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Fleetite, Cu₂RhIrSb₂, a New Species of Platinum-Group Mineral from the Miass Placer Zone, Southern Urals, Russia

Barkov, Andrei Y. and Bindi, Luca and Tamura, Nobumichi and Martin, Robert F. and Ma, Chi and Winkler, Björn and Shvedov, Gennadiy I. and Morgenroth, Wolfgang (2021) Fleetite, Cu₂RhIrSb₂, a New Species of Platinum-Group Mineral from the Miass Placer Zone, Southern Urals, Russia. Canadian Mineralogist, 59 (2). pp. 423-430. ISSN 0008-4476. doi:10.3749/canmin.2000073. https://resolver.caltech.edu/CaltechAUTHORS:20210609-081434126

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Abstract

Fleetite, Cu₂RhIrSb₂, a new species of platinum-group mineral (PGM), was discovered intergrown with an Os–Ir–Ru alloy in the Miass Placer Zone (Au–PGE), southern Urals, Russia. A single grain 50 μm across was found. Osmium, ruthenium, and iridium are the main associated minerals; also present are Pt–Fe alloys, laurite, Sb-rich irarsite, Rh-rich tolovkite, kashinite, anduoite, ferronickelplatinum, heazlewoodite, PGE-bearing pentlandite and digenite, as well as micrometric inclusions of forsterite (Fo_(93.7)), chromite–magnesiochromite, and Mg-rich edenite. In reflected light, fleetite is light gray; it is opaque, isotropic, non-pleochroic, and non-bireflectant. We report reflectance values measured in air. A mean of seven point-analyses (wavelength-dispersive spectrometry) gave Cu 13.93, Ni 8.60, Fe 0.10, Ir 28.07, Rh 7.91, Ru 1.96, Sb 39.28, total 99.85 wt.%, corresponding to (Cu_(1.41)Ni_(0.58)Fe_(0.01))_(Σ2.00)(Rh_(0.49)Ni_(0.36)Ru_(0.12))_(Σ0.97)Ir_(0.95)Sb_(2.08) on the basis of six atoms per formula unit, taking into account the structural results. The calculated density is 10.83 g/cm³. Single-crystal X-ray studies show that fleetite is cubic, space group Fd3m (#227), a = 11.6682(8) Å, V = 1588.59(19) ų, and Z = 16. A least-squares refinement of X-ray powder-diffraction data gave a = 11.6575(5) Å and V = 1584.22(19) ų. The strongest five reflections in the powder pattern [d in Å(I)(hkl)] are: 6.70(75)(111), 4.13(100)(220), 3.52(30)(311), 2.380(50)(422), 2.064(40)(440). Results of synchrotron micro-Laue diffraction experiments are consistent [a = 11.66(2) Å]. The crystal structure of fleetite was solved and refined to R = 0.0340 based upon 153 reflections with F_o > 4σ(F_o). It is isotypic with Pd₁₁Bi₂Se₂ and best described as intermetallic, with all metal atoms in 12-fold coordination. Fleetite and other late exotic phases were formed by reaction of the associated alloy phases with a fluid phase enriched in Sb, As, and S in circulation in the cooling ophiolite source-rock. The mineral is named after Michael E. Fleet (1938–2017) in recognition of his significant contributions to the Earth Sciences.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.3749/canmin.2000073DOIArticle
ORCID:
AuthorORCID
Bindi, Luca0000-0003-1168-7306
Tamura, Nobumichi0000-0002-3698-2611
Ma, Chi0000-0002-1828-7033
Morgenroth, Wolfgang0000-0001-8921-0052
Alternate Title:Fleetite, Cu2RhIrSb2, a New Species of Platinum-Group Mineral from the Miass Placer Zone, Southern Urals, Russia
Additional Information:© 2021 Mineralogical Association of Canada. Received June 18, 2020. Revised manuscript accepted September 25, 2020. This study was supported in part by the Russian Foundation for Basic Research (project # RFBR 19-05-00181). AYB thanks Sergey Silyanov for his assistance with the reflectance data. LB thanks MIUR, project "TEOREM Deciphering Geological Processes using Terrestrial and Extraterrestrial Ore Minerals", prot. 2017AK8C32 (PI: Luca Bindi). We thank Associate Editor Andrew M. McDonald and acknowledge the valuable suggestions for improvement offered by Drs. Herta Effenberger (Vienna) and Anna Vymazalová (Prague).
Funders:
Funding AgencyGrant Number
Russian Foundation for Basic Research19-05-00181
Ministero dell’Istruzione, dell’Università e della Ricerca (MIUR)2017AK8C32
Subject Keywords:fleetite, Cu₂RhIrSb₂, new mineral species, platinum-group elements, ore minerals, platinum-group minerals, ophiolites, placer deposits, Miass placer zone, southern Urals, Russia
Issue or Number:2
DOI:10.3749/canmin.2000073
Record Number:CaltechAUTHORS:20210609-081434126
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20210609-081434126
Official Citation:Andrei Y. Barkov, Luca Bindi, Nobumichi Tamura, Robert F. Martin, Chi Ma, Björn Winkler, Gennadiy I. Shvedov, Wolfgang Morgenroth; Fleetite, Cu2RhIrSb2, a New Species of Platinum-Group Mineral from the Miass Placer Zone, Southern Urals, Russia. The Canadian Mineralogist 2021; 59 (2): 423–430. doi: https://doi.org/10.3749/canmin.2000073
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:109453
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:09 Jun 2021 17:39
Last Modified:09 Aug 2021 21:37

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