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

该项目旨在更好地了解与撞击坑内形成的撞击角砾岩和蒸汽羽流有关的神秘和极其动态的过程，以及它们在陨石坑内外的分布模式(S)。选择了一种创新的双管齐下的调查方法。这包括对沿着Ries撞击结构从内到外的剖面钻取的撞击角砾岩进行全面和比较的岩石学(包括结构)分析，以及允许追踪物质从原始目标地层到最终沉积地点的移动的数值模拟。对于FBN 1973、Enkingen、Oting和Wörnitzostheim钻芯的样品，在收集硫锌矿基质的模式、粒度、颗粒形状和取向数据以及矿物成分和结构观察方面取得了重大进展。到目前为止，数值模拟已经表明，在陨石坑和结构周围观察到的撞击熔融量不能满足所建模型的熔融量。此外，我们的模拟结果也不能证实传统的假设，即自生撞击角砾岩是由撞击蒸汽羽流产生的尘埃形成的。火山口内的过程，如沿火山口底部的地面涌浪，因此具有更重要的意义。我们建模的另一个结果是，陨石坑内部必须形成一个大范围的熔池。由于这与地球物理和钻井观测结果不一致，因此需要一种新的方法来解决这一问题。我们申请将这一项目延长一年，以完成岩相-结构数据采集作为数据合成的先决条件，并开发一个数值模型，用于研究陨石坑内外隐伏岩浆型爆炸和相关硫锌矿沉积引起的撞击后传质。

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.