Geological Characteristics, Ore-Controlling Factors and Metallogenic Model of Muhu Manganese Deposit in West Kunlun, China

Abstract

Muhu manganese deposit is located in the eastern end of Malkansu manganese ore belt in the west Kunlun orogenic belt, and research for this deposit is relatively weak. The ore-bearing strata of Muhu manganese deposit is the Upper Carboniferous Kalaatehe Formation, which can be divided into three members from the bottom to the top: Breccia limestone, calcareous greywacke, and carbonaceous marlstone. This typical transgressive sequence reflects the basin evolution from gradual faulting to stable sedimentation. The manganese orebodies occur in carbonaceous marlstone in the upper part of Kalaatehe Formation, and are mainly composed of fine-grained pure rhodochrosite. Based on the detailed mineralogical observation and the previous research advance, we suggest that the rhodochrosite in Muhu formed as a result of manganese oxides reduction by organic matter during burial diagenetic reaction. Three basic conditions are needed for this metallogenic mechanism: Abundant manganese source, redox stratified basin, and large burial of organic matter. In Muhu area, the main favorable ore-controlling factors include extensional tectonic background, strong submarine hydrothermal activities, transgressive event, and warm-humid paleoclimate. Based on the w(Ba)-w(P2O5) diagram and regional comparative analysis, we consider that the oxygen minimum zone expansion model can explain the genesis of Muhu manganese deposit.