Late Paleoproterozoic granitic magmatism and crustal evolution in the Tonghua region, northeast China
通化地区古元古代晚期花岗质岩浆作用与地壳演化

The Paleoproterozoic metamorphic complex, widespread in the Liaoning-Jilin Region of northeastern North China Craton, was thought to be the result of intra-plate rifting. However, our filed observations show that the magmatites are not metamorphic rocks but granitic plutons with different degree deformation and metamorphism, consisting of gneissic hornblende syenogranite (termed by " striated granite" or " Liaoji granite") , gneissic quartz diorites, porphyric biotite monzogranite, porphyric-rapakivi garnet granite and hornblende pyroxene syenite. This paper presents the new zircon SHRIMP U-Pb data of gneissic quartz diorite and porphyric-rapakivi garnet granite. The results show that they were emplaced during 1872 - 1850 Ma, similar to those of porphyric biotite monzogranite and hornblende pyroxene syenitic complex. Petrography and geochemical features indicate that the gneissic quartz diorite belong to I-type granites with geochemistry of Arc-type granitoids, whereas, porphyric-rapakivi garnet-bearing granites with rapakivi texture have geochemistry of S-type granites. With consideration of the P-T path of the regional metamorphism coeval with the emplacement of these granites, the concurrence of I-, S- and A-type granites indicates that these granites formed in the post-orogenic setting. The difference of the basement rocks between Langlin (Korea)-Liaonan (China) block and Longgang block indicates that the North China Craton is composed of Langlin-Liaonan-Jiaodong and Longgang-Luxi-Wuhuai blocks in the east and west block, not of West and East blocks. These two blocks in the east North China Craton assembled at about 1.9 Ga, and then collided with the West Block at about 1.85 Ga.