Rift propagation is a 3D thermo-mechanical process that often precedes continental breakup. Pre-existing microcontinental blocks and the associated lithospheric strength heterogeneities influence the style of rift propagation. Interestingly, some rifts propagate into pre-existing blocks and eventually cut through them (e.g., the Zhongsha Block and the Reed Bank), while others bypass these microcontinental blocks forming distinct overlapping rift branches (e.g., the East African Rift System). In this study, we use 3D numerical models to investigate the interaction between microcontinental blocks and rift propagation under different far-field extension rates. In doing so, we assess the impact of mantle lithospheric thicknesses and lower crustal rheology on the style of rift propagation. Our models reproduce the two types of rift propagation, characterized by propagating rifts that either split or bypass the pre-existing microcontinental blocks. We find that lithospheric thickness exerts dominant control, while lower crustal rheology of microcontinental blocks and the extension rate have less effect on rift propagation. Our model results can explain rift propagation patterns, block rotation and strong lithospheric thinning in the South China Sea, the East African Rift System, and the Woodlark Basin.

中文翻译：

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裂谷传播与先前存在的微大陆块相互作用

裂谷传播是一种 3D 热机械过程，通常发生在大陆分裂之前。预先存在的微大陆块和相关的岩石圈强度异质性影响裂谷传播的方式。有趣的是，一些裂谷传播到预先存在的地块中并最终穿过它们（例如，中沙地块和礼乐滩），而另一些裂谷则绕过这些微大陆地块，形成明显的重叠裂谷分支（例如，东非裂谷系统）。在本研究中，我们使用3D数值模型来研究不同远场扩展率下微大陆块与裂谷传播之间的相互作用。在此过程中，我们评估了地幔岩石圈厚度和下地壳流变学对裂谷传播方式的影响。我们的模型再现了两种类型的裂谷传播，其特征是裂谷传播分裂或绕过预先存在的微大陆块。我们发现岩石圈厚度起主导控制作用，而微陆块的下地壳流变性和伸展速率对裂谷扩展的影响较小。我们的模型结果可以解释南海、东非裂谷系统和伍德拉克盆地的裂谷传播模式、地块旋转和强烈的岩石圈减薄。