Early–Middle Paleozoic subduction–collision history of the south-eastern Central Asian Orogenic Belt: evidence from igneous and metasedimentary rocks of central Jilin Province, NE China

Abstract:

We undertook zircon U–Pb dating and analyzed major and trace elements and zircon Hf isotope compositions of Late Cambrian to Middle Devonian igneous and metasedimentary rocks in central Jilin Province, NE China, in order to constrain the Early–Middle Paleozoic tectonic evolution of the south-eastern segment of the Central Asian Orogenic Belt (CAOB),. Zircon U–Pb dating indicates that the Early–Middle Paleozoic magmatism in central Jilin Province can be divided into four episodes: Late Cambrian (ca. 493 Ma), Middle Ordovician (ca. 467 Ma), Late Ordovician–Early Silurian (ca. 443 Ma), and Late Silurian–Middle Devonian (425–396 Ma). The progression from subduction initiation to maturity is recorded by Late Cambrian low-K tholeiitic meta-diabase and ultramafic rocks, Middle Ordovician medium-K calc-alkaline pyroxene andesite, and Late Ordovician to Early Silurian low-K tonalite, which all formed in an evolving supra-subduction zone setting. Late Silurian to Middle Devonian igneous rocks contain granodiorite, monzogranite, rhyolite, dacite, and trachydacite, show progressively increasing K₂O contents, from medium K to shoshonite series. Furthermore, the Early–Middle Devonian monzogranites were generated by the melting of thickened lower crust. These results suggest a transition from subduction to post-orogenic setting during the Late Silurian–Middle Devonian. Overall, we suggest that Late Cambrian tholeiitic meta-diabase and ultramafic rocks, Middle Ordovician pyroxene andesite, and Late Ordovician–Early Silurian tonalite formed above the northward-subducting and simultaneously seaward-retreating of Paleo-Asian Ocean plate. Subsequently, the northern arc collided with the North China Craton and post-orogenic extension probably occurred during the Late Silurian–Middle Devonian.

This work was supported by the National Basic Research Program of China (grant: 2013CB429802) and National Natural Science Foundation of China (grant: 41172057).