Abstract The arrival and subsequent stagnation of the Farallon/Nazca slab at the mantle transition zone below southern South America triggered seemingly unrelated large-scale geological processes in the second half of the Cenozoic. During this period, three poorly understood regional events have characterized the more recent geological history of Patagonia: i) the development of intense intraplate magmatism, ii) two large-scale marine transgressions, and iii) abnormally accelerated topographic uplift. We propose a geodynamic model that connects the subducting slab mechanisms to these events based on seismic tomography, 2-D kinematic reconstructions, dynamic subsidence models and a detailed literature review. According to our kinematic reconstruction, after the Paleocene-Eocene opening of the Aluk (Phoenix)/Farallon slab window, the Farallon oceanic slab arrived to the mantle transition zone below Patagonia at ~36–32 Ma. This event caused the physical perturbation of this mantle layer, and dehydration melting of the uplifted portions by wadsleyite breakdown, triggering an intense Oligocene-middle Miocene intraplate magmatism significantly influenced by subduction-derived fluids. Simultaneously, due to increasing disturbance of the lower mantle during the Farallon slab penetration and stagnation in the mantle transition zone, a large subduction-induced mantle flow cell began to tilt the South American plate. Tilting drove the two large marine transgressions which inundated much of the southern Argentina and Chile. Finally, in the latest Miocene-Pleistocene, Farallon-Nazca slab break-off induced the decompression melting of the sub-slab asthenosphere, generating the most recent magmatic episode in the north-central Patagonia. This magmatism was partially contemporaneous with the Chile ridge (Nazca/Antarctic) slab window-related southern Patagonian igneous activity; and although both episodes show evidence of mantle metasomatic inheritance, the north-central magmatism shows higher Th/La and 87Sr/86Sr ratios, and lower eNd values, suggesting possible contributions from the stagnant Farallon slab (wet plumes?). These modern magmatic episodes can be directly linked to the Quaternary uplift of Patagonia by mantle upwelling.

中文翻译：

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巴塔哥尼亚下方 Farallon 板块的命运及其与新生代板内岩浆作用、海侵和地形抬升的联系

摘要 法拉隆/纳斯卡板块在南美洲南部下方地幔过渡带的到达和随后的停滞引发了新生代下半期看似无关的大规模地质过程。在此期间，三个鲜为人知的区域事件表征了巴塔哥尼亚最近的地质历史：i) 强烈的板内岩浆作用的发展，ii) 两次大规模的海侵，以及 iii) 异常加速的地形抬升。我们提出了一个地球动力学模型，该模型基于地震层析成像、二维运动学重建、动态下沉模型和详细的文献综述，将俯冲板片机制与这些事件联系起来。根据我们的运动学重建，在 Aluk (Phoenix)/Farallon 板窗打开古新世-始新世之后，Farallon 大洋板块在~36-32 Ma 到达巴塔哥尼亚下方的地幔过渡带。这一事件引起了地幔层的物理扰动，以及由瓦德斯利岩分解引起的隆起部分的脱水熔化，引发了强烈的渐新世-中中新世板块内岩浆作用，受到俯冲衍生流体的显着影响。同时，由于法拉隆板块在地幔过渡带的穿透和停滞过程中对下地幔的扰动增加，一个大的俯冲诱发的地幔流动室开始使南美板块倾斜。倾斜推动了两次大型海侵，淹没了阿根廷南部和智利的大部分地区。最后，在最新的中新世-更新世，Farallon-Nazca 板块断裂引起了亚板块软流圈的减压熔化，在巴塔哥尼亚中北部产生最近的岩浆事件。这种岩浆活动与智利海脊（纳斯卡/南极）板块窗口相关的巴塔哥尼亚南部火成岩活动部分同时发生；尽管这两个事件都显示出地幔交代遗传的证据，但中北部岩浆活动显示出更高的 Th/La 和 87Sr/86Sr 比值，以及更低的 eNd 值，这表明可能来自停滞的法拉隆板块（湿羽流？）的贡献。这些现代岩浆事件可以通过地幔上涌与巴塔哥尼亚第四纪隆升直接相关。中北部岩浆活动显示出较高的 Th/La 和 87Sr/86Sr 比率，以及较低的 eNd 值，这表明可能来自停滞的 Farallon 板片（湿羽流？）的贡献。这些现代岩浆事件可以通过地幔上涌与巴塔哥尼亚第四纪隆升直接相关。中北部岩浆活动显示出较高的 Th/La 和 87Sr/86Sr 比率，以及较低的 eNd 值，表明可能来自停滞的 Farallon 板片（湿羽流？）的贡献。这些现代岩浆事件可以通过地幔上涌与巴塔哥尼亚第四纪隆升直接相关。