藏北商旭金矿床的碎屑锆石U-Pb年龄及其地质意义

发布时间：2018-10-14 17:26

【摘要】：商旭金矿床处于班公湖—怒江缝合带中段南侧,位于藏北双湖县境内,是班公湖—怒江缝合带已发现的一例造山型金矿。本文选择该矿床木嘎岗日群(J1-2M)的变质砂岩进行碎屑锆石U-Pb定年研究,以期获得碎屑沉积物物源区的丰富信息。随机选取114颗锆石进行分析,可知:(1)锆石颗粒大小在80~150μm之间,绝大多数锆石颗粒的Th/U比值0.4;(2)年龄分布范围在223~2 615 Ma之间,年龄峰值分别为280 Ma、451 Ma、908 Ma、1 900 Ma和2 430 Ma。将商旭矿区碎屑锆石U-Pb年龄谱图分别与拉萨地块、羌塘地块沉积岩的碎屑锆石年龄谱图对比分析,获得如下初步结论:该区的沉积物的最大沉积年龄为223 Ma,峰值为908 Ma的年龄群,可比于南羌塘沉积岩的碎屑锆石年龄峰值(~950 Ma),明显不同于拉萨地块沉积岩的碎屑锆石年龄峰值(~1 170 Ma)。综合分析表明,该区的沉积物可能为班公湖—怒江洋残余洋盆的产物,暗示班公湖—怒江洋壳在中生代存在北向俯冲。
[Abstract]:The Shangxu gold deposit is located in the south of the middle section of Bangong Lake-Nujiang suture zone and located in Shuanghu County of northern Tibet. It is a case of orogenic gold deposit found in Bangong Lake-Nujiang suture zone. In this paper, the metamorphic sandstone of Mugagangri group (J1-2M) of the deposit is selected to study the U-Pb dating of detrital zircon, in order to obtain abundant information of the source area of clastic sediments. The random analysis of 114 zircons shows that: (1) the size of zircon grain is between 80 渭 m and 150 渭 m, and the Th/U ratio of most zircon grains is 0.4; (2) the age distribution range is between 223 and 2615 Ma, and the peak ages are 280 Ma,451 Ma,908 Ma,1 900 Ma and 2 430 Ma., respectively. The U-Pb age spectrum of detrital zircon in Shangxu mining area is compared with that of sedimentary rocks in Lhasa block and Qiangtang block. The primary conclusions are as follows: the maximum sedimentary age of the sediments in this area is 223 Ma, with a peak value of 908 Ma. The detrital zircon age peak (~ 950 Ma),) of the southern Qiangtang sedimentary rocks is obviously different from that of the sedimentary rocks in Lhasa block (~ 1 170 Ma). The comprehensive analysis shows that the sediments in this area may be the product of the remnant ocean basin of Bangong Lake-Nujiang Ocean, suggesting that there was a northward subduction of Bangong Lake-Nujiang ocean crust in Mesozoic.
【作者单位】：中国地质科学院地质力学研究所;中国地质科学院矿产资源研究所;中国地质科学院地质研究所;中国地质大学(北京)地球科学与资源学院;黑龙江省水文地质工程地质勘察院;
【基金】：国家重点研发计划(深地资源勘查开采)(编号:2016YFC0600306) 国家重点基础研究发展计划(973计划)(编号:2011CB403104) 中国地质调查局地质调查项目(编号:12120113037901;DD20160026;DD20179142) 国家科技支撑计划(编号:2006BAB01A04)联合资助~~
【分类号】：P597.3;P618.51

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