大别山南缘月山岩体构造变形特征及其地质意义

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

锆石U Pb年龄表明鄂东月山岩体是一个古老花岗岩经后期重熔并于燕山中期(139Ma)侵入的花岗岩体,角闪石压力计得出侵位深度达24.5km。宏观构造、应变测量和石英C轴组构分析得出,月山岩体在深层侵位过程中受到NW—SE伸展和垂向挤压的区域应力作用。在南大别山分布众多类似岩体,从而表明在燕山中期,由NW—SE向的区域伸展体制控制南大别山的构造发展。

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.