闽东大湾钼铍矿的辉钼矿Re-Os同位素年龄——兼论福建省钼矿时空分布及构造背景

Molybdenite Re-Os Age of the Dawan Mo-Be Deposit,East Fujian——A Discussion on the Tempo-spatial Distribution and Tectonic Setting of the Molybdenite Deposit in Fujian Province

闽东大湾钼铍矿是海西(海峡西岸)经济区新近勘查取得重要进展的燕山期钼矿之一。铍钼矿体主要赋存于上侏罗统南园组火山岩中,隐伏的黑云母花岗岩体为主要的成矿母岩,属中-高温热液充填-交代型钼铍矿床。辉钼矿的Re-Os同位素测年结果显示,等时线年龄为92.2±1.3Ma,表明钼矿成矿时代为晚白垩世。结合近年来福建省钼矿成矿年代学资料,发现自闽西(武夷成矿带)到闽东(沿海火山岩成矿带),钼矿成矿时代从165～102Ma过渡到112～90Ma,显示逐渐变新的趋势。综合分析认为,165～131Ma的钼矿可能形成于岩石圈伸展背景,110～90Ma的钼矿可能形成于古太平洋板块俯冲背景之下。

The Dawan molybdenum and beryllium deposit in the East Fujian province is one of the Yanshanian mo- lybdenum deposits, which achieved great progress in geological and mineral exploration in West-strait Economic Zone recently. The deposit is hosted in volcanic rocks of the upper Jurassic Nanyuan Formation, while ore metals were mainly derived from the concealed biotite granite. It belongs to mesothermal to hyperthermal Mo-Be deposit. The Re-Os isochron age （92.2±1.3 Ma） of the molybdenites implies the mineralization took place in Late Creta- ceous. Combined with Re-Os isochron ages of the molybdenum deposits in Fujian province, the mineralization ages decrease from 165 - 102 Ma in the west to 112-90 Ma in the east part of the province. We believe that the molyb-denum deposits with ages of 165 - 131 Ma were mainly controlled by intraplate magmatism, however, the molybdenum deposits formed during 110 -90 Ma were probably influenced by the subduction of the Izanagi plate.