Geochronology of Neoproterozoic Xiajiang Group in Southeast Guizhou, South China,and Its Geological Implications
Qin Yongjun
Du Yuansheng
Mou Jun
Lu Dingbiao
Long Jianxi
Wang Anhua
Zhang Housong
Zeng Changxing
Abstract：Xiajiang Group in the Southeast Guizhou Province,as the western part of the Jiangnan orogen belt,consists of Pre-cambrian 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 81 9.8 ±6.4 Ma 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 clas-tic samples collected from each of the formation yield a series of age (779.5 Ma,764.0-756.0 Ma,733.9 Ma and 725.0 Ma)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 71 7.4 Ma,the sedimen-tary time of the Xiajiang Group can be constrained from 81 5 Ma to 71 7 Ma.Besides,the regional magmatic events further con-strain 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.
Keywords：stratigraphic agezircon U-Pb ageXiajiang GroupPrecambrianJiangnan orogenic beltgeochronology
Publication Date：2015-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：14( 1107-1120 )