line-level: 2" class=MsoNormal>Formation Mechanism of Precambrian Banded Iron Formation and Atmosphere and Ocean during Early Stage of the Earth

• 责任者：Li Yanhe (Key Laboratory of Isotope Geology ; MRL ; Institute of Mineral Resource ; Chinese Academy of Geological Sciences ; Beijing 100037 ; China) ; Hou Kejun
• 刊名：Acta Geologica Sinica
• 出版年：2010
• 卷期：84(9)
• 关键词：硅铁 ; ferrosilicon ; 华北地台 ; North China Platform
• 页码：p.1359-1373
• 图表：10 illus., 1 table, 58 refs.
• 分类号：1001
• issnNo：ISSN0001-5717
• isbnNo：CN11-1951/P

Isotopic compositions of S, Si and O of Precambrian BIFs at the North China Craton （NCC） were measured systematically. The δ³⁰SiNBS^-28 values of quartz in BIFs of different types and ages are low with most ranging from -2.0‰ to -0.3‰, similar to the δ³⁰SiNBS^-28 values of modern submarine black smoker and sinter. After 1.8 Ga, the ocean sulfate concentration was increased, and the ocean was from iron rich to sulfate rich that is a decisive factor for the disappearance of the BIFs. The large scale volcanic activities and submarine exhalation greatly influenced the compositions and evolution of the ocean, and postpone oxidation time of the ocean for at least 600 Ma compared with the atmosphere.