Geochemistry of Bedded Cherts in the Cap Carbonates in Three Gorges Region, Hubei Province, and Its Paleoenvironmental Implications
详细信息
- 责任者：Hu Guyue (Institute of Mineral Resources ; Chinese Academy of Geological Sciences ; Beijing 100037 ; China) ; Fan Changfu
- 刊名：Acta Geologica Sinica
- 出版年：2013
- 卷期：87(9)
- 关键词：燧石岩 ; chert ; 湖北 ; Hubei Province
- 页码：p.1469-1476
- 图表：3 illus., 3 tables, 47 refs.
- 分类号：0803
- issnNo：ISSN0001-5717
- isbnNo：CN11-1951/P
摘要
The bedded cherts,which is in conformity with the stratum of the first Member of Doushantuo Formation and chemical precipitation originally,were discovered in the"Cap Carbonates"of Three Gorges region of Hubei Province.This paper used BrF5 method to analyse the silicate and oxygen isotopes of the cherts.High compositions of δ30SiNBS-28（0.4‰1.7‰）and δ18OV-SMOW（24.0‰26.6‰）values of the bedded cherts indicate that the environment of silicate precipitate are warm littoral facies,and geothermometers of quartz-seawater oxygen isotope fractionation estimate that the seawater temperature of chert sedimentary is 35.447.7℃.The ratios of Al/（Fe+Mn+Al）and Si/Al are respectively 0.43 0.50and 257269,indicate a few terrigenous matters mixed in the progress of silicate sedimentation,while Ce positive anomalies（1.201.24）,the values of∑REE(2.19×10-63.59×10-6)and U/Th（3.7514.45）indicate a hydrothermal sedimentary genesis.Therefore,the origin of silicate maybe supplied from a distal volcanic hydrothermal activity and precipitated as bedded cherts in warm littoral facies when the concentration of silicate basic saturated,and this work verifies a guess proposed from early researchers that the environmental temperature in the cap carbonates was once hit to 50℃.