Effects of slab-window, alkaline volcanism, and glaciation on thermochronometer cooling histories, Patagonian Andes
Effects of slab-window, alkaline volcanism, and glaciation on thermochronometer cooling histories, Patagonian Andes
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DOI：
10.1016/j.epsl.2019.01.030
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发表时间：
2019-04
影响因子：
5.3
通讯作者：
V. Georgieva;K. Gallagher;A. Sobczyk;E. Sobel;T. Schildgen;T. Ehlers;M. Strecker
中科院分区：
文献类型：
--
作者：
V. Georgieva;K. Gallagher;A. Sobczyk;E. Sobel;T. Schildgen;T. Ehlers;M. Strecker
南巴塔哥尼亚是持续数百万年的洋脊碰撞和板窗形成的主要例子。这些现象对地壳热结构和折返的影响主要通过基岩样品的低温热年代学来评估。在这里，我们推断新的和现有的热年代学数据从最近的脊碰撞区域的热历史。特别是，我们评估了潜在的深远的热效应的不断发展的板窗口，这在以前被认为是负责晚中新世再加热模式与弧后碱性火山作用。我们的模型结果定义了自2015年以来的长期冷却和自晚中新世以来的逐步剥露。逐步折返的模式密切匹配的巴塔哥尼亚冰川在7 Ma的开始和连续脉冲的冰川切割coeval与新构造活动，自3-4 Ma以来，也记录在该地区的独立的地质和地貌证据。重要的是，我们的研究结果挑战了最近提出的缺乏冰川侵蚀和切割，因为在这个地区的5马。此外，与以前的建模研究相比，我们发现，现有的数据并没有证据表明以前提出的向北传播的加热事件与碱性火山作用。我们推测，巴塔哥尼亚弧后的异常碱性火山活动可能与俯冲板块中与转换断层对齐的沟槽正交裂缝有关。从以前的建模过程中的一些相同的样品的实质性差异被证明是由于一个重要的缺乏收敛模型运行。
Southern Patagonia is a prime example of ongoing oceanic ridge collision and slab-window formation sustained over several million years. The impact of these phenomena on the thermal structure and exhumation of the crust have been mainly assessed with low-temperature thermochronology of bedrock samples. Here, we infer thermal histories from new and existing thermochronological data from the region of most recent ridge collision. In particular, we evaluate the potential far-reaching thermal effects of the evolving slab window, which have previously been considered responsible for patterns of late Miocene reheating associated with back-arc alkaline volcanism. Our model results define protracted cooling since ∼15 Ma and stepwise exhumation since the late Miocene. The pattern of stepwise exhumation closely matches the onset of Patagonian glaciation at 7 Ma and the successive pulse of glacial incision coeval with neotectonic activity since 3–4 Ma that are also documented by independent geological and geomorphological evidence in the region. Importantly, our findings challenge the recently suggested lack of glacial erosion and incision since 5 Ma in this region. Furthermore, in contrast to previous modelling studies, we find that the available data do not evidence a previously proposed northward-propagating heating event associated with alkaline volcanism. We hypothesize that the anomalous alkaline volcanism in the Patagonian back-arc might be related to trench-orthogonal tears aligned with transform faults in the subducting plate. The substantial differences from the previous modelling procedure on some of the same samples is demonstrated to result from an important lack of convergence in model runs.