Composition and origin of Early Cambrian Tiantaishan phosphorite-Mn carbonate ores, Shaanxi Province, China

	Composition and origin of Early Cambrian Tiantaishan phosphorite-Mn carbonate ores, Shaanxi Province, China
	Hein, JR ; Fan, DL ; Ye, J ; Liu, TB ; Yeh, HW
刊名	ORE GEOLOGY REVIEWS
	1999-10-01
卷号	15 期号:1-3 页码:95-134
关键词	Yangtze platform phosphorite ore Mn-carbonate ore Early Cambrian global events coastal upwelling
ISSN号	0169-1368
文献子类	Review
英文摘要	The Tiantaishan phosphorite-Mn carbonate ores occur in the Early Cambrian Tananpo Formation in complexly folded and faulted rocks located in southern Shaanxi Province. About 65 x 10(6) tonnes of 17% P2O5 ore reserves exist and Mn-ore reserves are about 8.3 x 10(6) tonnes of +18% Mn. The stratigraphic sequence in ascending order consists of black phyllite, black to gray phosphorite ore, black phyllite, rhodochrostone ore, Mn mixed-carbonates, and dolostone. Data are presented from microprobe mineral chemistry, whole-rock chemistry, stable isotopes of carbonates, X-ray mineralogy, petrographic and SEM observations, and statistical analysis of chemical data. The dominant ore-forming minerals are hydroxy- and carbonate fluorapatite and Ca rhodochrosite, with Mg kutnahorite and dolomite comprising the Mn mixed-carbonate section. Pyrite occurs in all rock types and alabandite (MnS) occurs throughout the rhodochrostone section. The mean P2O5 content of phosphorite is 31% and argillaceous phosphorite is 16%, while the mean MnO content of rhodochrostone ore is 37%. Phosphorite ores are massive, spheroidal, laminated, and banded, while rhodochrostone ores have oolitic, spheroidal, and granular fabrics. The most distinguishing characteristics of the ores are high total organic carbon (TOC) contents (mean 8.4%) in the phosphorite and high P2O5 contents (mean 2.7%) in the rhodochrostone ore. The atypically high TOC contents in the Tiantaishan phosphorite probably result from very strong productivity leading to high sedimentation rates accompanied by weak reworking of sediments; poor utilization of the organic matter by bacteria; and/or partial replacement of bacterial or algal mats by the apatite. The depositional setting of the ores was the margin of an epicontinental seaway created as a direct consequence of global processes that included break-up of a supercontinent, formation of narrow seaways, creation of extensive continental shelves, overturn of stagnant, metal-rich deep-ocean waters, and marine transgression. Water depth increased from deposition of the black phyllite sequence through deposition of the Mn mixed-carbonate sequence, then shallowed again during deposition of the overlying dolostone sequence. Bottom waters were mostly dysoxic to suboxic, but fluctuated from oxic to anoxic. Productivity was high during deposition of the black phyllite sequence, increased during precipitation of phosphorite, and then decreased to moderate levels during precipitation of rhodochrostone ores. Biosilica contributions occur in each lithology, but are greatest in rhodochrostone. Changes in sedimentation were determined by changes in water depth, productivity, upwelling, sea-level change, and ventilation of the depositional basin. The source of the phosphorus was organic matter produced in great quantities during deposition of the black phyllite and phosphorite sequences in a zone of coastal upwelling. Organic matter accumulation was rapid.
WOS关键词	ANOXIC MARINE-SEDIMENTS ; MANGANESE CARBONATE ; BLACK SHALES ; PALEOMAGNETIC CONSTRAINTS ; RICH SEDIMENTS ; ORGANIC-MATTER ; MINOR ELEMENTS ; SEA SEDIMENTS ; GEOCHEMISTRY ; DEPOSITS
WOS研究方向	Geology ; Mineralogy ; Mining & Mineral Processing
语种	英语
出版者	ELSEVIER SCIENCE BV
WOS记录号	WOS:000083933600008
内容类型	期刊论文
源URL	[http://ir.iggcas.ac.cn/handle/132A11/75438]
专题	中国科学院地质与地球物理研究所
通讯作者	Hein, JR
作者单位	1.US Geol Survey, Menlo Pk, CA 94025 USA 2.Chinese Acad Sci, Inst Geol, Beijing 100029, Peoples R China 3.Acad Sinica, Inst Earth Sci, Taipei 11529, Taiwan
推荐引用方式 GB/T 7714	Hein, JR,Fan, DL,Ye, J,et al. Composition and origin of Early Cambrian Tiantaishan phosphorite-Mn carbonate ores, Shaanxi Province, China[J]. ORE GEOLOGY REVIEWS,1999,15(1-3):95-134.
APA	Hein, JR,Fan, DL,Ye, J,Liu, TB,&Yeh, HW.(1999).Composition and origin of Early Cambrian Tiantaishan phosphorite-Mn carbonate ores, Shaanxi Province, China.ORE GEOLOGY REVIEWS,15(1-3),95-134.
MLA	Hein, JR,et al."Composition and origin of Early Cambrian Tiantaishan phosphorite-Mn carbonate ores, Shaanxi Province, China".ORE GEOLOGY REVIEWS 15.1-3(1999):95-134.