Thermochronologic evidence for plateau formation in central Tibet by 45 Ma
Thermochronologic evidence for plateau formation in central Tibet by 45 Ma
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DOI：
10.1130/g32530.1
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发表时间：
2012-02
期刊：
影响因子：
5.8
通讯作者：
A. Rohrmann;P. Kapp;B. Carrapa;P. Reiners;J. Guynn;L. Ding;M. Heizler
中科院分区：
文献类型：
--
作者：
A. Rohrmann;P. Kapp;B. Carrapa;P. Reiners;J. Guynn;L. Ding;M. Heizler
青藏高原发展的时间仍然难以捉摸，尽管它对于评估大陆岩石圈变形模型以及与之相关的地表海拔和气候变化很重要。本文报道了青藏高原中部(拉萨和羌塘地体)的新的热年代学数据[黑云母和钾长石40Ar/39Ar，磷灰石熔融径迹和磷灰石(U-Th)/He]。这些资料表明，在白垩纪至始新世期间，大面积的岩石经历了快速至中度的冷却和折返。这与上地壳50%的缩短是同时代的，这表明地壳显著增厚，地表高度增加。组合温度计时仪的热模拟需要在85-45 Ma之间将大多数样品折返到<；3千米深度，然后将侵蚀折返速率降低到<；0.05 mm/a的低值。在形变和古高度史的背景下解释热年代学结果时，最好的解释是晚白垩世开始于西藏中部局部地区的高原生长情景，并在45 Ma之前扩展到包括西藏中部大部分地区。
The timing of Tibetan plateau development remains elusive, despite its importance for evaluating models of continental lithosphere deformation and associated changes in surface elevation and climate. We present new thermochronologic data [biotite and K-feldspar 40 Ar/ 39 Ar, apatite fi ssion track, and apatite (U-Th)/He] from the central Tibetan plateau (Lhasa and Qiangtang terranes). The data indicate that over large regions, rocks underwent rapid to moderate cooling and exhumation during Cretaceous to Eocene time. This was coeval with >50% upper crustal shortening, suggesting substantial crustal thickening and surface elevation gain. Thermal modeling of combined thermochronometers requires exhumation of most samples to depths of <3 km between 85 and 45 Ma, followed by a decrease in erosional exhumation rate to low values of <0.05 mm/yr. The thermochronological results, when interpreted in the context of the deformation and paleoaltimetric history, are best explained by a scenario of plateau growth that began locally in central Tibet during the Late Cretaceous and expanded to encompass most of central Tibet by 45 Ma.