安徽铜陵沙滩脚矿田中酸性侵入岩成因及构造意义

安徽省铜陵地区是中国著名的以矽卡岩和斑岩型矿床为主的铜-金多金属矿集区，区内广泛产出的中酸性侵入岩与成矿关系十分密切。沙滩脚矿田位于该矿集区的东部，出露沙滩脚、桂花冲和姚家岭岩体及其不同规模、不同矿化类型的铜、金、锌等矿床，岩体对成矿起了重要的控制作用。本文在前人研究的基础上，对该矿田内的沙滩脚、姚家岭、桂花冲3个岩体进行了详细的岩石学、地球化学和锆石U-Pb年代学研究，以期查明沙滩脚矿田中酸性侵入岩的成因及成岩构造环境。岩石地球化学分析表明，3个岩体具有准铝质特征，均属于高钾钙碱性I型花岗岩类，轻稀土富集，重稀土亏损，具有弱的负Eu异常，富集Rb、Th等元素，亏损Nb、Ta等高场强元素。姚家岭岩体的锆石U-Pb年龄为140.4~140.9 Ma，沙滩脚岩体形成时代相对较早（141.4~144.1 Ma），桂花冲岩体形成相对较晚（138.3Ma）。结合区域地质背景，笔者认为沙滩脚矿田的这些岩体形成于早白垩世伸展环境，是由来自于富集地幔的分异的碱性玄武质岩浆与地壳易熔组分部分熔融形成的花岗质岩浆混合后分期侵位形成的。

Petrogenesis and tectonic implications of the intermediate-acid plutons in Shatanjiao ore-field, Tongling, Anhui

The Tongling area of Anhui Province is a famous copper-gold polymetallic ore concentration area dominated by skarn and porphyry type deposits in China. The widely exposed intermediate-acid intrusive rocks in the area are closely related to mineralization. The Shatanjiao ore-field is located in the eastern part of the ore concentration area. The Shatanjiao, Guihuachong and Yaojialing rock bodies and their copper, gold and zinc deposits of different scales and mineralization types are exposed. Rock bodies play an important role in controlling mineralization. On the basis of previous studies, a detailed studies on petrography, geochemistry and zircon U-Pb chronology for Shatanjiao, Yaojialing and Guihuachong plutons in the ore-field were carried out in order to find out the petrogenesis of these plutons and their forming tectonic setting. Geochemically, the three plutons have a metaluminous characteristics, all of which belong to high-potassium calc-alkline series I-type granites with depletion in HREE, Nb, Ta, and enrichment in LREE, Rb, Th, and slightly negative Eu anomaly. The zircon U-Pb age of the Yaojialing pluton is 140.4-140.9Ma, while the Shatanjiao pluton formed relatively earlier (141.4-144.1 Ma), and the Guihuachong pluton formed later (138.3Ma). Combined with the regional geology, we infer that these plutons in the ore-field were emplaced in the early Cretaceous extended environment, which is crystallized from a mixed magma between a differentiated basaltic magma derived from the enriched mantle and a felsic magma from the partial melting of crustal fusible component.