甘肃龙首山207铀矿床成矿地质特征及其成矿机制探讨

Geological Characteristics and Mineralization Mechanism of the No.207 Uranium Deposit in Longshoushan,Gansu Province

207铀矿床位于龙首山成矿带西部,区内地质构造复杂,岩浆活动强烈,主要出露下元古界龙首山群变质岩和中条期伟晶状白岗岩。区域构造线呈北西-南东向。矿床铀矿化主要受岩体和断裂构造控制。铀矿化具有明显的多期次特点。铀矿化年龄是1750Ma,显示了相当小的矿岩时差。矿床具有花岗岩型铀矿床的一般特征。文章在阐述207铀矿床区域地质背景和成矿特征的基础上,分析了成矿物质来源、成矿溶液来源及成矿物质迁移途径,建立了矿床铀成矿模式。认为207矿床铀成矿是受区域地质背景控制的特定时空域内的客观产物,区域富铀地层是成矿的物质基础,成矿溶液源自岩浆水,岩浆及期后热液是铀迁移的载体,铀成矿模式强调了白岗岩成岩过程是成矿物质的富集过程。

The No.207 uranium deposit is located in the west of Longshoushan metallogenic belt, which is characterized by complex geological structure and intensive magma activity. The major outcrops are lower Proterozoic metamorphic rocks (named Longshoushan Group) and Zhongtiaoian granite. Regional structure trends from northwest to southeast. Uranium mineralization in this ore deposit is mainly controlled by granite body and fracture structures. Uranium mineralization is characterized by obvious multiple stages. Uranium mineralization age is 1750Ma, indicating small time difference between the ore and the rock. The ore deposit possesses the common characteristics of the granite type uranium deposits. Based on regional geological setting and metallogenic characteristics of No.207 uranium deposit, this study analyzed the sources of ore-forming materials and fluids, and channels for transport of ore materials, established metallogenic model for the No.207 uranium deposit. It is concluded that the uranium metallogenesis of the ore deposit took place in a specific temporal-spatial domain controlled by the regional geological setting. Regional uranium-rich strata provided substances for metallogenesis and ore fluids derived from magmatic water, magma and postmagmatic hydrothermal fluids were carriers of uranium transport. The uranium metallogenic model emphasizes that the formation process of alaskite was a process of ore substance concentration.