大垅铅锌矿床硫化物Rb-Sr同位素和主微量成分特征及矿床成因

摘要

Dalong Pb−Zn deposit is located in the north head of the Dengfuxian composite rock mass. The lead−zinc orebodies usually occur in the north to south tread silicified fracture zone. The Rb and Sr isotope characteristics of spheterite, the ore deposit geological characteristics and the main and trace elements characteristics of sulfide were analyzed based on electron probe. The results show that there are three kinds of mineralization forms in this area corresponding to the three stages of mineralization, i.e., the quartz-polymetallic-sulfide stage, the quartz-pyrite-sphalerite stage and the quartz-fluorite-sphalerice stage. The initial mass fraction ratio of w(87Sr)/w(86Sr)=0.709 9±0.009 7 is close to that of Batuan rock mass. The Rb−Sr isochron ages is (154±8.0) Ma, which is in line with the diagenetic age ((159.2±4.6) Ma), indicating that there is a close relationship between the mineralization and the yanshanian magmatic activity. The magmatic hydrothermal is the main mineralization. The temperature of mineralization is 161−229℃, which is low−medium temperature. Dalong Pb−Zn deposit belongs to low-middle temperature magmatic hydrothermal type Pb−Zn deposit, which is associated with the Yanshanian magmatic intrusion.%大垅铅锌矿床位于湘东邓阜仙复式岩体北端，其赋矿围岩为二云母花岗岩，矿体产于南北向硅化破碎带中。对闪锌矿的Rb−Sr同位素进行分析，对矿床地质特征及硫化物电子探针主微量成分进行分析。研究结果表明：本区有3种矿化形式，分别对应3个成矿阶段，即石英—多金属硫化物阶段、石英—黄铁矿—闪锌矿阶段和石英—萤石—闪锌矿阶段，其初始87Sr与86Sr质量分数之比即w(87Sr)/w(86Sr)=0.7099±0.0097，与八团岩体的相近，Rb−Sr等时线成矿年龄为(154±8.0) Ma，与成岩年龄(159.2±4.6) Ma一致，反映成矿与燕山期岩浆活动具有密切的成因联系；成矿作用以岩浆热液为主；黄铜矿—黄铁矿微量元素温度计、矿物对硫同位素温度计以及绿泥石温度计显示成矿温度为161~229℃，属中低温范畴。矿床成因属于与燕山期中酸性岩浆侵入作用有关的中低温岩浆热液型铅锌矿床。