陕西丹凤三角地区花岗伟晶岩铀-稀有元素矿化特征及成矿作用分析

Mineralization Characteristics and Metallogenesis of Granitic Pegmatite Uranium and Other Rare Metals in the Danfeng Triangle Area,Shaanxi

重点对北秦岭丹凤三角地带花岗伟晶岩的地质矿化特征及铀-稀有元素成矿作用进行了研究分析,认为花岗伟晶岩是在岩浆演化晚期,富含挥发分的残余岩浆进一步分异演化的结果,花岗伟晶岩主要侵位于加里东中晚期花岗岩体的内外接触带及秦岭岩群中,多沿背斜轴部和断裂、裂隙分布,多平行于区域构造线延伸方向。花岗伟晶岩的岩石类型有:黑云母伟晶岩、二云母伟晶岩、白云母伟晶岩、白云母钠长石伟晶岩、锂云母钠长石伟晶岩,是由交代分异作用引起的。花岗伟晶岩的成岩、成矿作用可划分为后岩浆、伟晶作用、气成作用和热水溶液4个阶段。花岗伟晶岩具明显的多元素矿化特征,富含U、Th、Nb、Ta、L等稀有金属和绿柱石、云母、钾长石等非金属矿产。

This paper focuses on geological characteristics of granitic pegmatite and mineralization of uranium and other rare elements in the Danfeng triangle area of North Qinling. According to the study, the granite pegmatite is produced by further differentiation of volatile-rich residual magma during late magmatic evolution. The granitic pegmatite mainly emplaced in Qinling rock group as well as the inner and outer contact zone of the mid-late Caledonian granite, distributing along the anticlinal axis and fracture, and parallel to the extension of structural lineament. Be- cause of the metasomatic differentiation, the granite pegmatite has a broad category including bio- tite pegmatite, two mica pegmatite, muscovite pegmatite, muscovite Na-spar pegmatite and mica Li-spar pegmatite. The diagenesis and mineralization of granitic pegmatite can be divided into four stages, i. e. subsequent magmatism, germination, pneumatolysis and hydrothermal solution. With obvious multi-element mineralization characteristics, the granitic pegmatite is rich in rare metals such as U, Th, Nb, Ta and L, as well as other non-metallic mineral like beryl, mica, potassium feldspar etc.