锡铁山铅锌矿床网脉状蚀变管道相的识别与研究  

Identification and study of stockwork altered pipe of Xitieshan lead-zinc deposit,Qinghai Province

作　　者：祝新友[1] 邓吉牛 王京彬[1] 林龙军[1] 樊俊昌 孙淑秋 

机构地区：[1]北京矿产地质研究院,北京100012 [2]西部矿业有限责任公司,青海西宁830001

出　　处：《地球化学》2007年第1期37-48,共12页Geochimica

基　　金：国家科技部科技攻关项目(2003BA612A-07);国家自然科学基金(40672061)

摘　　要：锡铁山大型铅锌矿床属喷流沉积型,赋存于柴达木盆地北缘早古生代裂陷形成的滩涧山群火山-沉积岩中。矿床中产有非层状和层状两类矿体,其中非层状铅锌矿体呈不规则状产于大理岩中,是锡铁山矿床的主要矿体类型,层状铅锌矿体产于大理岩边部,规模较小。在矿床深部大理岩层上盘滩涧山群b岩组的绿泥石英片岩中,深部整合发育有强烈的钠长石化与硅化,主要呈角砾状和网脉状结构,构成网脉状蚀变带,主要成分包括石英钠长岩、蚀变的绿泥石英片岩以及硅化石英岩等,其连续长大于2km,宽大于200m,呈不规则岩筒状。石英钠长岩交代结构普遍,与绿泥石英片岩呈渐变接触关系,广泛发育热水爆破角砾。地质地球化学研究表明,网脉状蚀变岩并非侵入岩或火山岩,而是形成于热水交代作用,代表了喷流沉积系统的管道相,相当于矿体下部供给带。结合容矿大理岩及矿体研究发现,锡铁山矿床发育规模巨大的喷流沉积系统,包括长>2km的管道相、大规模的喷流沉积岩-大理岩,以及近喷口相未喷出海底地表的非层状矿体。现已发现的层状矿体与非层状矿体比例的倒置显示出锡铁山矿床仍然存在巨大的铅锌矿找矿潜力。网脉状蚀变带分布于矿体及大理岩的上盘,也表明锡铁山矿区容矿的滩涧山群a和b岩组产状整体发生了倒转,网脉状蚀变岩最初分布于铅锌矿体及大理岩之下。由于网脉状蚀变岩(石英钠长岩)与成矿系统的密切关系,它可作为柴达木盆地北缘滩涧山群中寻找铅锌矿的重要找矿标志。Located in the northern margin of Qaidam Basin, Qinghai Province, Xitieshan lead- zinc deposit originally contains about 30 million tons of ore with a grade of 8% Zn and 10% Pb. It was formed in a rift basin in Ordovician. The lead-zinc orebody contained in marble can be divided into two types, i.e. unstratified and bedded ones. The unstratified orebody occurs unconformably in the marble and is the main orebody. The bedded one occurs conformably in the upper side of the marble that formed mainly by upflowing hydrothermal fluids and sedimentation, respectively during the exhalation period. The altered stoekwork pipe occurs in Ordovician Tanjianshan Group b member greenschist, and is between the red sandstone （c member） and the marble （a-2 member）, and above the orebody and the marble, with 〉 2 km in length and 〉 200 m in width. The sedimentary fabrics of the protolith are usually well reserved. The main alterations are albitization and silification, and the altered minerals are mainly albite of An 〈 4 and quartz of 0. 05 - 0.2 mm and minor muscovite and chalcopyrite, and both albite and quartz are of different generations. Hydrothermal eruption breccia and stockwork are widely occurred in the quartz-albitite.The REE distribution patterns of the rocks are similar to those of the greenschicts, and those of the silicated quartz rocks to those of the ores. The homogenization temperature of fluid inclusions of the quartz-albitite is about 250～350 ℃, and that of the ore is 150 ～250℃, but the gas and liquid compositions of the fluid inclusions between them are very similar. The studies of geology and geochemistry show that the stockwork altered rocks （quartz-albitites） are neither igneous rock nor volcanic rocks, but are formed by hydrothermal alteration, which represents the channel pipe or feeder zone of exhalation sedimentary system. A giant SEDEX system in the deposit has been recognized on the studies of the marble, orebody and the pipe, and it includes channel pipe with 〉 2 km in length,

关 键 词：铅锌矿床 喷流沉积型 钠长石化 石英钠长岩 角砾岩筒 矿床成因论 青海 

分 类 号：P594[天文地球—地球化学]