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

在基性岩浆系统中形成大型镍铜硫化物矿床似乎需要：1)通过岩石污染达到硫化物饱和，2)在岩浆管道内流体动力学有利的区域集中不混溶的硫化物液体，以及3)通过管道持续流动的岩浆反应使合并硫化物中的金属含量富集。中国中北部的金川矿床是世界上最大的导管类矿床。镍和铜硫化物的主要储量位于侵入元古代变质沉积层序的超基性岩石中。到目前为止，还没有对该矿床进行关于岩石污染在矿石成因中的潜在作用的调查，也没有对新鲜岩浆对硫化物金属升级的物理化学动力学进行评估。本文对金川岩体岩石类型中的橄榄石化学变化和稳定同位素分布进行了详细的研究。橄榄石化学将结合全岩主微量元素数据，确定是否有多岩浆参与了金川侵入体的形成，如果有，它们与硫化物相互作用的程度如何，以产生富集的Ni和Cu含量。将收集乡村岩石以及矿化和非矿化侵入岩的硫、氧同位素数据。这些数据将用于评价含矿侵入岩中所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度和浓度的历史。本文的研究成果不仅将提高我们对金川矿床和世界上其他类似类型矿床形成的认识，而且将提高我们对镁质岩浆导管系统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.