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4574648 
Journal Article 
Origin of the black shale-hosted Chadian phosphorus-manganese deposit, Shaanxi province, China 
Liu, TB; Fan, DL; Jie, Y 
1996 
Yes 
Economic Geology and the Bulletin of the Society of Economic Geologists
ISSN: 0361-0128
EISSN: 1554-0774 
91 
1 
48-54 
WOS:A1996UR28500005 
The Chadian phosphorus-manganese deposit occurs in the late Sinian Doushantuo Formation. The ore-bearing sequence consists of black phyllite, a phosphorite ore sequence, a manganese ore sequence, and dolostone. Phosphorite ores are divided into four types: psammitic, pelletal, micritic, and fine-grained crystalline phosphorites. The manganese ores, immediately overlying the phosphorite ores, consist of manganese carbonate (rhodochrosite) and P-bearing manganese oxide, both having pelletal and oolitic structures.



Chemical analyses show that phosphorite ores contain from 7.6 to 14.1 percent P, 0.3 to 6.7 percent Mn, and 0.6 to 0.9 percent organic carbon; manganese ores contain 11.3 to 24.2 percent Mn, 0.1 to 5.7 percent P, and about 0.4 percent organic carbon.



The occurrence and composition of the ore-bearing sequence indicate that phosphorite and manganese carbonate formed in a transition zone between reducing; (euxinic) and slightly oxidizing depositional environments. Deposition in relatively shallow-water, high-energy environments and changes in sources of ore-forming fluids controlled ore compositions and structures. Supergene processes altered primary manganese carbonate to manganese oxides.