Abstract

The Triassic (232–233 Ma) Ildeus mafic-ultrabasic massif is a fragment of a large mineralized magmatogenic system formed within the Stanovoy Mobile Belt at the Mesozoic stage of its evolution. Ultrabasic rocks are represented by cumulative plagioclase- and amphibole-bearing dunites, peridotites, websterites, and pyroxenites; basic rocks are gabbro-anorthosites, norites, and two-pyroxene gabbro. Most intrusive rocks of the Ildeus magmatogenic system experienced ultramafic (serpentine, chlorite, talc, and carbonates) and acidic (quartz, biotite, potassium feldspar, and secondary micas) metasomatism. Geochemical characteristics (calc-alkaline differentiation trend, negative anomalies of highly-charged incoherent elements) indicate the subduction nature of the primary magma in the Ildeus system. The ultrabasic rocks are intruded by intermediate-acidic intrusions with geochemical characteristics of adakite. Magmatic-stage silver mineralization is represented by microinclusions of cuprous silver, alloys of silver, copper, gold and zinc, acanthite and silver halides in association with pentlandite, chalcopyrite, bornite, and pyrrhotite. These rocks are characterized by microinclusions of native platinum, gold, tungsten, bismuth, lead, PGE alloys, W–Co–Ti, Sb–Pb, Cu–Zn–Sn, minerals of Ag–Cu–Sb–Se–S and Zn–Ni–Co–Fe–S systems, barite, chlorapatite and Bi–Sn–Pb chlorides. At the metasomatic stage, native silver, Au–Ag alloys, silver and copper chlorides, acanthite, silver and lead tellurides coexist with, pyrite, sphalerite, galena, native nickel and gold, Cu–Zn alloys, sulfides of the Pb–As–Cu–Fe–S and bismuth chloride. At the magmatic stage, silver minerals crystallized under reducing conditions in the presence of high-temperature aqueous fluids enriched in sulfide sulfur, halogens, and volatile siderophile (W, Pt) and chalcophile (Ag, Bi, Sn, Sb, and Pb) metals that entered the primary melt from serpentinites, metamorphosed gabbroids, and metal-bearing pelagic sediments of the subducting oceanic plate. Metasomatic parageneses of silver minerals were formed under oxidized near-surface conditions with the participation of low-temperature water–salt solutions with elevated concentrations of sulfate sulfur, arsenic, and tellurium. A two-stage model is proposed for the formation of silver mineralization in the island-arc magmatic systems, where the high-temperature magmatic stage of the formation in deep crustal parts is replaced by low-temperature hydrothermal ore formation processes in near-surface conditions.

中文翻译：

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古岛弧深部岩浆成因系统中的银矿化：伊尔德斯超基性地块，斯坦诺沃伊移动带（俄罗斯远东）

摘要

三叠纪（232-233Ma）Ildeus镁铁质-超基性地块是斯坦诺沃移动带内中生代演化阶段形成的大型矿化岩浆生成系统的一部分。超基性岩以累积的斜长石和角闪石纯岗岩、橄榄岩、韦氏辉石和辉石岩为代表；基性岩有辉长斜长岩、苏长岩、二辉石辉长岩。伊迪乌斯岩浆生成系统的大多数侵入岩经历了超镁铁质（蛇纹石、绿泥石、滑石和碳酸盐）和酸性（石英、黑云母、钾长石和次生云母）交代作用。地球化学特征（钙碱性分异趋势、高电荷非相干元素的负异常）表明了伊迪乌斯系统中原生岩浆的俯冲性质。超基性岩受中酸性岩体侵入，地球化学特征为埃达克岩。岩浆阶段银矿化以银铜微包裹体、银、铜、金和锌的合金、棘铁矿和卤化银与镍黄铁矿、黄铜矿、斑铜矿和磁黄铁矿伴生为代表。这些岩石的特征是含有天然铂、金、钨、铋、铅、PGE 合金、W-Co-Ti、Sb-Pb、Cu-Zn-Sn、Ag-Cu-Sb-Se-S 和 Zn 矿物。 –Ni-Co-Fe-S 体系、重晶石、氯磷灰石和 Bi-Sn-Pb 氯化物。在交代阶段，原生银、Au-Ag合金、银和氯化铜、棘铁矿、银和碲化铅与黄铁矿、闪锌矿、方铅矿、原生镍和金、Cu-Zn合金、Pb-As-的硫化物共存。 Cu-Fe-S 和氯化铋。在岩浆阶段，银矿物在还原条件下在富含硫化物硫、卤素和进入初级熔体的挥发性亲铁元素（W、Pt）和亲铜元素（Ag、Bi、Sn、Sb 和 Pb）金属的高温水流体存在下结晶来自蛇纹岩、变质辉长岩和俯冲海洋板块的含金属远洋沉积物。银矿物的交代共生体是在氧化近地表条件下、在硫酸硫、砷和碲浓度升高的低温水盐溶液的参与下形成的。提出了岛弧岩浆系统中银矿化形成的两阶段模型，