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首页> 外文期刊>Economic geology and the bulletin of the Society of Economic Geologists >Sulfide Saturation and Magma Emplacement in the Formation of the Permian Huangshandong Ni-Cu Sulfide Deposit, Xinjiang, Northwestern China
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Sulfide Saturation and Magma Emplacement in the Formation of the Permian Huangshandong Ni-Cu Sulfide Deposit, Xinjiang, Northwestern China

机译：中国西北地区二叠系黄山洞镍铜硫化物矿床形成中的硫化物饱和度和岩浆位置

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摘要

The eastern Tianshan orogenic belt, northwestern China, hosts ～120 mafic-ultramafic intrusions and at least six of them host significant Ni-Cu sulfide mineralization of which the Permian Huangshandong intrusion is the largest. The mafic-ultramafic rocks of the Huangshandong intrusion comprise Iherzolite, gabbronorite, gabbro, and diorite. Individual orebodies are composed of pyrrhotite, pentlandite, and chalcopyrite as disseminated to net-textured or massive to semimassive sulfide mineralization. Oxide-bearing sulfide mineralization contains 1 to 5% magmatic magnetite that has ilmenite and spinel exsolution lamellae.Silicate rocks and sulfide mineralization have variable whole-rock platinum group elements (PGE; 0.38-362 ppb), Cu (42-97,000 ppm), and Ni (26-33,000 ppm) concentrations. The mineralization is broken out into two types termed oxide rich and oxide poor. The oxide-rich sulfide mineralization has high PGE concentrations with low ~(187)Re/~(188)Os ratios (38.9-151), whereas oxide-poor sulfide mineralization has low PGE concentrations with high ~(187)Re/~(188)Os (159-781). Both oxide-rich and -poor sulfide mineralization have highly variable γ_(Os) values (49-189 and 30-278, respectively). Oxide-rich sulfide mineralization contains magnetite with variable amounts of MgO, TiO_2, Al_2O_3, FeO_(total), Cr, V, Zn, and Sn, indicating that they crystallized from different stages during magma differentiation.We propose that the host intrusion and associated sulfide mineralization were derived from high Mg basaltic magmas from a mantle source that was previously modified by subducted oceanic slab. Oxide-poor sulfide mineralization of the Huangshandong intrusion formed from a magma that underwent <0.03% sulfide removal before emplacement and was thus PGE depleted. Oxide-rich sulfide mineralization formed from magma that had much lower amounts of sulfide (<0.003%) removed in the early stage before entering the Huangshandong magma chamber. An early sulfide saturation event was likely associated with fractionation of silicate minerals in a deep-staging magma chamber. The second sulfide saturation event that formed the sulfide mineralization was probably triggered by selective crustal contamination and fractionation in the high-level chamber where mixing of magmas and accumulation of immiscible sulfide occurred.
机译：中国西北部的天山东部造山带有〜120个镁铁质-超镁铁质侵入体，其中至少有6个具有明显的镍-铜硫化物矿化作用，其中二叠纪黄山洞侵入带最大。黄山洞侵入带的镁铁质-超镁铁质岩石包括海泡石，辉长岩，辉长岩和闪长岩。单个矿体由黄铁矿，方铁矿和黄铜矿组成，散布到网状结构或块状到半块状硫化物矿化中。含氧化物的硫化物矿化包含1％至5％的磁铁矿磁铁矿，其中含有钛铁矿和尖晶石溶出层。硅酸盐岩和硫化物矿化具有可变的全岩铂族元素（PGE; 0.38-362 ppb），Cu（42-97,000 ppm），和Ni（26-33,000 ppm）浓度。矿化分为两种类型，称为富氧化物和贫氧化物。富含氧化物的硫化物矿化具有较高的PGE浓度且〜（187）Re /〜（188）Os比较低（38.9-151），而贫氧化物的硫化物矿化具有较低的PGE浓度且具有较高的〜（187）Re /〜（ 188）Os（159-781）。富含氧化物的硫化物和贫硫化物的矿化都具有高度可变的γ_（Os）值（分别为49-189和30-278）。富含氧化物的硫化物矿化包含的磁铁矿中MgO，TiO_2，Al_2O_3，FeO_（总计），Cr，V，Zn和Sn的含量可变，表明它们在岩浆分化过程中从不同的阶段结晶出来。硫化物矿化来自地幔来源的高镁玄武岩浆，该地幔源以前曾被俯冲的海洋平板修饰。黄山洞岩体中氧化物含量低的硫化物矿化是由岩浆形成的，该岩浆在就位前进行了<0.03％的硫化物去除，因此PGE被耗尽。岩浆形成的富氧化物硫化物矿化，进入黄山洞岩浆室前，早期除去的硫化物量少得多（<0.003％）。早期硫化物饱和事件可能与深部岩浆室内硅酸盐矿物的分馏有关。形成硫化物矿化的第二个硫化物饱和事件可能是由高位室内的选择性地壳污染和分馏引发的，在该高位室内发生了岩浆混合和不混溶硫化物的积累。

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