河西走廊东部香山群时代和物源讨论  

A discussion on the provenance and age of Xiangshan Group in Eastern Hexi Corridor

作　　者：张义平[1] 肖文霞 张进[3] 陈宣华[1] 张北航[3] 赵衡[3] 王艳楠[4] 李江瑜 史建杰[1] 

机构地区：[1]中国地质科学院,北京100037 [2]东方地球物理公司长庆分院,陕西西安710021 [3]中国地质科学院地质研究所,北京100037 [4]中国科学院新疆生态与地理研究所,新疆乌鲁木齐830011

出　　处：《中国地质》2015年第6期1774-1792,共19页Geology in China

基　　金：国家自然科学基金(41172198);中国地质调查局工作项目"中国主要陆块晚前寒武纪以来裂解重组过程的再造及其对成矿作用的制约"(1212011121064)共同资助

摘　　要：香山群是一套经历轻微区域变质作用的陆源碎屑岩,夹有少量碳酸盐岩和硅质岩,主要位于河西走廊东部香山地区。迄今为止,前人已经做过大量工作,但是对香山群与该区奥陶纪米钵山组的关系、香山群的时代以及香山群的物源等问题还存在较大争议。笔者对香山群的碎屑锆石做了定年(LA-ICP-MS)工作,通过香山群与米钵山组锆石年龄的对比,发现米钵山组最年轻锆石(451±8)Ma比香山群最年轻锆石(525±3)Ma年轻,且香山群不含米钵山组其他年轻锆石成分,香山群时代应该晚于(525±3)Ma,而早于中奥陶世米钵山组,应属中—晚寒武世。香山群碎屑锆石年龄谱与华夏地块、阿拉善基底、华北西部和北祁连岩浆变质事件年龄差异显著,华夏地块、阿拉善基底、华北西部和北祁连不是香山群物源,而与澳大利亚西南部地区相似,同时根据香山群古水流分析结果,推测澳大利亚西南部可能是香山群的沉积物源。The Xiangshan Group is composed of a set of marine clastic rocks with small amounts of limestone and siliceous rocks,which experienced the greenshist facies metamorphism, and is located mainly in the eastern Hexi Corridor. The comparison betweenthe detrital zircon ages（LA-ICP-MS） of the Xiangshan Group and the Miboshan Formation shows that the youngest zircon（451±8） Ma of Miboshan Formation is younger than the youngest（525±3） Ma of the Xiangshan Group, and Xiangshan Group does not contain other young zircons as the Miboshan Formation. Therefore, the age of Xiangshan Group should be younger than（525±3） Ma and older than the Ordovician Miboshan Formation. The Xiangshan Group may be the Middle-Late Cambrian in age. Furthermore,the striking comparison between detrital zircon ages of the Xiangshan Group with the ages of magmatic and/or metamorphic events of southwest Australia, Cathsysia Block, the basement of Alxa Block, the western margin of North China Block, and the North Qilian Orgenic Belt shows that the possibility of Cathsysia Block, the basement of Alxa Block, the western margin of North China Block, and the North Qilian Orgenic Belt as the provenance of Xiangshan Group should be ruled out. Combined with paleocurrent data of the Xiangshan Group, the authods argue that the southwestern Australia might have been the main provenance of the Xiangshan Group.

关 键 词：香山群 碎屑锆石 古水流 寒武纪 物源 

分 类 号：P535[天文地球—古生物学与地层学] P588.21[天文地球—地质学]