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    新疆北部玛因鄂博断裂带中片麻岩锆石U-Pb SHRIMP定年及其地质意义

    SHRIMP zircon U-Pb dating of gneisses in the Mayin Obo fault belt, northern Xinjiang, and its significance

    • 摘要: 提要:对包括青河一带片麻岩在内的阿尔泰地区中深变质岩石的时代一直存在争议,李天德等将阿尔泰山南缘冲乎尔—阿勒泰—青河一带、富蕴库卫—乌洽沟一带、富蕴县城一带的中深变质岩石划归为古—中元古代克木齐群和新元古代富蕴群,引起了广泛的关注和争议,特别是对位于青河县城西南玛因鄂博断裂带中片麻岩的时代问题争议颇多。笔者对该片麻岩采样进行锆石U -Pb SHRIMP年龄测定,虽然未能获得一致的谐和年龄,但不同时段的年龄数据均具有一定的地质意义,大量的前寒武纪古老锆石的年龄信息肯定了阿尔泰地区前寒武纪地层存在的可能,并确定了该片麻岩应形成于晚古生代之前。

       

      Abstract: Abstract:There is a long dispute over the age of medium- and high-grade metamorphic rocks in the Altay area, including gneiss in Qinghe. Li Tiande et al. assign medium- and high-grade metamorphic rocks in the Chonghuer-Altay-Qinghe area on the southern margin of the Altay Mountains, Kuwei-Wuqiagou area of Fuyun County and seat of Fuyun County to the Paleo- and Mesoproterozoic Kemuqi Group and Neoproterozoic Fuyun Group, which has attracted wide attention and debate, especially disputes over the age of gneiss in the Mayin Obo fault belt southwest of the seat of Qinghe County. The authors have performed zircon U-Pb SHRIMP dating of the gneiss. Although they failed to obtain concordia ages, the data of ages in different time intervals still have certain geological significance. The abundant age information of Precambrian zircons affirms the possibility of the occurrence of Precambrian strata in the Altay region and determines that the gneiss should form earlier than the Late Paleozoic.

       

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