西成矿田海底热水喷溢沉积成因硅质岩及其与矿化关系  

Hydrothermal Exhalitive Sedimentary Siliceous Rocks and Their Relationship with Pb- Zn Mineralization in Xicheng Orefield, Gansu, China

作　　者：宋春晖[1] 武安斌[1] 周少平[2] 

机构地区：[1]兰州大学地质系 [2]中国地质大学

出　　处：《沉积学报》1992年第4期60-67,共8页Acta Sedimentologica Sinica

基　　金：甘肃省自然科学基金资助项目

摘　　要：硅质(化)岩与铅锌矿化关系十分密切是西成矿田显著特征之一,特别是毕家山型矿床,其主要矿体的容矿岩石为硅质岩,本文重点研究了该矿田硅质岩岩石学和地球化学特征及其与矿体(层)时空关系,认为该区硅质岩不是正常生物化学沉积成因的,而属热水沉积形成;并讨论了硅质岩与矿化关系以及硅质在成矿中的作用,为确定该类矿床的成因提供了重要证据.Xicheng Pb-Zn Orefield is located in Huixian, Chengxian and Xihe counties, southeastern Gansu. The ore-bearing rock sequences consisting of marine clastic and carbonates rocks of middle Devonian. Two types of the strata-bound ore deposits have been divided based on the ore deposits feature: Changba and Bijiashan types. Especially Bijiashan type deposit, which's main host rocks are siliceous rocks. The siliceous rocks, distributing a little broader than ore bodies, are closely related to Pb- Zn mineralization and its thickness has a normal ratio with thickness of ore body. In section, the siliceous rocks, which are flatly contact with overlying phyllite and roughly contact with underlying carbonates, are bedded, bedded-like or lenticular and paralled or simultaneously folded with the adjoining rocks. The main types of the siliceous rocks are divided into brecciated siliceous rocks, dark-gyay or gray massive siliceous rocks, riband-band siliceous rocks and white vein quartzite. They have very obvious sedimentary charactes and coexist with hydrothermal sedimentary barite rocks except vein quartzite. Geochemical analysis show that the siliceous rocks possess characteristic geochemistry: (1) the content of silica and some significant ratios (SiO2 = 82.97% , Fe2O3 / FeO < 1, K2O > Na2O, A12O3 = 28.41, SiO2/ (K2O+Na2O) =143.05, SiO2/ MgO=60.56, Fe+Mn/ Ti= 30.18) are quite similar to those in hydrothermal sedimentary siliceous rocks, but different from those in normal sedimentary siliceous rocks and volcanic siliceous roks; (2) the contents of trace elements such as Ag, As, Hg, Sb, Ge and Cd are higher than Clark value by 1-3 logarithmic scales, this feature is one of the indicators of hydrothermal sedimentary origin; (3) the results of REE analysis show that the REE models of siliceous rocks are HREE-rich type and negative cerium or europium anomalies, REE models of different types of siliceous rocks and Pb- Zn ore are quite similar. The total contents of REE in the siliceous rocks (

关 键 词：硅质岩 热水沉积 海底 铅锌矿田 

分 类 号：P618.420.1[天文地球—矿床学]