投稿时间：2024-05-07
修订日期：2025-02-22
网络发布日期：2025-07-01
中文摘要:一水硬铝石是沉积型铝土矿矿石主要矿物成分，其成因机制尚不清晰，限制了对沉积型铝土矿成矿过程的全面认识。东兰-巴马-凤山成矿区是桂西沉积型铝土矿主要成矿区之一，文章以东兰-巴马-凤山成矿区沉积型铝土矿为研究对象，在野外地质调查基础上，通过岩相学观察、X射线衍射（XRD）、扫描电镜-能谱分析（SEM-EDS），探索沉积型铝土矿中一水硬铝石的形成机制。分析结果显示，桂西东-巴-凤地区铝土矿矿物组成主要为一水硬铝石、叶腊石、高岭石、针铁矿、黄铁矿、锐钛矿等，一水硬铝石晶体中普遍存在Fe、Si、Ti等元素，微细粒锐钛矿在一水硬铝石晶体中广泛存在，结合野外调查东兰-巴马-凤山成矿区含矿岩系顶、底板灰岩未出现变质迹象，指示一水硬铝石为简单结晶成因。在淋滤条件有利、季风性气候显著的条件下，黏土矿物水解形成大量Al离子，海水涌入碳酸盐岩台地使得台地内部呈现还原环境，水体因含矿岩系底板中二叠统茅口组灰岩碱性地球化学屏障作用和地下水位抬升作用呈碱性，Al离子在碱性、还原条件下结晶形成一水硬铝石。东兰-巴马-凤山成矿区一水硬铝石的形成经历了物质准备、风化、沉积、压实4个阶段，早世代一水硬铝石在风化阶段形成，晚世代一水硬铝石在沉积阶段形成。部分一水硬铝石在形成之后出现后期改造，受Si质流体交代作用形成高岭石。
中文关键词:沉积型铝土矿 一水硬铝石 形成机制 东兰-巴马-凤山成矿区 桂西
Abstract:Diaspore is the main mineral component of sedimentary bauxite ore, and its genetic mechanism remains unclear, which limits the comprehensive understanding of the sedimentary bauxite mineralization process. The Donglan-Bama-Fengshan metallogenic area is one of the main sedimentary bauxite mining areas in western Guangxi, China. In this research, the sedimentary bauxite in Donglan-Bama-Fengshan metallogenic area was taken as the research object. On the basis of field geological investigation, petrographic observation, X-ray diffraction (XRD), and scanning electron microscopy with energy dispersive analysis (SEM-EDS) were used to explore the formation mechanism of diaspore. The analysis results show that the bauxite in the Donglan-Bama-Fengshan metallogenic area is mainly composed of diaspore, pyrophyllite, kaolinite, goethite, pyrite, anatase, etc. The results of SEM-EDS analysis show that Fe, Si, Ti, and other elements exist in diaspore generally. Fine-grained anatase is widely present in diaspore crystals. There are no signs of metamorphism in the hanging and foot wall limestone of bauxite ore-bearing rock series in the Donglan-Bama-Fengshan metallogenic area, which indicates that the genesis of the diaspore is simple crystalline. Under the favorable leaching and monsoon climate, plenty of aluminum ions were hydrolyzed from clay minerals. The seawater flooded the carbonate platform resulted in the reducing environment inside the platform. The ore-forming water appeared alkaline due to the alkaline geochemical barrier of foot wall-rock limestone and the uplift of groundwater. Under the alkaline and reducing conditions, aluminum ions crystallized to form diaspore. The formation of diaspore in the Donglan-Bama-Fengshan metallogenic area went through four ore-forming stages: Material preparation, weathering, deposition and compaction. The early generation of diaspore was formed in the weathering stage, and the late generation of diaspore was formed in the deposition stage. A part of diaspore had late reformation forming kaolinite by siliceous fluid metasomatism.
keywords:sedimentary bauxite diaspore formation mechanism Donglan-Bama-Fengshan metallogenic area western Guangxi
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基金项目:本文得到国家自然科学基金项目(编号：41362006)资助
引用文本：
罗靖伟,庞保成,许箭琪,向绍立,卢光辉,徐海棚,姚双秋.2025.桂西沉积型铝土矿一水硬铝石形成机制——以东兰-巴马-凤山地区为例[J].矿床地质,44(3):617~634LUO JingWei,PANG BaoCheng,XU JianQi,XIANG ShaoLi,LU GuangHui,XU HaiPeng,Yao ShuangQiu.2025.Formation mechanism of diaspore in sedimentary bauxite from western Guangxi, China: A case study of Donglan-Bama-Fengshan area[J].Mineral Deposits44(3):617~634
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