Тип публикации: статья из журнала
Год издания: 2021
Идентификатор DOI: 10.3749/canmin.2000073
Ключевые слова: fleetite, cu2rhirsb2, new mineral species, platinum-group elements, ore minerals, platinum-group minerals, ophiolites, placer deposits, miass placer zone, southern urals, russia
Аннотация: 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 lm across was found. Osmium, ruthenium, and iridium are the main associated minerals; also present are Pt-Fe alloys, laurite, Sb-rich irarПоказать полностьюsite, 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 (Cu1.41Ni0.58Fe0.01)(Sigma 2.00)(Rh0.49Ni0.36Ru0.12)(Sigma 0.97)Ir0.95Sb2.08 on the basis of six atoms per formula unit, taking into account the structural results. The calculated density is 10.83 g/cm(3). Single-crystal X-ray studies show that fleetite is cubic, space group Fd (3) over barm (#227), a = 11.6682(8) angstrom, V = 1588.59(19) angstrom(3), and Z = 16. A least-squares refinement of X-ray powder-diffraction data gave a = 11.6575(5) angstrom and V = 1584.22(19) angstrom(3). The strongest five reflections in the powder pattern [d in angstrom 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) angstrom]. The crystal structure of fleetite was solved and refined to R = 0.0340 based upon 153 reflections with F-o > 4 sigma(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.
Журнал: CANADIAN MINERALOGIST
Выпуск журнала: Vol. 59, Is. 2
Номера страниц: 423-430
ISSN журнала: 00084476
Место издания: QUEBEC
Издатель: MINERALOGICAL ASSOC CANADA