Tectonic evolution of Mohe area, North‐east China: Evidence from the Early Ordovician to Early Cretaceous magmatism and tectonism

Abstract

This article presents new zircon U–Pb ages, data on whole‐rock major and trace elements for the Early Ordovician to Early Cretaceous granitic rocks exposed in the Mohe Basin of North‐east China, and reveals the tectonic evolution history of the Mohe area during this period. The zircon U–Pb dating results indicate that the magmatic activities from the Early Ordovician to Early Cretaceous in the Mohe area can be divided into six stages, which are ~473, ~281, ~247, ~215, ~130, and ~124 Ma, respectively. The granitic rocks mainly originated by partial melting of a depleted and heterogeneous lower crust, except for the quartz diorites at ~130 Ma, derived from the separated crystallization of mantle‐derived subalkaline basaltic magma. The rock associations and their geochemical features indicate that the granitic rocks of ~247 and ~215 Ma formed in an active continental margin setting, whereas the granitic rocks with formation ages of ~473, ~281, ~130, and ~124 Ma were formed in an extensional tectonic setting. Each stage of magmatic activity is consistent with the magmatism and tectonism of the Erguna Block. Based on the achievements of the previous studies, we put forward a comprehensive tectonic evolution of the Mohe area. From Early Ordovician to Late Permian (473 ~ 252 Ma), the Mohe area was influenced by the Palaeo‐Asian Ocean tectonic domain. Magmatism of Late Permian to Late Jurassic (247 ~ 155 Ma) is mainly due to the subduction of the Mongol–Okhotsk Ocean. During the Late Jurassic, the Erguna Block collided with the Siberian Craton and the southern margin of the Siberian Craton was uplifted and started furnishing sediments into the Mohe Basin. In the Early Cretaceous (~130 Ma), the Mohe area may have been controlled by the Palaeo‐Pacific Ocean and the Mongol–Okhotsk Ocean tectonic domains.