Genesis of Early Permian A-type granites in the middle of the Great Xing'an Range and constraints on tectonic evolution of the Zhalantun area

Hegenshan-Heihe suture zone is an important boundary in Great Xing'an Range that is located at the eastern segment of Central Asian Orogenic Belt and it is also important for understanding the tectonic evolution of Central Asian Orogenic Belt. Due to lacking of the detailed proof on magmatism, tectonic structure and paleogeography, the tectonic evolution in the middle of Hegenshan-Heihe suture zone is still in debate. The magmatic events in Zhalantun area are an essential clue to study the tectonic evolution of the middle of the Hegenshan-Heihe suture zone. Thereby, this study presents the petrology, geochronology and geochemistry of Permian granites in Zhanlantun area, middle Great Xing'an Range, Northeast China, with the aim of discussing their petrogenesis and tectonic setting, and constraints on tectonic evolution of Hegenshan-Heihe suture. Permian granites are composed of alkali-feldspar granite and monzogranite with the emplacing ages of 289 similar to 298Ma. All the samples have the high SiO2, Al2O3 contents, and low P2O5, CaO, MgO contents and show the low FeO/MgO ratios and low Ba, Sr, Eu contents, showing the geochemical features of A-type granites. The low Sc, Ni, Co, V contents and ratios of Nb/Ta (4.88 similar to 21.9) and Zr/Hf (8.32 similar to 29.1) indicate that the magma of Permian granites is the mixing magma between mantle-derived magma and crustal melt. The Permian A2-type granites were emplaced in extensional setting, indicating that the amalgamation of the Xing'an and Songliao blocks had been finishing before Early Permian. Zhalantun area in middle of Hegenshan-Heihe Suture was in a post collision extensional setting after the amalgamation of the Xing'an and Songliao blocks.