Partition behavior of platinum-group elements during the segregation of arsenide melts from sulfide magma

Piña, Rubén; Gervilla, Fernando; Helmy, Hassan M.; Fonseca, Raúl O. C.; Ballhaus, Chris

doi:10.2138/am-2020-7477

Cited by 10 publications

(2 citation statements)

References 33 publications

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“…This begins to happen mainly at temperature 1300 K, wherein the radius of the peaks decreases and peaks becomes smoother. This agrees with the experimental melting temperature of arsenide-PGMs which is between 1173 K and 1473 K [18]. Figure 3 shows the final structures for the 4×4×4 supercell of PtAs2 simulated at various temperatures.…”

Section: Structural Propertiessupporting

confidence: 83%

Structural and dynamical properties of sperrylite (PtAs₂): a molecular dynamics study

Ntobeng,

Mehlape,

Mkhonto

et al. 2023

MATEC Web Conf.

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There is a demand for platinum group minerals (PGMs) due to the increase in various applications such as electronics, industrial and medical. Sperrylite (PtAs2) is one of the major PGMs, however its recovery by flotation has been reported to be poor. The understanding of bulk properties of PtAs2 is still necessary for the recovery of minerals from ore deposits. The structural and dynamical properties of the PtAs2 are investigated using a computational modelling technique, i.e. molecular dynamics (MD). An accurate MD simulation requires the availability of robust interatomic potentials. In this article, the refined potential model was able to reproduce the lattice parameters and elastic properties, which are in good agreement with those from literature. Furthermore, the potential model was able to predict the melting point of PtAs2 at higher temperatures.

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Section: Structural Propertiessupporting

confidence: 83%

Structural and dynamical properties of sperrylite (PtAs₂): a molecular dynamics study

Ntobeng,

Mehlape,

Mkhonto

et al. 2023

MATEC Web Conf.

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“…Many experimental studies on the behavior of Pt and Pd in sulfide systems have been conducted during the last 2 decades, covering the temperature range of magmatic deposits, i.e., from 1,150 °C-750 °C (Helmy et al, 2007;2013;Bai et al, 2017;Helmy and Bragagni, 2017;Helmy and Fonseca, 2017;Helmy and Botcahrnikov, 2020;Piña et al, 2020). In these studies, Pt-and Pd-semimetal saturated sulfide systems were equilibrated at fixed temperatures.…”

Section: Introductionmentioning

confidence: 99%

How and when do Pt- and Pd-semimetal minerals crystallize from saturated sulfide liquids?

Helmy,

Botcharnikov,

Ballhaus

et al. 2024

Front. Earth Sci.

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Platinum and Pd-arsenides, antimonides, tellurides, bismuthinides, and sulfides are the major hosts of Pt and Pd in magmatic and hydrothermal Cu-Ni-sulfide ores. Textural relationships among such minerals in nature often provide contradictory messages about the mechanism and timing of their formation. To know how and when Pt and Pd mineral phases crystallize from sulfide-saturated liquids and how their compositions and textures evolve during cooling, we undertook controlled cooling experiments in evacuated silica tubes. A Cu-Ni-Fe sulfide mixture, similar in composition to the average Merensky Reef sulfide magma, was charged (in a 9:1 wt.% proportion) with one of the PtAs2, PtTe2, PtSb2, PtBi2, PdAs2, PdTe2, PdSb, and PdBi2 compounds, heated to 1,100°C, and slowly cooled (15°C/day) to room temperature. The run products were sampled at 950°C, 750°C, and 25°C by quenching the silica tubes in water. The results show that Pt formed stable phases with As, Te, and Sb above 950°C and with Bi and S below 750°C. The Pt phases were found mostly in the decomposed intermediate solid solution (ISS), and all the phases survived to 25°C with no compositional changes. At 950°C, Pd formed arsenide, telluride, and antimonide immiscible melts that coexisted with monosulfide solid solution (MSS) and sulfide melt. The composition of the Pd-semimetal melt droplets changed during cooling by equilibration with the host sulfide. Palladium mineral phases formed at temperatures below 750°C directly from the immiscible semimetal-rich melts where they kept the rounded shapes of the melt droplets. Ni-sulfarsenides preceded the formation of Pd arsenides. No Ni tellurides, antimonides, or bismuthinides formed in any of the systems, implying that their formation requires higher semimetal/Pt + Pd ratios. The decomposition of MSS and ISS to base metal sulfides led to significant textural changes in Pt and Pd mineral grains. The compositions of Pt and Pd phases are inherited from the magmatic stage, and their textures are low-temperature (<450°C) features.

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Micron-to-nanoscale investigation of Cu-Fe-Ni sulfide inclusions within laurite (Ru, Os)S2 from chromitites

González-Jiménez,

González-Pérez,

Plissart

et al. 2024

Miner Deposita

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This paper provides a top-down nanoscale analysis of Cu-Ni-Fe sulfide inclusions in laurite from the Taitao ophiolite (Chile) and the Kevitsa mafic-ultramafic igneous intrusion (Finland). High-resolution transmission electron microscopy (HRTEM) reveal that Cu-Ni-Fe sulfide inclusions are euhedral to (sub)-anhedral (i.e., droplet-like) and form single, biphasic or polyphasic grains, made up of different polymorphs, polytypes and polysomes even within a single sulfide crystal. Tetragonal (I4$$\stackrel{-}{2}$$d) and cubic (F$$\stackrel{-}{4}$$3m) chalcopyrite (CuFeS2) host frequent fringes of bornite (Cu5FeS4; cubic F$$\stackrel{-}{4}$$3m and/or orthorhombic Pbca) ± talnakhite (Cu9(Fe, Ni)8S16; cubic I$$\stackrel{-}{4}$$3m) ± pyrrhotite (Fe1 − xS; monoclinic C2/c polytype 4C and orthorhombic Cmca polytype 11C) ± pentlandite ((Ni, Fe)9S8; cubic Fm3m). Pentlandite hosts fringes of pyrrhotite, bornite and/or talnakhite. Laurite and Cu-Fe-Ni sulfide inclusions display coherent, semi-coherent and incoherent crystallographic orientation relationships (COR), defined by perfect edge-to-edge matching, as well as slight (2–4º) to significant (45º) lattice misfit. These COR suggest diverse mechanisms of crystal growth of Cu-Fe-Ni sulfide melt mechanically trapped by growing laurite. Meanwhile, the mutual COR within the sulfide inclusions discloses: (1) Fe-Ni-S melt solidified into MSS re-equilibrated after cooling into pyrrhotite ± pentlandite, (2) Cu-Ni-Fe-S melts crystallized into the quaternary solid solution spanning the compositional range between heazlewoodite [(Ni, Fe)3±xS2] (Hzss) and ISS [(Cu1±x, Fe1±y)S2]. Additionally, nanocrystallites (50–100 nm) of Pt-S and iridarsenite (IrAsS) accompanying the sulfide inclusions spotlight the segregation of PGE-rich sulfide and arsenide melt earlier and/or contemporarily to laurite crystallization from the silicate magmas. Cobaltite (CoAsS)-gersdorffite (NiAsS) epitaxially overgrown on laurite further supports the segregation of arsenide melts at early stages of chromitite formation.

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Partition behavior of platinum-group elements during the segregation of arsenide melts from sulfide magma

Abstract: Evidence of immiscibility between arsenide and sulfide melts has been observed both in experimental studies and natural samples from several localities

Cited by 10 publications

References 33 publications

Structural and dynamical properties of sperrylite (PtAs₂): a molecular dynamics study

Structural and dynamical properties of sperrylite (PtAs₂): a molecular dynamics study

How and when do Pt- and Pd-semimetal minerals crystallize from saturated sulfide liquids?

Micron-to-nanoscale investigation of Cu-Fe-Ni sulfide inclusions within laurite (Ru, Os)S2 from chromitites

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Partition behavior of platinum-group elements during the segregation of arsenide melts from sulfide magma

Abstract: Evidence of immiscibility between arsenide and sulfide melts has been observed both in experimental studies and natural samples from several localities

Cited by 10 publications

References 33 publications

Structural and dynamical properties of sperrylite (PtAs2): a molecular dynamics study

Structural and dynamical properties of sperrylite (PtAs2): a molecular dynamics study

How and when do Pt- and Pd-semimetal minerals crystallize from saturated sulfide liquids?

Micron-to-nanoscale investigation of Cu-Fe-Ni sulfide inclusions within laurite (Ru, Os)S2 from chromitites

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Structural and dynamical properties of sperrylite (PtAs₂): a molecular dynamics study

Structural and dynamical properties of sperrylite (PtAs₂): a molecular dynamics study