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7014534 
Journal Article 
Petrography and Geochemistry of the Carboniferous Ortokarnash Manganese Deposit in the Western Kunlun Mountains, Xinjiang Province, China: Implications for the Depositional Environment and the Origin of Mineralization 
Zhang, BLu; Wang, CLe; Robbins, LJ; Zhang, LC; Konhauser, KO; Dong, Z; Li, W; Peng, ZiD; Zheng, MT; , 
2020 
Yes 
Economic Geology and the Bulletin of the Society of Economic Geologists
ISSN: 0361-0128
EISSN: 1554-0774 
SOC ECONOMIC GEOLOGISTS, INC 
LITTLETON 
115 
7 
1559-1588 
WOS:000574404100009 
The Upper Carboniferous Ortokarnash manganese ore deposit in the West Kunlun orogenic belt of the Xinjiang province in China is hosted in the Kalaatehe Formation. The latter is composed of three members: (1) the Pt Member is a volcanic breccia limestone, (2) the 2nd Member is a sandy limestone, and (3) the 3rd Member is a dark gray to black marlstone containing the manganese carbonate mineralization, which, in turn, is overlain by sandy and micritic limestone. This sequence represents a single transgression-regression cycle, with the manganese deposition occurring during the highstand systems tract. Geochemical features of the rare earth elements (REE+Y) in the Kalaatehe Formation suggest that both the manganese ore and associated rocks were generally deposited under an oxic water column with Post-Archean Australian Shale (PAAS)-normalized REE+Y patterns displaying characteristics of modern seawater (e.g., light REE depletion and negative Ce anomalies). The manganese ore is dominated by fine-grained rhodochrosite (MnCO3), dispersed in Mn-rich silicates (e.g., friedelite and chlorite), and trace quantities of alabandite (MnS) and pyrolusite (MnO2). The replacement of pyrolusite by rhodochrosite suggests that the initial manganese precipitates were Mn(IV)-oxides. Precipitation within an oxic water column is supported by shale-normalized REE+Y patterns from the carbonate ores that are characterized by large positive Ce (>3.0) anomalies, negative Y (similar to 0.7) anomalies, low Y/Ho ratios (similar to 20), and a lack of fractionation between the light and heavy rare earth elements ((Nd/Yb)(PAAS) similar to 0.9). The manganese carbonate ores are also C-13-depleted, further suggesting that the Mn(II) carbonates formed as a result of Mn(III/IV)-oxide reduction during burial diagenesis.