Distribution and origin of protodolomite from the late Miocene-Pliocene Red Clay Formation, Chinese Loess Plateau

CORC > 西双版纳热带植物园 > 中国科学院西双版纳热带植物园 > 公共技术服务中心主要仪器相关文献 > 同位素质谱仪

	Distribution and origin of protodolomite from the late Miocene-Pliocene Red Clay Formation, Chinese Loess Plateau
	He, T.
刊名	Geochemistry Geophysics Geosystems
	2012
卷号	13
ISSN号	1525-2027
中文摘要	The Pliocene epoch is considered the most recent analog of modern warming because CO2 levels were similar to the present. To explore the carbonate minerals formed in the warmer Pliocene epoch, we studied two continuous sections of the Red Clay Formation on the Chinese Loess Plateau (CLP) by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Stable Isotope Mass Spectrometry. The Red Clay Formation on the CLP exhibits diagnostic FTIR absorption features of calcite and protodolomite. This allowed quantification of the two carbonate minerals by the FTIR method. Using the FTIR method we estimate the average concentration of protodolomite in Bajiazui is 3.6% whereas the Duanjiapo section is 6.0%. Protodolomite occurrence is more consistent and the concentration is higher from similar to 6.5-4.2 Ma B.P. and decreases markedly from 4.2-2.6 Ma B.P. Red Clay protodolomite is depleted in both delta C-13(PDB) and delta O-18(PDB), ranging from -4.1% to -10.4 and from -6.7% to -11.6, respectively, and has a slightly higher delta O-18 value than the calcites. SEM observations show that Red Clay protodolomite is composed of euhedral rhombic crystals that range from 1-20 mu m in diameter, grow into the soil voids and coexist with authigenic calcite and palygorskite. These observations imply that the protodolomite grew in situ and is authigenic from pedogenesis. Dolomitization in the Red Clay sequence appears to be the result of overcoming kinetic barriers. We propose that in the Red Clay a warm climate with seasonal dry conditions leads to the formation of calcrete from soil pore waters thereby enriching the pore solutions with respect to Mg2+ and significantly increasing the Mg/Ca ratio bringing about the formation of protodolomite.
公开日期	2015-03-27
内容类型	期刊论文
源URL	[http://ir.xtbg.org.cn/handle/353005/8490]
专题	西双版纳热带植物园_公共技术服务中心主要仪器相关文献_同位素质谱仪
推荐引用方式 GB/T 7714	He, T.. Distribution and origin of protodolomite from the late Miocene-Pliocene Red Clay Formation, Chinese Loess Plateau[J]. Geochemistry Geophysics Geosystems,2012,13.
APA	He, T..(2012).Distribution and origin of protodolomite from the late Miocene-Pliocene Red Clay Formation, Chinese Loess Plateau.Geochemistry Geophysics Geosystems,13.
MLA	He, T.."Distribution and origin of protodolomite from the late Miocene-Pliocene Red Clay Formation, Chinese Loess Plateau".Geochemistry Geophysics Geosystems 13(2012).