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Composition and genesis of ferromanganese deposits from the northern South China Sea
Zhong, Y; Chen, Z; Gonzalez, FJ; Hein, JR; Zheng, XF; Li, G; Luo, Y; Mo, AB; Tian, YH; Wang, SH;;;;;;;;;;
AbstractMarine ferromanganese (Fe-Mn) nodules and crusts are archives of past environmental conditions and potential mineral resources. Over the last 30 years, many have been discovered in the northern South China Sea (SCS). To determine the origin of the Fe-Mn deposits, a comprehensive laboratory analysis of physical properties, mineralogy and geochemistry was conducted on newly collected Fe-Mn nodule/crust samples. The results revealed that there are three types of Fe-Mn deposits: (1) Fe-rich nodules containing essentially goethite occur on the northeastern slope of the SCS, with high Fe, low Mn (Mn/Fe = 0.03) and low trace metals and rare earth elements concentrations; (2) Smooth Fe-Mn nodules and crusts composed of asbolane, todorokite and CFA occur along the northwestern marginal of the SCS that have similar Fe and Mn contents (Mn/Fe = 1.21), moderate trace metal enrichments, and a positive Ce anomaly; (3) Fe-Mn nodules and crusts composed of asbolane, todorokite and birnessite that occur in the central basin of the SCS have higher Mn and lower Fe contents (Mn/Fe = 1.45). This depositional pattern was associated with major changes in oceanographic conditions and tectonic regimes. The northeastern slope deposits occur in a contourite depositional system, are strongly enriched in Fe relative to Mn (average 38.7% and 0.96%, respectively), formed from the combination of hydrogenetic and diagenetic processes. We propose a new genetic model for Fe-Mn nodules, which formed through the oxidation of pyrite and pyrite-barite concretions that formed by rapid early diagenetic growth (average 3320 mm/Myr) on continental margins above the carbonate compensation depth, and dominated by hydrocarbon seep structures and strong erosive action of bottom currents along the northeastern slope. In contrast, the introduction of vigorous deep-water flow from the North Pacific promoted the slow growth (4-7 mm/Myr) of hydrogenetic Fe-Mn nodules and crusts along the northwestern margin. Finally, hydrogenetic growth of Fe-Mn nodules and crusts in the central basin may have been enhanced by volcanic processes. Our data provide new insights into the genesis and province characteristics of the Fe-Mn nodules and crusts of the northern SCS. (C) 2017 Elsevier Ltd. All rights reserved.
Department[Zhong, Yi; Chen, Zhong; Zheng, Xufeng; Li, Gang; Luo, Yun; Mo, Aibin; Tian, Yuhang; Wang, Shuhong] Chinese Acad Sci, South China Sea Inst Oceanol, CAS Key Lab Marginal Sea Geol, Guangzhou 510301, Guangdong, Peoples R China; [Zhong, Yi] Univ Chinese Acad Sci, Beijing 100049, Peoples R China; [Javier Gonzalez, Francisco; Luo, Yun; Mo, Aibin; Tian, Yuhang] Geol Survey Spain IGME, Marine Geol Dv, Madrid 28003, Spain; [Hein, James R.] US Geol Survey, 2885 Mission St, Santa Cruz, CA 95060 USA
KeywordFe-mn Deposits Genetic Model Rare Earth Elements Hydrogenetic-diagenetic Growth Hydrocarbon Seeps Northern South China Sea
Funding ProjectMSG
Document Type期刊论文
Recommended Citation
GB/T 7714
Zhong, Y,Chen, Z,Gonzalez, FJ,et al. Composition and genesis of ferromanganese deposits from the northern South China Sea[J]. JOURNAL OF ASIAN EARTH SCIENCES,2017,138:110-128.
APA Zhong, Y.,Chen, Z.,Gonzalez, FJ.,Hein, JR.,Zheng, XF.,...& and genesis of ferromanganese deposits from the northern South China Sea.JOURNAL OF ASIAN EARTH SCIENCES,138,110-128.
MLA Zhong, Y,et al."Composition and genesis of ferromanganese deposits from the northern South China Sea".JOURNAL OF ASIAN EARTH SCIENCES 138(2017):110-128.
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