Special Issue "Platinum-Group Elements and Platinum-Group Minerals: Inferences from Field, Geochemical, Mineralogical, and Petrological Findings"

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Mineral Geochemistry and Geochronology".

Deadline for manuscript submissions: 15 December 2022 | Viewed by 7542

Special Issue Editors

Dr. Andrei Y. Barkov
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Guest Editor
Research Laboratory of Industrial and Ore Mineralogy, Cherepovets State University, Cherepovets, Russia
Interests: platinum-group minerals; ore minerals; Ni-Cu-Cr-PGE mineralization; mafic-ultramafic complexes; layered intrusions; ore-forming processes
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Federica Zaccarini
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Guest Editor
Faculty of Science, Physical and Geological Sciences, Universiti Brunei Darussalam, Jalan Tungku Link, BE 1410 Gadong, Brunei
Interests: mineralogy; electron microprobe analyses; ultramafic rocks; ore minerals; geochemistry; ophiolite
Special Issues, Collections and Topics in MDPI journals
Dr. Robert F. Martin
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Guest Editor
Department of Earth and Planetary Sciences, McGill University, Montreal, QC, Canada
Interests: anorogenic felsic magmas, and associated metasomatic activity and mineralization; mineralogy of peraluminous and peralkaline granitic rocks; x-ray diffraction and electron microscopy applied to the characterization of the rock-forming minerals; mineralogy of feldspar-group and platinum-group minerals in all crustal environments

Special Issue Information

Dear Colleague,

We cordially invite you to submit an original research article or a topical review, intended to reach a broad audience and to present the latest advances in various areas of mineralogy, geology of ore deposits, geochemistry and petrology of PGE-bearing basic-ultrabasic complexes, associated placers and other sources of the PGE.

The following topics come to mind:

  • New mineral species, series of solid solutions or compositional varieties of PGM, and their structural characteristics
  • Uncommon or atypical associations of PGM, new environments or unconventional styles of PGE-rich mineralization;
  • Unusual geochemical patterns or trends involving PGE and accompanying elements;
  • Factors favoring the formation of PGE ores;
  • Petrology and geochemistry of ore zones enriched in the PGE, hosted by complexes in various geotectonic settings, including the Uralian-Alaskan-type complexes, ophiolites, layered intrusions, subvolcanic complexes of komatiitic, picritic or basaltic origin, chromitites, base-metal sulfide orebodies, among others;
  • Placer deposits of PGM and their provenance sources, features of geological background, mineral associations, and compositional variations.

All submitted manuscripts will undergo the peer review procedure of Minerals, and will be published rapidly upon acceptance.

We look forward to receiving your contributions.

Dr. Andrei Y. Barkov
Dr. Federica Zaccarini
Dr. Robert F. Martin
Guest Editors

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Published Papers (8 papers)

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Research

Article
Origin of Podiform Chromitites in the Sebuku Island Ophiolite (South Kalimantan, Indonesia): Constraints from Chromite Composition and PGE Mineralogy
Minerals 2022, 12(8), 974; https://doi.org/10.3390/min12080974 - 30 Jul 2022
Viewed by 336
Abstract
The presence of PGM associated with the podiform chromitites in the Jurassic–Cretaceous ophiolite of Sebuku Island (South Kalimantan, Indonesia) is reported for the first time. Two types of chromitite have been recognized; one with high-Cr composition (Cr/(Cr + Al) > 0.7) occurs in [...] Read more.
The presence of PGM associated with the podiform chromitites in the Jurassic–Cretaceous ophiolite of Sebuku Island (South Kalimantan, Indonesia) is reported for the first time. Two types of chromitite have been recognized; one with high-Cr composition (Cr/(Cr + Al) > 0.7) occurs in the deep mantle, the other, high-Al (Cr/(Cr + Al) < 0.6), is located close to the Moho transition zone. The TiO2-Al2O3 relations indicate affinity to IAT and MORB, for the high-Cr and high-Al chromitites, respectively. However, both are believed to have formed by mantle/melt reaction and differentiation of a magma characterized by an initial IAT composition related to an SSZ. Primary magmatic inclusions (<10 μm) of laurite characterized by Ru/Os chondritic ratio are the only PGM found in the high-Cr chromitites, indicating crystallization from undifferentiated magma, at low fS2 in the mantle. In contrast, the high-Al to chondrite, suggesting the increase of fS2 in the evolved melt. Besides laurite, the high-Al chromitite contains a complex assemblage of secondary PGM (Pt-Fe, garutiite, iridium, ruthenium–magnetite aggregates, zaccariniite and unnamed Ru and Mn oxides). These secondary PGM have an irregular shape and occur exclusively in the chlorite matrix sometimes associated with Mn-Ni-Fe-Cr hydroxides. They are interpreted to have formed by desulfuration of primary interstitial PGM sulfides or to have precipitated from secondary fluids during low T alteration. The relative abundance of PPGE in the high-Al chromitite is interpreted as a result of PGE fractionation during differentiation of the parent melt of the chromitites. Full article
Article
Mineralogical, Textural and Chemical Characteristics of Ophiolitic Chromitite and Platinum Group Minerals from Kabaena Island (Indonesia): Their Petrogenetic Nature and Geodynamic Setting
Minerals 2022, 12(5), 516; https://doi.org/10.3390/min12050516 - 21 Apr 2022
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Abstract
This contribution presents the first systematic mineralogical study of chromite composition, silicates and PGM (platinum group minerals) by electron microprobes in the podiform chromitite of Kabaena Island (Indonesia) mined in the past. The main target of this study is to understand the petrogenetic [...] Read more.
This contribution presents the first systematic mineralogical study of chromite composition, silicates and PGM (platinum group minerals) by electron microprobes in the podiform chromitite of Kabaena Island (Indonesia) mined in the past. The main target of this study is to understand the petrogenetic nature of the parental melt from which the chromitites of Kabaena Island precipitated and, indirectly, define the geodynamic tectonic setting of their emplacement. The evolution of PGM, from the magmatic stage to low-temperature processes, is also discussed. The variation of the Cr# = Cr/(Cr + Al), being comprised between 0.65 and 0.75, is similar to the podiform-type chromitite and indicates the absence of Al-rich chromitite. The calculated composition of the parental melt varies from arc to MORB (mid-ocean ridge basalts). Several grains of olivine and clinopyroxene have been found in the silicate matrix or included in fresh chromite. Olivine shows a composition typical of a hosted mantle, and clinopyroxene is similar to those analyzed in the forearc of an SSZ (supra-subduction zone). Small PGM, varying in size from 1 to 10 μm, occur in the chromitites. The most abundant PGM is laurite, which has been found included in fresh chromite or in contact with ferrian chromite along the cracks in the chromite. Laurite forms polygonal crystals, and it occurs as a single phase or in association with clinopyroxene and amphibole. Tiny blebs of Ir-Os alloy (less than 2 μm across) have been found associated with grains of awaruite in the serpentine gangue of the chromitites. The composition of the investigated chromitites suggests that they formed in the mantle of a forearc ophiolite. All the discovered grains of laurite are considered to be magmatic in origin, i.e., entrapped as solid phases during the crystallization of chromite at temperatures above 1000 °C and a sulfur fugacity below sulfur saturation. Iridium–osmium alloys are secondary in origin and represent a low-temperature, around 400 °C, exsolution product. Full article
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Article
Platinum-Group Minerals in the Placer of the Kitoy River, East Sayan, Russia
Minerals 2022, 12(1), 21; https://doi.org/10.3390/min12010021 - 23 Dec 2021
Cited by 1 | Viewed by 821
Abstract
The platinum-group minerals (PGM) in placer deposits provide important information on the types of their primary source rocks and ores and formation and alteration conditions. The article shows for the first time the results of a study of placer platinum mineralization found in [...] Read more.
The platinum-group minerals (PGM) in placer deposits provide important information on the types of their primary source rocks and ores and formation and alteration conditions. The article shows for the first time the results of a study of placer platinum mineralization found in the upper reaches of the Kitoy River (the southeastern part of the Eastern Sayan (SEPES)). Using modern methods of analysis (scanning electron microscopy), the authors studied the microtextural features of platinum-group minerals (PGM), their composition, texture, morphology and composition of microinclusions, rims, and other types of changes. The PGM are Os-Ir-Ru alloys with a pronounced ruthenium trend. Many of the Os-Ir-Ru grains have porous, fractured, or altered rims that contain secondary PGE sulfides, arsenides, sulfarsenides, Ir-Ni-Fe alloys, and rarer selenides, arsenoselenides, and tellurides of the PGE. The data obtained made it possible to identify the root sources of PGM in the placer and to make assumptions about the stages of transformation of primary igneous Os-Ir-Ru alloys from bedrock to placer. We assume that there are several stages of alteration of high-temperature Os-Ir-Ru alloys. The late magmatic stage is associated with the effect of fluid-saturated residual melt enriched with S, As. The post-magmatic hydrothermal stage (under conditions of changing reducing conditions to oxidative ones) is associated with the formation of telluro-selenides and oxide phases of PGE. The preservation of poorly rounded and unrounded PGM grains in the placer suggests a short transport from their primary source. The source of the platinum-group minerals from the Kitoy River placer is the rocks of the Southern ophiolite branch of SEPES and, in particular, the southern plate of the Ospa-Kitoy ophiolite complex, and primarily chromitites. Full article
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Article
Rh, Ir, and Ru Partitioning in the Cu-Poor IPGE Massive Ores, Talnakh Intrusion, Skalisty Mine, Russia
Minerals 2022, 12(1), 18; https://doi.org/10.3390/min12010018 - 22 Dec 2021
Cited by 1 | Viewed by 839
Abstract
Pyrrhotite (or Cu-poor) massive ores of the Skalisty mine located in Siberia, Russia, are unique in terms of their geochemical features. These ores are Ni-rich with Ni/Cu ratios in the range 1.3–1.9 and contain up to 12.25 ppm Ir + Rh + Ru [...] Read more.
Pyrrhotite (or Cu-poor) massive ores of the Skalisty mine located in Siberia, Russia, are unique in terms of their geochemical features. These ores are Ni-rich with Ni/Cu ratios in the range 1.3–1.9 and contain up to 12.25 ppm Ir + Rh + Ru in bulk composition, one of the highest IPGE contents for the Norilsk–Talnakh ore camp. The reasons behind such significant IPGE Contents cannot simply be explained by the influence of discrete platinum-group minerals on the final bulk composition of IPGE because only inclusions of Pd minerals such as menshikovite, majakite, and mertieite II in Pd-maucherite were observed. According to LA-ICP-MS data obtained, base metal sulfides such as pyrrhotite, pentlandite, and pyrite contain IPGE as the trace elements. The most significant IPGE concentrator being Py, which occurs only in the least fractionated ores, and contains Os up to 4.8 ppm, Ir about 6.9 ppm, Ru about 38.3 ppm, Rh about 36 ppm, and Pt about 62.6 ppm. High IPGE contents in the sulfide melt may be due to high degrees of partial melting of the mantle, interaction with several low-grade IPGE impulses of magma, and (or) fractionation of the sulfide melt in the magma chamber. Full article
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Article
Ferrotorryweiserite, Rh5Fe10S16, a New Mineral Species from the Sisim Placer Zone, Eastern Sayans, Russia, and the Torryweiserite–Ferrotorryweiserite Series
Minerals 2021, 11(12), 1420; https://doi.org/10.3390/min11121420 - 15 Dec 2021
Viewed by 936
Abstract
Ferrotorryweiserite, Rh5Fe10S16, occurs as small grains (≤20 µm) among droplet-like inclusions (up to 50 μm in diameter) of platinum-group minerals (PGM), in association with oberthürite or Rh-bearing pentlandite, laurite, and a Pt-Pd-Fe alloy (likely isoferroplatinum and Fe-Pd-enriched [...] Read more.
Ferrotorryweiserite, Rh5Fe10S16, occurs as small grains (≤20 µm) among droplet-like inclusions (up to 50 μm in diameter) of platinum-group minerals (PGM), in association with oberthürite or Rh-bearing pentlandite, laurite, and a Pt-Pd-Fe alloy (likely isoferroplatinum and Fe-Pd-enriched platinum), hosted by placer grains of Os-Ir alloy (≤0.5 mm) in the River Ko deposit. The latter is a part of the Sisim placer zone, which is likely derived from ultramafic units of the Lysanskiy layered complex, southern Krasnoyarskiy kray, Russia. The mineral is opaque, gray to brownish gray in reflected light, very weakly bireflectant, not pleochroic to weakly pleochroic (grayish to light brown tints), and weakly anisotropic. The calculated density is 5.93 g·cm–3. Mean results (and ranges) of four WDS analyses are: Ir 18.68 (15.55–21.96), Rh 18.34 (16.32–20.32), Pt 0.64 (0.19–1.14), Ru 0.03 (0.00–0.13), Os 0.07 (0.02–0.17), Fe 14.14 (13.63–14.64), Ni 13.63 (12.58–14.66), Cu 4.97 (3.42–6.41), Co 0.09 (0.07–0.11), S 29.06 (28.48–29.44), and total 99.66 wt.%. They correspond to the following formula calculated for a total of 31 atoms per formula unit: (Rh3.16Ir1.72Pt0.06Ru0.01Os0.01)Σ4.95(Fe4.48Ni4.11Cu1.38Co0.03)Σ10.00S16.05. The results of synchrotron micro-Laue diffraction studies indicate that ferrotorryweiserite is trigonal; its probable space group is R3¯m (#166) based on its Ni-analog, torryweiserite. The unit-cell parameters refined from 177 reflections are a = 7.069 (2) Å, c = 34.286 (11) Å, V = 1484 (1) Å3, and Z = 3. The c:a ratio is 4.8502. The strongest eight peaks in the X-ray diffraction pattern derived from results of micro-Laue diffraction study [d in Å(hkil)(I)] are 2.7950 (202¯5) (100); 5.7143 (0006) (60); 1.7671 (224¯0) (44.4); 3.0486 (202¯1) (39.4); 5.7650 (101¯2) (38.6); 2.5956 (202¯7) (37.8); 3.0058 (112¯6) (36.5); and 1.5029 (42¯ 2¯12) (35.3). Ferrotorryweiserite and the associated PGM crystallized from microvolumes of residual melt at late stages of crystallization of grains of Os- and Ir-dominant alloys occurred in lode zones of chromitites of the Lysanskiy layered complex. In a particular case, the residual melt is disposed peripherally around a core containing a disequilibrium association of magnesian olivine (Fo72.9–75.6) and albite (Ab81.6–86.4), with the development of skeletal crystals of titaniferous augite: Wo40.8–43.2En26.5–29.3Fs20.3–22.6Aeg6.9–9.5 (2.82–3.12 wt.% TiO2). Ferrotorryweiserite represents the Fe-dominant analog of torryweiserite. We also report occurrences of ferrotorryweiserite in the Marathon deposit, Coldwell Complex, Ontario, Canada, and infer the existence of the torryweiserite–ferrotorryweiserite solid solution in other deposits and complexes. Full article
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Article
Unnamed Pt(Cu0.67Sn0.33) from the Bolshoy Khailyk River, Western Sayans, Russia, and a Review of Related Compounds and Solid Solutions
Minerals 2021, 11(11), 1240; https://doi.org/10.3390/min11111240 - 08 Nov 2021
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Abstract
We describe a potentially new species of a platinum cupride–stannide mineral (PCSM) of composition Pt(Cu0.67Sn0.33). It occurs in a placer deposit in the River Bolshoy Khailyk, southern Krasnoyarskiy kray, Russia. A synthetic equivalent of PCSM was obtained and characterized. [...] Read more.
We describe a potentially new species of a platinum cupride–stannide mineral (PCSM) of composition Pt(Cu0.67Sn0.33). It occurs in a placer deposit in the River Bolshoy Khailyk, southern Krasnoyarskiy kray, Russia. A synthetic equivalent of PCSM was obtained and characterized. The PCSM occurs as anhedral or subhedral grains up to 15 μm × 30 μm in association with various platinum-group minerals, Rh–Co-rich pentlandite and magnetite, all hosted by a placer grain of Cu–Au–Pt alloy. Synchrotron micro-Laue diffraction studies indicate that the PCSM mineral is tetragonal and belongs to the inferred space-group P4/mmm (#123). Its unit-cell parameters are a = 2.838 (3) Å, c = 3.650 (4) Å, and V = 29.40 (10) Å3, and Z = 1. The c:a ratio calculated from the unit-cell parameters is 1.286. These characteristics are in good agreement with those obtained for specimens of synthetic Pt(Cu0.67Sn0.33). A review on related minerals and unnamed phases is provided to outline compositional variations and extents of solid solutions in the relevant systems PtNi–PtFe–PtCu, PdCu–PdHg–PdAu, PdHg–PtHg, and AuCu–PtCu. The PCSM-bearing mineralization appears to be related genetically with an ophiolitic source-rock of the Aktovrakskiy complex of the western Sayans. The unnamed phase likely crystallized from microvolumes of a highly fractionated melt rich in Cu and Sn. Full article
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Article
Atypical Mineralization Involving Pd-Pt, Au-Ag, REE, Y, Zr, Th, U, and Cl-F in the Oktyabrsky Deposit, Norilsk Complex, Russia
Minerals 2021, 11(11), 1193; https://doi.org/10.3390/min11111193 - 27 Oct 2021
Cited by 3 | Viewed by 588
Abstract
Highly atypical mineralization involving Pd-Pt, Au-Ag, REE, Y, Zr, U, Th, and Cl-F-enriched minerals is found in zones with base metal sulfides (BMS; ~5 vol.% to 20 vol.%) in the eastern portion of the Oktyabrsky deposit in the Norilsk complex (Russia). The overall [...] Read more.
Highly atypical mineralization involving Pd-Pt, Au-Ag, REE, Y, Zr, U, Th, and Cl-F-enriched minerals is found in zones with base metal sulfides (BMS; ~5 vol.% to 20 vol.%) in the eastern portion of the Oktyabrsky deposit in the Norilsk complex (Russia). The overall variations in Mg# index, 100 Mg/(Mg + Fe2+ + Mn), in host-rock minerals are 79.8 → 74.1 in olivine, 77.7 → 65.3 in orthopyroxene, 79.9 → 9.2 in clinopyroxene, and An79.0 → An3.7. The span of clinopyroxene and plagioclase compositions reflects their protracted crystallization from early magmatic to late interstitial associations. The magnesian chromite (Mg# 43.9) trends towards Cr-bearing magnetite with progressive buildups in oxygen fugacity; ilmenite varies from early Mg-rich to late Mn-rich variants. The main BMS are chalcopyrite, pyrrhotite, troilite, and Co-bearing pentlandite, with less abundant cubanite (or isocubanite), rare bornite, Co-bearing pyrite, Cd-bearing sphalerite (or wurtzite), altaite, members of the galena-clausthalite series and nickeline. A full series of Au-Ag alloy compositions is found with minor hessite, acanthite and argentopentlandite. The uncommon assemblage includes monazite-(Ce), thorite-coffinite, thorianite, uraninite, zirconolite, baddeleyite, zircon, bastnäsite-(La), and an unnamed metamict Y-dominant zirconolite-related mineral. About 20 species of PGM (platinum group minerals) were analyzed, including Pd-Pt tellurides, bismuthotellurides, bismuthides and stannides, Pd antimonides and plumbides, a Pd-Ag telluride, a Pt arsenide, a Pd-Ni arsenide, and unnamed Pd stannide-arsenide, Pd germanide-arsenide and Pt-Cu arseno-oxysulfide. The atypical assemblages are associated with Cl-rich annite with up to 7.54 wt.% Cl, Cl-rich hastingsite with up 4.06 wt.% Cl, ferro-hornblende (2.53 wt.% Cl), chlorapatite (>6 wt.% Cl) and extensive solid solutions of chlorapatite, fluorapatite and hydroxylapatite, Cl-bearing members of the chlorite group (chamosite; up to 0.96 wt.% Cl), and a Cl-bearing serpentine (up to 0.79 wt.% Cl). A decoupling of Cl and F in the geochemically evolved system is evident. The complex assemblages formed late from Cl-enriched fluids under subsolidus conditions of crystallization following extensive magmatic differentiation in the ore-bearing sequences. Full article
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Article
Tamuraite, Ir5Fe10S16, a New Species of Platinum-Group Mineral from the Sisim Placer Zone, Eastern Sayans, Russia
Minerals 2021, 11(5), 545; https://doi.org/10.3390/min11050545 - 20 May 2021
Cited by 2 | Viewed by 1835
Abstract
Tamuraite, ideally Ir5Fe10S16, occurs as discrete phases (≤20 μm) in composite inclusions hosted by grains of osmium (≤0.5 mm across) rich in Ir, in association with other platinum-group minerals in the River Ko deposit of the Sisim [...] Read more.
Tamuraite, ideally Ir5Fe10S16, occurs as discrete phases (≤20 μm) in composite inclusions hosted by grains of osmium (≤0.5 mm across) rich in Ir, in association with other platinum-group minerals in the River Ko deposit of the Sisim Placer Zone, southern Krasnoyarskiy Kray, Russia. In droplet-like inclusions, tamuraite is typically intergrown with Rh-rich pentlandite and Ir-bearing members of the laurite–erlichmanite series (up to ~20 mol.% “IrS2”). Tamuraite is gray to brownish gray in reflected light. It is opaque, with a metallic luster. Its bireflectance is very weak to absent. It is nonpleochroic to slightly pleochroic (grayish to light brown tints). It appears to be very weakly anisotropic. The calculated density is 6.30 g·cm−3. The results of six WDS analyses are Ir 29.30 (27.75–30.68), Rh 9.57 (8.46–10.71), Pt 1.85 (1.43–2.10), Ru 0.05 (0.02–0.07), Os 0.06 (0.03–0.13), Fe 13.09 (12.38–13.74), Ni 12.18 (11.78–13.12), Cu 6.30 (6.06–6.56), Co 0.06 (0.04–0.07), S 27.23 (26.14–27.89), for a total of 99.69 wt %. This composition corresponds to (Ir2.87Rh1.75Pt0.18Ru0.01Os0.01)Σ4.82(Fe4.41Ni3.90Cu1.87Co0.02)Σ10.20S15.98, calculated based on a total of 31 atoms per formula unit. The general formula is (Ir,Rh)5(Fe,Ni,Cu)10S16. Results of synchrotron micro-Laue diffraction studies indicate that tamuraite is trigonal. Its probable space group is R3m (#166), and the unit-cell parameters are a = 7.073(1) Å, c = 34.277(8) Å, V = 1485(1) Å3, and Z = 3. The c:a ratio is 4.8462. The strongest eight peaks in the X-ray diffraction pattern [d in Å(hkl)(I)] are: 3.0106(216)(100), 1.7699(420)(71), 1.7583(2016)(65), 2.7994(205)(56), 2.9963(1010)(50), 5.7740(102)(45), 3.0534(201)(43) and 2.4948(208)(38). The crystal structure is derivative of pentlandite and related to that of oberthürite and torryweiserite. Tamuraite crystallized from a residual melt enriched in S, Fe, Ni, Cu, and Rh; these elements were incompatible in the Os–Ir alloy that nucleated in lode zones of chromitites in the Lysanskiy layered complex, Eastern Sayans, Russia. The name honors Nobumichi Tamura, senior scientist at the Advanced Light Source of the Lawrence Berkeley National Laboratory, Berkeley, California. Full article
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