山东邹平火山岩盆地铜多金属矿SHRIMP 锆石U-Pb和辉钼矿Re-Os年龄

邹平火山岩盆地是山东省重要的铜多金属矿区之一，区内含有1套多旋回多期次的中生代火山-侵入杂岩，已发现的铜矿床、矿化点均与晚期侵入杂岩体及次火山岩有关。为了查明矿区的成岩成矿作用时代，采用SHRIMP同位素测定技术，对区内与铜多金属矿化有关的侵入岩中的锆石进行了U-Th-Pb同位素测定，获得王家庄铜矿床的赋矿围岩——石英二长闪长岩的侵位年龄为（128.8±0.8）Ma，盆地中部裂隙充填交代型铜金矿床的赋矿围岩环状二长岩岩墙的侵位年龄为（122.9±0.5）Ma；对王家庄铜矿中的5件辉钼矿样品进行了Re-Os同位素分析，获得的等时线年龄为（126.7±4）Ma及模式年龄加权平均值（128.2±0.8）Ma，代表了辉钼矿在流体中沉淀的时间。所获年龄数据准确地厘定了区内晚期岩浆活动及其矿化时限，表明王家庄杂岩体的侵位时间早于环状二长岩岩墙，其多金属矿化时间与成岩时间接近，岩体与矿化关系密切；而裂隙充填交代型铜矿的形成时间晚于环状二长岩岩墙，具有明显的构造控矿特征。所获得的年龄数据对于进一步研究区域成矿规律和指导找矿具有重要的意义。

SHRIMP zircon U-Pb and molybdenite Re-Os age of the copper polymetallic deposit in Zouping volcanic basin, Shandong Province

Zouping volcanic basin is one of the important copper, molybdenum and polymetallic mineral areas in Shandong Province. There is a series of multicycle multi-stage volcano-intrusive complexes in this area. The already-discovered copper deposits and mineralization spots have close relations with intrusive complex rocks and volcanic structures of late Yanshanian period. In order to identify diagenesis-mineralization age of the mine, the authors employed SHRIMP isotope measurement techniques to conduct zircon U-Pb dating of intrusive rocks related to copper, molybdenum polymetallic mineralization in this area. The results show that the emplacement age of quartz monzonite diorite which is the ore-hosting country rock of the Wangjiazhuang porphyry type copper (molybdenum) deposit is (128.8±0.8)Ma, while the emplacement age of cyclic monzonite dykes which serve as the country rock of the hydrothermal quartz vein type copper deposit is (122.9±0.5)Ma. Rhenium-osmium isotopes of five molybdenite samples collected from the Wangjiazhuang copper deposit were analyzed, and the results gave an isochron age of (127±4)Ma and a weighted average of (128.2±0.8)Ma for the model ages. The Re-Os age represents the age of molybdenite precipitation in the ore-forming fluid. The obtained ages can give the time limits of late magmatism and mineralization, so the emplacement of Wangjiazhuang igneous complex was earlier than that of the cyclic monzonite wall, the polymetallic mineralization took place close to the time of the crystallization, and the rock mass was closely related to the mineralization. The formation of the hydrothermal quartz vein type copper deposit was later than that of the ringed monzonite wall with clear structure-controlled mineralization characteristics. The results obtained by the authors have important significance for studying regional ore-forming regularity and further guiding the ore prospecting work.