黑龙江东安金矿床锆石U-Pb年龄及其地质意义

ZIRCON U-Pb AGES OF DONGAN GOLD DEPOSIT IN HEILONGJIANG PROVINCE: Geological Implication

摘要: 通过LA-ICPMS锆石原位定年方法，对黑龙江东安金矿成矿期脉岩流纹斑岩进行了年龄测定.结果显示，与矿化关系极为密切的流纹斑岩的U和Th含量分别为269.1×10^-6~956.0×10^-6和202.2×10^-6~1276.8×10^-6，Th/U比值介于0.43~1.80之间.流纹斑岩²⁰⁶Pb/²³⁸U年龄的加权平均值为109.6±1.7 Ma，与区内浅成低温热液金矿的成矿年龄相近，共同记录了本区早白垩世晚期的一次重要成岩成矿事件，反映了早白垩世晚期岩石圈大规模伸展减薄的动力学背景.

Abstract: The age of the rhyolite porphyry, which is closely related to mineralization in Dongan gold deposit, is tested with LA-ICPMS zircon dating method. The results show that, the U contents of the rhyolite porphyry range from 269.1×10^-6 to 956.0×10^-6, while the Th contents, from 202.2×10^-6 to 1276.8×10^-6, with Th/U ratio between 0.43 and 1.80. The age of rhyolite porphyry is (109.6±1.7) Ma, which is synchronous with other epithermal gold deposits in the area. It implies the large-scale lithospheric extension and thinning in the late period of Early Cretaceous.