Back-arc regions are usually punctuated by pulses of tectonic deformation, lasting for few tens of millions of years. Yet, the origin of those short-lived deformation episodes is disputed. Here, we compile structural, stratigraphic, geochemical, and geochronological data from Iran and we combine them with a kinematic reconstruction to show that the back-arc region of the Central Neotethys subduction zone was affected by alternating pulses of extension and compression, linked to episodes of trench retreat and advance, respectively. To back-up these observations and investigate the causes of such a trench behavior, we run 2D numerical models exploring (i) the dynamics of subduction into a viscously stratified mantle, and (ii) the deep slab deformation induced by mineral phase changes at the mantle transition zone. Our results indicate that episodes of trench retreat and trench advance, like those observed in the Central Neotethys domain, emerge spontaneously by slab folding, and penetration into the mantle transition zone. We propose a coupled mantle-surface tectonic evolution model of the Central Neotethys slab that reconciles back-arc deformation and short-lived pulses of upper-plate vertical motion in a unique, dynamically self-consistent model of deep mantle subduction.

中文翻译：

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伊朗移动带的板坯折叠和表面变形

弧后区域通常被构造变形脉冲打断，持续数千万年。然而，这些短暂变形事件的起源是有争议的。在这里，我们汇编了来自伊朗的结构、地层、地球化学和地质年代学数据，并将它们与运动学重建相结合，以表明中央新特提斯俯冲带的弧后区域受到与事件相关的交替拉伸和压缩脉冲的影响分别为战壕撤退和前进。为了支持这些观察并研究这种沟槽行为的原因，我们运行了二维数值模型，探索 (i) 向粘性分层地幔中俯冲的动力学，以及 (ii) 由矿物相变引起的深板变形地幔过渡带。我们的研究结果表明，海沟退缩和海沟前进的情节，就像在新特提斯中央域中观察到的那样，通过板块折叠和渗透到地幔过渡带而自发出现。我们提出了中央新特提斯板块的耦合地幔-表面构造演化模型，该模型在深部地幔俯冲的独特动态自洽模型中协调弧后变形和上板块垂直运动的短寿命脉冲。