Diachronous onset and polyphase cooling of the Taili-Yiwulüshan metamorphic core complex corridor, NE China, and its relationships to the formation of adjacent extensional basins

Abstract

The aim of the study to investigate the cooling and exhumation history of deep crustal rocks along the Taili-Yiwulüshan metamorphic core complex (MCC) corridor and correlate these with volcanic-clastic deposition in the Late Jurassic to Early Cretaceous supra-detachment Fuxin-Yixian basin in the west and the mostly Eocene Liaohe basin in the east. This corridor exposes low- to medium-grade metamorphic Neoarchean rocks and Late Triassic, Late Jurassic and Early Cretaceous granitic rocks, which exhumed from the middle to shallow crustal levels. New 40Ar/39Ar ages of muscovite, biotite, K-feldspar and apatite (U-Th-Sm)/He ages in combination with compiled published geochronological data from the granitic rocks constrain three major stages of cooling exhumation and deformation from Late Jurassic through Early Cretaceous to Eocene interrupted by Late Cretaceous tectonic quiescence. The onset of activity and exhumation and cooling is diachronous along the MCC corridor. At Taili in the south, the main activity of the sinistral shear zone is constrained between 160 and 140 Ma with major cooling from crystallization temperatures of granitoids from 700–750 °C to 160 °C (first stage). Along the Waziyu ductile detachment at the western border of the Yiwulüshan MCC major cooling and exhumation is bracketed between 130 Ma and 100 Ma (second stage) and thus indicates a northward progradation of deformation and exhumation activity. However, cooling ages as old as 159 Ma along the eastern margin of the Yiwulüshan MCC indicate an earlier initiation of cooling and westward rolling-hinge type propagation (first stage). Late Cretaceous and Paleogene times are characterized by a tectonically quiet period with only minor cooling and exhumation (stage three). The fourth and final stage of exhumation and cooling to very low temperatures occurred during Late Paleocene to earliest Eocene times and is associated with the transtensional or extensional opening of the Liaohe basin.