广西大瑶山大黎斑岩型钼铜矿床辉钼矿Re-Os同位素年龄及其地质意义

Molybdenite Re-Os dating for the Dali porphyry Mo-Cu deposit of Dayaoshan area and its geological implications

广西大黎钼铜矿床位于钦杭成矿带西南端大瑶山多金属成矿带上,是近年新发现的与中酸性岩体有关的斑岩型钼铜矿床。利用Re-Os同位素方法对矿体中的5件辉钼矿样品进行了成矿时代测定,获得的模式年龄为101.1±1.5 Ma至103.5±1.5 Ma,加权平均年龄为101.7±1.2 Ma,等时线年龄为100.1±3.7 Ma,与前人获得的大黎岩体石英二长岩和石英二长斑岩的LA-ICP-MS锆石U-Pb年龄102.8±0.9 Ma和101.7±1.2 Ma相吻合,表明成岩和成矿时代一致,为燕山晚期构造岩浆活动的产物。因此,大黎斑岩型钼铜矿床形成于华南地区中生代第三次大规模成矿期,为早白垩世晚期华南地区岩石圈伸展拉张的大地构造背景下的产物。目前的研究表明,大瑶山地区斑岩型矿床除加里东期的钨多金属矿床外,燕山期的铜钼矿床、金多金属矿床也是重要的矿床类型,大瑶山地区具有良好的寻找斑岩型矿床前景。

The Dali porphyry Mo-Cu deposit in Teng County, Guangxi, was discovered in 2009.The deposit is located in the Dayaoshan polymetallic metallogenicbelt at the southwest part of Qinhang metallogenic belt. Five molybdenite samples collected from Dali ore bodies were used for Re-Os dating. The obtained model ages range from 101.1±1.5Ma to 103.5±1.5 Ma, with a weighted mean age of 101.7±1.2 Ma and an isochronal age of 100.1±3.7 Ma. The ages are similar to the LA-ICP-MS zircon U-Pb isotopic ages of the quartz monzonite and quartz monzonite porphyry (102.8±0.9 Ma and 101.7±1.2 Ma) in the deposit, indicating that the emplacement age of the plutons and the mineralization age of the deposit were coeval. Both the intrusion and mineralization could have formed at the same magmatic event at the late Early Cretaceous period of Late Yanshanian Orogeny, due to lithospheric thinning and extension. There are not only Yanshanian Cu-Mo porphyry deposits, but also Caledonian W-Cu porphyry deposits in Dayaoshan Terrane, indicating huge potential for more Early Paleozoic to Mesozoic deposits.