Geochemical studies on Permian manganese deposits in Guichi, eastern China: Implications for their origin and formative environments

Permian manganese ore deposits are widely distributed in southwestern and eastern China. Guichi Permian manganese district in southern Anhui Province, central eastern China, is currently the most important manganese metal producers in eastern China. Manganese ores (MnO = 18.2-45.4 wt.%) in Guichi region occur in calcareous, argillaceous and siliceous Mn-bearing sequence of the Permian Gufeng Formation. In contrast to Mn-bearing rocks, the ores have higher Mn, Fe, P, Sr (more than 1500 ppm) and Ni contents (>480 ppm), higher Mn/Fe (>5) and La-n/Ce-n (>2) values, and lower Co/Ni (<0.05) ratios. The Guichi manganese deposits also have low Co/Ni (<1) and Co/Zn ratios, low in total REE contents (mostly < 100 ppm) with negative Eu (0.46-0.75) and Ce (0.42-0.76) anomalies. The mineralogy and geochemistry of manganese deposits in the Guichi region strongly indicate hydrothermal activities, which is supported by high paleotemperatures (49-71 degrees C) of Permian Mn-carbonate ore and Mn-bearing carbonate. The low Ce-anom. values (<-0.1) and high strontium contents indicate that the Guichi manganese deposits were formed in high-salinity and oxidative marine sedimentary environment. The Al2O3/TiO2 (9.23-48.2) and Y/Ho (25.9-44.4) ratios, REE patterns, delta C-13(V-PDB) (-10.2 parts per thousand to 5.00 parts per thousand) and delta O-18(SMOW) (20.7-28.0 parts per thousand characteristics of Permian manganese deposits reveal a mixed Mn source of volcanic, terrigenous and organic matter. (C) 2013 Elsevier Ltd. All rights reserved.