Full-Text Search:
Home|About CNKI|User Service|中文
Add to Favorite Get Latest Update

Geochemical Characteristics and Origin of Ediacaran Piyuancun Chert in the Lantian Section,Xiuning,Southern Anhui Province

HE Tianchen;LING Hongfei;CHEN Yongquan;LI Da;YANG Aihua;WANG Dan;WU Hepin;State Key Laboratory for Mineral Deposits Research,School of Earth Sciences and Engineering,Nanjing University;Research Institute of Exploration and Development,Tarim Oilfield Company,PetroChina;  
To determine the origin of silica in terminal Ediacaran chert,we have undertaken a variety of sedimentary geochemical proxies,in conjunction with geological features,on well-characterised Piyuancun chert at Lantian section from southern Anhui province.The Piyuancun cherts are typical marine siliceous deposits with microcrystalline structure and high content of SiO2.Silica constituting the chert is partially derived from submarine hydrothermal fluid,indicated by geochemical ratios of Fe/Ti20 and Al/(Al+Fe)0.4,as well as position in Al-Fe-Mn triangular diagram.However,Y/Ho ratios close to seawater from modern open sea and seawater-like rare earth element distribution patterns demonstrate that the sedimentary water body of Piyuancun chert primarily sourced from seawater.The isotope compositions of silicon and oxygen illustrate no variation trend stratigraphically whilst relatively high δ30 Si values indicate that Piyuancun cherts were formed by chemical precipitation of dissolved silica from seawater rather than direct precipitation from hydrothermal fluid.Moreover,estimated values from oxygen isotopic geothermometer are also consistent with normal coeval seawater temperature.Bottom seawater was first mixed with silicarich submarine hydrothermal fluid and subsequently driven by upwelling to relatively acidic waters far away from hydrothermal activity center.As a result,silica within the regional seawater became over-saturated and thus precipitated.Extensively existence of microfossils and algae mats includingPalaeopascichnus jiumenensisin Piyuancun chert indicates the thriving ocean paleoproductivity.Acidic substance produced through degradation of organic matter and biodegradation process would have,to some extent,dropped the solubility of dissolved silica in seawater and thus promoted the deposition of Piyuancun chert.
Download(CAJ format) Download(PDF format)
CAJViewer7.0 supports all the CNKI file formats; AdobeReader only supports the PDF format.
©CNKI All Rights Reserved