The Epilchik Ural-Alaskan type mafic-ultramafic zoned complex, located in the northernmost part of the Koryak-Kamchatka Platinum Belt (Russian Far East), contains lode platinum mineralization. The outcrops of the complex are crossed by the Snegovaya River, which hosts placer platinum-group minerals (PGM) occurrences. The primary PGM assemblage of the Epilchik lode chromitites is typical for Ural-Alaskan type complexes, dominated by Ir-rich isoferroplatinum which occurs as small euhedral inclusions within chromite. Secondary alloys include tetraferroplatinum (PtFe), tulameenite (Pt 2 FeCu), an unnamed Fe 3 Pt compound, and Pt-bearing native iron, which form alteration rims around isoferroplatinum or occupy fractures in chromite. Other secondary minerals from lode chromitites are hollingworthite (RhAsS) and Os-Fe alloy (“hexaferrum”). The PGM assemblages of the Snegovaya River placer occurrences are comparable with those of the lode chromitites with a predominance of Ir-rich isoferroplatinum and secondary alloys, including tetraferroplatinum, tulameenite, and an unnamed Fe 3 Pt compound. However, placer occurrences are much richer in regard to mineral diversity, comprising native osmium (Os,Ir), native iridium (Ir,Os), laurite (RuS 2 ), erlichmanite (OsS 2 ), cuprorhodsite (CuRh 2 S 4 ), cuproiridsite (CuIr 2 S 4 ), Co-malanite (Cu(Pt,Co) 2 S 4 ), unnamed sulfides Rh 3 S 4 , (Rh,Pt)S, sperrylite (PtAs 2 ), platarsite (PtAsS), irarsite (IrAsS), hollingworthite (RhAsS), osarsite (OsAsS), cooperite (PtS), native gold, unnamed telluride (Pt 2 Te), and an unnamed Fe-Ir-Rh alloy. Similarities between lode and placer mineralization indicate that the Epilchik complex was the dominant source for the placers. The larger diversity of PGM in placers may be attributed to the heterogeneity of samples which could be derived from unsampled or unexposed outcrops of the complex. Alteration of isoferroplatinum to secondary intermetallic compounds occurred via progressive development of reduced conditions as a result of serpentinization. Subsequent pervasive As-mineralization redistributed platinum-group elements, including Os and Ir. A final mineralizing pulse deposited sporadic native gold and Pt telluride minerals. A comparison of key mineralogical and physical features between the Epilchik complex and other Ural-Alaskan type complexes is used to determine the economic potential for placers along the Snegovaya River. Key criteria include (1) the size and degree of erosion of the outcrop area of the complex; (2) the predominance of isoferroplatinum over native platinum; (3) high Ir content in Pt-Fe alloys; and (4) the predominance of secondary intermetallic compounds over sulfides. Based on these criteria, the occurrences associated with the Epilchik complex are considered prospective for high volume and economic grade accumulations of PGE. This method is useful for assessing the economic potential of placer occurrences during indirect early-stage prospecting with a limited sample suite.

中文翻译：

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Epilchik Ural-Alaskan 类型带状复合体的铂矿化（远东俄罗斯）

Epilchik Ural-Alaskan 型镁铁质-超镁铁质带状复合体，位于科里亚克-堪察加白金带（俄罗斯远东）的最北端，含有矿脉铂矿化。该复合体的露头被 Snegovaya 河穿过，该河拥有砂铂族矿物 (PGM) 矿床。Epilchik 矿脉铬铁矿的主要 PGM 组合是乌拉尔-阿拉斯加型复合体的典型特征，主要是富含 Ir 的异铁铂，它在铬铁矿中作为小的自面形包裹体出现。二次合金包括四铁铂 (PtFe)、tulameenite (Pt 2 FeCu)、一种未命名的 Fe 3 Pt 化合物和含铂的天然铁，它们在异铁铂周围形成蚀变边缘或占据铬铁矿的裂缝。来自铬铁矿脉的其他次生矿物是 hollingworthite (RhAsS) 和 Os-Fe 合金 (“六铁”)。Snegovaya 河砂矿矿点的 PGM 组合与以富含 Ir 的异铁铂和次生合金为主的铬铁矿脉相比较，包括四铁铂、tulameenite 和未命名的 Fe 3 Pt 化合物。然而，砂矿在矿物多样性方面更为丰富，包括天然锇（Os,Ir）、天然铱（Ir,Os）、月桂石（RuS 2 ）、埃立锰矿（OsS 2 ）、铜锰矿（CuRh 2 S 4 ）、铜铁矿 (CuIr 2 S 4 )、钴马龙石 (Cu(Pt,Co) 2 S 4 )、未命名的硫化物 Rh 3 S 4 、(Rh,Pt)S、闪锌矿 (PtAs 2 )、菱铁矿 (PtAsS)、铁镁石 ( IrAsS)、hollingworthite (RhAsS)、osarsite (OsAsS)、cooperite (PtS)、天然金、未命名的碲化物 (Pt 2 Te) 和未命名的 Fe-Ir-Rh 合金。矿脉和砂矿矿化之间的相似性表明 Epilchik 复合体是砂矿的主要来源。砂矿中 PGM 的更大多样性可能归因于样品的异质性，这可能来自未采样或未暴露的复合体露头。由于蛇纹石化，通过还原条件的逐步发展，异铁铂变为次级金属间化合物。随后普遍存在的 As 矿化重新分布了铂族元素，包括 Os 和 Ir。最后的矿化脉冲沉积了零星的天然金和碲化铂矿物。通过比较 Epilchik 复合体与其他乌拉尔-阿拉斯加类型复合体之间的关键矿物学和物理特征，可以确定 Snegovaya 河沿岸砂矿的经济潜力。关键标准包括 (1) 综合体露头区域的大小和侵蚀程度；(2)异铁铂优于天然铂；(3) Pt-Fe合金中Ir含量高；(4) 次生金属间化合物优于硫化物。根据这些标准，与 Epilchik 杂岩体相关的矿点被认为是 PGE 的大量和经济等级积累的前景。该方法可用于在有限的样本组中间接早期勘探期间评估砂矿矿点的经济潜力。与 Epilchik 杂岩体相关的矿点被认为是 PGE 的大量和经济级积累的前景。该方法可用于在有限的样本组中间接早期勘探期间评估砂矿矿点的经济潜力。与 Epilchik 杂岩体相关的矿点被认为是 PGE 的大量和经济级积累的前景。这种方法可用于在有限的样本组中间接早期勘探期间评估砂矿矿点的经济潜力。