沅麻盆地砂岩型铜矿成矿地质特征及其控矿条件研究

Geological characteristics and ore-control condition of sandstone-type copper deposit in Yuan-Ma Basin,Hunan province

沅麻盆地是湖南省重要的铜矿成矿区之一,盆地内砂岩型铜矿床(点)多,铜矿具有规模大、品位高、矿石选冶性能好等特点。因此,研究该盆地砂岩型铜矿的成矿地质背景和控矿条件,为沅麻盆地砂岩型铜矿的评价及扩大找矿前景提供科学依据和成矿背景资料具有重要意义。笔者在前人研究的基础上,结合麻阳铜矿矿床地质特征对盆地成矿条件和控矿因素进行分析和研究,提出区内矿体的产出状态主要受三角洲的分流河道及构造的控制,矿体在空间上的分布则主要受岩相与构造的制约;区内含铜岩系"红层"与"浅色层"的互层为有利于成矿物质汇集成矿的岩性组合;地下水在成矿过程中把岩碎屑中的铜质溶离出来和把溶离出来的铜质运移到弱碱性环境下的岩性-构造有利部位聚集成矿起到了重要作用;生物有机质在铜质的吸附还原、铜质的溶解和运移及铜质的富集都起了重要作用。认为:该矿床的形成受物源、古构造、岩相、地下水活动以及生物有机质等因素的联合控制,沅麻盆地铜矿床主要是以机械沉积为主,后经地下含矿热卤水叠加改造而最终形成的砂岩型铜矿床,并指出有利的找矿部位。

Yuan-Ma basin is one of the most important copper metallogenic regions in Hunan province. The copper deposits in Yuan-Ma basin have the characteristics of large scale, high grade and ore metallurgical performance etc. It has significance to provide scientific basis and mineralization background information for reevaluating sandstone-type copper deposits in Yuan-Ma basin and expanding the periphery prospecting by researching sandstone-type copper metallogenic geological background in Yuan-Ma basin and its control on sandstone-type copper deposits. Based on the geological characteristics of Mayang copper deposits and some previous information, the mineralization conditions and ore controlling factors of the sandstone-type copper deposits in Yuan-Ma basin are researched. It shows that the distribution of ore bodies are mainly restricted by petrographic and tectonics in space, A lithology combination for minerals with the copper hearing rock series ＂red layer＂ and ＂light＂ cross. Groundwater plays an important role in the oreforming process of the rock debris of copper leaching from the leaching from copper migration to the weak alkaline environment litho tectonic favorable sites for poly metallogenic. The biological organic matter plays an important role on the copper adsorption and reduction, dissolution and migration and enrichment of the copper. Studies suggest that the formation of joint control by material source deposits, ancient structures, lithofaeies,groundwater activities and organic matter and other factors that is based on the geological characteristics of Yuan-Ma sandstone-type copper deposit. The deposit is mainly mechanical deposition,after superposition of hot brine underground ore transformation and ultimately the formation of sandstone-type copper. At last, the favorable prospecting areas are pointed.