U-Pb SHRIMP dating of zircon from quartz veins of the Yangshan gold deposit in Gansu Province and its geological significance.

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• 责任者：Qi Jinzhong ; Yuan Shisong ; Liu Zhijie ; Liu Dunyi ; Wang Yanbin ; Li Zhihong ; Guo Junhua ; Sun Bin
• 年：2004
• 作者单位：China Armed Police Force, Gold Geology Institute, Lanfang, China.
• 刊：Acta Geologica Sinica English Edition.
• 期：78,2

摘要

The Yangshan gold deposit is a super-large fine-grained disseminated gold deposit located in southern Gansu Province. Its metallogenic age was determined by using cathodoluminescence imagery and ion probe U-Pb dating techniques. It was found that zircons from quartz veinlets of the fine-grained disseminated gold ore show characteristics of magmatic origin with prism idiomorphism, oscillatory zoning and dominant Th/U ratios of 0.5-1.5. Three main populations of zircons were obtained, giving average Pb/U ages of 197.6+ or -1.7 Ma, 126.9+ or -3.2 Ma and 51.2+ or -1.3 Ma, respectively. The first age corresponds to the K-Ar age of the plagiogranite dike, while the latter two ages indicate that buried Cretaceous and Tertiary intrusives exist in the orefield, suggesting that the Yangshan gold deposit is genetically related to the three magmatic hydrothermal activities. By contrast, zircons from a coarse gold-bearing quartz vein in the mining area are much older than the host rock, indicating that the vein was formed earlier and was not contaminated by later magmatic fluids. It is concluded that the coupling of multiperiodic hydrothermal activities in the mining area has contributed a lot to mineralization of the Yangshan gold deposit.