西藏南部热水沉积硅质岩岩石学和地球化学特征及地质意义  

Petrologic and Geochemical Characteristics of the Hydrothermal Chert in Southern Tibet and Its Geological Significance

作　　者：何俊国[1] 周永章[1] 聂凤军[2] 杨志军[1] 张澄博[1] 付伟[1] 

机构地区：[1]中山大学地球科学系地球环境与地球资源研究中心,广州510275 [2]中国地质科学院矿产资源研究所,北京100037

出　　处：《矿物岩石地球化学通报》2007年第1期74-81,共8页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：国家重点基础研究发展规划资助项目(2002CB412600-V);国家自然科学基金资助项目(40573019);全国高等学校博士点基金资助(20040558050);教育部优秀青年教师资助项目(200139)

摘　　要：西藏南部广泛分布大规模中、新生代蛇绿岩套硅质岩、非蛇绿岩套硅质岩和硅质泉华体，本文通过对藏南日喀则、泽当等地区硅质岩的野外岩石学特征、镜下观察和地球化学分析测试，研究其地质意义。藏南硅质岩普遍发育层状、纹理状、块状和角砾状构造，化学成分与广西丹池盆地等典型热水沉积硅质岩相似，Fe／Ti值为12．88～30．60，（Fe＋Mn）／Ti为13．25～33，Co／Ni小于1，REE总量低，δCe呈负异常，重稀土相对轻稀土元素富集，Eu呈正异常，反映为热水成因，个别样品为生物成因。硅质岩形成与藏南拆离系和伸展构造碰撞造山带所造成的构造热事件有关，Au、Sb、Cs等多金属矿化与硅质岩密切相关．赋矿岩石石英硅同位素与马里亚纳海槽现代海底黑烟囱热水沉积物相似，为热水喷流沉积的产物。The Mesozoic and Cenozoic chert formations are widely distributed in Southern Tibet. The paper has studied the petrological and geochemical characteristics and its significance of the chert from Xigaze and Zedang districts, Southern Tibet, through microscopy and chemical analysis. The cherts distributed in the Southern Tibet have bedded, laminated, massive, and brecciated structures, with chemical composition similar to those of the typical hydrothermal cherts in Danchi basin, Guangxi, China. The cherts contain low REE contents, with Fe/Ti ratio of 12.88-30. 60, （Fe＋ Mn）/Ti ratio of 13.25 - 33, Co/Ni〈 1, relatively enriched HREE, positive Eu anomaly and negative Ce anomaly. These indicate that the cherts are mainly hydrothermal origin, with a few exception of biologic origin. The formation of cherts is associated with the tectonic hydrothermal events took place in STD through extensional orogenic movement. The Au,Sb.Cs polymetallic mineralization is closely related to the formation of cherts and they are believed to belong to sedimentary exhalative deposit.

关 键 词：硅质岩 沉积构造 多金属矿化 热水成因 西藏南部 

分 类 号：P588.2[天文地球—岩石学]