Geochemistry of cherts from the northern Jiangxi region,South China:Implication for paleoenvironment  

作　　者：Guo-Liang Xie Gao-Jie Zhou Yu-Yong Sun Yan-Ran Hu Wei-Duo Hao 

机构地区：[1]Schoolof Civil Engineering and Architecture,Tongling University,Tongling 244000,Anhui Province,China [2]State Key Laboratory of Oil and Gas Reservoir Geology and Exploration,Chengdu University of Technology,Chengdu 610059,SichuanProvince,China [3]Department of Geology,Northwest University,Xian 710069,Shaanxi Province,China

出　　处：《Journal of Palaeogeography》2024年第4期823-838,共16页古地理学报（英文版）

基　　金：financially supported by the National Natural Science Foundation of China (Grant No.42207293);the Natural Science Foundation of Anhui Province (Grant No.2208085QD110);the Key Scientific Research Foundation of the Education Department of Anhui Province (Grant No.2022AH051748,KJ2021ZD0125);the Key Programs of the Tongling University (Grant No.2021tlxy ZD03);the Tongling University Starting Research Project (Grant No.2021tlxyrc16);the Anhui University Excellent Research and Innovation Project (Grant No.2022AH010094);the National College Student Innovation and Entrepreneurship Training Program of Tongling University (Grant No.202310383117)。

摘　　要：The extensive bedded cherts deposited during the Ediacaran-Cambrian(E-C)transition period play a crucial role in understanding the geological evolution of this period,yet the origin of these cherts remains disputed.Here,we present new geochemical data for cherts of the Piyuancun(PYC)Formation deposited during the Late Ediacaran and the Hetang(HT)Formation deposited during the Early Cambrian in northern Jiangxi region,Lower Yangtze region,South China.The PYC cherts contain a small amount of monaxons sponge spicules and radiolarian fragments,while the HT cherts lack siliceous organism evidence.Major and trace element analysis,coupled with discriminant diagrams,indicate a possible shift in redox conditions of seawater during the E-C transition in the northern Jiangxi region.The shift suggests a change from weakly-moderately restricted euxinic conditions to strongly restricted euxinic conditions.Furthermore,the location of both cherts are distant from the source area of siliceous organisms.Fossil evidence,as well as the values of Fe/Ti and Fe/(Mn+Ti),Eu anomalies,Post-Archean Australian Shale(PAAS)normalized REE+Y patterns,and various discriminant diagrams,support the conclusion that the PYC and HT cherts originated primarily from direct seawater precipitation,with the PYC cherts exhibiting weak hydrothermal evidence.Upwelling contributes to the formation of HT cherts and organic matter(OM)accumulation.Ocean acidification,triggered by OM degradation and biodegradation processes during the E-C transition period,leads to the extensive silica precipitation and preservation.These results enhance our understanding of the geological processes during the E-C transition.

关 键 词：Redox condition Origin of cherts E-C transition Lower Yangtze JIANGXI 

分 类 号：P534[天文地球—古生物学与地层学] P736.22[天文地球—地质学]