Geology, Geochemical Characteristics, and Sedimentary Environment of Mn-bearing Carbonate from the Late Carboniferous Muhu Manganese Deposit in West Kunlun

Key words: 
• Late Carboniferous /
• terrigenous clastics-carbonate /
• sedimentary environment /
• Muhu manganese deposit /
• West Kunlun

Abstract: A set of clastic-carbonate rocks developed in the Maerkansu of West Kunlun during the Late Carboniferous recently revealed that it has a great potential for rhodochrosite prospecting and has attracted significant attention. The clastic-carbonate lithofacies division and sedimentary environment analyses were carried out by measuring the manganese-bearing rock series profile, thin section identification, electron probe, scanning electron microscope, geochemical analysis, and strontium isotope testing of the carbonate rocks in the Muhu manganese mine. Our study indicates that the manganese-bearing rock series consists of eight clastic-carbonate rock facies:marlite, arenaceous limestone, microcrystalline manganese carbonate, microcrystalline-micrite limestone, gravelly limestone, gravelly arenaceous limestone, calcareous sandstone, calcareous conglomerate, and combinations of three rock facies. Based on the geochemical and strontium isotope characteristics of the ore body and its roof and floor rocks, the ancient seawater temperature averaged 22.68℃, which belongs to the subtropical zone. In all, the manganese-bearing rocks are clastic shore facies and shallow sea-land shelf facies deposits with shallow seawater. The roof and floor rocks of the ore body were in a relatively shallow oxidation-weak reduction environment with seawater, while the rhodochrosite was formed in shallow sea-land shelf sedimentary depressions with relatively deep seawater under a reduced sedimentary environment, which is related to submarine volcanic hydrothermal activity.