Native elements, sulfides, oxides, & hydroxides JD Price.

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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Copyright © 2002 - James A. Burbank, Jr.

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