What can trigger destabilizing of Atlantic passive margins?

尽管人们一直在努力了解俯冲开始的过程，但新的俯冲带是如何、在何处以及何时形成的，仍然是一个谜。一些位置，如洋内转换断层/破裂带、已灭绝的洋中脊和被动边缘，被认为可能是新的俯冲带可能开始的位置。地质观测证实，在一些建议的位置发生了俯冲。然而，由于缺乏新生代的例子，使得沿被动边缘的俯冲起始更具争议性，尽管这一概念继续被广泛传播。被动边缘被广泛接受为海沟形成的有利地点，是因为它们在威尔逊旋回中发挥了关键作用，威尔森旋回解释了地质时期海洋盆地的反复开合。在威尔逊周期的最后阶段，被动保证金转化为主动保证金是至关重要的。以前的大多数模拟研究都没有成功地用真实的参数模拟旧被动边缘向俯冲带的转变。在这里，我们的目标是通过解决以下问题来促进这一重要的地球科学问题的进展：—在什么条件下，与被动大陆边缘相邻的旧海洋岩石圈可以自发塌陷并开始俯冲？—如果不可能发生自发俯冲，那么与过去和现在的俯冲带相关的地幔流能否将被动大陆边缘转变为俯冲带？根据我们对前两个问题的回答，在不久的将来是否有任何现代被动边缘可能转变为俯冲带？我们将通过使用复杂的三维数值模型来回答这些问题。目的是建立具有现实参数和假设的模型。我们相信，回答上述问题将是理解俯冲带如何沿着旧被动边缘开始的一大步，这是地球科学中最模棱两可的问题之一。

Despite continued efforts to understand subduction initiation processes it is still enigmatic how, where and when new subduction zones form. Some localities such as intra-oceanic transform faults/fracture zones, extinct mid-oceanic ridges and passive margins have been proposed as likely sites where new subduction zones are likely to begin. Geological observations confirm subduction initiation along some of the proposed locations. However, lack of Cenozoic examples makes subduction initiation along passive margins more controversial, even though the concept continues to be widely promulgated. The broad acceptance of passive margins as favourable site for trench formation comes from the key role that they play in Wilson cycle, which explains the repeated opening and closing of ocean basins in geological time. The conversion of a passive margin into an active one is vital in the closing phase of the Wilson cycle. Most previous modelling studies have not succeeded in simulating conversion of an old passive margin into a subduction zone with realistic parameters. Here we aim to contribute to progress on this important geo-scientific problem by addressing the following questions:- What are the conditions under which an old oceanic lithosphere adjacent to a passive continental margin can spontaneously collapse and begin to subduct?- If spontaneous subduction initiation is impossible, can mantle flow associated with past and present subduction zones convert a passive continental margin into a subduction zone? - Given our answers to the first two questions, are any modern passive margins likely to convert into subduction zones in the near future?We will answer these questions by using sophisticated 3d numerical models. The aim is to construct models with realistic parameters and assumptions. We believe that answering the above questions will be a big step forward in understanding how subduction zones might begin along old passive margins, which is one of the most ambiguous issues in geosciences.