湖北省鹤峰县走马地区王家界锰矿地球化学特征及成因分析

Geochemical Characteristics and Cause Analysis of Wangjiajie Manganese Ore in Zouma Area,Hefeng County,Hubei Province

王家界锰矿为鹤峰县走马地区发现的"大塘坡式"锰矿。通过对大塘坡组含锰岩系样品进行主微量和稀土元素地球化学分析,发现本区含锰岩系有陆源物质的加入,并显示出热水沉积特征; Al2O3/(Al2O3+Fe2O3)、Al/(Al+Fe)、Al/(A1+Fe+Mn)、δCe、(La/Ce)N等值与被动大陆边缘沉积物特征相似;Al2O3/(Al2O3+Fe2O3)-(La/Ce)N和Fe2O3/(100-Si O2)-Al2O3/(100-Si O2)关系图及V/Cr值、U/Th-Ni/Co图解,表明本区与长阳古城锰矿形成于类似的构造环境。走马地区含锰岩系形成于被动大陆边缘的沉积构造体系,成岩成矿物质具有多来源。含锰岩系和锰矿石的形成可以分为两个阶段:早阶段洋底热液上涌的Mn2+与陆源输入的Mn2+在氧化性水体中形成了锰的氧化物,随后下沉被掩埋在缺氧带之下,在成岩过程中和有机物质相互作用,氧化物被还原释放出的Mn2+和有机碳被氧化释放出的CO2-3结合形成碳酸锰(菱锰矿)。

Wangjiajie manganese deposits is“Datangpo type”manganese ore discovered in the Zouma area of Hefeng County.Through geochemical analysis of major trace elements and rare earth elements in the samples of the manganese-bearing rock series of the Datangpo Formation,it is found that the terrestrial source materials are added to the manganese-bearing rock series in this area and showed the characteristics of hydrothermal sedimentation.Al2O3/(Al2O3+Fe2O3),Al/(Al+Fe),Al/(Al+Fe+Mn),δCe,(La/Ce)N equivalence is similar to that of passive continental margin sediments;Al2O3/(Al2O3+Fe2O3)-(La/Ce)N and Fe2O3/(100-SiO2)-Al2O3/(100-SiO2)diagram and V/Cr value,U/Th-Ni/Co diagram show that this area and Changyang ancient manganese ore formed in similar tectonic environment.The manganese-bearing rock series in the Zouma area were formed in the sedimentary structural system of the passive continental margin,and the diagenesis and mineralization materials have many sources.The formation of manganese-bearing rocks and manganese ores can be divided into two stages:in the early stage,manganese oxides were formed in the oxidized water body by the upwelling Mn^2+from the oceanic hydrothermal solution and the inputting Mn^2+from the terrestrial source.Subsidence was buried under the anoxic zone.During the process of diagenesis,manganese oxides were reduced to release Mn^2+and organic matter.Carbon dioxide is oxidized to form manganese carbonate(rhodochrosite).