Origin of Archean Continental Crust in the Tarim Craton: Progresses and Issues

The Tarim Craton is one of the three ancient continental blocks in China, but the formation and evolution of its ancient basement have been poorly studied due to extensive sedimentary cover. However, in recent years, Archean rocks have been found in the Kuruktag, Dunhuang, North Altyn Tagh, Tiekelike areas on the periphery of the Tarim Basin, as well as in the drill core from its basement, indicating that there may be a widespread Archean basement. In this paper, the study history and recent progress of Archean rocks in the Tarim Craton are summarized, the formation time, mechanism and geodynamics of Archean continental crust are discussed, and the future research direction is pointed out. The results show that the formation of the Archean continental crust in the Tarim Craton appears to have regional differences. Neoarchean magmatism was widely developed in the Kuruktag, Dunhuang and North Altyn areas, with peaks of ～2.5 Ga and ～2.7 Ga. The discovery of ～3.7 Ga rocks in the North Altyn Tagh area provides reliable evidence for the existence of an Eoarchean continental nucleus in the Tarim Craton. The Tiekelike area and basin basement in the southwest Tarim are characterized by Mesoarchean (3.2～2.8 Ga) crustal growth and reworking, and no Neoarchean rocks have been found. Geochemistry, thermodynamic modelling and zircon oxybarometer-hygrometer indicate that the Archean continental crust might have been produced by water-induced melting of different source rocks at different depths (pressures) and formed in subduction-related tectonic settings, indicating that early plate tectonics have been in operation since the Eoarchean. The elucidation of the components of the Archean continental crust, the identification of metamorphism and deformation, and the determination of the physical and chemical conditions of magma formation are still the focus of future studies of the Archean geology in the Tarim Craton.