geologic process produces its own unique set of minerals. melting: Igneous: bowen's Reaction series, olivine, pyroxene- horneblend, biotite weathering: low temp processes: gypsum, quartz, gruss-weatherd granite sedimentation: low temp: calcite, dolomite- clays, zeolites hydrothermal activity: hi to low temp: gold, silver, sulfides metamorphism: moderate to high P, T: garnet, muscovite, epidote
What is the origin of the Earth's early atmosphere? How did it change with time? What is the evidence for its change?
Volcanoes outgasing, creates clouds, precipitation, early oceans, oceans absorb greenhouse gases. limestone fossils
What are the economic uses of quartz?
abrasives, cement mortar, glass making, optics, submarine detection, oscillators, time pieces, high pressure experiments,
Why is melting in the mantle capable of producing such great volumes of homogeneous basalt?
all composotions of the melt reach the eutectic all ends up at the same composotion and temp
What is the asthenosphere, lithosphere, atmosphere, hydrosphere, and biosphere of Earth?
asthenosphere: mantle 700km deep, hot & weak lithosphere: crust and uppermost mantle, cool & rigid atmosphere: gaseous envelope around earth hydrosphere: dynamic mass of liquid, vapor, solid water biosphere: where life exists: consists of parts of the lithosphere, hydrosphere, and atmosphere
What is a batholith? stock? pluton? dike? sill?
batholith- large bodies of grantitic rock exposed on surface and go deep into crust <100km, diapir shape, contain basalt, most likely gets heat from mantle intrusions of basalt stock- smaller bodied batholith, cylindrical shape, composition not limited to granite >100km, feeds into crust pluton- smaller than a batholith dike- discordant sheet that cuts across rock layers sill- concordant sheet that parallels rock layers, able to be thicker than dikes
What is a cinder cone, a shield volcanoe, and lava plateau?
cinder cone: fountaining of cinder build up of pyroclast basalt cinder shield volcano: fissure eruptions build up high standing pieces of land made out of basalt lava plateau: fissure eruption that fills land depressions, climate effect
Why are andesite and rhyolite so explosive when they erupt?
high viscousity and silica content
What two settings form ocean crust?
hot spots and divergent faults
What is the origin of quartz veins?
hydrothermal vents
What is a hypersolvus granite? subsolvus granite? What are the P-T implications? Why are only pegmatites, aplites, and leucogranites applicable to this classification?
hypersolvus: crystallizes above the alkai-feldspar solvus creating one feldspar creates perthite(unmixing of albite and orthoclase) subsolvus: cystallizes below solvus get two diff types of alkai feldspar at once P-T implications
What is an anorthosite? Lherzolite?
igneous rock 90% plagioclase l: variety of perdiotite from midocean ridge
What happens at the 400 and 650 km discontinuity in the Earth's upper mantle?
interefremce of S wave and D'' layer start
Draw a two-component phase diagram for minerals having solid solution such a Fo-Fa or An-Ab. What is the liquidus? the solidus? Show a liquid path for equilibrium crystallization. How can a liquid continue to lower temperatures?
liquidus- a curve in a graph of the temperature and composition of a mixture, above which the substance is entirely liquid. solidus- a curve in a graph of the temperature and composition of a mixture, below which the substance is entirely solid.
What is plate tectonics and the three types of plate boundaries?
lithosphere broken into 8 major plates, convection of mantle and movement of lithosphere, related to earth's cooling Divergent: pulling apart, midocean ridge with median valley, dense. if on contintenal plate causes rift valley convergent: one plate subducted beneath the other, older denser crust sinks. continental crust sinks or crumbles form orogenic belts
What is the lithosphere of the Earth? the low velocity zone? the asthenosphere? How does the latter lead to plate tectonic movement of the lithosphere?
lithosphere: the crust and upper mantle of the earth asthenosphere: contains partial melt of the mantle material. convection of the plastic like mantle causes movement low velocity zone: occurs close to the boundary between the lithosphere and the asthenosphere in the upper mantle. It is characterized by unusually low seismic shear wave velocity compared to the surrounding depth intervals
What SiO2 polymorph forms at low temperature? What are some of the mineral examples?
low temp: quartz tridymite, quartz, cristobalite, coesite, stishovite
How does the granite solidus temperature change with increasing PH2O?
lowers
How do "hot spot ocean plumes form? How are they not part of plate tectonics?
mantle plume originating from deep and enriched mantle. maybe D'' layer on core-mantle boundary. extremely hot rise through plates forming hot spots on surface
What are mantle plumes and hot spots?
mantle plumes: from deep mantle D'' layer near core mantle boundary large mushroom shape, break through crust and release magma creating a hot spot trail
What is a mass balance equation? Show one for melt and solids.
mass balance Co = XLCL + SumXsCs CL = (Co-SumXsCs)/(XL) Where Co = concentration of original liquid CL = concentration of derived melt Cs = concentration of solid(s) XL = wt. fraction of melt (liquid) Xs = wt. fraction of solids
What are the two origins of andesite?
melting of mantle wedge at subduction zone and fractional crystallization of baslaitc magma
What are some useful products made from minerals?
metals, rubber, fertilizer, plastics, medicines
What are the implication of mafic enclaves? Mafic schlieren?
more mxing than mingling pancake batter globs are enclaves two diff kinds of magam sclieren same type of magma separated
What is the difference between equilibrium crystallization and perfect Rayleigh crystallization?
opposites E: maintain composition with varied crystallization, mass balance no loss of element, no removal PR: crstallys removed, everything crystallized immediatley removed
What is pahoehoe and aa lava? What causes the difference?
pahoehoe- ropey, slow flow, aa- blocky, fast flow,
What structures are indicative of magma mingling?
pankcake globs
What rock type forms the upper mantle? What is its mineralogy when fertile, that is capable of melting to form basalt? What is it's mineralogy when depleted by melt extraction and no longer capable of producing basalt?
peridotite fertile-> aluminus plagioclase, spinon, garnet depending on pressure. depleted-> olivine, or orthoperoxyene and no longer aluminus
What is pumice? Scoria? Volcanic tuff and breccia? Pillow lava?
pumice- lighter colored, air holes, light, vesicular glass scoria- vesicular basalt, dark color, larger holes, less holes tuff- fine volcanic ash breccia- chunks of broken up rock pillow lava- lava that cooled in the ocean in a pillow shape
What leads to metallic bonding between atoms? What are the properties of minerals with a high degree of metallic bonding? Offer an example.
result when loosely bound valence electrons move freely throughout the structure-shared by many atoms, not just two, explains the high conductivity of metals. are common in transition metals (Zn, Fe, Cu Au). are the weakest bond types.
What is liquid immiscibility and offer four examples? How does this happen? What is their economic importance?
separation of liquid, one turning into two a single magma evolves through fractional crystallization or other process to a state where it unmixes. silicate- magnetite (iron deposits) silicate - carbonate (carbonatites) silicate - sulfide (massive sulfides) silicate - silicate (alkali gabbro -syenite) produce rare earth metals
What is a "smoker"? Where are they found? What are the minerals?
smoker: hydrothermal vent. found along mid ocean ridge. minerals are sulfides, gold, silver, quartz
What is meant by the following terms: solidus liquidus eutectic peritectic cotectic incongruent melting
solidus:a curve in a graph of the temperature and composition of a mixture, below which the substance is entirely solid liquidus:a curve in a graph of the temperature and composition of a mixture, aboce which the substance is entirely liquid eutectic: a mixture of substances (in fixed proportions) that melts and solidifies at a single temperature that is lower than the melting points of the separate constituents or of any other mixture of them. peritectic: reaction when solid melts incongrunetly a liquid and solid that are different from original solid cotectic: line of two diff compostion consititing at once incongruent melting:
Why is ocean crust young, less than 220 my?
subduction, old ocean crust very dense and most likely to sink down and be melted, divergent plate boundaries create new ocean crust
What is the cause of a negative Eu anomaly?
suggests plagioclase feldspar
What is the difference between the terrestrial and gas giant planets?
terrestrial: inner disc, high temps, carbon , nitrogen, hydrogen present as gases. Solid material of silicon, magnesium, iron-> small planets limited elements gas: lower temp, water, carbon dioxide, ammonia, methane more abundant larger planets
What is the habit of a mineral. What are some minerals and their characteristic habit?
the external shape (appearance) of a mineral, the way the mineral naturally grows. Galena-cubic, diamond- octahedron, Quartz-prismatic, pyrite-striated
What are the mechanisms of fractional crystallization?
the process of crystallizing and removal of crystals from the magma, composition of crystals is different than magma, results in chemical change in the magma, high temp minerals crystallize first and melt last
Why are wet magmas incapable of ascending to shallow levels?
turn to solid rock before reaching surface