Multi-stage tectono-magmatic events of the Eastern Kunlun Range, northern Tibet: Insights from U-Pb geochronology and (U-Th)/He thermochronology

To understand the magmatic and tectonic events in the Eastern Kunlun Range, we conducted systematic zircon U-Pb geochronology, and paired zircon (ZHe) and apatite (AHe) (U-Th)/He themchronology investigations in the central and eastern segments of this range. Zircon U-Pb ages show two-stage magmatic events of Late Silurian and latest Permian-Early Jurassic. ZHe and AHe ages and multi-system thermochronometers reveal multi-stage rapid cooling events. From a combination of these data with previously published geochronological and thermochronological ages, and regional geological setting, we confirm several important Phanerozoic tectono-magmatic events in this region. Whereas the Silurian granites might be related to a small paleo-ocean subduction and subsequent collision, the latest Permian-Early Triassic granitoids were produced by northward subduction of the Songpan-Ganzi Paleo-Tethyan ocean. The Late Triassic-earliest Jurassic granitoids and Late Triassic-Early Jurassic exhumation are interpreted as response to the collision between Kunlun-Qaidam and Qiangtang. Samples close to the Kunlun Fault show rapid Late Oligocene-Early Miocene exhumation (1.3-1.6 km/Ma), whereas those from the northern part of central segment display extremely low exhumation rates (0.02-0.05 km/Ma). This heterogeneous denudation during 30-20 Ma between northern and southern part of the central segment requires that crustal thickening was completed by lower-crustal underthrusting with little exhumation or crustal thickening in pre-Cenozoic times, The activity of the Kunlun Fault and associated normal faulting component were probably responsible for this stage of rapid exhumation in the southern part. The complex tectono-magmatic evolution of the Eastern Kunlun Range is controlled by pre-Cenozoic paleo-ocean subductions and subsequent continent collisions and Paleogene India-Asia collision. (C) 2013 Elsevier B.V. All rights reserved.