GEOCHEMICAL EVIDENCE FOR THE HYDROTHERMAL SEDIMENTARY ORIGIN OF RHODOCHROSITE DEPOSIT IN GAOYAN, CHONGQING

The Gaoyan manganese deposit in Chongqing is located in the Late Sinian Qinba Mn sedimentary basin. The rhodochrosite ores occur in the top of Doushantuo Formation in the form of ooid or pellet. Based on previous researches, samples of the ooid rhodochrosite are systematically taken from 5 boreholes in the Doushantuo Formation to test the geochemical items of Mn, Fe, P, SiO₂, CaO, MgO, Al₂O₃ and LOI. The values of Mn/Al, (MgO/Al₂O₃)×10² and SiO₂/Al₂O₃ are analyzed with indicating element geochemistry. The results show that the rhodochrosite is mainly marine authigenic product related to marine sedimentation, with little affection of terrigenous material. The deposition process of rhodochrosite is involved with hot water. The rhodochrosite is the result of hydrothermal sediment.