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

To constrain the Early–Middle Paleozoic tectonic evolution of the south-eastern segment of the Central Asian Orogenic Belt (CAOB), 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. LA–ICP–MS zircon U–Pb dating indicates that the Early–Middle Paleozoic magmatism in central Jilin Province can be divided into four episodes: Late Cambrian (ca. 493Ma), Middle Ordovician (ca. 467Ma), Late Ordovician–Early Silurian (ca. 443Ma), and Late Silurian–Middle Devonian (425–396Ma). The progression from subduction initiation to maturity is recorded by Late Cambrian low-K tholeiitic meta-diabase, Middle Ordovician medium-K calc-alkaline pyroxene andesite, and Late Ordovician to Early Silurian low-K tonalite, which all have subduction-related characteristics and formed in an evolving supra-subduction zone setting. Late Silurian to Middle Devonian calc-alkaline igneous rocks, with the lithological association of granodiorite, monzogranite, rhyolite, dacite, and trachydacite, show progressively increasing K2O contents from medium K to shoshonite series. Furthermore, the Early–Middle Devonian monzogranites are characterized by high K2O, Sr/Y, and [La/Yb]N values, indicating they 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. Our interpretation is supported by the maximum age of molasse deposition in the Zhangjiatun member of the Xibiehe Formation. Overall, we suggest that Late Cambrian tholeiitic meta-diabase, 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 occurred during the Late Silurian–Middle Devonian.