南秦岭核桃坪钨矿控矿构造特征及流体性质研究

Study on Ore-Controlling Structure and Fluid Properties of Hetaoping Tungsten Deposit in South Qinling

【目的】核桃坪矿区位于秦岭中央复合造山带的商丹缝合带南部南秦岭构造带内,矿区主要矿体赋存在白龙洞组、两岔口组中,多与区内石英脉体共生,受构造控制明显。【方法】通过野外实地调研,发现矿区石英脉体与裂隙方位基本一致。通过区内节理方位统计分析得出,该区石英脉体可大致分为近EW向和NE—NNE向两组,同时NE—NNE向石英脉多形成时代较晚且与成矿过程关系密切;选取成矿期石英脉进行包裹体测温研究,测得该区成矿流体均一温度、冰点温度,进一步估算矿区成矿流体盐度、成矿压力和成矿深度等数据。【结果】核桃坪矿区成矿流体具有中-高温、中-高盐度、低密度流体特征,矿床成矿过程中流体性质变化较大。【结论】流体混合作用可能对钨矿化形成起到了有利作用。

[Purposes]Hetaoping ore area is located in the southern Qinling tectonic belt in the south of Shangdan suture zone of the central Qinling composite orogenic belt.The main orebodies occur in Bail⁃ongdong Formation and Liangchakou Formation,which are mostly symbiosis with quartz veins in the area and are obviously controlled by the structure.[Methods]Through the field investigation,it is found that the orientation of quartz veins in the mining area is basically the same as that of cracks.According to the statistical analysis of joint orientation in the area,the quartz veins in the area can be roughly divided into two groups:nearly EW trending and NE—NNE trending.Meanwhile,the NE—NNE trending quartz veins are mostly formed in a late age and closely related to the mineralization process.The homogeniza⁃tion temperature and freezing temperature of ore-forming fluid in the ore-forming period were measured.The salinity,pressure and depth of ore-forming fluid in the ore-forming area were further estimated.[Findings]The ore-forming fluid in Hetaoping mining area has the characteristics of medium-high tem⁃perature,medium-high salinity and low density fluid.The fluid properties change greatly during the ore-forming process.[Conclusions]Fluid mixing may play a favorable role in the formation of tungsten mineralization.