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.

在墨西哥尤卡坦（Yucatán）的200公里直径Chicxulub撞击火山口是在IODP-ICDP Expedition 364 Chicxulub的框架内钻孔并核心的：钻k-pg撞击火山口。这种钻孔首次针对峰环，这是一个在大型复杂撞击火山口上发现的山环，它升高到火山口地形地形上方，并且是火山口边缘的内部。该提案的重点是解决在探险框架内假定的两个主要问题364：1）峰环的性质和形成机制是什么？ 2）在大撞击过程中，岩石如何减弱以使它们塌陷并形成相对较宽的平坦陨石坑？关于第一个问题，有两个相互竞争的峰环形成模型：i）基于月球和其他行星体上峰环的地质和遥感观察的概念地质模型，该模型强调了大量影响峰值形成的影响熔体的作用，以及II）使用氢化模型来计算氢化模型来计算形成过程。这两个模型预测了峰环中明显不同的运动学路径和结构变形特征，初步调查显示，变形探险364钻芯是固有的。我们将使用定量的微观和宏观结构方法分析核心，以阐明峰环的变形历史，从而产生地面真实数据，以证明或反驳地层模型。第二个问题解决了长期存在的临时问题，即临时降低针对轨道口和持久性问题所需的目标的临时强度。已经提出了三种模型作为弱化的机制：1）声流化，该声流化假设地震振动以减少摩擦，2）热软化，这会假设休克加热和塑性变形，3）应变速率弱/摩擦融化，例如。提出了局部熔体以局部减少摩擦。钻头使我们能够评估这三个模型的相关性，我们将研究核心，以区分基于特定微观结构指标的弱机制。此外，将通过岩石机械测试来测量撞击损伤的强度降解。此外，我们还将评估依赖性脆性变形的重要性，从而导致岩石粉碎作为影响岩石强度的过程。我们的宏观和微观结构分析将合并为Chicxulub峰环的形式运动模型，因此将有助于对太阳能系统中峰环形成的更深入了解。这将有助于改善对其他行星机构大型影响陨石坑的远程敏感性研究的解释，并有可能有助于了解Chicxulub撞击引起的K-PG质量扩展事件中发生的过程的细节。