Published by De Gruyter

Volume 100 Issue 11-12

Issue of American Mineralogist

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Open Access November 24, 2015

Trace element partitioning into sulfide: How lithophile elements become chalcophile and vice versa

Bernard J. Wood, Ekaterina S. Kiseeva

Page range: 2371-2379

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Abstract

Sulfides, although modally of low abundance in most igneous rocks, have strong influences on the geochemical behavior of many elements including Pb, Cu, Ni, and the PGEs. In a recent paper, we demonstrated a simple relationship between the sulfide-silicate partition coefficients D M sulf/sil of such elements and the FeO content of the coexisting silicate me lt (Kiseeva and Wood 2013). where n is the valency of element M, [FeO] is the concentration of FeO in the silicate in wt%, and A is a constant that depends on temperature and pressure. Elements that closely obey the simple model are Pb, In, Sb, Cd, Co, Zn, and Cr. We show here, however, that the fitted slope n depends not only on the valency of element M, but also on how M interacts with oxygen, the dissolution of which as FeO in the sulfide increases as the FeO content of the silicate melt increases. To take account of interactions of trace element M with FeO dissolved in the sulfide we introduce an additional parameter ε FeOsulf MSn/2 (Wagner 1962), which represents the difference between the lithophile and chalcophile properties of M and those of Fe. If ε FeOsulf MSn/2 is positive, then element M is more chalcophile than Fe and if negative more lithophile. We performed experiments to investigate partitioning of lithophile Nb, Ta, Ce, and Ti between sulfide and simplified basaltic melt and find that they all exhibit, as expected, concave upward behavior on a plot of logD vs. log[FeO]. New experiments on Cu at low FeO contents confirm that it is more chalcophile than Fe, yielding a concave-downward curve of logD vs. log[FeO]. The combined results mean that nominally lithophile elements may partition more strongly into sulfide than nominally chalcophile elements at either very low or very high FeO contents of the silicate melt. For example, as the FeO content of the silicate melt declines below about 1 wt%, the partition coefficient of Cu, D Cu sulf/sil declines to an unusually low value (D Cu sulf/sil ~80), whereas those for Nb (D Nb sulf/sil ~600), and rare earths (REE’s) increase strongly. Under these conditions, Nb is, therefore, substantially more “chalcophile” than Cu in that it partitions much more strongly into sulfide. The implications of these observations for the Earth are that under a wide range of conditions one would expect significant partitioning of REE, Nb, Ta, Ti, and other lithophile elements into sulfides. Wohlers and Wood (2015) have, for example, shown that the partitioning of U and the REE into sulfides at low FeO content of the silicate is sufficiently pronounced that addition of a reduced sulfur-rich body to the accreting Earth could generate observable fractionation of Nd from Sm and, together with S, transfer sufficient U to the core to provide a significant energy source for the geodynamo.

Open Access November 24, 2015

Petrology on Mars

Xiande Xie, Hexiong Yang, Xiangping Gu, Robert T. Downs

Page range: 2753-2756

Abstract

Merrillite, ideally Ca 9 NaMg(PO 4 ) 7 , is an important accessory phosphate mineral in many different groups of meteorites, including martian meteorites, and a major carrier of rare earth elements (REE) in lunar rocks. By means of electron microprobe analysis, single-crystal X‑ray diffraction, and Raman spectroscopy, we present the first structure determination of merrillite with a nearly ideal chemical composition, Ca 9.00 Na 0.98 (Mg 0.95 Fe 0.06 )Σ 1.01 (P 1.00 O 4 ) 7 , from the Suizhou meteorite, a shock-metamorphosed L6-chondrite. Suizhou merrillite is trigonal with space group R3c and unit-cell parameters a = 10.3444(3), c = 37.0182(11) Å, and V = 3430.5(2) Å 3 . Its crystal structure, refined to R 1 = 0.032, is characterized by a structural unit consisting of a [(Mg,Fe)(PO 4 ) 6 ] 16- complex anion that forms a “bracelet-and-pinwheel” arrangement. Such structural units are linked by interstitial complexes with a formula of [Ca 9 Na(PO 4 )] 16+ , which differs from that of [Ca 9 (PO 3 [OH])] 16+ , [Ca 9 (PO 3 F)] 16+ , [Ca 9 (Ca 0.5 □ 0.5 )(PO 4 )] 16+ , or [(Ca 9-x REE) x (Na 1-x □ x ) (PO 4 )] 16+ in terrestrial whitlockite, terrestrial/extraterrestrial bobdownsite, meteoritic Ca-rich merrillite, or lunar REE-rich merrillite, respectively. The Suizhou merrillite is found to transform to tuite at high pressures, pointing to the likelihood of finding REE-bearing tuite on the Moon as a result of shock events on REE-merrillite.

About this journal

Objective
American Mineralogist: Journal of Earth and Planetary Materials (Am Min), is the flagship journal of the Mineralogical Society of America (MSA), continuously published since 1916. Am Min is home to some of the most important advances in the Earth Sciences. Our mission is a continuance of this heritage: to provide readers with reports on original scientific research, both fundamental and applied, with far reaching implications and far ranging appeal. Topics of interest cover all aspects of planetary evolution, and biological and atmospheric processes mediated by solid-state phenomena. These include, but are not limited to, mineralogy and crystallography, high- and low-temperature geochemistry, petrology, geofluids, bio-geochemistry, bio-mineralogy, synthetic materials of relevance to the Earth and planetary sciences, and breakthroughs in analytical methods of any of the aforementioned.

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Topics

Planetary evolution
Biological and atmospheric processes mediated by solid-state phenomena
Mineralogy
Crystal chemistry
High- and low-temperature geochemistry
Biomineralization
Geofluids
Bio-geochemistry
Bio-mineralogy
Synthetic materials
Mineral Physics
Crystallography
Crystal structure
Martian rock and soil
Raman spectroscopy
Petrology
Planetary materials
Infrared spectroscopy

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Original, fundamental and applied research articles

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Volume 100 Issue 11-12

Issue of American Mineralogist

On understanding the structure and composition of crystals

Abstract

Stable and metastable silicate liquid immiscibility in ferrobasalts

Abstract

When was the Earth’s conveyor belt set in motion?

Abstract

Trace element partitioning into sulfide: How lithophile elements become chalcophile and vice versa

Abstract

Petrology on Mars

Abstract

Hf and Nd isotope systematics of early Archean komatiites from surface sampling and ICDP drilling in the Barberton Greenstone Belt, South Africa

Abstract

Quasicrystals at extreme conditions: The role of pressure in stabilizing icosahedral Al63Cu24Fe13 at high temperature

Abstract

Tracking the thermal decomposition of plasma-sprayed hydroxylapatite

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Experimental constraints on bubble formation and growth during magma ascent: A review

Abstract

Ankerite grains with dolomite cores: A diffusion chronometer for low- to medium-grade regionally metamorphosed clastic sediments

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Crystal structure, high-pressure, and high-temperature behavior of carbonates in the K2Mg(CO3)2–Na2Mg(CO3)2 join

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Temperature micro-mapping in oscillatory-zoned chlorite: Application to study of a green-schist facies fault zone in the Pyrenean Axial Zone (Spain)

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Micro- and nano-characterization of Zn-clays in nonsulfide supergene ores of southern Peru

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Mineralogical characterization of individual growth structures of Mn-nodules with different Ni+Cu content from the central Pacific Ocean

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The magma plumbing system of the Emeishan large igneous province and its role in basaltic magma differentiation in a continental setting

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Weathering of the Ethiopian volcanic province: A new weathering index to characterize and compare soils

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Recommended mineral-melt partition coefficients for FRTEs (Cu), Ga, and Ge during mantle melting

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Tetrahedral plot diagram: A geometrical solution for quaternary systems

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Investigations on alunogen under Mars-relevant temperature conditions: An example for a single-crystal-to-single-crystal phase transition

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Crystallization of calcium oxalate hydrates by interaction of calcite marble with fungus Aspergillus niger

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Direct and indirect evidence for free oxygen (O2–) in MO-silicate glasses and melts (M = Mg, Ca, Pb)

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Effect of fluid composition on growth rate of monazite in quartzite at 1.0 GPa and 1000 °C

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Determination of the full elastic tensor of single crystals using shear wave velocities by Brillouin spectroscopy

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Temperature dependence of the velocity-density relation for liquid metals under high pressure: Implications for the Earth’s outer core

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Thermal, compositional, and compressional demagnetization of cementite

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The MnCO3-II high-pressure polymorph of rhodocrosite

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Lanthanide tetrads in normalized rare element patterns of zircon from the Koktokay No. 3 granitic pegmatite, Altay, NW China

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Hydrogrossular, Ca3Al2(SiO4)3–x(H4O4)x: An ab initio investigation of its structural and energetic properties

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High-pressure synthesis of skiagite-majorite garnet and investigation of its crystal structure

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Mineralogical evolution of Fe–Si-rich layers at the olivine-water interface during carbonation reactions

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High-pressure spectroscopic study of siderite (FeCO3) with a focus on spin crossover

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Exploring the potential of Raman spectroscopy for crystallochemical analyses of complex hydrous silicates: I. Amphiboles

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Apexite, NaMg(PO4)·9H2O, a new struvite-type phase with a heteropolyhedral cluster

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The mechanism of infiltration of metamorphic fluids recorded by hydration and carbonation of epidote-amphibolite facies metabasaltic sills in the SW Scottish Highlands

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The axial ratio of hcp Fe and Fe–Ni–Si alloys to the conditions of Earth’s inner core

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Shock-induced mobilization of metal and sulfide in planetesimals: Evidence from the Buck Mountains 005 (L6 S4) dike-bearing chondrite

Abstract

The accretion and differentiation of Earth under oxidizing conditions

Abstract

Dislocation microstructures in simple-shear-deformed wadsleyite at transition-zone conditions: Weak-beam dark-field TEM characterization of dislocations on the (010) plane

Abstract

Chemical composition and crystal structure of merrillite from the Suizhou meteorite

Abstract

Quasicrystals at extreme conditions: The role of pressure in stabilizing icosahedral Al₆₃Cu₂₄Fe₁₃ at high temperature

Crystal structure, high-pressure, and high-temperature behavior of carbonates in the K₂Mg(CO₃)₂–Na₂Mg(CO₃)₂ join

Direct and indirect evidence for free oxygen (O^2–) in MO-silicate glasses and melts (M = Mg, Ca, Pb)

The MnCO₃-II high-pressure polymorph of rhodocrosite

Hydrogrossular, Ca₃Al₂(SiO₄)_3–x(H₄O₄)_x: An ab initio investigation of its structural and energetic properties

High-pressure spectroscopic study of siderite (FeCO₃) with a focus on spin crossover

Apexite, NaMg(PO₄)·9H₂O, a new struvite-type phase with a heteropolyhedral cluster