皖南歙县砚石板岩赋矿层位地质特征及找矿方向:以双河口砚石矿床为例

GEOLOGICAL CHARACTERISTICS OF THE HOST STRATA OF INKSTONE IN SHEXIAN COUNTY IN SOUTHERN ANHUI AND THE PROSPECTING DIRECTION: A CASE STUDY OF THE SHUANGHEKOU INKSTONE DEPOSIT

通过野外地质调查,查明了矿区内地层、构造特征及成矿地质条件。确认砚石矿赋存于大谷运组上段黑色板岩发育地段,并受地层层位控制。确定矿床类型为区域高变形浅变质沉积型。矿区围岩蚀变主要为绢云母化、绿泥石化、硅化、钠长石化、黄铁矿化和高岭土化等。以双河口砚石矿床为例,通过地表工程揭露与钻探工程控制,圈定出砚石矿体5条,该区砚石品级可为特等品、一级品、二级品、三级品四个品级。结合区域成矿条件,对皖南砚石资源的找矿方向进行了论述,区域上可找寻赋存黑色板岩的地层,沉积环境相差不大,变质程度相似的中元古代-青白口纪的牛屋组、大谷运组、镇头组等板岩相对发育层位。

Through field geological survey, the stratigraphic, tectonic characteristics and metallogenic geological conditions are made clear in the mineral district. It is confirmed that the ink-stone deposits occur in the black slate development area of the upper member of the Daguyun Formation and are controlled by the strata. The deposittype is determined to be regional highly deformed and shal lowly metamorphosed sedimentary type. The wall rock alterations are mainly sericitization, chloritization, silicification, albitization, pyritization and kaolinization. Taking the Shuanghekou inkstone deposit as an example, five inkstone bodies were delineated through sur face engineer ing exposure and drilling engineer ing control . The inkstones in this area can be classified into four grades: special grade, first grade, second grade and third grade. Combined with the regional metallogenic conditions, this paper discusses the ore-prospecting direction of ink-stone resources in southern Anhui Province. Regionally, the strata in which black slate occurs can be targeted, such as the Niuwu, Daguyun and Zhentou Formations of mid-Proterozoic Qingbaikou period, which are not much different in sedimentary environment and are similar in metamorphic degree, in which slate is relatively developed.