黔东北大塘坡组菱锰矿矿床控矿因素研究

Ore_controlling factors of rhodochrosite ore bed from Datangpo Formation in northeast Guizhou

黔东北黑色泥岩盆地中菱锰矿的品位普遍偏低,高品位的块状菱锰矿在横向上和垂向上并非稳定存在,弄清菱锰矿的空间分布规律可以为勘探开发提供指导。文章首先从区域尺度分析了菱锰矿矿床分布与黑色泥岩盆地内部次级洼陷的关系,然后以杨家湾锰矿床为例,分析了同一次级洼陷内锰品位与含锰岩系厚度和矿层厚度的相关性。最后选取次级洼陷内的典型探井,从矿石的结构特征和矿物共生组合规律等微观尺度,研究了菱锰矿矿床的垂向非均质性,探讨了黑色泥岩盆地中菱锰矿富集的控制因素。研究表明,菱锰矿主要赋存于有机质含量较高的大塘坡组一段底部,锰矿品位与矿层厚度呈正相关,高品位的锰矿主要为泥晶结构的块状菱锰矿,平面上主要分布于黑色泥岩盆地的次级洼陷沉积中心;锰矿层在横向上并非稳定的均质沉积,从洼陷中心到洼陷边缘,菱锰矿的品位逐渐降低;锰矿层与粉砂质泥页岩交互沉积,具有很强的垂向非均质性。

The grade of rhodochrosite deposits in black shale basins is generally low, and the distribution of high grade bulk rhodochrosite is not steady horizontally and vertically. Therefore, investigating the spatial distribution regularity of rhodochrosite can serve as a guidance of exploitation. In this study, the authors first analyzed the rhodochrosite ore distribution in relation to the inner secondary sag of the basin at the regional scale. The Yangjiawan manganese deposit in northeast Guizhou was used as an example to analyze the grade of manganese in the same secondary sag related to the thickness of manganese_bearing rock series and the thickness of ore bed. Finally, typical drill holes in secondary sag were selected to study the vertical anisotropism of manganese in view of micro_scales like petrosal structural features and the rule of paragenetic association of minerals. In addition, the controlling factors of enrichment of rhodochrosite in black shale basins were also discussed. The results show that the rhodochrosite mainly occurrs within the bottom of the first member of Datangpo Formation, where there is a high content of organic matter,the grade of rhodochrosite has a positive relation with the thickness of ore beds, and the high grade rhodochrositelayers are mainly massive rhodochrosite with mud structure, which are mainly occur at the center of the secondary sag in plain view; horizontally rhodochrosite ore beds are not steady homogeneous deposit, the grade of rhodochrosite decreases from the center to the boundary of the sag; rhodochrosite ore beds have strong vertical heterogeneity because of the interaction of sediments with silty shale.