Apatite fission track evidence for Neogene uplift in the eastern Kunlun Mountains, northern Qinghai-Tibet Plateau, China

Forty-one apatite fission track ages (AFT) were determined on samples collected along a N-S section of the eastern Kunlun Mountains across the Middle and South Kunlun Faults between Buqingshan and Dulan. Measured AFT ages lie between 25 +/- 2 and 130 +/- 10 Ma, and all are significantly younger than their host rock formation or sediment deposition ages. Modelling the AFT data identifies a two stage regional cooling history that spans the last 100 Myrs. The earliest cooling phase occurred between the late Jurassic and early Tertiary and involved a moderate level of cooling between 20 and 40 degrees C, equivalent to average exhumation rates of = 15 m/Myr. The second phase of cooling took place from similar to 20 Ma with cooling rates increasing tenfold. Average exhumation rates for this period are estimated to be in the range of similar to 100-150 m/Myr. The first stage of protracted cooling is consistent with regional evidence from the Qiantang and Lhasa terrans where previous studies have noted low rates of denudation in relation to a back-arc extensional setting. The more recent acceleration in cooling seen in the Kunlun data coincides with an increase in sedimentation rates in the adjacent Qaidam Basin. This points to a phase of Neogene uplift and increased erosion of the Kunlun Range, although contemporaneous monsoon strengthening may also have had a role. (c) 2006 Elsevier Ltd. All rights reserved.