An outstanding question in the geological evolution of the Chilean Andes is the cause of the westward shift and relocation of magmatism from the High Andes (HA) to the Coastal Cordillera (CC) during the Late Triassic, Pre–Andean stage. The spatiotemporal distribution of Permian–Triassic–Jurassic igneous rocks in northern-central Chile (20°S–32°S) reveals a significant westward magmatic shift of ∼120 km during the Norian time. Despite diverse proposed models, the precise geodynamic mechanism behind this shift remains unclear. To address this, we used 2D numerical modeling to investigate two contrasting scenarios: (a) subduction rollback and (b) subduction transference/jump and reinitiation by terrane accretion. Our modeling results strongly support Scenario B, where mantle density and the size of the oceanic plateau are crucial for triggering subduction jump and reinitiation. This model aligns with geological and geophysical evidence and offers new insights into unraveling the Pre– and Early–Andean evolution.

中文翻译：

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揭示前安第斯和早安第斯边缘的地球动力学演变：来自数值建模的见解


智利安第斯山脉地质演化中一个悬而未决的问题是晚三叠世、前安第斯阶段岩浆作用从安第斯山脉高地 （HA） 向沿海科迪勒拉山脉 （CC） 西移和迁移的原因。智利中北部（南纬 20°-32°）二叠纪-三叠纪-侏罗纪火成岩的时空分布揭示了诺里安时期约 120 公里的显著西向岩浆移动。尽管提出的模型多种多样，但这种转变背后的确切地球动力学机制仍不清楚。为了解决这个问题，我们使用 2D 数值建模来研究两种截然不同的情景：（a） 俯冲回滚和 （b） 俯冲转移/跳跃和地层吸积的重新启动。我们的建模结果强烈支持情景 B，其中地幔密度和海洋高原的大小对于触发俯冲跳跃和重新起始至关重要。该模型与地质和地球物理证据一致，并为解开前安第斯和早期安第斯的演变提供了新的见解。