Iron speciation in cherts from the Laobao Formation,South China:Implications for anoxic and ferruginous deep-water conditions  

作　　者：CHANG HuaJin CHU XueLei FENG LianJun HUANG Jing 

机构地区：[1]School of Life and Geography Sciences, Qinghai Normal University, Xining 810008, China [2]Key Laboratory of Tibetan Plateau Environment and Resources, Ministry of Education, Xining 810008, China [3]Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China

出　　处：《Chinese Science Bulletin》2010年第27期3189-3196,共8页

基　　金：supported by the National Natural Science Foundation of China(40532012,40873007 and 40603021);the Knowledge Innovation Program of the Chinese Academy of Sciences(KZCX3-SW-141)

摘　　要：Cherts in the Laobao Formation in the Silikou section,South China were deposited in terminal Ediacaran deep-water.The speciations of iron in cherts,such as pyrite Fe(FeP),HCl-extractable Fe(FeH),and total Fe(FeT),and their interrelationships,are proxies for distinguishing oxic,anoxic but ferruginous,and sulfidic conditions,which is an effective method for studying the terminal Ediacaran ocean environment.For chert samples from the Laobao Formation,pyrite concentrations are generally low(<0.56%),degree of pyritization(DOP)ranges from<0.01 to 0.78 and most are<0.45;(FeP+FeH)/FeT ratios are between 0.27 and 0.84 and most exceed 0.38,and most of FeT/Al ratios range from 0.55 to 5.87(averaging 1.1).Relatively high content of highly reactive Fe and low content of pyrite indicate a scarcity of H2S and Fe-enriched deep-water.These features suggested that the deposition setting of Laobao cherts was anoxic and ferruginous.Terminal Ediacaran deep-water in the South China Basin was most likely anoxic and ferruginous,which played a key role in the emergence and evolution of early multicellular life.Cherts in the Laobao Formation in the Silikou section, South China were deposited in terminal Ediacaran deep-water. The speciations of iron in cherts, such as pyrite Fe （Fep）, HCl-extractable Fe （Fe H）, and total Fe （FeT）, and their interrelationships, are proxies for distinguishing oxic, anoxic but ferruginous, and sulfidic conditions, which is an effective method for studying the terminal Ediacaran ocean environment. For chert samples from the Laobao Formation, pyrite concentrations are generally low （〈0.56%）, degree of pyritization （DOP） ranges from 〈0.01 to 0.78 and most are 〈0.45; （Fep＋FeH）/FeT ratios are between 0.27 and 0.84 and most exceed 0.38, and most of FeT/Al ratios range from 0.55 to 5.87 （averaging 1.1）. Relatively high content of highly reactive Fe and low content of pyrite indicate a scarcity of H2S and Fe-enriched deep-water. These features suggested that the deposition setting of Laobao cherts was anoxic and ferruginous. Terminal Ediacaran deep-water in the South China Basin was most likely anoxic and ferruginous, which played a key role in the emergence and evolution of early multicellular life.

关 键 词：深水条件 硅质岩 铁质 缺氧 中国 o形 形态 场效应晶体管 

分 类 号：TQ341.1[化学工程—化纤工业] TU473.1[建筑科学—结构工程]