Nanhuan manganese deposits within restricted basins of the southeastern Yangtze Platform, China: Constraints from geological and geochemical evidence

	Nanhuan manganese deposits within restricted basins of the southeastern Yangtze Platform, China: Constraints from geological and geochemical evidence
	Chengquan Wu; Zhengwei Zhang; Jiafei Xiao; Yazhou Fu; Shuxun Shao; Chaofei Zheng; Junhua Yao; Chaoyi Xiao
	2016
发表期刊	Ore Geology Reviews
卷号	75 期号:1 页码:76-99
摘要	he Nanhuan manganese deposits in the southeastern Yangtze Platform occur in the black shale series in the lower part of the Datangpo Formation. In order to constrain the genesis of the deposits, a detailed study was undertaken that involved field observations, major and trace element analyses, organic carbon analyses, and isotope analyses (C, O, S). The major findings are as follows. (1) The ore-bearing rock series, morphology of the ore bodies, and characteristics of ores in several deposits are similar. The ore minerals are rhodochrosite and manganocalcite. The gangue minerals are mainly quartz, feldspar, dolomite, and illite. Minor apatite and bastnaesite occur in the manganese ores. (2) The ores are enriched in Ca and Mg, whereas they are depleted in Si, Al, K, and Ti compared to wall rocks. The ores normalized to average Post-Archean Australian shale (PAAS) are enriched in Co, Mo, and Sr. The chondrite-normalized rare earth element (REE) patterns for ores and wall rocks are between those of typical hydrogenous and hydrothermal type manganese deposits. Additionally, the ores have positive Ce anomalies with an average Ce/Ce* of 123 and positive Eu anomalies with an average Eu/Eu* of 1.18 (normalized to PAAS). (3) The average content of organic carbon is 2.21% in the samples, and the average organic carbon isotopic value (delta C-13(V-PDB)) is-33.44 parts per thousand. The average inorganic carbon isotopic value (delta C-13(V-PDB)) of carbonates in Gucheng is-3.07 parts per thousand, while the values are similar in the other deposits with an average of 8.36 parts per thousand. The oxygen isotopic compositions (delta O-18(V-PDB)) are similar in different deposits with an average of-7.72 parts per thousand. (4) The sulfur isotopic values (delta S-34(V-CDT)) of pyrite are very high and range from +37.9 parts per thousand to +62.6 parts per thousand (average of 52.7 parts per thousand), which suggests that the pyrite was formed in restricted basins where sulfate replenishment was limited. The sulfate concentrations in the restricted basins were extremely low and enriched in delta S-34, which resulted in the very high delta S-34 values for the pyrite that formed in the manganese deposits. Therefore, a terrigenous weathering origin for manganese can be excluded; otherwise, the sulfate would have been introduced into the basins together with terrigenous manganese, which would have decreased the delta S-34 values of pyrites. The manganese, which originated from hydrothermal processes, was enriched in the restricted and anoxic basins, and then, it was oxidized to manganese oxyhydroxide in the overlying oxic waters whereby the products precipitated into the sediments. The manganese oxyhydroxide in the sediment was then reduced to Mn2+ and released to the pore waters during the process of diagenesis. Some organic carbon was oxidized to CO32-, which made the depletion of C-13 in manganese carbonates. Therefore, we suggest that the Nanhuan manganese deposits are hydrothermal sedimentary/diagenetic type deposits.
学科领域	矿床地球化学
收录类别	SCI
语种	英语
文献类型	期刊论文
条目标识符	http://ir.gyig.ac.cn/handle/352002/6212
专题	矿床地球化学国家重点实验室_矿床地球化学国家重点实验室_期刊论文
推荐引用方式 GB/T 7714	Chengquan Wu,Zhengwei Zhang,Jiafei Xiao,et al. Nanhuan manganese deposits within restricted basins of the southeastern Yangtze Platform, China: Constraints from geological and geochemical evidence[J]. Ore Geology Reviews,2016,75(1):76-99.
APA	Chengquan Wu.,Zhengwei Zhang.,Jiafei Xiao.,Yazhou Fu.,Shuxun Shao.,...&Chaoyi Xiao.(2016).Nanhuan manganese deposits within restricted basins of the southeastern Yangtze Platform, China: Constraints from geological and geochemical evidence.Ore Geology Reviews,75(1),76-99.
MLA	Chengquan Wu,et al."Nanhuan manganese deposits within restricted basins of the southeastern Yangtze Platform, China: Constraints from geological and geochemical evidence".Ore Geology Reviews 75.1(2016):76-99.

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