甘肃阿尔金南缘白石头沟石墨矿地质特征、成矿条件及找矿标志

Geological Characteristics,Metallogenic Conditions and Prospecting Signs of the Baishitougou Graphite Deposit in the Southern Margin of the Altun,Gansu

甘肃白石头沟石墨矿位于阿尔金南缘敦煌地块,赋存于前寒武纪敦煌岩群大理岩和石英片岩之中,目前圈定矿体33条,主要矿体2条。作为研究白石头沟石墨矿理想地层的敦煌岩群,是一套以变质碎屑沉积岩和变质基性岩为主的变质岩浆杂岩。本文从矿床角度出发,立足于区域地质勘查资料,结合前人研究成果,在对白石头沟石墨矿成矿地质背景、矿床及矿体特征、组合样化学分析、矿石矿物赋存状态及特征研究的基础上,对矿床的成因进行初步探讨并归纳区域找矿标志。研究表明,白石头沟石墨矿可分为大理岩型和石英片岩型两种类型,是古元古代经历区域动力热液变质作用而形成的沉积变质型矿床,成矿物质主要来源于变质碎屑沉积岩类的原岩(海相陆源碎屑岩和碳酸盐岩)本身,成矿环境为古老活动大陆边缘。找矿标志具有特定层位、岩性、矿化及物探特征。

The Baishitougou graphite deposit is located at the Dunhuang block in the southern margin of the Altun,and occurs in marble and quartz schist of the Precambrian Dunhuang group. So far,33 ore bodies,including 2 main ore bodies,have been delineated. As an ideal stratum for study of the Baishitougou graphite deposit,the Dunhuang group is a set of metamorphic magmatic complexes dominated by metamorphic clastic sedimentary rocks and metamorphic basic rocks. This article presents a preliminary discussion on the genesis of the deposit and summarizes the ore-prospecting signs from the perspective of the deposit and regional geological survey data,in combination with previous work. It is also based on the research of mineralization geological background of the deposit,features of the deposit and ore-bodies,analysis of composite samples,ore mineral occurrence state and characteristics. The research shows that the Baishitougou graphite deposit can be divided into two types:marble type and quartz schist type. It is a sedimentary metamorphic deposit formed by regional dynamic hydrodynamic metamorphism in the Palaeoproterozoic. The ore-forming material was mainly derived from the protolith of the metamorphic clastic sedimentary rocks(marine terrigenous clastic rock and carbonate). Its metallogenic environment was an ancient active continental margin. The ore-prospecting signs in this area have special horizons,lithology,mineralization,and geophysical features.