The role of footwall deformation and denudation in controlling cooling age patterns of detachment systems: An application to the Kongur Shan extensional system in the Eastern Pamir, China
The role of footwall deformation and denudation in controlling cooling age patterns of detachment systems: An application to the Kongur Shan extensional system in the Eastern Pamir, China
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DOI：
10.1016/j.tecto.2010.10.003
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发表时间：
2010-12
期刊：
影响因子：
2.9
通讯作者：
A. C. Robinson;A. Yin;O. Lovera
中科院分区：
文献类型：
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作者：
A. C. Robinson;A. Yin;O. Lovera
确定主要低角度正断层下盘岩石变形与折返历史之间的关系（即，拆离断层）提供了一种方法来量化大陆伸展的不同模式。虽然压力-温度-时间（P-T-t）数据集通常用于推断滑脱断层的幅度和速率，但正确使用这些数据集需要充分了解下盘变形和平流等温线对冷却年龄分布的耦合效应。在这项研究中，我们提出了热运动学模拟结果，研究不同的下盘运动学模型，侵蚀，白云母和黑云母40 Ar/39 Ar冷却年龄的空间分布之间的关系。我们的研究结果表明，大幅度的下盘侵蚀在正常断层显着影响冷却年龄模式的下盘岩石在不同的距离，从断层面通过不同的热梯度。我们应用我们的模拟结果来模拟白云母和黑云母冷却年龄模式从下盘的新生代孔古尔山正断层系统在帕米尔。以前的研究解释了记录的~ 2 Ma时冷却速率增加了~5倍，表明第四纪期间折返速率增加。然而，我们的研究结果表明，所观察到的冷却年龄模式和冷却速率的增加，可以产生一个恒定的折返率在过去的7 Ma由于等温平流的变化率的影响，在折返过程中。
Determining the relationship between deformation and exhumation history in the footwall rocks of major low-angle normal faults (i.e., detachment faults) provides a way to quantify different models of continental extension. Although pressure–temperature–time (P–T–t) datasets are commonly used to infer magnitude and rates of slip across detachment faults, correct use of these datasets requires a sound understanding of coupling effects between footwall deformation and advection of isotherms on the distribution of cooling ages. In this study we present thermo-kinematic modeling results which examine the relationship between different footwall kinematic models, erosion, and the spatial distribution of muscovite and biotite40Ar/39Ar cooling ages. Our results show that large magnitudes of footwall erosion during normal faulting significantly affect cooling age patterns as footwall rocks at different distances from the fault surface pass through different thermal gradients. We apply our modeling results to simulating muscovite and biotite cooling-age patterns from the footwall of the Cenozoic Kongur Shan normal fault system in the Pamir. Previous studies had interpreted a documented ~5-fold increase in cooling rate at ~2Ma to indicate an increase in exhumation rate during the Quaternary. However, our results show that the observed cooling age patterns and increase in cooling rate can be produced by a constant exhumation rate over the last 7Ma due to the effect of changes in the rate of isotherm advection during exhumation.