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

• The Guichi Mn district is the important Mn metal producing area in eastern China.
• The geochemical data of manganese deposits support a hydrothermal origin.
• The Guichi Mn deposits were formed in high-salinity and oxidative environment.
• The sources of manganese include volcanic, terrigenous and organic materials.

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 Lan/Cen (>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 °C) of Permian Mn-carbonate ore and Mn-bearing carbonate. The low Ceanom. 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, δ13CV-PDB (−10.2‰ to 5.00‰) and δ18OSMOW (20.7–28.0‰) characteristics of Permian manganese deposits reveal a mixed Mn source of volcanic, terrigenous and organic matter.