A largescale manganese carbonate metallogenic belt is newly found in the Carboniferous sedimentary rocks of the Malkansu area in the northern part of the West Kunlun orogenic belt, which is a breakthrough of manganese ore prospecting in northern China. The manganese ore belt in Malkansu area is stratigraphically stable with large thickness and high grade. The Orto Karnash manganese deposit is the largest and the most representative deposit within the Malkansu manganese carbonate belt. Systematic studies of the regional and deposit geology show that the Orto Karnash manganese deposit is a typical marine sedimentary manganese carbonate deposit. The formation of the manganese ore may be related to the backarc basin sedimentary—hydrothermal activity system, and the local depression in the shallow continental shelf environment is the most favorable site for the deposition of manganese. It is speculated that the manganese carbonate deposit is formed by the reduction of original manganese oxide through acting with organic matter during diagenesis. The offset between the ore body and associated rocks and the presence of calcite veins and manganesebearing silicate minerals suggest a latestage tectonic and hydrothermal superimposition.