西昆仑玛尔坎苏地区奥尔托喀讷什大型碳酸锰矿床地质特征及成因探讨

摘要

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 Kamash 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.%西昆仑造山带北段玛尔坎苏地区石炭纪沉积岩系中探明一大型碳酸锰成矿带,是中国北方近年最重要的锰矿找矿新发现.该锰矿带层位稳定,厚度较大,且品位富.奥尔托喀讷什锰矿是该锰矿带规模最大、最具代表性的矿床.区域和矿床地质系统研究表明,奥尔托喀讷什锰矿属典型的海相沉积型碳酸锰矿床.该锰矿的形成可能与伸展背景的弧后盆地沉积—海底热液活动系统有关,浅海陆棚环境中的局部洼地是沉积锰矿形成的最有利地段;推测该碳酸锰矿床是成岩过程中由原始沉积的锰氧化物经有机质还原而形成,且微生物参与该成矿过程;后期构造作用使矿体与顶底板围岩发生了明显的滑脱,沿滑脱碎裂面发育热液方解石脉,同时形成锰硅酸盐矿物.