| 黔东南地区新元古代下江群的地层年代及其地质意义 |
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| 引用本文： | 覃永军,杜远生,牟军,卢定彪,龙建喜,王安华,张厚松,曾昌兴.黔东南地区新元古代下江群的地层年代及其地质意义[J].地球科学,2015,40(7):1107-1120. |
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| 作者姓名： | 覃永军 杜远生 牟军 卢定彪 龙建喜 王安华 张厚松 曾昌兴 |
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| 作者单位： | 1.中国地质大学生物地质与环境地质国家重点实验室, 湖北武汉 430074 |
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| 基金项目： | 中国地质调查局项目，国土资源部公益性行业科研专项，贵州省地矿局地质科研专项(黔地矿科合 |
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| 摘 要： | 黔东南地区下江群是分布在江南造山带西段的一套前寒武纪浅变质陆源碎屑岩夹火山碎屑岩组合, 其地层时代归属与划分特别是区域地层对比一直未能得到很好解决.在对该区前寒武纪地层广泛而详细的剖面测制和地质调查基础上, 运用LA-ICP-MS技术, 对地层中沉凝灰岩、含凝灰质碎屑岩和碎屑岩进行锆石U-Pb年代学测试, 获得一批高精度的年龄.四堡群河村组顶部的碎屑岩和下江群乌叶组第1段顶部的含凝灰质碎屑岩、清水江组底部与中部的沉凝灰岩、平略组中上部的含凝灰质碎屑岩、隆里组中下部的碎屑岩等样品中锆石U-Pb最小年龄组的加权平均年龄分别为819.8±6.4Ma和779.5±4.7Ma、764.0±6.3Ma与(756.8±7.6Ma、756.0±13.0Ma)、733.9±8.8Ma及725.0±10.0Ma.这些数据将四堡群和下江群的时代限制为新元古代.结合研究区隆里组与长安组整合接触关系和全球低纬度南华系冰期起始年龄(717.4Ma)的地质事实, 将下江群沉积时限约束在815~717Ma之间.根据区域岩浆事件进一步约束了下江群各组段的地层时限, 并开展江南造山带下江群及其相当层位的地层划分与对比, 认为新元古代岩浆作用制约着黔东南下江群盆地的演化.
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| 关 键 词： | 地层时代 锆石U-Pb年龄 下江群 前寒武纪 江南造山带 地质年代学 |
| 收稿时间： | 2014-12-12 |
Geochronology of Neoproterozoic Xiajiang Group in Southeast Guizhou,South China,and Its Geological Implications |
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| Qin Yongjun,Du Yuansheng,Mou Jun,Lu Dingbiao,Long Jianxi,Wang Anhua,Zhang Housong,Zeng Changxing.Geochronology of Neoproterozoic Xiajiang Group in Southeast Guizhou,South China,and Its Geological Implications[J].Earth Science-Journal of China University of Geosciences,2015,40(7):1107-1120. |
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| Authors: | Qin Yongjun Du Yuansheng Mou Jun Lu Dingbiao Long Jianxi Wang Anhua Zhang Housong Zeng Changxing |
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| Abstract: | Xiajiang Group in the Southeast Guizhou Province, as the western part of the Jiangnan orogen belt, consists of Precambrian low metamorphic terrisenous clastic sequence interlayer volcaniclastic rocks. But its age and stratigraphic correlation of the Precambrian are still controversial due to absence of lithologic marked bed and fossils and insufficient geochronological data. On the basis of detailed regional geology mapping of the sections, and zircon LA-ICP-MS geochronological study on tuff, tuffaceous and clastic rock of the Precambrian stratum in the study area, high resolution geological data to constrain the age of the Sibao and Xiajiang groups were obtained. It is found that the youngest weighted average ages of 819.8±6.4Ma from the clastic rock at the top of the Hechun Fm., Sibao Gp., for constraining the boundary age between the Sibao and Xiajiang groups. The Xiajiang Gp. can be divided into Wuye, Qingshuijiang, Pinglue and Longli formations from bottom to top. Tuffaceous clastic samples collected from each of the formation yield a series of age (779.5Ma, 764.0-756.0Ma, 733.9Ma and 725.0Ma) to represent the sedimentary times of these four formations. Based on these data, it is proposed that the depositional age of the Xiajiang and Sibao groups is limited to the Neoproterozoic. Combined with the field observation that the Longli and Chang'an formations are continuous deposits and the global low latitude glaciation event of Nanhuaian began from 717.4Ma, the sedimentary time of the Xiajiang Group can be constrained from 815Ma to 717Ma. Besides, the regional magmatic events further constrain the ages of the formations in the Xiajiang Group. The division and the stratigraphic correlation of the Xiajiang Group and the coeval strata help us to comprehend the evolution of the Xiajiang basin. |
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| Keywords: | stratigraphic age zircon U-Pb age Xiajiang Group Precambrian Jiangnan orogenic belt geochronology |
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