Peak ring formation at Chicxulub: Unraveling its deformation path and rock mechanical behavior

希克苏鲁伯峰环的形成：揭示其变形路径和岩石力学行为

• 批准号: 387883313
• 负责人: Professor Dr. Thomas Kenkmann
• 金额: --
• 依托单位: Lehrstuhl Allgemeine Geologie
• 依托单位国家: 德国
• 项目类别: Infrastructure Priority Programmes
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/387883313?language=en
• 关键词: Peak; ring; formation; Chicxulub; Unraveling

The 200-km diameter Chicxulub impact crater in Yucatán, Mexico, was drilled and cored within the framework of IODP-ICDP Expedition 364 Chicxulub: Drilling the K-Pg Impact Crater. This drilling has for the first time targeted a peak ring, which is a mountainous ring found in large complex impact craters that rises above the crater floor topography and is internal to the crater rim. This proposal is focused on addressing two major questions posed within the framework of Expedition 364: 1) What is the nature and formational mechanism of peak rings? 2) How are rocks weakened during large impacts to allow them to collapse and form relatively wide, flat craters? Regarding the first question, there are two competing peak ring formation models: i) A conceptual geological model based on geological and remote sensing observations of peak rings on the moon and other planetary bodies that emphasize the role of a large amount of impact melt for the peak ring formation, and ii) a numerical model which uses hydrocode simulations to compute the formation process. The two models predict distinctly different kinematic paths and structural deformational features in the peak rings, which a preliminary survey shows are inherent in the deformed Expedition 364 drill cores. We will analyze the cores using quantitative micro- and macro-structural methods to unravel the deformational history of the peak ring, and thus yield ground-truth data to prove or disprove the formation models.The second question addresses the long-standing issue of considerable temporal strength reduction of the target that is required for crater formation and remains an enduring problem in cratering mechanics. Three models have been proposed as weakening mechanisms: 1) acoustic fluidization, which assumes seismic vibrations to reduce friction, 2) thermal softening, which postulates shock heating and plastic deformation, and 3) strain rate weakening/frictional melting, where e.g. localized melts are proposed to locally reduce friction. The drill core allow us to assess the relevance of the three models, and we will investigate the cores to distinguish between the weakening mechanisms based on specific microstructural indicators. Moreover, the strength degradation by impact damaging will be measured by means of rock mechanical testing. In addition, we will also evaluate the significance of rate dependent brittle deformation leading to rock pulverization as a process that influences rock strength.Our macro-and microstructural analyses will be combined to a form kinematic model for Chicxulub's peak ring, and will thus contribute to a deeper understanding of the formation of peak rings in the Solar system. This will help to improve the interpretation of remote sensing studies on large impact craters on other planetary bodies, and can potentially help to understand details of the processes that occurred during the K-Pg mass extinction event caused by the Chicxulub impact.

墨西哥尤卡坦州直径 200 公里的希克苏鲁伯陨石坑是在 IODP-ICDP 第 364 次希克苏鲁伯探险队的框架内进行钻探和取芯的：钻探 K-Pg 陨石坑 该钻探首次针对峰环，即在大型复杂撞击坑中发现的山环，高于陨石坑底部地形，位于陨石坑边缘内部。该提案的重点是解决两个主要问题。探险364框架内提出的问题： 1）峰环的自然和形成机制是什么？ 2）岩石在大的撞击过程中如何被削弱，从而使其塌陷并形成相对宽阔、平坦的陨石坑？是两个相互竞争的峰环形成模型：i）基于对月球和其他行星体峰环的地质和遥感观测的概念地质模型，强调大量撞击融化对峰环形成的作用，以及ii ) 一个数值该模型使用水力编码模拟来计算形成过程，这两个模型预测了峰环中明显不同的运动路径和结构变形特征，初步调查显示这是变形的 Expedition 364 钻芯所固有的，我们将使用定量分析岩芯。微观和宏观结构方法来揭示峰环的变形历史，从而产生地面实况数据来证明或反驳地层模型。第二个问题解决了长期存在的相当大的时间问题弹坑形成所需的目标强度降低仍然是弹坑力学中的一个持久问题，已提出三种模型作为弱化机制：1）声流化，假设地震振动可以减少摩擦，2）热软化，假设冲击。加热和塑性变形，以及 3) 应变率弱化/摩擦熔化，例如，提出局部熔化以局部减少摩擦。钻芯使我们能够评估这三个模型的相关性。我们将研究岩心，以根据特定的微观结构指标区分弱化机制。此外，我们还将通过岩石力学测试来测量冲击损伤造成的强度下降。此外，我们还将评估导致脆性变形的速率相关的重要性。岩石粉碎是影响岩石强度的过程。我们的宏观和微观结构分析将结合起来形成希克苏鲁伯峰环的运动学模型，从而有助于更深入地了解太阳峰环的形成这将有助于改进对其他行星体上大型撞击坑的遥感研究的解释，并可能有助于了解希克苏鲁伯撞击引起的K-Pg大规模灭绝事件期间发生的过程的细节。