海南省新村钼矿床LA-ICP-MS锆石U-Pb和辉钼矿Re-Os年龄及其地质意义

摘要

The Xincun Mo ore deposit is a newly discovered medium-size deposit in Hainan Province.The LA-ICP-MS zircon U-Pb analysis of monzonite yielded a weighted 206 pb/238U mean age of (102.0 ± 1.5) Ma (MSWD =2.3).Re-Os dating of five molybdenite samples separated from the Xincun Mo ore deposit yielded model ages from (97.29 ± 1.43) Ma to (98.52 ± 1.55) Ma,a weighted average age of (97.84 ± 0.64) Ma and an isochron age of (98.90 ± 3.40) Ma.These ages suggest that the mineralization in the Xincun Mo ore deposit was genetically associated with the monzonite,and the rock-and ore-forming process was continuous.The Re content of molybdenite and Hf isotopic compositions of zircon imply that the rock-and ore-forming materials were derived from the mixture of the mantle and the crust.These data indicate that the ages of the intrusion and orebody from the Xincun Mo ore deposit are identical with those (95～105 Ma) of most Mo deposits in Hainan Province,being part of the molybdenum mineralization event in the period of the late stage of early Cretaceous and the early stage of late Cretaceous in eastern China.Accordingly,the metallogenic geodynamical setting of the Xincun Mo ore deposit might have been related to a pull-apart and stretching environment accompanied by asthenosphere upwelling and strong crust-mantle interaction.%新村钼矿床是海南省近年来发现的具中型规模的钼矿床.文章对赋矿二长花岗岩进行LA-ICP-MS锆石U-Pb同位素测年,获得206Pb/238U年龄加权平均值为(102.0±1.5) Ma(MSWD=2.3);对辉钼矿进行Re-Os同位素定年,获得5件样品的模式年龄范围为(97.29±1.43)Ma～～ (98.52±1.55) Ma,加权平均年龄为(97.84±0.64)Ma,等时线年龄为(98.90±3.40) Ma,成岩年龄与成矿年龄在误差范围内一致.辉钼矿的Re含量和锆石Hf同位素特征指示新村钼矿的成岩成矿物质来自于壳幔混源.新村钼矿床的成岩成矿年龄与海南岛最重要的钼成矿期(95～～105Ma)一致,属中国东部早白垩世晚期—晚白垩世早期钼成矿事件的一部分,与该时期岩石圈大规模拉伸减薄、软流圈上涌及强烈壳-幔作用密切相关.