Tectonic transition from the Paleo-Asian Ocean to the Paleo-Pacific Ocean in central Jilin (NE China): Constraints from the early Mesozoic high-Mg andesites

Abstract

The Jilin–Yanji Suture is situated at the convergent margin between the North China Craton and Jiamusi-Khanka Massif, playing as a key hinge to link up the tectonic transition from the Paleo-Asian Ocean to the Paleo-Pacific Ocean. However, many parameters of this suture, e.g. the timing of its emplacement, tectonic setting and precise location remain controversial. For addressing these issues, we focused on the high-Mg andesites within the Seluohe Group which is a typical subduction-related volcanic association along the Jilin–Yanji Suture. Seven chlorite schist and six andesite samples were collected for petrological, geochemical and geochronological analyses. The geochemical results indicate the protoliths of chlorite schists and the andesite samples are high-Mg andesites, and their magma source was produced by the metasomatized mantle wedge by subducted slab-derived fluids in a continental island arc setting. Eight high-Mg andesites give the crystallization ages of 249 ± 3 Ma–246 ± 4 Ma, with a weighted mean age of 247 ± 1 Ma (MSWD = 0.27) yielded by 69 youngest zircons, indicative of an Early Triassic age. Based on our new results and the field investigation, we propose that the Seluohe Group is a set of Early Triassic volcanic-sedimentary association with continental island arc affinity related to the south-westward subduction of the Heilongjiang Ocean, rather than a Mesoproterozoic sequence or Late Permian accretionary complex as previously considered. Integrated with previous studies on the regional tectonic evolution, we suggest the Jilin-Yanji Suture belongs to the southern extension of the Jilin-Heilongjiang high-pressure metamorphic belt, which records the final collision between the Jiamusi-Khanka Massif and North China Craton during the Triassic caused by the subduction of the Paleo-Pacific Ocean, and the Late Permian-Late Triassic is a key period of tectonic transition from the Paleo-Asian Ocean to the Paleo-Pacific Ocean in the eastern edge of Eurasia.