湖北恩施双河硒矿矿床地质特征

双河硒矿区位于扬子准地台，上扬子台褶带的东北部，受双河向斜构造控制。硒矿床的赋矿层位，严格受下二叠统等口组含炭质硅质岩与含硅质炭质页岩控制，长可达数十千米。矿体位于上述岩性界面附近，共圈定９个矿体，长３０～１５０ｍ，厚０．７～５．２ｍ。延深（伸）１４～３５ｍ，平均品位为０．１３％，厚度、品位属不均匀变化类型。矿体位于潜水面之上，是透镜状，矿石具典型同生沉积组构。常具隐晶质结构、生物结构、层纹状构造、块状构造等。矿石中硒呈分散状以灰质吸附为主，仅见少量硒铁铜矿。硒（Ｓｃ）、硫（Ｓ）、有机炭（Ｃ）呈明显的线性相关关系。硒主要来自沉积源，成岩阶段初步富集成矿源层，经大气降水的溶解、氧化淋滤，硒以络合物形式迁移渗滤，在构造有利部位沉淀并吸附于有机物，富集成矿，其成因类型属层控矿床。

GEOLOGICAL CHARACTERISTICS OF SHUANGHE SELENIUM ORE DEPOSIT IN ENSHI, HUBEI PROVINCE

Controlled by Shuanghe synclinal structure, Shuanghe selenium mine is located in the northeastern Upper Yangtze platformal fold belt of the Yangtze paraplatform. With tens of kilometers long, the ore - bearing beds are controlled by carbonaceous siliceous - rocks and siliceous carbonaceous - shales in Maokou Formation of Lower Perminan Series. The nine delimited lens - shaped orebodies occurs above the water - table, near the lithological interfaces of the above - mentioned rocks with 30 - 150m long, 0. 7-5. 2m thickness, 14 - 35m extension and an average grade of 0. 13 % among which the thickness and the grade belong to the type of heterogeneous change. The ores have typical syngenetic depositonal fabric, commonly including cryptocrystaline texture, organic texture, laminated structure, block structure, etc. Selenium dispeses mastly in .the ores absorbed by carbonaceous materials and there only occurs a few eskebornites. A distinct linear correlation exists between Se, S and organic - carbon.The selenium sourced mainly from sedimentary derivation and the source beds formed in diagenetic stage with priliminary enrichment. By meteoric water dissolving, oxidized leaching,transfering and filtrating, selenium complex deposited in the favorable structure positions, absorbed by organic materials. Finally, the selenium ore deposit formed through the enrichment,belonging to stratabound ore deposit.