GEOLOGY AND GENESIS OF THE GRANITIC NIOBIUM-TANTALUM-RUBIDIUM DEPOSIT IN SHIHUIYAO AREA, INNER MONGOLIA
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摘要: 内蒙锡林浩特石灰窑铌钽矿床是我国最近发现的一处大型稀有金属矿床.通过详细分析该矿床地质特征、控矿因素及其成因，主要获得如下认识：1）该矿床矿石属于碱性花岗岩系列；2）矿石中的铌钽矿物主要包括铌锰矿、铌钽铁矿、铌钽锰矿、锡锰钽矿和细晶石；3）该矿床可能是前期花岗岩岩浆结晶和后期热液交代综合作用的产物，热液交代是铌钽铷主要成矿阶段；4）从铌钽铷矿化成因和富集规律可知，金属矿化与钠长石化、云英岩化密切相关，且矿体赋存于蚀变花岗岩中，分布上严格受北东向构造的控制，因此，钠长石化、云英岩化的花岗岩是寻找上述稀有金属的直接找矿标志，同时石灰窑燕山早期花岗岩出露地段很可能是寻找稀有金属矿的有希望地区；5)围绕石灰窑花岗岩主岩体周围寻找晚期侵位的钠长石化花岗岩小岩体的隆起和浅部部位,是寻找钽铌铷矿的基本思路.Abstract: The Shihuiyao Nb-Ta-Rb polymetallic deposit is a large rare metal deposit that was recently found in Xilinhot City, Inner Mongolia, China. By electronic microprobe (EMP) and X-ray fluorescence spectrometry (XRF) analyses on minerals and whole rock compositions of ores, with discussion on the geological characteristics and controlling factors as well as genesis of the deposit, the following results can be demonstrated: 1) The ores of this deposit belong to alkaline granite type series. 2) The Nb-Ta minerals in the ores mainly include manganocolumbite, columbite-tantalite, columbitemanganotantalite, wodginite and microlite. 3) This deposit may be an integrated product of crystallization of granitic magma in early stage and hydrothermal metasomatic interaction later, of which the latter is the main metallogenic stage of Nb, Ta and Rb; 4) The Nb-Ta-Rb mineraling genesis and enrichment patterns show that the mineralization is closely related to the albitization and greisenization of granite. The ore bodies mainly occur in altered granites, strictly controlled by NE-trending structures in distribution. Therefore, the albitized and greisenized granites are direct indicators for the prospecting of these metals. In addition, the areas where the Early Yanshanian granites outcrop are probably prospective targets for the rare metals. 5) The basic idea for Nb-Ta-Rb prospecting in Shihuiyao area is to seek for the uplift and the shallow parts of the small albitized granite rock mass emplaced in later stage around the main granite bodies.
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Key words:
- granitic Nb-Ta-Rb deposit /
- ore controlling factor /
- deposit genesis /
- Inner Mongolia
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