Post-collisional lithospheric delamination in eastern Iran, revealed by non-linear teleseismic tomography and residual topography

IF 2.4 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS
Meysam Mahmoodabadi , Farzam Yamini-Fard , Mohammad Tatar , Ahmad Rashidi
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引用次数: 0

Abstract

The Eastern Iranian Mountain Ranges (EIR) emerged as a consequence of the Late Cretaceous collision between the Afghan and Lut blocks. However, the response of the uppermost mantle to this collision remains enigmatic. Additionally, although petrological evidence suggests that post-collisional delamination is possible, it has not been conclusively identified in prior regional seismic imagery. This observation leads us to further explore this possibility using a dense seismic network. To gain insight into the geodynamic implications for eastern Iran and address knowledge gaps, we extensively investigated the seismic structure of the uppermost mantle beneath the EIR using a dense seismic network of 34 temporary stations, complemented by data from nine additional local permanent stations. By meticulously analyzing 6589 relative arrival time residuals from teleseismic records with favorable signal-to-noise ratios, we applied a non-linear tomography method to map P-wave velocity perturbations in a relative sense. Our tomographic images unveiled distinct instances of rapid high-velocity anomalies beneath low-velocity regions in the shallow mantle, suggesting the potential occurrence of lithospheric dripping, followed by subsequent asthenospheric upwelling. This observation offers a plausible explanation for the observed post-collisional magmatism over the Lut Block. Furthermore, to maintain the approximately 1.5-km positive residual topography across the EIR, beyond the influence of crustal properties, additional support from the hot and buoyant asthenosphere becomes crucial, particularly in the absence of a substantial lithospheric mantle.

Abstract Image

非线性远震断层扫描和残余地形揭示的伊朗东部碰撞后岩石圈脱层情况
东伊朗山脉(EIR)的出现是晚白垩世阿富汗地块和卢特地块碰撞的结果。然而,最上层地幔对这一碰撞的反应仍然是个谜。此外,尽管岩石学证据表明碰撞后的分层是可能的,但在之前的区域地震图像中并未得到确证。这一观察结果促使我们利用密集的地震网络进一步探索这种可能性。为了深入了解地球动力学对伊朗东部的影响并填补知识空白,我们利用由 34 个临时台站组成的密集地震网络,并辅以另外 9 个当地永久台站的数据,对伊朗东部地区下方最上地幔的地震结构进行了广泛研究。通过细致分析 6589 个信噪比良好的远震记录的相对到达时间残差,我们采用非线性层析方法绘制了相对意义上的波速扰动图。我们的层析成像揭示了浅地幔低速区域下快速高速异常的明显实例,表明可能发生了岩石圈滴落,随后发生了星体层上涌。这一观测结果为在卢特区块观测到的碰撞后岩浆活动提供了一个合理的解释。此外,在地壳特性的影响之外,要维持整个 EIR 约 1.5 千米的正残余地形,来自炽热且具有浮力的星体层的额外支持变得至关重要,尤其是在缺乏大量岩石圈地幔的情况下。
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来源期刊
Physics of the Earth and Planetary Interiors
Physics of the Earth and Planetary Interiors 地学天文-地球化学与地球物理
CiteScore
5.00
自引率
4.30%
发文量
78
审稿时长
18.5 weeks
期刊介绍: Launched in 1968 to fill the need for an international journal in the field of planetary physics, geodesy and geophysics, Physics of the Earth and Planetary Interiors has now grown to become important reading matter for all geophysicists. It is the only journal to be entirely devoted to the physical and chemical processes of planetary interiors. Original research papers, review articles, short communications and book reviews are all published on a regular basis; and from time to time special issues of the journal are devoted to the publication of the proceedings of symposia and congresses which the editors feel will be of particular interest to the reader.
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