一个铀钨矿床的成矿地质条件及成因特征

GEOLOGICAL CONDITIONS AND GENETIC CHARACTERISTICS OF A URANIUM-TUNGSTEN DEPOSIT

至今,在国内外已发现的单铀或单钨的脉状矿床或层控矿床为数不少,但铀钨均具工业意义的铀钨(沥青铀矿-白钨矿)组合的矿床却极其少见。本文介绍了一个这样的矿床的成矿地质条件及成因特征:该矿床的形成受花岗岩、地层、岩相、构造、地下水及区域地球化学环境的联合控制;从矿石建造和有用元素组合角度看,这是一个矿床新类型,从成因上看,是花岗岩型热液矿床与层控矿床之间的过渡类型。

Up till now, lots of single uranium or single tungsten veinlike or stratabound deposits have been found; nevertheless, ore deposits with both economic uranium and tungsten (pitchblende-scheelite assemblage) are very rarely seen. In this paper, a deposit of such a type is described with special reference to its geological conditions and genetic characteristics. In the light of ore formation and association of useful elements, this ore deposit belongs to a new type; genetically, it is a transitional type between the granite type hydrothermal deposit and the stratabound deposit. The ore deposit is located in the exocontact zone of a complex granitemass, with its orebodies confined to the interstratified structural zone in Middle-Upper Devonian lagoonal facies strata. Assuming stratoid and lenticular forms, orebodies are parallel to the structural zone in attitude. Although formed in several stages, these orebodies have simple mineral asssemblages. In addition, wall rock alteration is characterized by fewer types, low intensity and narrow range. Lying within the tungsten-tin mineralization belt, the ore deposit is genetically closely related to the metallogenic series of granitic type tungsten (tin), niobium, tantalum, uranium, fluorite and barite deposits. Metallogenic elements were derived from granite and strata, and the oredeposit owes its formation mainly to the hydrothermal process of groundwater with the superimposition of eluviation. Groundwater served not only as media for transporting ore-forming materials but also as the activating agent of thesematerials. The formation of this deposit was on the whole controlled by such factors as granite, lithofacies of strata, structure, groundwater and regional geological environment of uranium and tungsten. It is thus concluded that in future we ought to search for this type of ore deposits in similar geological environments.