重庆市上二叠统硫铁矿沉积环境及成矿模式

Upper Permian Sedimentary Environment and Metallogenic Model of Pyrite in Chongqing

重庆市硫铁矿床主要为沉积型矿床,赋存层位主要为上二叠统龙潭组(P3l)、吴家坪组(P3w)(同时异相沉积)底部,该层硫铁矿含量约占重庆市硫铁矿总量的92%。对重庆市域范围内上二叠统硫铁矿含矿岩系和矿体特征的分析表明,龙潭组含矿岩系主要为高岭石化基性凝灰岩、高岭石黏土岩,吴家坪组主要为黏土质页岩,煤层中硫铁矿亦较发育。重庆市上二叠统硫铁矿主要富集在4个区域:渝东北城口、开县、云阳、奉节等区县;东部的石柱县以东地区;合川、璧山、渝北等华蓥山地区;綦江、南川、武隆等南部地区。分析认为中二叠世峨眉山玄武岩喷发沉降带来硫铁矿铁质物源,而二叠纪晚期海平面升高,海水携带大量硫元素分别自东部、北部、南部侵入渝东北及东部地区、重庆北部华蓥山地区、南部綦江—南川等区县,硫铁矿在还原环境中于成岩—后生作用阶段重结晶而成。基于重庆市上二叠统硫铁矿厚度、品位分布规律及其沉积环境的研究,分析了硫铁矿的成矿模式,提出硫铁矿主要发育于低地残积平原、沼泽、潮坪及海湾环境,多在海侵环境中形成。

Available pyrite occurs in sedimentary formation in Chongqing City. The pyrite that lies on the bottom of Longtan Formation （P3l） and Wujiaping Formation （P3w） accounts for about 92% of total. The ore-bearing formation and pyrite-formated deposited environment are studied and analyzed. The rocks are mainly kaolinization basic tuff, kaolinite claystone and grapholith, as well as coal-bed. Four areas rich in pyrite in Chongqing are northeast countries, east district, Huayingshan area and south of Chongqing. The material sources and its mineralization mechanism are discussed. The ferrum comes from Emeishan basalt and the sulfur is carried by seawater from different direction（north, northeast, south and east and so on）. In the reducing environment, the pyrite was formed via recrystallization at the stage of diagenesis -epigene- sis. The distribution regularity on thickness and grade are partly revealed and a primary metallogenic mod- el is proposed. The sedimentary facies are mainly eluvial plain, marsh, tidal flat, and gulf, and the pyrite are chiefly formed in the transgression system.