We investigate the evolution of the Gulf of Aden from rift initiation to the development of active oceanic spreading center by means of 2D thermo-mechanical numerical models, in which the formation of oceanic crust and serpentinite due to the hydration of the uprising mantle peridotite has been implemented. Our analysis highlights that evolution of the models is characterized by four main tectonic phases: a) a first phase (phase I) characterized by low deformation rates throughout the divergent crustal blocks, except near the future ridge where a high crustal velocity gradient generates an intense strain rates; b) a second phase (phase II) during which the crust undergoes an intense, stable and widespread strain, with the localization of the thinning near the future ridge that ends into crustal breakup c) a third phase (phase III) that characterizes the post- crustal breakup evolution of the models during which a mechanical relaxation of the system and a continuum decreasing of the strain rate can be observed, until the occurrence of lithospheric breakup, and d) fourth phase (phase IV) that lasts up to the end of the evolution and during which the two continental blocks move rigidly. We also find that the timing of mantle serpentinization is not affected by the initial thermal configuration of the lithosphere, but a relationship with the crustal thickness can be observed. Rather, the timing of mantle partial melting strongly depends on the initial thermal conditions of both the lithosphere and the crust. We constrain the crustal and lithospheric thickness at 40 and 150 km, respectively, considering the timing of breakup that occurs 20 Myr after the onset of the extension for 0.05% percentage of mantle hydration (in agreement with magma-poor rift margins). Finally, model prediction supports the hypothesis that the Gulf of Aden developed as a slow passive rift of a thin lithosphere with a thick crust and the variation of the features along the passive margins could be related to a lateral variation in the amount of HO in the mantle, which determines different timing in the mantle melting.

中文翻译：

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亚丁湾从裂谷到海洋化：二维数值模型的见解

我们通过二维热力数值模型研究了亚丁湾从裂谷萌生到活跃海洋扩张中心发展的演化过程，其中由于上升地幔橄榄岩的水化而形成了洋壳和蛇纹岩。实施的。我们的分析强调，模型的演化具有四个主要构造阶段的特征：a）第一阶段（第一阶段）的特征是整个不同地壳块的变形率较低，除了未来的山脊附近，那里的高地壳速度梯度会产生强烈的变形。应变率； b) 第二阶段（第二阶段），在此期间地壳经历强烈、稳定和广泛的应变，减薄区域位于未来的山脊附近，最终导致地壳破裂 c) 第三阶段（第三阶段），其特征是后- 模型的地壳破裂演化，在此期间可以观察到系统的机械松弛和应变率的连续降低，直到岩石圈破裂的发生，以及 d) 第四阶段（第四阶段）持续到结束演化过程中两个大陆块刚性移动。我们还发现地幔蛇纹石化的时间不受岩石圈初始热配置的影响，但可以观察到与地壳厚度的关系。相反，地幔部分熔融的时间很大程度上取决于岩石圈和地壳的初始热条件。我们将地壳和岩石圈的厚度分别限制在 40 和 150 km，考虑到地幔水化百分比为 0.05% 的伸展开始后 20 Myr 发生的破裂时间（与岩浆贫乏的裂谷边缘一致）。最后，模型预测支持这样的假设：亚丁湾发展为薄岩石圈和厚地壳的缓慢被动裂谷，沿被动边缘特征的变化可能与亚丁湾中 H2O 含量的横向变化有关。地幔，它决定了地幔熔化的不同时间。