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.

该项目的目的是更好地了解在不断变化的撞击坑和蒸气羽流内形成撞击角砾岩的神秘和极其动态的过程，以及它们在撞击坑内外的分布模式。已选择了一种创新的双管齐下的调查办法。这包括全面和比较岩相学（包括纹理）分析的影响角砾岩钻沿着剖面从内部到外部的里斯影响结构，以及数字建模，允许跟踪运动的材料从原来的目标地层，其最终的沉积地点。在FBN 1973、Enkingen、Otting和Wörnitzostheim钻孔岩芯样品上，从苏埃维特基块收集模态、粒度、颗粒形状和取向数据，以及矿物组成和结构观察方面取得了重大进展。到目前为止，数值模拟表明，在火山口suevite和周围的结构观察到的冲击熔体的量不满足建模的熔体体积。此外，传统的假设，suevitic影响角砾岩的发展，从一个冲击蒸气羽沉降不能与我们的模拟结果证实。坑内的过程，例如沿着坑底的地面涌浪，因此获得了更大的意义。我们的建模的进一步结果是，一个广泛的熔池必须在陨石坑内部发展。由于这与地球物理和钻井观测不一致，因此需要一种新的方法来解决这个问题。我们申请将该项目延长一年，以完成作为数据合成先决条件的岩石学-纹理数据采集，并开发一个由潜水岩浆型爆炸和火山口内外苏埃维特相关沉积引起的撞击后质量转移的数值模型。