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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    新疆西昆仑造山带康西瓦含绿柱石白云母伟晶岩的地质特征与年代学研究

    Geologicial Feature and Chronology Study of Kangxiwar Beryl-Bearing Muscovite Pegmatite in Weste Kunlun Orogen, Xinjiang

    • 摘要: 新疆康西瓦-大红柳滩伟晶岩带是西昆仑造山带重要的LCT型稀有金属伟晶岩矿床密集区,其中康西瓦绿柱石白云母伟晶岩和大红柳滩锂辉石伟晶岩分别为矿带内具代表性的伟晶岩型铍矿床和锂矿床。该矿带受自然条件所限,研究程度不高。现有的对矿带中伟晶岩的研究主要针对大红柳滩岩体及大红柳滩锂矿床的地球化学及成岩成矿时代,获得的成岩成矿年龄为220~210 Ma,而对于康西瓦铍矿的研究成果很少。笔者在野外地质调研的基础上,总结了康西瓦铍矿床的地质特征,利用锆石LA-ICP-MS U-Pb定年方法,获得康西瓦绿柱石白云母伟晶岩结晶年龄为(209±4.4)Ma,与大红柳滩锂辉石伟晶岩及大红柳滩岩体形成时代一致,反映了三者为同一期岩浆活动产物。同时康西瓦伟晶岩中锆石还记录了200Ma左右经历了一次热液活动和160Ma左右的变质作用。前人利用白云母40Ar-39Ar法获得康西瓦伟晶岩的年龄为185~156Ma,明显年轻于该地区岩体与伟晶岩中锆石、锡石及铌钽铁矿的U-Pb年龄,可能为康西瓦伟晶岩遭受变质作用使白云母40Ar-39Ar同位素体系发生热扰动所致。

       

      Abstract: The Kangxiwar-Dahongliutan pegmatite field is an important area with abundant LCT family rare-metal pegmatites in the West Kunlun Orogen. The Kangxiwar beryl-bearing muscovite pegmatite and Dahongliutan spodumene pegmatites are the representative beryllium deposit and lithium deposit, respectively in this pegmatite field. Previous studies were focused on the Dahongliutan granitic pluton and lithium deposits that were formed at 220~210Ma in the Dahongliutan area. Nevertheless, there are few studies on the Kangxiwar pegmatite. Based on the field observation, this study summarizes geological features of the Kangxiwar beryl-bearing muscovite pegmatite and presents the latest zircon U-Pb dating results. According to our dating results, the crystallization age of the Kangxiwar beryl-bearing muscovite pegmatite is (209±4.4)Ma, which is consistent with the ages of the Dahongliutan spodumene pegmatite and Dahongliutan granitic pluton, indicating that theberyl-bearing muscovite pegmatite, spodumene pegmatites and granite were likely the products of the same magmatic event. In addition, the zircon from the Kangxiwar pegmatite also has recorded a hydrothermal event around 200Ma and a metamorphic event at~160Ma. Based on muscovite 40Ar-39Ar dating, previous studies suggested that the age of the Kangxiwar pegmatite is 185~156 Ma. The reported 40Ar-39Ar age is significantly younger than the crystallization ages of the beryl-bearing muscovite pegmatite, granitic pluton and spodumene pegmatites that had been obtained using U-Pb dating of zircon, cassiterite and columbite, but it is comparable to the age of the metamorphic zircon in this study, which suggested that the muscovite 40Ar-39Ar isotope system of the Kangxiwar pegmatite underwent thermal disturbance due to the metamorphic event in the Kangxiwar-Dahongliutan pegmatite field.

       

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