Chronological characteristics and tectonic significance of Her-cynian intrusive rocks at Yongzhuquan, Ejina Banner, Inner Mongolia

The Yongzhuquan intrusive rocks to the north of the Yueyashan tectonic melange zone in Inner Mongolia constitute a large intrusive body. 1:50000 regional geological survey shows that the rock mass is decomposed into granodiorite, monzonitic gran-ite and syenogranite. The zircon U-Pb age of the monzogranite is 330.7±2.9 Ma, suggesting Early Carboniferous and indicating that the Late Paleozoic magmatism in the Beishan area was very active. Through the analysis of rock chemistry and geochemical character-istics, the authors hold that it was formed in a tension tectonic setting and that the tectonic setting of the Beishan area in the Early Carboniferous entered into a stretching environment. This conclusion is of great significance for the study of the crustal evolution of Late Paleozoic in Beishan area.