扬子陆块新元古代首次冰期前的区域沉降及其沉积响应研究  

Study on the regional subsidence and its sedimentary response before the first Neoproterozoic glaciation in Yangtze Block

作　　者：王田 汪正江[2,3] 肖渊甫 杨菲[2] 杜秋定[2,3] WANG Tian;WANG Zhengjiang;XIAO Yuanfu;YANG Fei;DU Qiuding(College of Earth Sciences,Chengdu University of Technology,Chengdu,610059;Chengdu Center,China Geological Survey,Chengdu,610081;Key Laboratory for Sedimentary Basin and Oil and Gas Resources,Ministry of Land and Resources,Chengdu,610081)

机构地区：[1]成都理工大学地球科学学院,成都610059 [2]中国地质调查局成都地质调查中心,成都610081 [3]自然资源部沉积盆地与油气资源重点实验室,成都610081

出　　处：《地质论评》2020年第4期1060-1080,共21页Geological Review

基　　金：国家自然科学基金资助项目(编号:41372124,41772115,41672108);中国地质调查局项目(编号:DD20160193)的成果。

摘　　要：赣北及邻区休宁组(莲沱组)与湖北宜昌、通山地区的莲沱组是华南新元古代中期的重要地层单元,但对其沉积大地构造背景和时代归属一直存在不同认识。本文在详细的沉积学调查和区域对比研究基础上,对采自通山石门塘剖面莲沱组底部含砾砂岩、上部的沉凝灰岩和上饶华坛甘岭剖面的上墅组顶部英安岩、休宁组中部沉凝灰岩分别进行了LA-ICP-MS锆石U-Pb定年,获得通山莲沱组最大沉积年龄为784.0±11.0 Ma,莲沱组中上部沉积年龄约为727.3±6.7 Ma;获得华坛甘岭剖面上墅组顶部英安岩形成年龄为779.0±6.6 Ma、休宁组中部沉积年龄为733.6±5.9 Ma,因此,赣北及邻区的莲沱组或休宁组沉积时限与宜昌地区基本一致。沉积学调查显示,华坛甘岭休宁组沉积构造不发育,主体为冲积扇—滨浅海至深水陆棚相沉积;通山莲沱组沉积构造发育,斜层理、交错层理、沙纹层理及波痕等牵引流沉积构造发育,为河流—三角洲沉积序列。研究认为,在扬子陆块内,浙皖赣邻区的莲沱组(休宁组)与宜昌莲沱组、滇中澄江组及湘黔桂地区的板溪群及其相当地层的上部沉积时限(780~720 Ma)大体相当,为南华冰期开启前在区域热沉降背景下,南华裂谷系的第一套呈区域性展布的裂谷盖沉积。Objectives: The Xiuning Formation in the North Jiangxi Province and the Liantuo Formation in the Yichang and Tongshan areas, Hubei Province, are two important stratigraphic units of the middle Neoproterozoic in the Yangtze Block. However, there have been controversies on the sedimentary geotectonic settings and depositional interval. Combined with field sedimentary survey and the LA-ICP-MS U-Pb dating of the sandstone and tuff of the Liantuo Formation, we analyzed the deposition interval and tectonic properties of the Liantuo Formation.Methods: On the basis of detailed regional sedimentological and regional comparative study, LA-ICP-MS zircon U-Pb dating has been carried out for gravel-bearing sandstone and sedimentary tuff from the bottom and middle of the Liantuo Formation in Shimentang section, Tongshan County, and the dacite from the top of the Shangshu Formation and sedimentary tuff from the middle Xiuning Formation in the Ganling section, Huatan, Shangrao City, respectively. Results: The maximum deposition age of the Liantuo Formation is 784. 0 ± 11 Ma, the middle Liantuo Formation is 728. 7 ± 9. 6 Ma in the Shimentang section, and the dacite from the topmost of the Shangshu Formation is 779. 0 ± 6. 6 Ma, the middle Liantuo Formation is 733. 6 ± 5. 9 Ma in the Ganling section, respectively. The sedimentological investigation shows that the sedimentary structure of the Xiuning Formation in the Ganling section is not developed. Instead, they are represented by deposited facies from alluvial fan—shallowwater shelf—deep-water shelf. The sedimentary structures of the Liantuo Formation in Tongshan County are developed, such as diagonal bedding, cross bedding, sand cross lamination and ripples, which are indicative of coastal to shallow shelf depositional settings.Conclusions: Based on previous research results, therefore, the deposition interval of the Liantuo Formation or the Xiuning Formation in northern Jiangxi and its adjacent areas is constrained to be about 780 ~ 720 Ma. The regional comparative stu

关 键 词：赣北地区 板溪期 板溪系 莲沱组 休宁组 沉积序列 沉积时限 热沉降 

分 类 号：P534.3[天文地球—古生物学与地层学] P512.2[天文地球—地质学]