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    鄂东南地区铜绿山岩体的侵入期次和物源:锆石U-Pb年龄和Hf同位素证据

    Stage division and origin of Tonglushan pluton in southeast Hubei Province: Evidence from zircon U-Pb ages and Hf isotopes

    • 摘要: 提要:铜绿山岩体的主要岩石类型为石英正长闪长玢岩,其次是闪长岩、石英闪长岩和闪长玢岩。利用LA-ICPMS和LA-MC-ICPMS对岩石中的锆石进行微区原位U-Pb年龄和Lu-Hf同位素测定,结果表明,该岩体至少有三次以上的侵入活动,分别为150 Ma、145 Ma和140 Ma,从西到东、由深到浅侧向迁移侵位,分别形成鸡冠嘴矿区深部的石英闪长岩和Ⅶ号铜金矿体,鸡冠嘴矿区较浅部的闪长岩和Ⅰ、Ⅱ、Ⅲ号等铜金矿体,铜绿山矿区及其周边的石英正长闪长玢岩和铜绿山、鲤泥湖、桃花嘴等铁铜矿床。岩浆锆石和继承锆石的U-Pb年龄和Hf同位素等信息显示,岩体的源区物质为混含有少量亏损地幔成分的古元古代(约1730 Ma)下地壳物质,并有中元古代晚期(1100~1200 Ma)和新元古代(800 Ma)地壳物质的加入。不同类型岩石的物源组成有明显差别,并形成不同的矿床。石英闪长岩和闪长岩形成铜金矿床,可能与其岩浆源区物质含有地幔成分有关。在继承锆石中获得新太古代、中太古代、古元古代、中元古代晚期和新元古代五组年龄数据,与宜昌崆岭群TTG片麻岩,京山、宁乡、镇远煌斑岩筒,宜昌莲沱砂岩、石门渫水河组(莲沱组)凝灰岩中的锆石年龄可以对比,表明鄂东南地区与扬子陆块其他地区的地壳演化历史基本一致,深部同样存在古元古代和太古宙基底。

       

      Abstract: Abstract:The Tonglushan pluton is mainly composed of quartz-orthoclase diorite porphyry, together with diorite, quartz diorite and diorite porphyry. In this paper, zircon U-Pb ages and Lu-Hf isotopic data were obtained by using LA-ICPMS and LA-MC-ICPMS analysis. The results show that there existed at least three times of intrusive activities in the Tonglushan complex, which occurred at 150 Ma, 145 Ma and 140 Ma, respectively. These magmatic activities successively occurred from west to east and from the depth to the shallow part and formed quartz diorite and Ⅶ Cu-Au ore body at the depth of the Jiguanzui mining area, the diorite and Ⅰ,Ⅱ,Ⅲ Cu-Au ore bodies in the shallow part of the Jiguanzui ore district, as well as the quartz-orthoclase diorite porphyries in and around the Tonglushan mining area and the Tonglushan Fe-Cu deposit, the Jiguanzui Fe-Cu deposit and the Taohuazui Fe-Cu deposit, respectively. The U-Pb ages and Hf isotopic data of igneous zircons and inherited zircons indicate that the Tonglushan complex was mainly derived from Paleoproterozoic (Ca.1730Ma) lower crust with a little depleted mantle components, with the involvement of variable amounts of the Late Mesoproterozoic (1100~1200Ma) and Neoproterozoic (800 Ma) crustal materials. Different rock units had different magmatic sources and were related to different ore-forming processes. The quartz diorite and diorite were associated with Cu-Au mineralization, which probably resulted from the involvement of mantle components in the magma source. The age data of inherited zircons, which include Neoarchean, Mesoarchean, Paleoproterozoic, Late Mesoproterozoic and Neoproterozoic, are comparable with zircon ages of the Kongling Group TTG gneiss in Yichang, lamprophyre pipes in Jingshan, Ningxiang and Zhenyuan, sandstones of Liantuo Formation in Yichang, and tuffs of Xieshuihe Formation (Liantuo Formation) in Shimen, indicating that the crustal evolution of southeast Hubei Province was basically in accordance with that of the other areas in the Yangtze block, and Paleoproterozoic and Archean basement might also exist in the deep crust of southeast Hubei Province.

       

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