浙江缙云骨洞坑萤石矿床成矿流体特征

浙江缙云骨洞坑大型萤石矿床位于华夏古板块北东端，紧邻钦杭结合带。矿床产出于下白垩统馆头组与燕山晚期花岗岩的接触带中，矿体严格受NW向断裂控制。在系统的地质调查基础上，对其微量和稀土元素及流体包裹体开展研究。结果表明，缙云骨洞坑萤石矿轻稀土相对弱富集，重稀土相对弱亏损，具有较强的Eu负异常以及较弱的Ce负异常，配分曲线表现出典型的“V”字特征。La/Ho-Y/Ho图解表明，不同位置萤石样品表现出重结晶方向演化的趋势。Tb/Ca-Tb/La成因图解表明骨洞坑萤石矿属于热液成因类型矿床。流体包裹体测温结果表明，成矿均一温度主要在150~190℃，盐度主要在0.3%~1.5% NaCleqv，密度平均值为0.86 g/m³，成矿流体应属于中-低温、低盐度、低密度的NaCl-H₂O体系。结合地质特征认为，缙云骨洞坑萤石矿床属中低温热液裂隙充填型矿床。

Ore-forming Fluids Characteristics of Fluorite Deposits in Gudongkeng,Jinyun County,Zhejiang Province

A large-scale fluorite deposit is located in Gudongkeng, Jinyun County, Zhejiang Province. Tectonically, it is located at the northeastern side of the Cathaysia Plate, adjacent to the Qinhang (Qinzhou Bay to Hangzhou Bay) bonding zone. The Gudongkeng fluorite deposit occurs in the contact zone of the Lower Cretaceous Guantou Group and Late Yanshan granite. The ore is strictly controlled by a NW-striking structure. Based on a systematical geological survey, studies were carried out on trace elements, rare earth elements, and fluid inclusions. The results show that the light rare earth in the Gudongkeng fluorite is a relatively weak enrichment and that the heavy rare earth is depleted relatively weakly. The fluorite has a strong Eu negative anomaly and a weak Ce negative anomaly. The distribution plots show a typical "V" shape feature. According to the La/HoY/Ho diagram, the fluorite samples in different positions show a tendency for recrystallization. The Tb/Ca-Tb/La diagram indicates that this fluorite is a hydrothermal genetic deposit. The temperature measurement results of fluid inclusions show a homogenizing temperature of ore-forming concentrates between 150 and 190℃. The salinity concentrates are between 0.3 and 1.5 NaCl equiv. The average density is 0.86 g/m³. The ore-forming fluids are characterized by medium-low temperature, low salinity, and a medium-low density NaCl H₂ Osystem. It can be inferred therefore that the fluorite deposit in Gudongkeng is a medium-low-temperature hydrothermal, fracture-filled deposit.