安徽省庐江县泥河铁硫矿床地质特征及成因初步分析

Geological Characteristics and Genesis of the Nihe Fe-S deposit, Lujiang Country, Anhui Province

泥河铁硫矿床位于长江中下游成矿带内庐枞盆地的西北部,矿床中铁、硫储量均达到大型矿床规模,硬石膏储量达到中型规模,是长江中下游成矿带内近年来重大找矿突破之一,其发现具有重要的理论意义和勘探价值。泥河矿区内主要地层为砖桥组和双庙组安山质火山熔岩和碎屑岩,侵入岩体主要为辉石闪长玢岩。磁铁矿体呈厚大的透镜状分布于闪长玢岩穹窿顶部,硫铁矿体和硬石膏矿体主要呈透镜状、似层状产于砖桥组地层中。矿床中金属矿物主要为磁铁矿和黄铁矿,非金属矿物主要为硬石膏、辉石和石英。矿石以磁铁矿-硬石膏-辉石组合为特征。矿石的结构构造主要为浸染状构造,块状构造,自形-半自形粒状结构、他形粒状结构、交代假象结构和筛状结构等。矿区围岩蚀变强烈,自下往上划可分为深色蚀变带、叠加蚀变带和浅色蚀变带,主要蚀变类型包括硬石膏-辉石岩化,黄铁矿化、硅化和泥化等。泥河矿床的形成经历了热液期和四个成矿阶段,即磁铁矿-黄铁矿阶段、石英-碳酸盐-黄铁矿阶段、石英-黄铁矿阶段和脉状碳酸盐硫酸盐阶段。通过对矿床地质特征的分析以及与宁芜盆地典型玢岩型铁矿床对比研究,本文认为泥河铁矿床的形成与辉石闪长玢岩关系密切,属于"陶村式"玢岩型铁矿床。

Nihe Fe-S deposit is located in northwest of the Luzong volcanic basin on the metallogenic belt along the Middle-Lower reaches of Yangtze River,with Fe and S reserves up to the large scale and anhydrite reserves up to middle scale.It is one of the key breakthroughs in ore exploration and of great academic significance and exploration value.The main strata in the Nihe mine district are andesitic volcanic rocks and clastic rock of the Zhuanqiao Formation and Suangmiao Formations,while the main intrusive rock is pyroxene diorite porphyrite.Lenticular magnetite ore bodies occur as lens at top of the diorite porphyrite dome,and the lenticular and stratiform pyrite and anhydrite ore bodies occur in the Zhuanqiao Formation volcanic rocks.The metallic minerals are magnetite and pyrite and the main gangue minerals are anhydrite,pyroxene and quartz.The ore is characterized by magnetite-anhydrite-pyroxene assemblage.The ore structures mainly include massive structure and disseminated structure.The ore texture includes euhedral- subhedral granular texture,anhedral granular texture,metasomatic pseudomor-phic texture,and sieve texture.The alteration in the Nihe iron deposit can be divided into melanocratic alteration zone,hybrid alteration zone and leucocratic alteration zone from top to bottom.The main alteration types include anhydrite-pyroxene alteration,pyrite alteration,siliceous alteration and argillation alteration.The formation of the Nihe iron deposit can be divided into four stages,magnetite-pyrite stage,quartz-carbonate-pyrite stage,quartz-pyrite stage,and carbonate-sulfate stage.Based on the geological characteristics of the Nihe iron deposit and comparison with the porphyry iron deposit in the Ningwu volcanic basin,the Nihe iron deposit has closely relationships with the pyroxene diorite porphyrite,and belongs to the ＂Taocun type＂ porphyrite iron deposit.