Abstract

The article presents the results of studying the chemical composition of ore-bearing rocks, as well as the mineralogy of base metal sulfides and platinum group elements (PGE), of the Nyud-II sulfide PGE–Cu–Ni deposit in the southwestern part of the Nyud massif of the Monchegorsk Pluton (Monchepluton). The ores of the deposit are represented by vein-disseminated and nest-schlieren types. They are characterized by significant predominance of Pd over Pt, fractionation of low-melting PGE (PPGE subgroup) with respect to high-melting ones (IPGE subgroup), and close correlations of Ni and Cu with S in the presence of increased As, Se, Te, and Bi contents. The S/Se ratios in ore (3470−3530) correspond to the mantle values. Among the platinum group minerals (PGM), the most widespread are Pt and Pd bismuth–tellurides and tellurides (merenskyite, michenerite, and moncheite), subordinate amounts of Pt–Fe alloys and sperrylite, and native osmium and Ir, Rh, and Pt sulfoarsenides (irarsite, hollingworthite, and platarsite). The formation of ore sulfide concentrations resulted from separation of an immiscible sulfide liquid upon cooling of a sulfur-saturated silicate magma with a mafic composition. Subsequent fractional crystallization of the sulfide liquid contributed to the uneven distribution of Ni, Cu, and PGE. PGE–sulfide ore formation took place in a fairly wide temperature range, starting at 1100−1000°C and ending at 600−400°C. At an early stage, IPGE minerals (native osmium and erlichmanite) separated. Upon cooling to a temperature of 1000−900°C, the sulfide liquid fractionated with the formation of monosulfide solid solution (mss), in which compatible IPGE were concentrated, and a residual sulfide liquid enriched in Ni, Cu, PtPGE, and chalcophile elements. With a further decrease in temperature (to 600°C), Pt–Fe alloys, sperrylite, and IPGE + Pt sulfoarsenides crystallized, with separation of the residual sulfide melt enriched in Cu, PPGE and chalcophile elements. At 600−400°C, ore formation ended with the complete crystallization of base metal sulfides and the formation of Pt and Pd bismuth–tellurides and tellurides.

中文翻译：

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俄罗斯科拉半岛蒙切戈尔斯克岩体硫化物PGE-Cu-Ni Nyud-II矿床铂含量及形成条件

摘要

本文介绍了研究西南地区 Nyud-II 硫化物 PGE-Cu-Ni 矿床含矿岩石的化学成分以及贱金属硫化物和铂族元素 (PGE) 的矿物学的结果。 Monchegorsk Pluton (Monchepluton) 的 Nyud 地块。矿床的矿石以脉播散型和巢纹型为代表。它们的特点是 Pd 显着高于 Pt，低熔点 PGE（PPGE 亚组）相对于高熔点 PGE（IPGE 亚组）的分馏，以及在 As、Se 增加的情况下 Ni 和 Cu 与 S 的密切相关性、Te 和 Bi 含量。矿石中的 S/Se 比 (3470-3530) 对应于地幔值。在铂族矿物 (PGM) 中，分布最广的是 Pt 和 Pd 铋-碲化物和碲化物（merenskyite、michenerite、和 moncheite)、少量的 Pt-Fe 合金和闪锌矿，以及天然锇和 Ir、Rh 和 Pt 硫砷化物（镁铁矿、hollingworthite 和 platarsite）。矿石硫化物浓度的形成是由于在具有镁铁质成分的硫饱和硅酸盐岩浆冷却时分离出不混溶的硫化物液体。随后硫化物液体的分步结晶导致 Ni、Cu 和 PGE 的不均匀分布。PGE-硫化物矿石的形成发生在相当宽的温度范围内，从 1100-1000°C 开始，到 600-400°C 结束。在早期阶段，IPGE 矿物（天然锇和蛇纹石）分离。冷却至 1000-900°C 后，硫化物液体分馏，形成单硫化物固溶体 (mss)，其中相容的 IPGE 被浓缩，以及富含 Ni、Cu、PtPGE 和亲硫元素的残余硫化物液体。随着温度的进一步降低（至 600°C），Pt-Fe 合金、闪锌矿和 IPGE + Pt 硫代砷化物结晶，分离出富含 Cu、PPGE 和亲硫元素的残余硫化物熔体。在 600-400°C 时，矿石的形成以贱金属硫化物的完全结晶以及 Pt 和 Pd 碲化铋和碲化物的形成结束。