贵州戈塘金矿滑脱构造及其与成矿的关系

通过对戈塘矿区野外地质现象的实地考察,矿床的矿体主要赋存于茅口组之上的古岩溶面,龙潭组一段为主要的含矿层。茅口组之上的古岩溶不整合面与龙潭组三段与四段之间的面均为层滑构造,龙潭组二段、三段以炭质黏土岩与薄层粉砂岩为主,为矿区的能干层。叠瓦构造体系是在印支期到燕山期的构造运动过程中形成的,这一时间段中区域压力由南北向转变为东西向,该体系是多期构造运动的结果。在软弱层中形成的叠瓦状逆冲断层的断裂面处于最大应力状态,呈挤压封闭状态,不利于成矿流体的运移,加之岩性的透水性差,对矿液起到了地球化学障的作用,对含矿溶液在层滑构造中的成矿提供了有力条件。另外,软弱层中存在炭质且向上逐渐变薄,当含矿热液经过时,pH值发生改变,热液含金浓度增大,并还原出了络合物中的金并将其吸附,由于进入软弱层中的矿质少,所以在该层中只发现了矿化而未发现矿体。

Decollement Structures and Its Relationship with Mineralization in Getang Gold Deposit in Guizhou Province

According to the field survey of geological phenomenon in Getang Gold deposit，the ore body of the deposit mainly occurs in the ancient karsts surface which is upon the Maokou formation，Section 1 of Longtan formation is the major ore-bearing layer.Both of ancient karsts side and the surface between the section three and four of Longtan formation are slip-sheet structure，the lithological combination of the second and third section of Longtan formation are clay stone with carbon and siltstone and this two sections are the intensified layer.The imbricate structure system is formed during the tectonic movement process between Indo-Chinese epoch and Yanshan epoch.During this period，the direction of regional pressure is changed from north-south to east-west，and the imbricate structure system is the result of multiphase tectonic movement.The fracture surface of imbricate thrust fault which is formed in the intensified layer is in a condition of maximum stress and closed extrusion，and this condition has disadvantage of the migration of ore-forming fluid.Additionally，poor water permeability of the rock plays a role of geochemical barrier to ore fluid，which provides the favorable conditions to the ore-forming of ore-bearing solution in the slip-sheet structure.Moreover，carbon exists in the intensified layer and becomes upward thinning.When the ore-bearing fluid flow through，the value of pH will be changed，the concentration of gold in fluid will be increased，and gold will be extracted from the clathrate and adsorbed by the carbon.Only relatively less mineral flow into the intensified layer，so just mineralization is found instead of ore body.