Mo isotope and trace element patterns of Lower Cambrian black shales in South China Multi-proxy constraints on the paleoenvironment

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	Mo isotope and trace element patterns of Lower Cambrian black shales in South China Multi-proxy constraints on the paleoenvironment
	Xu, LG (Xu, Lingang); Lehmann, B (Lehmann, Bernd); Mao, JW (Mao, Jingwen); Nagler, TF (Naegler, Thomas F.); Neubert, N (Neubert, Nadja); Bottcher, ME (Boettcher, Michael E.); Escher, P (Escher, Peter)
刊名	CHEMICAL GEOLOGY
	2012
卷号	318 页码:45-49
关键词	Molybdenum isotopes Trace elements Black shales Paleoenvironment Lower Cambrian South China
ISSN号	0009-2541
英文摘要	The Precambrian/Cambrian boundary marks a critical interval in Earth history. Paleoenvironmental changes of the oceans have been suggested as a possible explanation for some significant events such as the marine biological evolution ("Cambrian explosion"). Here we report a remarkable variation range in trace element, iron speciation and molybdenum isotope signatures of black shales from the Early Cambrian Dingtai profile (Guizhou province) and three synsedimentary polymetallic Ni-Mo-(PGE-Au) sulfide ore deposits (Dazhuliushui and Maluhe in Guizhou province, and Sancha in Hunan province) on the Yangtze Platform, South China. Based on the (isotope) geochemical features, we classify the Dingtai profile into three intervals interval 1 (0-1 m) has extreme metal and TOC enrichment and heavy delta(98)/Mo-95 values. This unit has all features of a euxinic environment, and is then followed by interval 2 (1-11 m) with variable delta(98)/Mo-95 composition. Elevated contents of redox-sensitive elements and their ratios, and relatively high Fe-HR/Fe-T ratios ("reactive iron") suggest anoxic conditions. The overlying interval 3 (11-33 m) reveals oxic to suboxic conditions with generally light delta(98)/Mo-95 values in the lowermost part and fluctuant delta(98)/Mo-95 values in the uppermost part, and relatively low redox-sensitive element contents. We propose a model of a partly closed ocean basin with periodic replenishment together with changing redox conditions for the remarkable variability of delta(98)/Mo-95 values. Light delta(98)/Mo-95 values indicate restricted seawater circulation dominated by local continental input, periodically replenished by fresh seawater with heavy delta(98)/Mo-95. A global compilation of Mo isotope data from black shales indicates that the Mo isotopic variations have a consistent temporal trend, reflecting the oxygen evolution of the oceans. Relatively light delta(98)/Mo-95 values of the Lower Cambrian black shales compared to those of modern euxinic sediments are indicative of more widespread anoxic marine environments during the Early Cambrian. (C) 2012 Elsevier B.V. All rights reserved.
学科主题	火成岩岩石学
WOS关键词	PGE-AU MINERALIZATION ; PLASMA-MASS SPECTROMETRY ; PB ZIRCON AGE ; MARINE-SEDIMENTS ; RE-OS ; YANGTZE PLATFORM ; DOUSHANTUO FORMATION ; REDOX CONDITIONS ; NORTHERN AUSTRALIA ; PROTEROZOIC OCEAN
WOS研究方向	Geochemistry & Geophysics
语种	英语
出版者	ELSEVIER SCIENCE BV
WOS记录号	WOS:000306771200005
内容类型	期刊论文
源URL	[http://119.78.100.197/handle/2HKVOGP0/39540]
专题	中国地质调查局
作者单位	Leibniz Inst Balt Sea Res IOW, Geochem & Isotope Geochem Grp, Marine Geol Sect, D-18119 Warnemunde, Germany
推荐引用方式 GB/T 7714	Xu, LG ,Lehmann, B ,Mao, JW ,et al. Mo isotope and trace element patterns of Lower Cambrian black shales in South China Multi-proxy constraints on the paleoenvironment[J]. CHEMICAL GEOLOGY,2012,318:45-49.
APA	Xu, LG .,Lehmann, B .,Mao, JW .,Nagler, TF .,Neubert, N .,...&Escher, P .(2012).Mo isotope and trace element patterns of Lower Cambrian black shales in South China Multi-proxy constraints on the paleoenvironment.CHEMICAL GEOLOGY,318,45-49.
MLA	Xu, LG ,et al."Mo isotope and trace element patterns of Lower Cambrian black shales in South China Multi-proxy constraints on the paleoenvironment".CHEMICAL GEOLOGY 318(2012):45-49.