Olivine Geochemistry and Stable Isotope Studies of the Giant Jinchuan Ni-Cu Sulfide Deposit, Western China: Investigation of Ore Genesis in a Magma Conduit

镁铁质岩浆系统中大型镍铜硫化物矿床的形成似乎需要：1)通过围岩污染达到硫化物饱和度，2)在岩浆管道内流体动力学有利的区域浓缩不混溶的硫化物液体，3)与持续流经管道的岩浆反应，使合并硫化物中的金属含量增加。中国中北部的金川矿床是世界上最大的与管道有关的矿床。镍和铜硫化物的主要储量位于侵入元古代变质沉积序列的超镁铁质岩石中。到目前为止，该矿床还没有研究围岩污染在成矿中的潜在作用，也没有评价新鲜岩浆对金属硫化物升级的物理化学动力学。我们建议对金川侵入体中存在的岩石类型中的橄榄石化学变化和稳定同位素分布进行详细的研究。橄榄石化学结合全岩常量元素和微量元素数据，将确定金川岩体的形成是否涉及多个岩浆，如果是，它们与硫化物相互作用的程度如何，以产生丰富的镍和铜含量。硫和氧同位素数据将从围岩和矿化和非矿化侵入岩中收集。这些数据将被用来评估在含矿侵入岩中记录的围岩同化程度，并建立混合模型，用于模拟岩浆系统中硫化物饱和和浓缩的历史。这些研究成果不仅将加深我们对金川矿床和世界上其他类似类型矿床形成的认识，而且也将提高我们对镁铁质岩浆输导系统中的动态岩石学过程的认识。

Li&RipleyEAR-0104580The formation of large Ni-Cu sulfide deposits in mafic magmatic systems appears to require: 1) attainment of sulfide saturation through country rock contamination, 2) concentration of immiscible sulfide liquid in fluid dynamically favored areas within magma conduits, and 3) enrichment of the metal content of the coalesced sulfide by reaction with continued flow of magma through the conduit. The Jinchuan deposit in north-central China is the largest conduit-related occurrence in the world. Major reserves of Ni- and Cu-sulfides are located within ultramafic rocks that intrude a Proterozoic metasedimentary sequence. To date the deposit has not been investigated with respect to the potential role of country rock contamination in ore genesis, nor have the physicochemical dynamics of metal upgrading of sulfide by fresh magma been evaluated.We propose a detailed study of olivine chemical variations and stable isotopic distributions within the rock types present in the Jinchuan intrusion. Olivine chemistry, in conjunction with whole rock major and trace element data, will be used to determine if multiple magmas have been involved in building the Jinchuan intrusion, and if so, to what extent they have interacted with sulfide to produce enriched Ni and Cu contents. Sulfur and oxygen isotopic data will be collected from country rocks and both mineralized and non-mineralized intrusive rocks. These data will be used to evaluate the extent of country rock assimilation recorded in the ore-bearing intrusive rocks, and to construct mixing models that will be utilized in simulating the history of sulfide saturation and concentration in the magmatic system. Findings from the proposed research will not only improve our understanding of the formation of the Jinchuan deposit and other deposits of similar type around the world, but will also improve our knowledge of dynamic petrological processes in mafic magmatic conduit systems.