Genetic mineralogical study of zircons in dikes in the Jiuling gold deposit of the central Taihang Mountains
The Jiuling gold deposit located in central section of the Taihang Mountains is a typical quartz-vein type gold deposit,and its auriferous quartz veins are closely related to acidic dikes in time and space.In this study,we have conducted systematically the zircon U-Pb chronology and zircon Hf isotopes,and genetic mineralogy of granite porphyry and granodiorite dikes in the Jiuling gold deposit.The results show that the emplacement ages of dikes are 128~130 Ma,and the magmatic materials of dikes were sourced mainly from the Archean crust and partly from the mantle.The morphological and typological characteristics of zircons indicate that the magmas of dikes in this area had undergone relatively long processes of differentiation and evolution,which are related to their high water contents.The evolution process of granite porphyry magma can be divided into three stages,and its magma property was transitioned from a peralkaline one to a peraluminous one with the decrease of temperature.The zircons in the granodiorite can be clearly classified into two groups based on their zoning textures.Their evolutionary characteristics indicate that they were products of a mixture of peraluminous and peralkaline magmas.The calculation results of thermometer and oxybarometer of zircons indicate that the oxygen fugacities of the magmas in the Jiuling gold deposit were as high as ΔFMQ+5~ΔFMQ+7,which are very beneficial for the activation,migration,enrichment,and mineralization of gold.
zircongenetic mineralogypetrogenesismagmatic evolutioncentral section of the Taihang Mountains