湖南省湘潭县毛塘矿区海泡石黏土矿床地质特征及成因探讨

Geological characteristics and genesis discussion of sepiolite clay deposit in Maotang mining area,Xiangtan County,Hunan

通过在湘潭县毛塘海泡石黏土矿区留君庵矿段开展矿产勘查工作,基本查明了海泡石黏土矿床的地质特征。矿区海泡石黏土矿赋存于中二叠统小江边组“含泥质段”风化层中,矿体形态平面上呈长条带状,剖面上矿体形态呈透镜体状、似层状,矿床规模为小型。根据X衍射定量测试分析和化学分析,矿石主要矿物成分为海泡石、石英、方解石、滑石和蒙脱石等组成;矿石化学成分总体富硅、镁、低钾、钠。矿石中海泡石含量与MgO、SiO_(2)含量呈正相关关系,与CaO含量总体呈负相关,结合矿石扫描电镜分析结果,区内海泡石形成于沉积过程的新生作用。综合矿区成矿地质特征和矿石物理化学特点,矿区位于古陆边缘局限性的富Mg^(2+)、Si^(4+)及高pH值的浅海环境中,海泡石经原生沉积于钙镁质页岩、泥灰岩,再经长期化学风化改造,在表生条件下不断富集形成海泡石黏土矿床,矿床成因类型为沉积风化残余型。

The geological characteristics of the Liujun'an ore segment of Maotang sepiolite clay deposit in Xiangtan County have been basically found out by carrying out mineral exploration.Sepiolite clay orebody is located in the weathered layer of"argillaceous section"of the Middle Permian Xiaojiangbian Formation.The ore bodies present a shape of long strip on the plane,and appear as lenticular shape or layered on the section.The scale of the deposit is small.According to X-ray diffraction quantitative test and chemical analysis,the main mineral components of the ore are sepiolite,quartz,calcite,talc and montmorillonite,and the chemical composition of the ore is generally rich in silicon and magnesium,but poor in potassium and sodium.The content of sepiolite in the ore is positively correlated with the contents of MgO and SiO_(2),and negatively correlated with the content of CaO as a whole.Combined with the analysis result of scanning electron microscope,it is concluded that sepiolite in the deposit is formed during the neogenesis of sedimentation.Based on the ore-forming geological characteristics and the physical and chemical characteristics of ore,it is inferred that the deposit is located in the limited shallow sea environment rich in Mg^(2+),Si^(4+)and with a high pH value at the margin of an ancient continent.Sepiolite is originally deposited in calc-magnesian shale and marl,and then after long-term chemical weathering and transformation,sepiolite is continuously enriched under the supergene condition to form a sepiolite clay deposit.The genetic type is sedimentary weathering residual type deposit.