In-situ U–Pb, Hf and Re–Os isotopic analyses of the Xiangshan Ni–Cu–Co deposit in Eastern Tianshan (Xinjiang), Central Asia Orogenic Belt: Constraints on the timing and genesis of the mineralization
In-situ U–Pb, Hf and Re–Os isotopic analyses of the Xiangshan Ni–Cu–Co deposit in Eastern Tianshan (Xinjiang), Central Asia Orogenic Belt: Constraints on the timing and genesis of the mineralization
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DOI：
10.1016/j.lithos.2010.09.019
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发表时间：
2010-12
期刊：
影响因子：
3.5
通讯作者：
Chunming Han;W. Xiao;Guochun Zhao;S. Ao;Ji’en Zhang;W. Qu;A. Du
中科院分区：
文献类型：
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作者：
Chunming Han;W. Xiao;Guochun Zhao;S. Ao;Ji’en Zhang;W. Qu;A. Du
本文根据新近获得的U-Pb、Hf和Re-Os同位素资料，对相山岩体中主要的Ni-Cu-Co硫化物存款矿床的形成时间和成因进行了研究。含Ni-Cu-Co硫化物存款辉长岩的西姆斯U-Pb年龄表明，相山岩体侵位于279.6±1.1Ma（95%置信水平，MSWD=1.30，n=15）。综合地质和年代学证据，我们认为相山镍铜矿床与邻近的其他镍铜矿床形成于同一时期。硫化物具有低的普通锇浓度和高的Re/Os比率，类似于杜卢斯、萨利马来和Voisey湾复合体的硫化物矿石。相山岩体中浸染状和块状矿石的Re-Os同位素数据不形成单一的等时线，因为它们具有不同的初始Os比值。Hf、Os同位素数据表明，相山岩体及伴生的Ni-Cu-Co成矿作用来自地壳混染的地幔熔体。地球化学数据显示拉斑玄武岩的亲和力和强烈的俯冲带签名负Nb，Sr和Ti异常类似于N-MORB和E-MORB。东天山镁铁-超镁铁岩及其伴生的镍铜矿化形成于阿拉斯加型俯冲带弧环境。中国东天山造山带具有一些脊-沟相互作用的特征（如花岗岩、埃达克岩、高镁安山岩、近海沟岩浆作用、阿拉斯加型镁铁质-超镁铁质杂岩、从低变质带快速侵入的高温变质带和造山型金矿）。上述独特的岩石群可能与阿拉斯加新生代造山带中的同一热事件-洋脊俯冲有关。我们认为，洋脊俯冲是最合理的机制，以提供必要的热量。洋脊俯冲为理解中国东天山造山带的许多方面的演化提供了一个重要的有前途的模式，并推断，在整个中亚。
The timing and genesis of the major Ni–Cu–Co sulfide deposit in the Xiangshan intrusion have been studied based on newly obtained in-situ U–Pb, Hf and Re–Os isotopic analyses. The SIMS U–Pb zircon ages of the gabbro hosting the Ni–Cu–Co sulfide deposit indicate that the Xiangshan intrusion was emplaced at 279.6±1.1Ma (95% confidence level, MSWD=1.30, n=15). On the basis of combined geological and geochronological evidence, we suggest that the Xiangshan and other adjacent Ni–Cu deposits were formed in the same period. Sulphides have low common Os concentrations and high Re/Os ratios, similar to sulphide ores from the Duluth, Sally Malay and Voisey Bay complexes. The Re–Os isotopic data from the disseminated and massive ores from the Xiangshan intrusion do not form a single isochron, as they have different initial Os ratios. The Hf and Os isotopic data suggest that the Xiangshan intrusion and associated Ni–Cu–Co mineralization were derived from crustally contaminated mantle melts. The geochemical data show a tholeiitic affinity and a strong suprasubduction zone signature with negative Nb, Sr, and Ti anomalies similar to N-MORB and E-MORB. We suggest that the mafic–ultramafic rocks and associated Ni–Cu mineralization of the Eastern Tianshan orogen formed in an Alaska-type subduction zone-arc setting. Some diagnostic features of ridge–trench interaction are present in the Chinese East Tianshan orogen (e.g. granites, adakites, high-Mg andesites, near-trench magmatism, Alaskan-type mafic–ultramafic complexes, high-temperature metamorphic belts that prograde rapidly from low-grade belts, and orogenic gold deposits). The above distinctive rock groups are probably related to the same thermal event, ridge subduction, as in the Cenozoic orogen of Alaska. We suggest that ridge subduction is the most plausible mechanism to provide the necessary heat. Ridge subduction provides an important promising model for understanding many aspects of the evolution of the Chinese Eastern Tianshan orogen, and by inference, throughout much of Central Asia.