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【“华南古大陆演化及其资源环境效应”专辑】
doi: 10.14027/j.issn.1000-0550.2024.014
Depositional Age, Provenance and Tectonic Significance of the Huodiya Group in Wangcang Area, Northwestern Margin of the Yangtze Block: Constraints from Detral Zircon U-Pb Geochronology
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摘要: 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。本文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，获得样品最大沉积年龄为837.6 ± 6.0 Ma（MSWD = 0.60，n = 5），结合已有研究成果，将火地垭群的沉积时代限定为~910 Ma至~835 Ma。碎屑锆石谱系特征研究表明，样品年龄集中分布于832~843 Ma 、855~883 Ma 、895~936 Ma 和952~988 Ma 四个区间，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。Abstract: The Huodiya Group is an important Precambrian stratigraphic unit in the northwestern margin of the Yangtze Block and a significant graphite-bearing stratum in China. However, its depositional age, provenance and tectonic attribution have been controversial for a long time. In this paper, LA-ICP-MS zircon U-Pb dating were carried out on the sericite phyllite from the Shangliang Formation of Huodiya Group, Wangcang area. The results show that maximum depositional age of the sample is 837.6 ± 6.0 Ma (MSWD = 0.60, n = 5). Combined existing data, the depositional age of Huodiya Group is constrained between ~910 Ma and ~835 Ma. The age populations of detrital zircons are concentrated in the four peaks of 832-843 Ma, 855-883 Ma, 895-936 Ma and 952-988 Ma, and the detrital provenance is mainly from the southeast and northwest magmatic rocks. A synthesis of depositional age, provenance and regional geological background, the Shangliang Formation of Huodiya Group in Wangcang area probably deposited in the backarc 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.
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附表1 旺苍地区火地垭群上两组绢云千枚岩样品SM-5锆石U-Pb 同位素定年结果.docx
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