Abstract The giant Dexing porphyry copper ore field, containing 9.7 Mt copper, is the largest porphyry copper system in South China. The petrogenesis of andesitic dikes in the Dexing ore field and their genetic link with porphyry mineralization remain unclear. This paper presents LA-ICP-MS zircon U-Pb dating, elemental and Sr-Nd-Hf isotopic data of the andesitic dikes in the Dexing porphyry copper ore field. The Dexing andesitic dikes were emplaced during the Middle Jurassic at ca. 166 Ma. The Dexing andesitic dikes have relative high MgO contents and Mg# ratios but low TiO2 contents. They also have obvious Nb, Ta and Ti depletion in the primitive mantle normalized spider diagrams. The geochemical affinity of arc magma and low Ti contents indicate that the magma source is probably lithosphere mantle modified by subduction process. A non-arc setting during the Middle Jurassic is inferred due to the absence of typical arc rocks and the presence of rifting-related magmatic rocks in the interior of South China. The non-arc setting implies that the Neoproterozoic Jiangnan Orogen was likely responsible for the arc geochemical features. The concentration of copper in the andesitic dikes is not high, supporting that remelting of the metal-rich Neoproterozoic juvenile lower continental crust instead of the mantle is the critical factor for the giant porphyry style mineralization. The mantle derived mafic magma may play a key role for providing significant heat for remelting of the metal-rich lower continental crust via underplating into the crust-mantle boundary.

中文翻译：

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华南德兴大型斑岩铜矿田中侏罗统安山岩脉的成因：对成矿的影响

摘要 德兴巨型斑岩铜矿田，含铜9.7 Mt，是华南地区最大的斑岩铜矿系统。德兴矿田安山岩脉的成因及其与斑岩成矿的成因联系尚不清楚。本文介绍了德兴斑岩铜矿田安山岩脉的 LA-ICP-MS 锆石 U-Pb 定年、元素和 Sr-Nd-Hf 同位素数据。德兴安山岩脉在中侏罗世时期就位。166 马。德兴安山岩脉具有相对较高的 MgO 含量和 Mg# 比率，但 TiO2 含量较低。它们在原始地幔归一化蜘蛛图中也有明显的 Nb、Ta 和 Ti 贫化。弧形岩浆的地球化学亲和性和低钛含量表明岩浆源可能是俯冲作用改造的岩石圈地幔。由于缺乏典型的弧形岩石和在华南内部存在与裂谷相关的岩浆岩，推断出中侏罗世非弧形环境。非弧环境意味着新元古代江南造山带可能是造成弧形地球化学特征的原因。安山岩脉中铜的浓度不高，支持富含金属的新元古代下陆地壳而不是地幔的重熔是巨斑岩型成矿的关键因素。地幔衍生的基性岩浆可能在为富含金属的下陆地壳通过底侵进入壳幔边界提供大量热量的重熔过程中发挥关键作用。