Geochronological framework of the Xiadian gold deposit in the Jiaodong province, China: Implications for the timing of gold mineralization

Abstract

The Xiadian gold deposit, located in the Zhaoyuan–Laizhou belt of the Jiaodong gold province, is a typical Jiaojia-type gold deposit, which is characterized by disseminated and stockwork ores enclosed by hydrothermally altered wall rocks. The exact age and the genesis of the gold deposit remain controversial. Here, we present precise in-situ monazite U-Pb dating to constrain the age of the gold mineralization, which we integrate with published geochronological work on the associated geological events to understand the genesis of the gold deposit. The Linglong granite represents the earliest magmatic event at Xiadian, and yielded a zircon LA–ICPMS U-Pb age of 159.5±0.9Ma (2σ, MSWD=0.63). Subsequent geologic events were recorded by minor amounts of quartz–pyrite–molybdenite veins which are dated at 124.8±2.1Ma (2σ, MSWD=0.01) by molybdenite Re–Os dating in a granitic pegmatite. The formation of such veins was close to the emplacement of adjacent Guojialing granodiorite (~130Ma), and thus may be considered as a product of post–magmatic hydrothermal activity. It is proposed that the molybdenum–bearing hydrothermal fluids acted as a prelude to gold mineralization and participated in the formation of the latter ore fluids. Gold mineralization took place at 120.0±1.4Ma (2σ, MSWD=0.59), determined by LA–ICPMS U–Pb dating on hydrothermal monazite from quartz–polymetallic sulfide veins. Prior to and post mineralization, voluminous hydrothermally altered porphyritic diorite and fresh quartz diorite porphyry dykes were emplaced, which yielded U–Pb ages of 121.3±1.4Ma (2σ, MSWD=0.28) and 115.8±1.9Ma (2σ, MSWD=0.71), respectively. Based on these geochronological data, we have established a comprehensive geochronologic framework, which suggests that the genesis of the Xiadian deposit might be related to the craton destruction and lithosphere thinning in the North China Craton.