冀东峪耳崖金矿床辉钼矿Re-Os年龄及其地质意义

峪耳崖金矿床是冀东地区重要的金矿之一,位于华北板块燕山造山带东段,马兰峪复背斜北翼。金矿体赋存于峪耳崖花岗岩及其与灰质白云岩接触带中,矿化类型包括石英脉型和细脉浸染型,属中温热液型矿床。本次工作采用Re-Os同位素测年技术,对该矿床主成矿阶段的7件辉钼矿样品进行了精确定年,获得模式年龄为(168.4±2.5)Ma~(171.7±3.0)Ma,加权平均年龄为(169.84±0.95)Ma,等时线年龄为(171.9±2.7)Ma,表明矿床形成于中侏罗世,与成矿花岗岩侵位时间基本一致。辉钼矿的铼含量为50.63×10-6~116.1×10-6,平均84.61×10-6,指示成矿物质可能为壳幔混合来源。结合前人研究成果资料分析,峪耳崖金矿是冀东地区燕山早期区域性强烈构造-岩浆-成矿作用的产物。

Re-Os age of molybdenite from the Yuerya Au deposit in eastern Hebei Province and its geological significance

Abstract: The Yuerya Au deposit, one of the important Au deposits in eastern Hebei Province, is located in the northern limb of the Malanyu anticlinorium on the eastern side of the Yanshan orogenic belt. The gold orebodies, which belong to mesothermal hydrothermal type, are mainly hosted in the granite and its contact zone with the limy dolomite, and the ores include quartz vein type and veinlet-disseminated type. The Re-Os isotopic dating of 7 molybdenum samples of the main ore-forming stage yielded model ages ranging from (168.4±2.5) to (171.7±3.0) Ma, with the average model age being (169.84±0.95) Ma and the isochron age being (171.9±2.7) Ma, indicating that the mineralization of the Yuerya Au deposit took place in the Middle Jurassic, corresponding to the intruding epoch of the Yuerya granite. The content of Re, 50.63×10-6-116.1×10 -6 with an average of 84.61×10-6, shows that its material was mainly derived from crust-mantle mixture. In combination with the previous research results, the authors hold that the Yuerya Au deposit resulted from the strong tectono-magmatic-mineralization activities during early Yanshanian period of Mesozoic in eastern Hebei Province.