ISSN 1009-6248CN 61-1149/P 双月刊

主管单位:中国地质调查局

主办单位:中国地质调查局西安地质调查中心
中国地质学会

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    鄂东南铁铜金钨钼多金属矿集区基底属性:来自继承锆石年龄和Hf同位素的约束

    Basemental Attribution of the Fe-Cu-Au-W-Mo Polymetallic Ore Cluster in the Southeastern Hubei: Constraint from the Ages and Hf Isotopes of the Inherited Zircons

    • 摘要: 长江中下游成矿带鄂东南矿集区的基底存在统一的川中式基底和北部川中式基底、南部江南式基底的争议。笔者对灵乡岩体西段闪长玢岩开展锆石U-Pb定年和Hf同位素分析,结果显示闪长玢岩的锆石具有复杂的组成与来源:最年轻的4颗锆石加权平均年龄为(141±4) Ma,结合前人测年结果推测其可作为闪长玢岩的成岩年龄;其余16颗锆石具有较为宽泛的年龄(217~2550 Ma)和Hf同位素组成(εHf(t) = −11.2~11.7)。进一步结合前人获得的鄂东南矿集区岩浆岩继承锆石数据,分别对比川中式基底崆岭杂岩、江南式基底梵净山群及下江群的锆石数据,发现其与崆岭杂岩具有明显差异,但和梵净山群及下江群具有高度相似性。并且鄂东南矿集区岩浆岩继承锆石和梵净山群、下江群均记录了~1.5 Ga地壳增生事件。结合区域地球物理特征,笔者认为鄂东南矿集区南部为江南式基底,北部为川中式基底,两者的分界线大致为灵乡-大冶-网湖一线。

       

      Abstract: There are two different opinions about the basemental attribution of the ore cluster in the southeastern Hubei Province, Middle-Lower Yangtze Metallogenic Belt that all attributed to the Chuanzhong-type basement or the north part related to Chuanzhong-type basement and the south part classified to the Jiangnan-type basement. In this study, zircon U-Pb dating and Hf isotope analysis were conducted for diorite porphyrite in the western Lingxiang pluton. The results indicate that the zircons of diorite porphyrite show complex compositions and sources. The youngest four zircons yield a mean 206Pb/238U age of (141±4)Ma, which coincide with previous researches and interpreted as the crystallization age of the diorite porphyrite. In addition, The other 16 older zircons have varied ages (217~2 550 Ma) and Hf isotopic compositions (εHf(t) = −11.2~11.7). Combined with the reported ages and εHf(t) values of inherited igneous zircons from the ore cluster in the southeastern Hubei, we compared with the data from Chuanzhong-type and Jiangnan-type basements respectively. The results suggest that they are different from Kongling Complex of the Chuanzhong-type basement, but are similar to the Fanjingshan and XiaJiang Groups of the Jiangnan-type basements. Particularly, the ~1.5 Ga crustal accretion both record in the ore cluster in the southeastern Hubei and the Fanjingshan and XiaJiang Groups. Combined with the regional geophysics, bounded by the line from Lingxiang, Daye to Wanghu Lake, the north part of ore cluster in the southeastern Hubei belong to Chuanzhong-type basement and the south part relate to Jiangnan-type basement.

       

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