native elements, sulfides, oxides, & hydroxides jd price
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Native elements, sulfides, oxides, & hydroxides
Native elements, sulfides, oxides, & hydroxides
JD Price
Gold AuSilver AgDiamond CGraphite CSulfur S
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Native ElementsNative Elements
Gold depositsGold deposits
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Cyanide LeachingCyanide Leaching
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NaCN combines with Au or Ag to form a liquid. Gold can be removed from the gangue.
4Au + 8NaCN + O2 +2H20 = 4Na[Au(CN)2] +4NaOH
This is employed at a number of scales.
Sphalerite ZnSChalcopyrite CuFeS2
Bornite Cu5FeS4
Tetrahedrite Cu12Sb4S13
Octahedral coordinationPyrrhotite Fe1-xS2
Galena PbSNiccolite NiAs
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Tetrahedral SulfidesTetrahedral Sulfides
Image from Klein and Hurlbut, 1993
Tetrahedral SulfidesTetrahedral Sulfides
Molybdenite MoS2
Arsenopyrite FeAsSMarcasite FeS2
Pyrite FeS2
Stibnite Sb2S3
Orpiment As2S3
Realgar AsSCinnabar HgSCovellite CuSChalcocite Cu2S
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Other SulfidesOther Sulfides
Pyrite
Arsenopyrite
Marcasite
Image from Klein and Hurlbut, 1993
Image from Klein and Hurlbut, 1993
Marcasite habitMarcasite habit
CoveliteCuS
Image from Klein and Hurlbut, 1993
WHOI
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Seafloor Hydrothermal “Black Smoker” DepositsSeafloor Hydrothermal “Black Smoker” Deposits
Grow as fast as 30 centimeters per day. Begins with a ring of anhydrite around a jet of 350°C fluid, which exits the seafloor at velocities of between 1 and 5 meters per second
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WHOI
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MVTMVT
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Migration of hydrothermal fluid and its interactions with limestone form large sulfide deposits
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Tri-state (KS-OK-MO)Tri-state (KS-OK-MO) 200 foot tall tailings (chat) piles from Zn-Pb mines.
Mining concentrates, relocates, and makes accessible materials to the surface environment
Time
Ground water
Cd 93 µg/L
Pb 130 µg/L
Zn 240,000 µg/L (Parkhurst, 1987).
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Disseminated SulfideDisseminated Sulfide
Igneous rocks may host small amounts of sulfide minerals. At Bingham canyon, these are economic.
Oxides are typically either
Tetrahedral
Octahedral
Mixed (Tetra- and Octahedral)
Simple packing of O with cations in interstices - packing!
These are clear representations of the ionic crystal structures we talked about in the first few weeks of the class.
OxidesOxides
Few significant Tetrahedral Oxides
ZnO, BeO
Octahedral oxides more common
MgO, Al2O3, Fe2O3,
FeTiO3, TiO2
Coordination in oxidesCoordination in oxides
Corundum groupCorundum Al2O3
Hematite Fe2O3
Ilmenite FeTiO4
Rutile typeRutile TiO2
Cassiterite SnO2
Pyrolusite MnO2
Periclase MgOColumbite (Fe,Mn)Nb2O6
Tantalite (Fe,Mn)Ta2O6
Perovskite CaTiO3
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Octahedral OxidesOctahedral Oxides
Octahedral OxidesOctahedral Oxides
Corundumgroup
Spinel GroupSpinel MgAl2O4
Magnetite Fe3O4
Chromite FeCr2O4
Ulvospinel Fe2TiO4
Franklinite ZnFe2O4
Cuprite Cu2O
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Mixed Coord. OxidesMixed Coord. Oxides
XY2O4
X octahedral
Y tetrahedral
Chromite FeCr2O4
Spinel MgAlAlO4
Magnetite FeFe2O4
Mixed OxidesMixed Oxides
TiO2 - FeO - Fe2O3TiO2 - FeO - Fe2O3
Iron oxides differ because of the valency of the transition element, Fe.
The result of oxidation
2 FeFe2O4 + 0.5 O2 = 3 Fe2O3
With increasing depth, there is less oxygen available. Fe becomes more reduced.
Oxygen and oxidesOxygen and oxides
Yet another thermodynamic parameter
f fugacity
Chemical potential µ (not really new)
µ = U+PV-TS (that’s G) for an individual component
f = exp µ = exp [µT,P - µss]
Fugacity as a measure of how much the chemical potential of the component in the gas deviates from the chemical potential of the standard state due to changes in P and/or the mole fraction of the component.Just like a partial pressure (just not so ideal).
Oxygen and oxidesOxygen and oxides
MH - 2Fe3O4 +O = 3Fe2O3
WM - 3FeO + O = Fe3O4
IW - Feº + O = FeONNO - Niº + O = NiO
Maun and Osborne
Now with fO2Now with fO2
Meet BIF (Banded Iron Formation)
Rock is 2.5 billion years old (found world wide from 3 - 1.8 Ga)
Dark: Hematite (Fe2O3)Red: Quartz (with iron)Yellow: Crocidolite (blue asbestosform)
The accumulation of iron as seafloor sediments is thought to result from early photosynthesis on the ocean surface
under N2 – CO2 rich conditions.
A lack of atmospheric O2 permits Fe ions in surface seawater – these bond with O2 produced by photosynthesis.
Prolonged runs at high temperature produce a solid state reaction between MgO and Al2O3, forming a layer of spinel
This study
•Evaluated spinel growth rate as function of t, T, and P
•Constrained the thermodynamic stability of spinel at elevated P
•Constructed Al-Mg coupled diffusion model
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EMPA traverses of spinel
Stoich. spinel
Al enriched
1400 oC4 GPa89 hr30 m
600 oC3.2 GPa16 hr66 m
1978 oC2.5 GPa0.4 hr115 m
Goethite FeO(OH)BauxiteMonhydrateDiaspore AlO(OH)Boehmite AlO(OH)TrihydrateGibbsite Al(OH)3
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HydroxidesHydroxides
