&nbsp;德兴张家畈金矿远景区花岗闪长斑岩年代学、Lu－Hf同位素及成矿指示意义

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南京大学学报(自然科学版) ›› 2018, Vol. 54 ›› Issue (2) : 386.

德兴张家畈金矿远景区花岗闪长斑岩年代学、Lu－Hf同位素及成矿指示意义

李　利1，倪　培1*，王国光1，朱安冬1，范明森1，黄卫平2

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Geochronology and Lu－Hf isotopes of granodiorite porphyries of Zhangjiafan gold prospect area in Dexing and its indication significance for mineralization

Li Li1，Ni Pei1*，Wang Guoguang1，Zhu Andong1，Fan Mingsen1，Huang Weiping2

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摘要

德兴矿集区是我国重要的Cu－Au－Mo－Pb－Zn－Ag矿产资源产地，张家畈金矿远景区位于德兴斑岩铜矿田的北西部. 选取张家畈成矿远景区深部的矿化花岗闪长斑岩作为研究对象，对其进行了系统的LA－ICP－MS锆石U－Pb年代学和锆石Lu－Hf同位素分析. 张家畈花岗闪长斑岩两件样品中锆石14个分析点206Pb/238U的加权平均年龄为171±1 Ma(MSWD＝0.54). 张家畈花岗闪长斑岩锆石Lu－Hf同位素结果为：εHf(t)为＋5.2～＋6.3，两阶段模式年龄为813 Ma～883 Ma. 该岩体的原始岩浆来源于新元古代下地壳物质的部分熔融，并在形成过程中可能加入了地幔组分. 中侏罗世，伊泽纳崎板块向华南板块北西向俯冲，在华南内陆产生了一系列伸展型岩浆作用，指示了局部拉伸的环境，因此，张家畈花岗闪长斑岩形成于陆内拉伸的构造背景. 张家畈矿化花岗闪长斑岩的成岩时代及Hf同位素特征均与德兴斑岩铜矿田的成矿花岗闪长斑岩相似，且张家畈成矿远景区内自然金与黄铜矿伴生，因此，其深部可能具有斑岩型矿化．

Abstract

Dexing ore－concentrated area is the important source of Cu，Au，Mo，Pb，Zn and Ag. Zhangjiafan metallogenic prospect area locates at the northwestern of the Dexing porphyry copper ore field. This paper assesses the deep－seated mineralized granodiorite porphyries in the Zhangjiafan prospect area. A combined study of comprehensive LA－ICP－MS zircon U－Pb dating and Lu－Hf isotopes of the Zhangjiafan mineralized granodiorite porphyries was carried out. The Zhangjiafan mineralized granodiorite porphyries emplaced during Middle Jurassic with a 206Pb/238U weighted average age of ca. 171 Ma(MSWD＝0.54). The εHf(t) values and two stage Hf model ages of the Zhangjiafan mineralized granodiorite porphyries are ＋5.2～＋6.3 and 813 Ma～883 Ma respectively. The Zhangjiafan mineralized granodiorite porphyries were probably derived from partial melting of Neoproterozoic lower crust similar with the ore－related granodiorite porphyries in the Dexing porphyry copper ore field. Mantle components probably added in during the formation process of the mineralized granodiorite porphyries. In middle Jurassic，the Izanagi plate initially subducted northwest beneath the South China Block. The stress that may have been quickly propagated to the inland area of the rigid South China Block may have reactivated pre－existing deep fault. The reactivation of the pre－existing deep fault might produce an association of A type，alkaline and bimodal magmatic rocks，suggesting a local extensional environment. Therefore，similar to the ore－related granodiorite porphyries in the Dexing porphyry copper ore field，the Zhangjiafan mineralized granodiorite porphyries might also formed in an intra－continental extensional setting. The age and Hf isotopes of the Zhangjiafan mineralized granodiorite porphyries are similar to the ore－related granodiorite porphyries in the Dexing copper ore field，together with the native gold hosted in chalcopyrite，this paper infer that the Zhangjiafan metallogenic prospect has a porphyry－mineralized potentiality in the deep.

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李　利1，倪　培1*，王国光1，朱安冬1，范明森1，黄卫平2. 德兴张家畈金矿远景区花岗闪长斑岩年代学、Lu－Hf同位素及成矿指示意义[J]. 南京大学学报(自然科学版), 2018, 54(2): 386

Li Li1，Ni Pei1*，Wang Guoguang1，Zhu Andong1，Fan Mingsen1，Huang Weiping2. Geochronology and Lu－Hf isotopes of granodiorite porphyries of Zhangjiafan gold prospect area in Dexing and its indication significance for mineralization[J]. Journal of Nanjing University(Natural Sciences), 2018, 54(2): 386

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(责任编辑　吴劲薇)