Abstract:

Tungsten mineralization of Wudaogou ore deposit occurs mainly in the Late Indosinian altered granodiorite as parallel scheelite-quartz veins. Compared with the adjacent Yangjingou ore deposit, some of the ore veins in Wudaogou are characterized by large thickness and high ore grade. As the most important ore mineral, the scheelite grains are distributed in massive, coarse-grained disseminated and veinlet forms in quartz veins and altered host rocks. Fluid inclusions are dominated by gas-liquid ones in both scheelite and quartz grains formed at the major ore-forming stage. Moreover, two CO₂-bearing three-phase inclusions are also observed in scheelite grains. Homogenization temperatures and salinities of gas-liquid inclusions in quartz vary mainly from 171.2 to 268.0℃ and from 0.70%NaCl to 10.74%NaCl, respectively, whereas those in scheelite grains vary from 209.6 to 253.3℃ and from 1.39%NaCl to 8.67%NaCl respectively. Homogenization temperatures of two CO₂-bearing three-phase inclusions in the scheelite are 287.2 and 294.7℃. A comprehensive study of compositional and microthermometric analytical results of fluid inclusions has led to the conclusion that the oreforming fluid from Wudaogou ore deposit belongs to the NaCl-H₂O-CO₂ hydrothermal system with medium temperature, low salinity and minor N₂. A comparative study of Wudaogou and Yangjingou scheelite deposits indicates that they were formed in similar geological settings with the same hydrothermal alteration, mineral assemblage, ore textures and structures as well as modes of occurrence of the scheelite. The two ore deposits are genetically related to a common hydrothermal scheelite mineralization event. Since the two ore deposits have different ore-controlling structures, the ore bodies in the two ore deposits have different attitudes, shapes and sizes.

Key words: geological characteristics, fluid inclusion, ore genesis, Wudaogou scheelite deposit, eastern Yanbian area