Projectile-target interaction, melting and vaporization in hypervelocity experiments and natural impactites

确定陨石抛射物质是化学痕迹或物理残留物是评估过去与地面撞击记录有关的撞击者群体的唯一途径。在梅明研究小组的框架内，这一分项目的目的是更好地了解在撞击事件期间控制射弹命运和陨石示踪元素分馏的参数。这将通过结合(I)特征良好的钢和玄武岩抛射体，以及砂岩、石英岩和碳酸盐为目标的超高速实验，(Ii)用时间分辨高速光谱仪追踪非常早期的喷发阶段，(Iii)对来自瓦巴尔、卡米勒和流星雨陨石坑的选定天然撞击岩进行研究，(Iv)激光熔化实验，以及(V)化学模拟。在MEMINI过程中，我们从超高速陨石坑实验收集的喷射物中证明了在弹丸与目标熔体相互作用过程中，陨石示踪元素之间发生了强烈的分馏。该项目包括新的实验参数，如新的目标和弹丸材料，斜撞击，以及研究撞击非常早期阶段的新探测技术。我们将研究碳酸盐解离和靶熔化对弹丸命运的影响。玄武岩弹丸在本质上将作为软骨质弹和非软骨质弹的类似物。利用激光熔化实验分别对靶材和弹丸材料的非均质高温熔化过程进行了约束。弹丸和目标材料的汽化发生在撞击的非常早期阶段，包括喷射阶段。喷射材料的成分和温度将通过高速光谱仪进行测量。使用高灵敏度和高分辨率分析工具(LA-ICPMS、EMP、TEM、INAA)进行的尸检分析集中在高度震惊的喷出物质上，这些物质在梅敏I号中被发现含有抛射体熔体和可能的凝析物。对自然撞击物的研究，目前还没有高空间分辨率的研究，主要集中在我们的实验结果与自然的可比性上。用LA-ICPMS分析天然冲击岩中&gt；50μm铁质陨石熔体中的铂族元素是本项目的一个主要问题。这对于理解与撞击相关的PGE分馏很重要，PGE通常用于识别陆地陨石坑中的抛射物。最后，将对金属-硅酸盐体系进行化学模拟，以更好地限制温度和熔体组成对在实验和自然中观察到的陨石示踪元素分配的影响。

Identification of meteoritic projectile matter as either chemical trace or physical remnant is the only way to assess the past impactor population related to the terrestrial impact record. In the frame of the MEMIN research group this subproject is aimed to reach a better understanding of the parameters that control the fate of projectile and fractionation of meteoritic tracer elements during impact events. This will be achieved by combining (i) hypervelocity experiments with well characterized steel and basaltic projectiles, and sandstone, quartzite, and carbonates as target, (ii) tracing of the very early ejecta stage by time-resolved high-speed spectrometry, (iii) studies on selected natural impactites from the Wabar, Kamil, and Meteor craters, (iv) laser melting experiments, and (v) chemical modelling. In the course of MEMIN I, we were able to demonstrate in ejecta collected from hypervelocity cratering experiment that strong fractionation among meteoritic tracer elements occurs during interaction of projectile and target melts. This project of MEMIN II includes new experimental parameters, such as new target and projectile materials, oblique impact, and new detection techniques to investigate the very early stages of impact. We will study effects of carbonate dissociation, and target melting on the fate of the projectile. Basaltic projectiles will serve as analogue for chondritic and achondritic projectiles in nature. Laser melting experiments are used to constrain the processes of heterogeneous high-temperature melting of target and projectile materials separately. Vaporization of projectile and target material occurs during the very early stages of impact including the jetting stage. The composition and temperature of jetted material will be measured via high-speed spectrometry. The post-mortem analyses using high-sensitive and high resolution analytical tools (LA-ICP-MS, EMP, TEM, INAA) is concentrated to highly shocked ejecta material that turned out in MEMIN I to contain projectile melts and probably condensates. The study of the natural impactites, which has not been done so far with high spatial resolution, is focussed on the comparability of our experimental results to nature. The analysis of platinum group elements (PGE) in >50μm iron-meteoritic melt spheres in the natural impactites by LA ICP MS is a major issue in this project. This is important to understand impact-related fractionation of PGE, which are commonly used to identify the projectile in terrestrial craters. Last not least chemical modelling of the metal-silicate system will be performed to better constrain the effects of temperature and melt composition on the partitioning of the meteoritic tracer elements observed in both, experiments and nature.