Geological Setting Of Metallogenesis And Evaluation Of Prospecting Potential For The Meiyaogou Cu-Ag Deposit, Yakashi City, Inner Mongolia, China

This paper takes transmagmatic fluid metallogenic theory as the guiding ideology with field geology, petrology, geochemistry as the methods. Then systematic research is conducted on Meiyaogou Cu-Ag ore deposit, with the conclusions as follows:1.Field relation and petrographic characteristics of an outcrop show that porphyry syenite intrused in diorite grantoid, copper mineralization mainly appears on one side of the syenite dike,there are some copper mineralization in dike too. Diorite bodies developed K alteration。 Llimonite veins, quartz veins and malachite can be seen in the diorite grantoid.2.Systematic research on zircon separated from diorite and syenite including petrography, in-situ trace element, Ti-in-zircon thermometer, Ce-in-zircon oxygen-fugacity meter, U/Pb isopotic geochronometer indicates that the emplacement age of the host parent rock of the ore body is 344 Ma, porphyry syenite forming time is 324 Ma, and the syenite experienced high-temperature reduced fluid(T ≈ 970 ℃, log?O2 ≈-17.5).The diorite has a similar temperature to the porphyry syenite and a higher oxygen fugacity(T ≈ 987 ℃, log?O2 ≈-7.5). The REE characteristics of some zircons separated from diorite and syenite show that they were formed in fluid, while the rest were showing typical magmatic REE characteristics. The in situ zircon Lu-Hf isotope results show Meiyaogou diorite and porphyry syenite have obvious characteristics of depleted mantle source.3.The Major element and trace element of whole rocks suggest the diorite and the porphyry syenite have the geochemical characteristics of the volcanic arc, except slightly lower Sr content, the other elements content are in line with Adakite geochemical characteristics. But we can tell it is not Adakite through Sr/Y-Y and LaN/YbN-YbN diagrams.Trace elements also show the loss of HFSE like Nb and Ta, while the in situ zircon Lu-Hf characteristics indicates the properties of depleted mantle. This implys it maybe related to newborn basaltic lower crust.Although Meiyaogou rock samples are subject to varying degrees of weathering and alteration, but the overall judgment on the various aspects of the overall data is that Meiyaogou diorite and porphyry syenite are belong to I-type granites,4. Finally, elaborated Meiyaogou mine ore-forming geological background and made mine and regional metallogenic prospect evaluation. Meiyaogou grantoid may be a subduction-related magma, the newborn partial melting of basaltic lower crust produced with similar geochemical characteristics Adakite rock. And under the guidance of transmagmatic fluid theory the ore body position may be under the diorite grantoid, close to the stress center of porphyry syenite intrusion.