福建平和包围山钼矿床锆石U-Pb和辉钼矿Re-Os年龄及其地质意义

Zircon U-Pb and molybdenite Re-Os dating of Baoweishan molybdenum deposit in Pinghe County, Fujian Province, and its geological significance

通过对平和包围山钼矿床成矿岩体、赋矿火山岩及辉钼矿开展同位素年代学研究,结果表明:包围山深部花岗斑岩LA-ICP-MS锆石U-Pb年龄为(98.1±1.1)Ma,容矿围岩-石帽山群底部凝灰熔岩成岩年龄为(104.6±1.1)Ma;矿体中辉钼矿的Re-Os同位素模式年龄为(95.2±1.5)Ma。辉钼矿中Re的含量指示成矿来源与壳幔物质混合或幔源物质进一步演化有关。结合矿床地质特征及已有的研究成果,笔者认为包围山钼矿床的形成可能与125~92 Ma古太平洋板块的俯冲作用机制有关。受该期区域伸展构造背景的影响,上杭-云霄成矿带下地壳或上地幔部分熔融诱发了平和包围山一带岩浆-热液-成矿事件。

Based on isotopic chronological study of the ore-forming rock body, ore-bearing volcanic rocks and molybdenite from the Baoweishan molybdenum deposit in Pinghe County, the authors conducted LA-ICP-MS zircon U-Pb dating and revealed that the age of the Baoweishan porphyry-like granite is（ 98. 1 ± 1. 1） Ma, and the age of the tuff-lava in the bottom of the Shimaoshan Group＂ formation, which is the host rock of this deposit, is（ 104. 6 ± 1. 1） Ma.Re-Os dating of molybdenite from the orebodies yielded a model age of（ 95. 2 ± 1. 5） Ma. These age data indicate that the Baoweishan molybdenum deposit was formed at the early stage of late Cretaceous. Furthermore, the rhenium values of molybdenum samples from the deposit indicate that the mineralization is genetically closely related to the crust-mantle or the further evolution of the mantle. Based on geological features of the Baoweishan molybdenum deposit and the research results in this study, the authors consider that this deposit was probably generated in an extensional setting related to the subduction process of the Paleo-Pacific plate beneath the Eurasian continent during 125 ~ 92 Ma, which triggered the partial melting of the lower crust or the upper lithospheric mantle to form the magmatic-hydrothermal ore-forming event in Baoweishan area along the Shanghang-Yunxiao ore-forming belt.