“三江”喜马拉雅期沉积岩容矿贱金属矿床基本特征与成因类型

"三江"的兰坪、昌都、玉树、沱沱河地区发育丰富的沉积岩容矿贱金属矿床,构成一条极具成矿潜力的巨型矿化带。综合分析表明,带内矿床形成于新生代印-亚大陆碰撞环境,发育在大陆碰撞造山带内部的褶皱-逆冲带内,与逆冲和走滑构造控制的新生代盆地相伴。不同矿区均发育逆冲断层,矿体主要赋存于逆冲断层上盘的碳酸盐岩或碎屑岩内,受与逆冲相关的盐底辟、逆冲断裂的次级断裂、热液溶洞、白云岩化、灰岩破碎、矿前溶洞垮塌、与褶皱有关的密集劈理或断裂等构造或岩相变化控制。金属呈现Pb-Zn、Pb-Zn(-Cu-Ag)、Cu-Co、Cu等组合,其中,Pb-Zn矿床主要发育闪锌矿、方铅矿、黄铁矿、±白铁矿、方解石、白云石,一些矿床富硫酸盐矿物和萤石,也常见沥青,矿化以交代和开放空间充填为主;Pb-Zn(-Cu-Ag)矿床主要发育闪锌矿、细/灰硫砷铅矿、方铅矿、黝铜矿、黄铁矿、方解石、白云石,矿化以脉体或热液溶洞内交代/开放空间充填式出现;Cu矿床由石英-方解石/白云石-Cu硫化物(黄铜矿、黝铜矿、斑铜矿、辉铜矿)脉构成。Pb-Zn和Pb-Zn(-Cu-Ag)矿床成矿流体以低温(<210℃)和高盐度主体w(Na Cl)>10%]的盆地卤水为主,脉状Cu矿床成矿流体可能来自富CO2、具相对高温(180~230℃)和低盐度w(NaCl)<11%]的变质流体。盆地卤水中硫酸盐遭受细菌还原±有机热还原或仅经历有机热还原,为Pb-Zn和Pb-Zn(-Cu-Ag)矿床提供了还原硫,下伏火山岩和沉积地层中的硫可能是脉状Cu矿床硫的来源,它们的成矿金属物质均来自于上地壳。该带矿床是一套与岩浆活动无关的后生矿床,以世界上已知的矿床类型来划分,金顶、赵发涌、东莫扎抓、莫海拉亨和茶曲帕查矿床等Pb-Zn矿床及白秧坪东矿带的Pb-Zn(-Cu-Ag)矿床可归为类MVT矿床,白秧坪西矿带脉状Pb-Zn(-Cu-Ag)矿床和脉状Cu矿床可归为多金属脉状矿床。其中,金顶等类MVT矿床以其形成于大陆碰撞带内部、受控于逆冲推覆构造等特点不能被已建立的MVT成矿模型所涵盖,成矿作用独特。

Sediment-hosted Himalayan base metal deposits in Sanjiang region: characteristics and genetic types

Significant economic sediment-hosted base metal deposits occur in Lanping,Changdu,Yushu and Tuotuohe areas of Sanjiang region in southwest China.The authors hold that they were formed during Indian-Asian continental collision and developed within the fold-thrust belt combined with thrust and/or strike-slip-related Cenozoic basins in the interior of the collsional zone.Ore bodies are hosted by carbonate and/or clastic rocks as hanging wall of the thrust fault,controlled by thrust-related salt diapir,second-o...