气候变化领域集成服务门户(CCPortal): Volcanic sources and diagenetic alteration of Permian–Triassic boundary K-bentonites in Guizhou Province; South China

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DOI	10.1016/j.palaeo.2018.01.019
	Volcanic sources and diagenetic alteration of Permian–Triassic boundary K-bentonites in Guizhou Province; South China
	Hong H.; Zhao L.; Fang Q.; Algeo T.J.; Wang C.; Yu J.; Gong N.; Yin K.; Ji K.
发表日期	2019
ISSN	0031-0182
起始页码	141
结束页码	153
卷号	519
英文摘要	Terrestrial Permian–Triassic boundary (PTB) sequences in South China usually contain one to three ash beds (K-bentonites), which provide evidence of a possible trigger for the terrestrial mass extinction and are useful as a distinct marker for correlation of the PTB boundary interval from terrestrial to marine areas. Here, we investigate the clay mineralogy and geochemistry of ash beds in the Zhejue and Jiucaichong sections, representing paludal and lacustrine environments, respectively, in order to better understand the source(s) and preservation of these ash beds. The two Zhejue K-bentonites exhibit similar compositions that are distinctly different from that of the Jiucaichong K-bentonite. The former contain mainly clay minerals with minor quartz, anatase, and lepidocrocite, and the clay minerals in these layers are mainly R1 and R3 mixed-layer illite/smectite (I/S) and well-crystallized to poorly-crystallized kaolinite, whereas the latter consists mainly of R3 I/S with minor quartz, feldspars, and anatase. The former have higher CIA values (92.2 and 93.8) than the latter (79.4), indicating more intense chemical weathering that may have been related to deposition in a paludal setting with high organic acid concentrations in pore fluids. These K-bentonites also exhibit differences in major-element chemistry (MgO and K 2 O contents are higher at Jiucaichong due to lesser weathering intensity and, possibly, early diagenetic uptake from pore fluids), REE chemistry (Jiucaichong exhibits a larger Eu anomaly), and Nd isotopic compositions (Zhejue K-bentonites have 143 Nd/ 144 Nd ratios of 0.512436 and 0.512400, higher than the 0.512190 ratio for Jiucaichong). Although some of these compositional differences may be related to the dissimilar chemical environments in which diagenesis occurred (i.e., paludal vs lacustrine), the differences in Eu anomalies and Nd isotopic compositions imply heterogeneous volcanic ash sources. The source of these K-bentonites was probably a continental volcanic arc located on the paleo-southern margin of the South China Craton, within which multiple volcanic vents may have been active concurrently. © 2018 Elsevier B.V.
英文关键词	Kaolinite; Lacustrine; Mixed-layer; Paludal; Rare earth elements; Tephra
语种	英语
scopus关键词	bentonite; chemical composition; chemical weathering; clay mineral; diagenesis; geochemistry; isotopic composition; kaolinite; lacustrine environment; lepidocrocite; mass extinction; mixed layer; Permian-Triassic boundary; rare earth element; tephra; terrestrial environment; volcanic ash; China; Guizhou
来源期刊	Palaeogeography, Palaeoclimatology, Palaeoecology
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/151050
作者单位	School of Earth Sciences, China University of Geosciences, Wuhan, 430074, China; State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan, Hubei 430074, China; State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan, Hubei 430074, China; Department of Geology, University of Cincinnati, Cincinnati, OH 45221-0013, United States; Gemmological Institute, China University of Geosciences, Wuhan, 430074, China
推荐引用方式 GB/T 7714	Hong H.,Zhao L.,Fang Q.,等. Volcanic sources and diagenetic alteration of Permian–Triassic boundary K-bentonites in Guizhou Province; South China[J],2019,519.
APA	Hong H..,Zhao L..,Fang Q..,Algeo T.J..,Wang C..,...&Ji K..(2019).Volcanic sources and diagenetic alteration of Permian–Triassic boundary K-bentonites in Guizhou Province; South China.Palaeogeography, Palaeoclimatology, Palaeoecology,519.
MLA	Hong H.,et al."Volcanic sources and diagenetic alteration of Permian–Triassic boundary K-bentonites in Guizhou Province; South China".Palaeogeography, Palaeoclimatology, Palaeoecology 519(2019).