Eocene onset and late Miocene acceleration of Cenozoic intracontinental extension in the North Qinling range-Weihe graben: Insights from apatite fission track thermochronology
Eocene onset and late Miocene acceleration of Cenozoic intracontinental extension in the North Qinling range-Weihe graben: Insights from apatite fission track thermochronology
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北秦岭-渭河地堑新生代陆内伸展的始新世开始和晚中新世加速：来自磷灰石裂变径迹热年代学的见解
DOI：
10.1016/j.tecto.2012.01.025
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发表时间：
2013-01-22
期刊：
影响因子：
2.9
通讯作者：
Zhang, Huiping
中科院分区：
文献类型：
--
作者：
Liu, Jianhui;Zhang, Peizhen;Zhang, Huiping
鄂尔多斯地块两侧的新生代地堑（如渭河地堑）可容纳中国中部的陆内伸展，其伸展速率为5-6 mm/a。为了确定新生代主要伸展作用的开始和演化，我们研究了北秦岭与渭河地堑相邻的出露下盘岩石的冷却历史。本文报道了47个新的磷灰石裂变径迹（AFT）样品的研究结果，这些样品主要来自北秦岭下盘北方两个起伏1.5- 2.5km的垂直断面。AFT年龄逐渐变老的距离增加，从活跃的，范围界定，正断层表明，新生代隆起和向南倾斜是一个响应范围平行的扩展。AFT年龄与海拔和径迹长度的相关性以及代表性样品的热模拟结果表明，北秦岭新生代经历了两个主要的折返阶段：（1）相对缓慢的折返，对应于一个约50 Ma的小幅度伸展;（2）相对快速的折返作用是对10 Ma左右开始的大幅度加速伸展的响应。此外，冷却速率在近似35 Ma和近似25 Ma时的微小变化可能反映了断裂速率的微小变化。我们认为，50 Ma左右的初始伸展作用是印度-亚洲大陆初始碰撞的远场效应。相反，沿秦岭沿着约10 Ma后的加速伸展可能与青藏高原的向上和向外生长有关。另外，秦岭下地壳流动可能在晚中新世加速了折返。(C)2012爱思唯尔有限公司版权所有。
Intracontinental extension in central China is accommodated by Cenozoic grabens flanking the Ordos Block, such as the Weihe graben, which accommodate 5-6 mm/yr of extension. To define the onset and evolution of major Cenozoic extension, we examine the cooling history of exhumed footwall rocks in the North Qjnling range adjacent to the Weihe graben. We present results from 47 new apatite fission track (AFT) samples primarily from two vertical transects of 1.5-2.5 km relief located on the northern flank of the North Qjnling footwall. AFT ages that get progressively older with increasing distance from the active, range bounding, normal fault suggest that Cenozoic uplift and southward tilting was a response to range-parallel extension. Correlations between AFT ages and both elevation and track lengths, combined with thermal modeling of representative samples, reveal that the North Qinling experienced two major stages of Cenozoic exhumation: (1) relatively slow exhumation in response to a small magnitude of extension that initiated at similar to 50 Ma; (2) relatively rapid exhumation in response to a large magnitude of accelerated extension that initiated at similar to 10 Ma. In addition, small changes in cooling rate at similar to 35 Ma and similar to 25 Ma may reflect minor changes in faulting rate. We interpret initial extensional at similar to 50 Ma to be a far-field effect of initial India-Asia continental collision. In contrast, accelerated extension after similar to 10 Ma along the Qinling is likely linked to the upward and outward growth of the Tibetan Plateau. Alternatively, lower crustal flow beneath the Qjnling may have progressively accelerated exhumation in late Miocene time. (C) 2012 Elsevier B.V. All rights reserved.