Journal/NDM55 2021 eng

New Data on Minerals, Volume 55, 2021

DEADLINES FOR ARTICLES

Issue 1 - March 31, 2021
Issue 2 - May 31, 2021
Issue 3 - August 31, 2021
Issue 4 - November 30, 2021

Editorial Board

Editor in Chief:
Plechov P.Yu. - Doctor of Geology and Mineralogy, Professor
Members of Editorial Board:
Pekov I.V. - Corresponding Member of the Russian Academy of Sciences
Garanin V.K. - Doctor of Geology and Mineralogy, Professor
Novgorodova M.I. - Doctor of Geology and Mineralogy, Professor
Borutsky B.E. - Doctor of Geology and Mineralogy
Spiridonov B.E. - Doctor of Geology and Mineralogy
Kamenetsky V.S. - Professor (University of Tasmania)
Nenasheva S.N. - PhD in Geology and Mineralogy
Matvienko E.N. - PhD in Geology and Mineralogy
Generalov M.E. - PhD in Geology and Mineralogy
Pautov L.A. - Senior Researcher
Layout Designer
Kronrod E.V. - PhD in Chemistry

Content

Issue 1

Kutyrev A.V., Kamenetskiy V.S., Nekrylov N.A. Silicate inclusions in minerals of the Os-Ir-Ru system of the Adamsfield placer (Western Tasmania), p. 5-13

The collection of the native osmium grains from the Adamsfield placer (Western Tasmania) was studied. The majority of these grains and compositionally homogeneous (average composition of native osmium – 52.9 wt.% of Os, 41.2 wt.% of Ir, and 6.4 wt.% of Ru), while other minerals (native iridium, isoferroplatinum, native ruthenium, and arsenides of platinum) are rare. The chromitites from the ultramafic ophiolites of the Adamsfield complex are likely the source of the placer. Polymineralic inclusions consisting of olivine, orthopyroxene, chromium spinel, hornblende, low-Ca amphiboles (cummingtonite and anthophyllite), quartz, anorthite, and micas were found within the native osmium grains. These inclusions typically have a hexagonal shape exhibiting the habit of a negative crystal. Their origin can hardly be explained by the model suggested in previous studies (direct crystallization of the native osmium from the boninitic melt), and they rather support the modern view on the origin of chromitite and platinum mineralization in ophiolites as a result of a reaction of harzburgites with slab-derived fluids and melts. A number of morphological and compositional features of minerals hosted by these inclusions suggest the extreme heterogeneity of the mineral-forming environment, as well as the crucial role of metamorphic and metasomatic processes in the origin of studied mineral association.
Keywords: PGM, osmium, inclusions, metamorphism, subduction.
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Pautov L.A., Mirakov M.A., Iskandarov F.Sh. On dearsenization of sperrylite during heavy cоncentrates heating, p. 14-23

The article presents the results of experiments on heating of sperrylite under conditions close to the conditions of heating of pyrite-rich concentrates for the conversion of sulfides into magnetic stub ends and their separation from minerals of the platinum group elements (PGE). During heating a mixture of pyrite and sperrylite (–0.5 – +0.1 mm fraction) under oxidizing conditions at 420–450 ^оС, sperrylite undergoes dearsenization along the periphery of the grains in 1 hour with the occurrence of incomplete pseudomorphoses of platinum on sperrylite. Such products of PtAs₂ heating have the structure of a nut: the core consists of a relict sperrylite, and the rim (with a capacity of up to 100 microns) is metallic platinum. Rarely, crescent-shaped fracture cracks are observed in the platinum border. During heating at 600 ^оС in 1.5 hours, sperrylite completely drop into metallic platinum, regardless of whether the pure fraction of sperrylite was or mixed with pyrite. Dearsenization of sperrylite is accompanied with the formation of structures, which are characteristic for this process (zones with different porosity and peculiar crescent-shaped cracks).
Based on these experiments, it is concluded that the method of heavy соncentrates heating in order to separate pyrite from PGE minerals by converting sulfides into magnetic stubs has serious limitations. The advantage of this method is its simplicity, the short time required for the material separation and a very high enrichment coefficient, which practically excludes the non-detection of sperrylite, as well as the other non-magnetic PGE minerals, if they were present in the heavy соncentrates. The disadvantage of the heavy соncentrates heating method is that sperrylite, even for a relatively short time (1 hour), undergoes dearsenization, and therefore the method is applicable to establish the presence of sperrylite in the heavy соncentrates, but it is not suitable for separating the heavy соncentrates in order to isolate precious metal minerals for their further detailed study.
Keywords: sperrylite, platinum, dearsenization, platinum group elements minerals, heavy соncentrates, heating.
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Russian version (V. 55)