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.