Geochemistry and geochronology of late Carboniferous granites from eastern Russia: Implications for the evolution of the Heihe–Nenjiang suture zone

The Heihe–Nenjiang suture zone, which is one of the major sutures in the eastern Central Asian Orogenic Belt, occurs between the Xing’an and Songnen–Zhangguangcai Range massifs and extends from southern Mongolia via northeastern China into eastern Russia. The amalgamation history of these massifs is controversial, especially for that during the late Paleozoic. Here we report whole-rock geochemical and zircon U–Pb geochronological data for two granite intrusions in the northeastern Heihe–Nenjiang suture zone with the aim of constraining the emplacement timing and their tectonic setting. In addition, combined with our previously published data for the Russian part of this suture zone, we compare tectonic processes between the two regions. We identified two monzogranites dated at 313 ± 3 and 307 ± 3 Ma, and a hornblende–biotite granite dated at 306 ± 2 Ma. The ca. 313 Ma and ca. 307 Ma monzogranites contain annite and have geochemical affinity to A₂-type granites. The geochemistry of the ca. 306 Ma hornblende–biotite granite, and the presence of edenite, pargasite, and siderophyllite, indicate it is an I-type granite. These late Carboniferous A₂- and I-type granites in the Russian part of the Heihe–Nenjiang suture zone formed during a 313–295 Ma magmatic event, which include 306 ± 4 Ma monzogranites, 301 ± 4 Ma rhyolites, and 295 ± 4 Ma plagiogranites with an adakitic signature. These rocks are all related to the post-collisional extension setting after the amalgamation of the Xing’an and Songnen–Zhangguangcai Range massifs.