黔北铝土矿不同类型矿石地球化学特征及其对成矿作用的指示  

Geochemistry of Varied Type Ores of Northern Guizhou Bauxites and its Implication for Mineralization

作　　者：张莹华[1,2] 凌文黎[1,2] 吴慧[1,2] 张亚男[1,2] 丁晓英[1,2] 崔滔[3,4] 杜远生[2] 雷志远[5] 翁申富[5] 

机构地区：[1]中国地质大学地质过程与矿产资源国家重点实验室,武汉430074 [2]中国地质大学地球科学学院,武汉430074 [3]中国地质大学构造与油气资源教育部重点实验室,武汉430074 [4]中国地质大学资源学院,武汉430074 [5]贵州省地质矿产勘查开发局106地质大队,贵州遵义563000

出　　处：《地质科技情报》2013年第1期71-79,共9页Geological Science and Technology Information

基　　金：贵州省地勘基金项目“贵州务正道地区铝土矿基础地质与成矿规律研究”

摘　　要：黔北务川-正安-道真铝土矿带是我国铝土矿重要的成矿带之一。矿床中发育有4种典型的矿石类型:致密状、碎屑状、豆鲕状和土状。通过对不同类型矿石及矿体下伏高Al黏土岩和志留系韩家店组泥质岩的系统元素地球化学研究,采用元素质量平衡的示踪方法,对矿床的成因进行了探讨。研究表明,成矿作用发生于开阔海岸环境、与多频次海进-海退循环对陆缘古风化剖面的侵蚀作用有关;海进-还原过程导致了古风化剖面中部大量黄铁矿等硫化物的形成,而随后的海退-氧化过程产生高硫酸介质水溶液,使得杂质元素大量移出和铝土矿化发生;强酸溶液带出的大量元素随环境向pH值中性化和氧逸度下降条件的演化,以化学沉淀形式形成了杂质元素含量相对较高的致密状矿石,而海进-海退循环对碎屑状-豆鲕状矿石的多期次改造,导致了土状矿石的形成。The Wuchuan-Zhengran-Daozhen bauxite zone is one of the major Al-metallogenic belts in China. The bauxite deposits dominantly comprise four ore types featured by massive, brecciated, pisolitic to oolitic and earthy structures respectively. This study presents a comprehensive element geochemical study of the distinct ores, underlain high-A1 claystone and Silurian shales of the Hanjiadian Formation by ele- mental mass balance modeling, and then the ore genesis is discussed. It is suggested that the metallogene- sis occurred at a broad coastal plain and was closely related with seawater encroaching upon the weathering profiles along continental margin by multiple marine transgression-regression recycling. Reduction condi- tion during transgression resulted in formation of a large amount of pyrite-dominated sulfides under a cer- tain depth range of the weathering profiles, whereas the oxidation reaction during regression produced strong sulfuric acid aqueous solution, which carried out a large quantity of matrix elements and advanced bauxitization. It is further suggested that the massive ore, featured by relatively high impurity, was formed by chemical precipitation when the matrix-bearing aqueous solution evolved toward a pH neutraliza- tion and oxygen fugacity decreasing, whereas the earthy ore is the end product of Al-purification by the multiple transgression-regression recycling.

关 键 词：黔北 铝土矿 矿石类型 地球化学 成因 

分 类 号：P618.45[天文地球—矿床学]