Origin of the Neoproterozoic Baijianshan Banded Iron Formation at the Southeastern Margin of the Tarim Block in NW China:Implication for an Extremely Reducing Ocean

作     者：HAO Xiaoshu ZHANG Chuanlin ZHANG Huichao DING Teng YE Xiantao HAO Xiaoshu;ZHANG Chuanlin;ZHANG Huichao;DING Teng;YE Xiantao

作者机构：College of OceanographyHohai UniversityNanjing 210024China 

出 版 物：《Acta Geologica Sinica(English Edition)》 (地质学报（英文版）)

年 卷 期：2022年第96卷第1期

页      面：208-220页

核心收录：

学科分类：081803[工学-地质工程] 08[工学] 0818[工学-地质资源与地质工程] 

基　　金：funded by the Fundamental Research Fund for central universities(Grant No.B16020127) 

主　　题：Neoproterozoic banded iron formations(BIFs) Sr-Nd isotope Fe isotope Tarim Block 

摘      要：The Neoproterozoic banded iron formations(BIFs)were closely associated with the“Snowball Earthduring the breakup of the Rodinia,thus they played an important role in our understanding of the atmospheric and oceanic oxygen levels during this *** this contribution,the Neoproterozoic(ca.737 Ma)Baijianshan BIF at Southeast Tarim,northwestern China was *** is the dominated iron-species,which occurs as the lamina interbedded with *** BIF contains low concentrations of trace elements,and is depleted in light rare earth elements(LREEs)based on comparison with the Post-Archean Australian Shale(PAAS).In addition,the BIF exhibits slightly positive La-Eu anomalies,negligible Ce anomalies,insignificant Y anomalies,chondritic Y/Ho ratios(23-32),and slightly chondritic initial ε_(Nd)(t=737 Ma)values(−0.45 to 1.46,averaging 0.37).All these features indicate that the precipitation of Baijianshan BIF was closely related to the submarine low-T hydrothermal fluids with little detrital ***,the Baijianshan BIF is characterized by the significant enrichment of heavy Fe isotopes,with δ^(57)Fe_(IRMM-014) values ranging from 1.78‰ to 3.05‰,revealing the partial oxidation of Fe^(2+) into Fe^(3+) during the precipitation of this *** data suggest that the formation of Baijianshan BIF was closely associated with a significantly reducing ocean,which most likely was isolated from the oxidized atmosphere by a local ice *** Neoproterozoic Baijianshan ocean has the initial oxygen levels as low as,or even lower than that of Archean and Paleoproterozoic oceans.