河南新县大银尖钼矿床流体包裹体研究

大银尖钼矿床是大别钼多金属成矿带近期取得较大勘查进展的一个重要矿床,成因上与燕山晚期大银尖二长花岗岩有关。通过对主成矿期矿化石英脉流体包裹体岩相学观察和显微测温,将捕获的流体包裹体分为4类,富液相的两相水溶液包裹体、富气相的两相水溶液包裹体、含子矿物三相水溶液包裹体和含CO2的三相水溶液包裹体。数据分析显示,均一温度的峰值分别出现于280～320℃和200～220℃,盐度的峰值处于5.11%～9.98%(NaCleq)低盐度区间和36.06%～42.78%(NaCleq)的高盐度区间。密度为0.91～1.10g/cm3。激光拉曼光谱分析表明,石英中流体包裹体的组分以水蒸汽为主,伴有少量的CO2和微量N2。H和O同位素具有典型的氧同位素漂移特征,指示岩浆热液和大气降水混合作用的发生。研究结果表明,大银尖钼矿床总体上属中高温浅成热液矿床,流体混合作用可能是矿床形成的主要机制。

Study on Fluid Inclusions of the Dayinjian Mo Deposit in Xinxian County, Henan Province, China

The Dayinjian Mo deposit, as an important deposit in the Dabieshan Mo-polymetallic belt, has genetic links to monzogranite intrusion of Late Yanshanian, and has attracted extensive attention for great progress in recent exploration. Based on the petrography and microthermometry of fluid inclusions in the quartz veins formed in main mineralization stage, 4 types of primary fluid inclusions were identified, including: (1) aqueous-rich two-phase inclusions (L-type), (2) vapor-rich two-phase inclusions (V-type), (3) daughter mineral-bearing three-phase inclusion (S-type) and (4) CO2-bearing three-phase inclusions (C-type), The analysis results indicate that two main homogenization temperatures present at 280~320 ℃ and 200~220 ℃, respectively, while the salinities range in two intervals of 5.11%~9.98% (NaCleq) and 36.06%~42.78%(NaCleq), respectively. The densities of the trapped fluids vary from 0.91 g/cm3 to 1.10 g/cm3. Raman spectra of the inclusions indicate that water vapor is the dominant component with minor amount of CO2 (possibly a little N2 in some cases) in the gasous phase of the inclusions. The typical shift in oxygen isotope compositions suggests a mixing event between magmatic and meteoric water. In summary, the deposit is an intermediate-high temperature epithermal deposit, and the fluid mixing plays crucially significant roles in the mineralization.