Accommodation of transpressional strain in the Arabia‐Eurasia collision zone: new constraints from (U‐Th)/He thermochronology in the Alborz mountains, north Iran
Accommodation of transpressional strain in the Arabia‐Eurasia collision zone: new constraints from (U‐Th)/He thermochronology in the Alborz mountains, north Iran
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DOI：
10.1029/2012tc003159
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发表时间：
2013
期刊：
影响因子：
4.2
通讯作者：
P. Ballato;D. Stockli;Mohammad Reza Ghassemi;A. Landgraf;M. Strecker;J. Hassanzadeh;A. Friedrich;S. Tabatabaei
中科院分区：
文献类型：
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作者：
P. Ballato;D. Stockli;Mohammad Reza Ghassemi;A. Landgraf;M. Strecker;J. Hassanzadeh;A. Friedrich;S. Tabatabaei
伊朗北部的Alborz山脉提供了阿拉伯-欧亚大陆碰撞带时空演化和特征的关键信息。西南部的Alborz范围构成了一个转换挤压的双重，它容纳伊朗中部和南里海盆地之间的斜缩短。该复式包括NW-走向的正面坡道，这些坡道在运动学上与继承的EW-走向、右行走的斜向坡道横向相连。新的锆石和磷灰石（U-Th）/He数据提供了一个高分辨率的框架，以揭示该地区碰撞构造的演化。我们的数据记录了两个快速冷却脉冲，与约18-14和9.5 - 7.5 Ma的SW向逆冲作用有关，导致了化石锆石部分保留区的构造重复和半U形几何形状的冷却模式。沿最南端的东西走向斜坡道及其相关的西北走向前坡道的~ 7-6 Ma沿着的均匀冷却年龄表明，坡道作为一个主要的贯通、北倾逆冲断层被重新激活。我们解释这一重大的变化，断层运动学和变形风格有关的缩短方向从NE到N/NNE的变化。逆冲断层活动强度的降低可能表明伊朗高原上的走滑断层（可能还有逆冲断层）的终止，这可能是由海拔的增加引发的。此外，我们认为，约7 - 6百万年前的S向逆冲早于南里海盆地向西运动的开始。
The Alborz range of N Iran provides key information on the spatiotemporal evolution and characteristics of the Arabia‐Eurasia continental collision zone. The southwestern Alborz range constitutes a transpressional duplex, which accommodates oblique shortening between Central Iran and the South Caspian Basin. The duplex comprises NW‐striking frontal ramps that are kinematically linked to inherited E‐W‐striking, right‐stepping lateral to obliquely oriented ramps. New zircon and apatite (U‐Th)/He data provide a high‐resolution framework to unravel the evolution of collisional tectonics in this region. Our data record two pulses of fast cooling associated with SW‐directed thrusting across the frontal ramps at ~ 18–14 and 9.5‐7.5 Ma, resulting in the tectonic repetition of a fossil zircon partial retention zone and a cooling pattern with a half U‐shaped geometry. Uniform cooling ages of ~ 7–6 Ma along the southernmost E‐W striking oblique ramp and across its associated NW‐striking frontal ramps suggests that the ramp was reactivated as a master throughgoing, N‐dipping thrust. We interpret this major change in fault kinematics and deformation style to be related to a change in the shortening direction from NE to N/NNE. The reduction in the obliquity of thrusting may indicate the termination of strike‐slip faulting (and possibly thrusting) across the Iranian Plateau, which could have been triggered by an increase in elevation. Furthermore, we suggest that ~ 7‐6‐m.y.‐old S‐directed thrusting predated inception of the westward motion of the South Caspian Basin.