What can trigger destabilizing of Atlantic passive margins?

尽管人们一直在努力了解俯冲的启动过程，但新的俯冲带是如何形成的，何时何地形成，仍然是个谜。一些地方，如大洋内转换断层/断裂带、灭绝的大洋中脊和被动边缘，被认为可能是新俯冲带可能开始的地点。地质观测证实了沿着一些拟议位置的俯冲启动。然而，缺乏新生代的例子使得沿着被动边缘的俯冲开始更具争议，尽管这一概念继续被广泛传播。被动边缘被广泛认为是海沟形成的有利位置，这是因为它们在威尔逊旋回中所起的关键作用，这解释了地质时代洋盆的反复打开和关闭。在威尔逊周期的结束阶段，被动边际向主动边际的转换至关重要。大多数以前的模拟研究都没有成功地用真实的参数模拟旧的被动边缘到俯冲带的转换。在这里，我们的目标是通过解决以下问题来为这一重要的地球科学问题的进展做出贡献：-在什么条件下，毗邻被动大陆边缘的旧海洋岩石圈可以自发坍塌并开始俯冲？-如果不可能自发俯冲启动，与过去和现在俯冲带相关的地幔流动能否将被动大陆边缘转变为俯冲带？-给出前两个问题的答案，现代被动边缘是否有可能在不久的将来转变为俯冲带？我们将使用复杂的3D数值模型来回答这些问题。其目的是构建具有现实参数和假设的模型。我们认为，回答上述问题将是理解俯冲带如何沿着旧的被动边缘开始的一大步，这是地球科学中最模糊的问题之一。

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.