The newly discovered stratiform Mn-carbonate ore from the Zhuwuluke deposit occurs within the fine-grained clastic rocks-carbonate of the Lower Carboniferous Talong Group. Here we utilize petrographical, mineralogical and geological data to shed light on the ore-forming materials sources and metallogenic mechanism of the manganese carbonate mineralization. The ore minerals are composed mainly of Fe-rhodochrosite, rhodochrosite, Ca-rhodochrosite, and kutnahorite. The positive Eu anomalies (average 3.03) of Mn-carbonate ores and Mn-bearing limestones reveal a hydrothermal source. The MoEF (from 2.09 to 196.18) and UEF (from 0.74 to 3.60) values of most Mn-bearing limestone and wall rock sample suggest that they were deposited under reducing conditions where sulfide was restricted to the pore waters. The higher UEF values of Mn-carbonate ores (mean 24.19) and incomplete separation of Fe from Mn suggest that they were deposited under rapid oxidation conditions. The negative S isotope compositions of pyrite (δ34Spy) and Mn-bearing carbonates (average −10.16‰ and −7.17‰, respectively) indicate the microbially mediated diagenetic sulfate reduction (BSR) and a relatively sufficient supply of sulfate in hemipelagic conditions. The C isotope compositions of Mn-bearing carbonates (δ13Ccarb, average −10.92‰) and its negative correlation with Mn content suggest that the initial Mn precipitated as Mn (oxyhydr)oxides, followed by reduction during burial diagenesis. Apart from that, paragenetic relationships indicate some Mn-carbonates were formed during authigenesis. We suggest that the high contents of Fe in Mn-carbonates were due to rapid oxidation conditions and relatively enough sulfate supply. The redox conditions and relatively stable sedimentary environment during the Early Carboniferous collectively facilitate the formation of manganese carbonate deposit. © 2022 The Author(s)
