Multiple Accretionary Orogenesis and Episodic Growth of Continents: Insights from the Western Kunlun Range, Central Asia

摘要

The Western Kunlun Range in northwestern Tibet records a history of enlargement of the Central Asian crust. In the Early Ordovician a south-dipping intro-oceanic subduction-accretion complex was accreted to the Tarim block, forming an Andean-type margin in the Late Ordovician. This margin grew southward (present-day coordinates) in the Early Silurian, with an accretionary complex on its southern side against which the Kudi gneiss-schist complex was attached. Clastic sediments continued to infill forearc/intra-arc basins on the top of the arc-accretionary complexes (luring Devonian-Carboniferous time. In the Early to Mid-Carboniferous, tectonic and magmatic quiescence is indicated by an absence of volcanic and plutonic rocks in the Kudi area, whereas subduction was still active in the western part of the range in the Gaz area near the present-day Pamir syntaxis. A Late Carboniferous-Permian to Early Mesozoic accretionary arc and forearc developed in front of the Andean-type margin, indicating that north-dipping subduction was renewed in the Late Carboniferous. Final collision of the Karakoram-North Qiangtang block to the western Kunlun orogenic collage by the Mid-Jurassic resulted in closure of Paleo-Tethys. The accretion and development of the Western Kunlun orogen contributed huge quantities of material for the crustal growth of Asia.