扬子陆块西北缘旺苍地区火地垭群沉积时代、物源及构造意义——来自碎屑锆石U⁃Pb年代学的约束  

Depositional Age,Provenance and Tectonic Significance of the Huodiya Group in the Wangcang Area,Northwestern Margin of the Yangtze Block:Constraints from detral zircon U-Pb geochronology

作　　者：邓奇 汪正江 宁括步 崔晓庄 熊国庆 任光明 任飞 DENG Qi;WANG ZhengJiang;NING KuoBu;CUI XiaoZhuang;XIONG GuoQing;REN GuangMing;REN Fei(Chengdu Center,China Geological Survey(Geosciences Innovation Center of Southwest China),Chengdu 610218,China;Key Laboratory for Sedimentary Basin and Oil and Gas Resources,Ministry of Natural Resources,Chengdu 610218,China)

机构地区：[1]中国地质调查局成都地质调查中心(西南地质科技创新中心),成都610218 [2]自然资源部沉积盆地与油气资源重点实验室,成都610218

出　　处：《沉积学报》2024年第6期1948-1957,共10页Acta Sedimentologica Sinica

基　　金：四川省自然科学基金项目(2023NSFSC0275,2023ZYD0153);国家自然科学基金项目(41772115,U2344209);中国地质调查局项目(DD20230208,DD20230227)。

摘　　要：【目的】火地垭群是扬子陆块西北缘前寒武纪重要的地层单元,同时也是中国重要的石墨矿含矿层位,但其沉积时代、物源及形成的构造背景长期存在争论。【方法】对旺苍地区火地垭群上两组的绢云千枚岩进行了LA-ICP-MS锆石U-Pb定年研究。【结果与结论】获得碎屑锆石的年龄范围为832~988 Ma,集中分布于832~843 Ma、855~883 Ma、895~936 Ma和952~973 Ma四个区间,最大沉积年龄为837.6±6.0 Ma(MSWD=0.60,n=5)。结合已有研究成果,将旺苍地区火地垭群的沉积时代限定为910~835 Ma,而非前人长期认为的中元古代;物源主要来自周围的岩体,主体方向为东(南)和西北;综合沉积时代、物源、碎屑锆石年龄及区域地质特征,旺苍地区火地垭群上两组形成于接收双向物源的弧后盆地,是Rodinia超大陆聚合晚期在扬子陆块西北缘的响应。[Objective]The Huodiya Group is an important Precambrian stratigraphic unit in the northwestern margin of the Yangtze Block and an important graphite-bearing stratum in China.However,its depositional age,provenance,and tectonic attribution have long been debated[.Methods]In this study,laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS)zircon U-Pb dating was conducted on the sericite phyllite from the Shangliang Formation of the Huodiya Group,Wangcang area.[Results and Conclusions]The results show that maximum depositional age of the sample is 837.6±6.0 Ma(MSWD=0.60,n=5).Combined with existing data,the depositional age of Huodiya Group in the Wangcang area is constrained between ca.910 Ma and ca.835 Ma,rather than previously-considered Mesoproterozoic strata.The age populations of detrital zircons are concentrated in four peaks of 832-843 Ma,855-883 Ma,895-936 Ma,and 952-973 Ma,and the detrital provenance is mainly from the southeast and northwest magmatic rocks.A synthesis of depositional age,provenance and regional geological background indicates that the Shangliang Formation of the Huodiya Group in the Wangcang area were likely deposited in a back-arc basin receiving provenance from both sides,which is a response to the late-stage convergence of the Rodinia supercontinent in the northwestern margin of the Yangtze Block.

关 键 词：火地垭群 沉积时代 物源 锆石U-PB定年 扬子陆块 新元古代 

分 类 号：P512.2[天文地球—地质学]