广西龙头山斑岩型金矿成岩成矿锆石SHRIMP U-Pb年代学研究

Zircon SHRIMP U-Pb Chronology of Diagenetic Mineralization of the Longtoushan Porphyry Gold Orefield,Gui County,Guangxi

贵县龙头山金矿位于大瑶山隆起西南部,成矿作用与燕山晚期流纹斑岩和花岗斑岩有关。金(银)矿体主要赋存于斑岩和断裂破碎带中。运用高分辨率和高灵敏度离子探针(SHRIMP)分析技术,作者对矿区流纹斑岩和花岗斑岩进行了锆石U-Pb定年,获得流纹斑岩和花岗斑岩的年龄分别为103.3±2.4Ma(95%可信度,MSWD=2.1)和100.3±1.4Ma(95%可信度,MSWD=0.40),表明龙头山金矿区的成岩成矿作用都发生于中-晚白垩世。并认为花岗斑岩和流纹斑岩系同期岩浆作用的产物,矿床是在同一成矿作用下形成的,似乎不存在多期矿化的可能。

Located in the southwestern part of the Dayaoshan uplift, the Longtoushan porphyry gold deposit, Gui county, Guangxi, is closely related to the Late Yanshanian rhyolitic porphyry and granite-porphyry within the orefield. The authors carried out with high decision SHRIMP dating technique U-Pb chronology of zircons from the rhyolitic porphyry and granite-porphyry and gained ideal ages of 103.3 ± 2.4Ma（95 % confidence, MSWD= 2. 1） and 100. 3± 1. 4Ma （95% confidence, MSWD = 0. 40）, respectively. The result shows that diagenetic mineralization of the Longtoushan gold orefield happened during the Middle to Late Cretaceous. Based on the zircon ages, the authors concluded that the rhyolitic porphyry and granite-porphyry resulted from the same magmatic event, but only one mineralization event occurred in the orefield rather than two stages of diagenetic mineralizations as the earlier researches believed.