CHARACTERISTICS OF TECTONIC DEFORMATION OF THE YUESHAN PLUTON ON THE SOUTHERN MARGIN AND ITS GEOLOGICAL SIGNIFICANCE

Zircon U-Pb ages of the Yueshan pluton in eastern Hubei indicate that this pluton is a granite body resulting from anatexis of an old granite body and its intrusion in the middle Yanshanian(139 Ma).The depth of emplacement of this granite body obtained by the hornblende geobarometer is up to 24.5 km.Macroscopic structures,strain measurements and quartz c-axis fabric analysis suggest that the Yueshan pluton underwent NW-SE extension and vertical compression during its deep-level emplacement.Numerous similar rock bodies are distributed in the southern Dabie Mountains,thus suggesting that the NW-SE regional extensional regime controlled the tectonic development in the southern Dabie Mountains in the middle Yanshanian period.