黔西南低温成矿区地质构造演化与金矿成矿作用

发布时间：2018-07-28 19:57

【摘要】：黔西南地跨扬子陆块和华南褶皱系的右江造山带两个大地构造单元,从更广义的角度来说,研究区毗邻环太平洋构造域与特提斯构造域的结合部位。黔西南众多金矿床属于典型的微细浸染型金矿床,以地质构造为首要控矿因素,所以从地质构造的角度对金矿的成矿模式进行讨论就显得恰得其分。本次论文选择了研究区几个典型金矿床(水银洞金矿、烂泥沟金矿、丫他金矿和戈塘金矿)为切入点,在了解区域地质特征、地质构造演化、矿区地质特征和矿体地质特征的基础上,结合矿相学分析、流体包裹体分析以及同位素分析等技术手段,同时,归纳比较前人研究成果,从而对区域地质构造演化与区域金矿成矿作用进行讨论研究。从大地构造划分的角度,除戈塘和水银洞等少数金矿床产于扬子陆块西南缘(毗邻右江造山带),几乎所有黔西南微细浸染型金矿都产于右江造山带,反映黔西南微细浸染型金矿床的形成与右江盆地之间存在某种必然的联系。此外,黔西南各微细浸染型金矿床有着极相似的矿化蚀变特征与成矿理化条件,反映了这些金矿床成矿过程中成矿流体与物质的同源性,以及成矿过程中相同的动力学背景。黔西南金矿床赋矿层位主要有上二叠统龙潭组(P_3l)、上二叠统龙潭组(P_3l)和中二叠统茅口组(P_2m)之间的构造蚀变体(Sbt)(形成于区域性构造活动)、中三叠统边阳组(T_2by)和中三叠统许满组(T_2xm)中。其中赋矿于二叠统龙潭组和构造蚀变体的有水银洞金矿床、戈塘金矿床;赋矿于中三叠统许满组和边阳组的有烂泥沟金矿和丫他金矿(以许满组为主)。水银洞、丫他以及戈塘金矿床的流体包裹体分析测试得出,成矿流体温度范围为100~293.3℃,盐度范围为0.18~13.62wt%,密度范围为0.75~1.06g/cm~3,成矿压力范围为178.51~731.73×10~5Pa,表明黔西南金矿床是典型的中低温热液金矿床。此外,综合对比前人研究,成矿流体还具富CO_2和CH_4、偏还原、弱酸性和低氧逸度等特点。微细浸染型金矿具典型的构造控矿特征,从构造演化的角度出发,黔西南微细浸染型金矿与右江盆地的裂解、碰撞造山及后碰撞侧向挤压存在必然的、十分密切的联系,含矿流体的产生和汇聚皆与右江盆地的形成和碰撞过程密切相关,而含矿热液中矿质在后碰撞造山侧向挤压阶段发生沉淀作用而富集成矿。综合黔西南地区地质构造演化与金矿成矿的特点,黔西南微细浸染型金矿的成矿经历了三个阶段:中泥盆世—早三叠世,右江盆地裂解-弧后盆地阶段,形成含矿建造;中三叠世—中侏罗世,右江盆地前陆盆地阶段,初步形成含矿流体;晚侏罗世—早白垩世,右江盆地碰撞造山侧向挤压阶段:成矿物质的富集成矿。
[Abstract]:There are two geotectonic units, the Yangtze block and the Youjiang orogenic belt of the South China fold system in southwest Guizhou. In a more general sense, the study area is adjacent to the conjunctions of the circum-Pacific tectonic domain and the Tethys tectonic domain. Many gold deposits in southwestern Guizhou are typical micro-disseminated gold deposits, and the geological structure is the primary ore-controlling factor, so it is obvious that the metallogenic model of gold deposits can be discussed from the perspective of geological structure. In this paper, several typical gold deposits (Shuiyindong gold deposit, Luanjigou gold deposit, Yata gold deposit and Gotang gold deposit) are selected as the entry point to understand the regional geological characteristics and tectonic evolution. On the basis of geological characteristics of mining area and orebody, combined with the technical means of mineralogical analysis, fluid inclusion analysis and isotope analysis, and at the same time, the previous research results are summarized and compared. The evolution of regional geological structure and mineralization of regional gold deposits are discussed. From the perspective of tectonic division, a few gold deposits, such as Gegotang and Shuiyindong, occur in the southwestern margin of the Yangtze block (adjacent to the Youjiang orogenic belt), and almost all micro-disseminated gold deposits in southwest Guizhou are located in the Youjiang orogenic belt. It shows that there is an inevitable relationship between the formation of microdisseminated gold deposits in southwest Guizhou and the Youjiang basin. In addition, the microdisseminated gold deposits in southwest Guizhou have very similar mineralization alteration characteristics and metallogenic physicochemical conditions, which reflect the homology of ore-forming fluid and material and the same dynamic background in the metallogenic process of these gold deposits. The ore-bearing strata of the gold deposit in southwest Guizhou mainly include the Upper Permian Longtan formation (PSP 31), the Upper Permian Longtan formation (P 31 1) and the Middle Permian Maokou formation (P Permian), the tectonic alteration (Sbt) (formed in the regional tectonic activity), the Middle Triassic Bian Yang formation (T_2by) and the Middle Triassic Xuman formation (T_2xm). Among them, there are Shuiyindong gold deposit and Gotang gold deposit in Longtan formation and tectonic alteration of Permian and Luannigou gold deposit and Yata gold deposit in the middle Triassic Xuman formation and Bian Yang formation (mainly Xuman formation). The fluid inclusions of the Mercury Cave, Yatta and Gotang gold deposits show that the ore-forming fluid temperature ranges from 100 to 293.3 鈩，

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