摘要
桂西铝土矿是我国喀斯特型铝土矿的典型代表。前人对该地区主要矿区铝土矿的物质组成、物质来源与成因机制已开展了大量研究,并取得了丰富成果,但对该地区铝土矿成矿后改造作用研究较少,且关于桂西铝土矿的成矿环境仍然存在争论。本文基于矿物组合与地球化学指标,划分了铝土矿的矿物演化期次,认为那端铝土矿形成于陆相环境:其陆源风化期为酸性氧化环境,埋藏成岩期为碱性还原环境,表生期为酸性氧化环境。上、下层铝土矿矿石结构的差异、埃洛石与下伏灰岩的接触关系和上层铁铝岩中针铁矿的产出形态均指示,该矿床在表生期经历了强烈的地表淋滤作用。铝土矿与埃洛石在微量元素和稀土元素配分模式上的差异表明,表生期发生了稀土元素的再分配,轻稀土(LREE)向下迁移并富集于埃洛石中。这一作用同时使铝土矿品位提高、有害组分降低。在表生氧化条件下,含铝岩系中的黄铁矿转变为针铁矿与黄钾铁矾。
Bauxite in Western Guangxi is a typical representative of Karstic Bauxite in China.Previous researchers have conducted extensive studies on the material composition,material sources,and genesis mechanisms of bauxite in the main mining areas of this region(Western Guangxi)and achieved rich results.However,there are fewer studies on the post-mineralization modification of bauxite in this region,and there remains controversy regarding the metallogenic environment of Western Guangxi bauxite.Based on mineral assemblages and geochemical indicators,this paper divides the mineral evolution stages of bauxite and holds that the Naduan bauxite formed in a terrestrial environment:the terrigenous weathering stage was an acidic oxidation environment,the burial diagenetic stage was an alkaline reduction environment,and the epigenetic stage was an acidic oxidation environment.The differences in ore structure between the upper and lower bauxite layers,the contact relationship between halloysite and the underlying limestone,and the occurrence morphology of goethite in the upper ferralitic rocks all indicate that the deposit experienced intense surface leaching during the epigenetic stage.The differences in trace element and rare earth element(REE)distribution patterns between bauxite andhalloysite indicate that REE redistribution occurred during the epigenetic stage,with light rare earth elements(LREE)migrating downward and being enriched in halloysite.This process also increased the bauxite grade and reduced harmful components.Under epigenetic oxidizing conditions,pyrite in the alumina-bearing rock system was transformed into goethite and jarosite.
作者
覃荣峰
杨淑娟
马欢
陈方戈
QIN Rongfeng;YANG Shujuan;MA Huan;CHEN Fangge(State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences(Beijing),Beijing 100083,China;School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing 100083,China)
出处
《现代地质》
北大核心
2025年第6期1527-1540,共14页
Geoscience
基金
国家自然科学基金项目(42172073)。
关键词
喀斯特型铝土矿
成矿环境
次生地表改造作用
淋滤作用
桂西
karstic bauxite
metallogenic environment
epigenetic surface modification
leaching
Western Guangxi
