特提斯成矿域中新世斑岩铜矿岩石成因、源区、构造演化及其成矿作用过程

Petrogenesis, source, tectonic evolution and mineralization process of the Miocene porphyry Cu deposits in the Tethyan metallogenic domain

作为全球三大成矿域之一,特提斯成矿域发育众多的世界级成矿带(矿床),例如,旁地德斯、萨汉德-巴兹曼、贾盖、玉龙、冈底斯成矿带等。为了进一步了解特提斯成矿域中新世斑岩铜矿的成因及成矿作用,本文对萨汉德-巴兹曼、贾盖和冈底斯铜矿带典型矿床的地质、地球化学、Sr-Nd-Pb数据进行对比分析,探讨含矿斑岩岩石成因、源区特征和构造环境,归纳其构造演化与其成矿作用过程。地球化学数据显示,这三个铜矿带中新世斑岩体总体显示钙碱性I型花岗岩的特征,具有埃达克岩亲和性。与冈底斯铜矿带相比较,萨汉德-巴兹曼铜矿带和贾盖铜矿带斑岩体显示出弧岩浆岩与埃达克岩过渡的地球化学特征,暗示其岩浆源区MORB质角闪榴辉岩或榴辉岩可能发生的较大程度的部分熔融。Sr-Nd-Pb同位素数据显示,这些含矿斑岩主要来源于受岩浆作用控制的壳幔混合物质,显示DUPAL异常。综合研究分析,认为这些含矿斑岩可能形成于岛弧造山带演化过程中,是洋壳俯冲消减和大陆碰撞过程中增厚下地壳部分熔融的结果。

Several world class ore-forming belts(deposits) such as the Pontides, the Sahand-Bazman, the Chagai, the Yulong and the Gangdeseoccur in the Tethyanmetallogenic domain, referred to as one of the three giant metallogenic domains. In order to further understand the genesis and mineralization of Miocene porphyry copper deposits in the Tethyan domain, the geological, geochemical and Sr-Nd-Pb isotopic data of ore-bearing porphyries from typical porphyry Cu deposits in the Sahand-Bazman, the Chagai and the Gangdese belts have been analyzed and compared, their petrogenesis, source and tectonic environment have been discussed, and their tectonic evolution and metallogenic process have been deduced and summarized in this paper. The geochemical results suggest that the Miocene porphyries in these three belts show the characteristics of calc-alkaline I-type granite, with adakite magmatic affinity. Compared with the lithogeochemical features of porphyries in the Gangdese belt, the ones in the Sahand-Bazman and the Chagai belts show the transitioning characteristics from arc magmatic suites to adakites, which might be caused by the partial melting of MORB-derived amphibole eclogite or eclogite occurred in the magma source with a greater degree. The Sr-Nd-Pb isotopic data suggests that these ore-bearing porphyries might have been sourced from a mixture of crust and mantle controlled by magma, showing DUPAL anomaly. After comprehensively analyzing the geological, geochemical and isotopic characteristics of these porphyry deposits, it is believed that these ore-bearing porphyries were formed in the island arc setting of collision-orogenic belt, serving as the partial melting products of thickened lower crust during the subduction of oceanic crust and the continental collision.