Formation and collapse of ejecta plumes from large meteorite impact - a case study at the Ries crater, Germany

大型陨石撞击导致的喷射物羽流的形成和崩溃——以德国里斯陨石坑为例

• 批准号: 35635560
• 负责人: Professor Dr. Wolf Uwe Reimold
• 金额: --
• 依托单位: Museum für Naturkunde - Leibniz-Institut für Evolutions- und Biodiversitätsforschung (MfN)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2007
• 资助国家: 德国
• 起止时间: 2006-12-31 至 2011-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/35635560?language=en
• 关键词: Formation; collapse; ejecta; plumes; large

This project aims at obtaining better understanding of the enigmatic and extremely dynamic processes related to formation of impact breccias within the evolving impact crater and vapour plume, and their mode(s) of distribution within and outside of the crater. An innovative two-prong investigative approach has been chosen. This comprises comprehensive and comparative petrographic (including textural) analysis of impact breccias drilled along a profile from the interior to the exterior of the Ries impact structure, as well as numerical modeling which allows to trace movement of material from the original target stratigraphy to its final place of deposition. Significant progress has been made with collection of modal, grain size, particle shape and orientation data, and mineralogical composition and textural observations from the groundmass of suevite, on samples from the FBN 1973, Enkingen, Otting and Wörnitzostheim drill cores. Numerical modeling has so far indicated that the amount of impact melt observed in crater suevite and surroundings of the structure does not satisfy the modeled melt volume. Also, the traditional hypothesis that suevitic impact breccias develop by fallout from an impact vapor plume can not be confirmed with our modeling results. Within-crater processes, such as ground-surge along the crater floor, thus attains enhanced significance. A further outcome of our modeling is that an extensive melt pool must develop within the crater interior. As this is not consistent with geophysical and drilling observations, a new approach to solve this problem is required. We apply for a 1-year extension of this project in order to complete petrographic-textural data acquisition as a prerequisite for data synthesis, and to develop a numerical model for post-impact mass transfer caused by phreato-magmatic type of explosions and related deposition of suevite inside and outside of the crater.

该项目旨在更好地了解与不断变化的撞击坑和蒸气羽流中的撞击角砾岩形成相关的神秘且极其动态的过程，以及它们在撞击坑内外的分布模式，这是一项创新的双管齐下的调查。这包括对沿着里斯冲击结构内部到外部的剖面钻探的冲击角砾岩进行全面和比较的岩相（包括结构）分析，以及允许通过收集模态、晶粒尺寸、颗粒形状和方向数据，以及对来自铁钙石基质的矿物学成分和结构观察，追踪材料从原始目标地层到最终沉积地点的移动已经取得了重大进展。 FBN 1973、Enkingen、Otting 和 Wörnitzostheim 钻芯迄今为止的数值模拟表明，在陨石坑和结构周围观察到的冲击熔化量不满足要求。此外，我们的模拟结果无法证实砂砾岩撞击角砾岩是由撞击蒸气羽流的沉降物形成的传统假设。陨石坑内的过程，例如沿陨石坑底部的地面涌动，因此具有更大的意义。我们的模型的进一步结果是，陨石坑内部必须形成一个广泛的熔池，因为这与地球物理和钻探观测结果不一致，我们需要一种新的方法来解决这个问题。这个项目为了完成岩相-结构数据采集作为数据合成的先决条件，并开发由岩浆型爆炸引起的撞击后质量传递以及陨石坑内外相关的铁钙石沉积的数值模型。