During the late Paleozoic and Mesozoic, convergent plate boundary processes in northeastern Asia shifted from the Paleo-Asian Ocean to Paleo-Pacific Ocean, influencing the tectonic regime. To better understand this tectonic transition, we investigated the petrology, geochronology and geochemistry of igneous rocks from the Jilin area in the eastern part of the Central Asian Orogenic Belt. We identified four stages of magmatism at ~261, 253–244, 183–175 and 173–164 Ma. The ~261 Ma magmatism was generated in an active continental margin by partial melting of juvenile mafic lower crustal material. This stage of continental arc magmatism continued with the emplacement of 253–244 Ma adakitic magamas, which were generated by partial melting of subducted oceanic crustal material and metasomatized with overlying mantle wedge. The 183–175 Ma monzogranitic and dioritic magmas were generated in a continental arc environment via melting of juvenile lower continental crust and mixing of basaltic magma with crustal melt, respectively. Magmatism at 173–164 Ma was developed in an active continental margin, and were generated by melting of a juvenile lower continental crust. The integrated evidence suggests that the closure of the Paleo-Asian Ocean could occur at 244–227 Ma, whereas the timing of tectonic regime transition from the convergence of Paleo-Asian Ocean to the subduction of the Paleo-Pacific Ocean occurred at 223–185 Ma. The Changchun-Yanji Suture, which marks the easternmost closure of the Paleo-Asian Ocean, experienced multiple tectonic mode switches, and was controlled by subduction of the Paleo-Pacific Ocean since Early Jurassic.

Amphibole is a common hydrous mineral in mantle rocks. To better understand the processes leading to the formation of amphibole-bearing peridotites and pyroxenites in mantle rocks, we have undertaken an experimental study reacting lherzolite with hydrous basaltic melts in Au-Pd capsules using the reaction couple method. Two melts were examined, a basaltic andesite and a basalt, each containing 4 wt% of water. The experiments were run at 1200°C and 1 GPa for 3 or 12 h, and then cooled to 880°C and 0.8 GPa over 49 h. The reaction at 1200°C and 1 GPa produced a melt-bearing orthopyroxenite-dunite sequence. The cooling stimulates crystallization of orthopyroxene, clinopyroxene, amphibole, and plagioclase, leading to the formation of an amphibole-bearing gabbronorite–orthopyroxenite–peridotite sequence. Compositional variations of minerals in the experiments are controlled by temperature, pressure, and reacting melt composition. Texture, mineralogy, and mineral compositional variation trends obtained from the experiments are similar to those from mantle xenoliths and peridotite massif from the field including amphibole-bearing peridotites and amphibole-bearing pyroxenite and amphibolite that are spatially associated with peridotites, underscoring the importance of hydrous melt-peridotite reaction in the formation of these amphibole-bearing rocks in the upper mantle. Amphiboles in some field samples have distinct textual and mineralogical features and their compositional variation trends are different from that defined by the melt-peridotite reaction experiments. These amphiboles are either crystallized from the host magma that entrained the xenoliths or product of hydrothermal alterations at shallow depths.