Late Paleozoic and Mesozoic Magmatism in Jilin Area, NE China:
Implications for 2 the Transition from Convergence at the Paleo-Asian
Ocean to Paleo-Pacific Subduction 4
Abstract
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.