Mechanisms of target-rock deformation during peak-ring formation

大型陆地撞击结构的火山口底部，也称为撞击盆地，大部分是平坦的，被两个或更多的形态环分割。最里面的环，也就是所谓的峰环的形成，以及目标岩石弱化导致平坦陨石坑底部的原因仍然未知。解开这些机制是第364次考察钻探K-Pg撞击坑的主要结构地质目标，这项建议使用墨西哥的希克苏鲁布撞击结构作为行星撞击盆地形成的陆地模拟物。具体而言，将从以下方面分析岩芯：（1）撞击引起的变形机制;（2）变形的运动学;（3）成坑期间目标岩石的弱化;（4）火山口底部地壳长期松弛的结构证据。这将通过微组构分析来完成，该分析使用内部工作流程、电子显微探针分析、电视数据和通过X射线计算机显微断层扫描进行的高分辨率3D体积成像进行定量图像分析。结构数据将与来自加拿大萨德伯里撞击结构的等效数据进行比较，以便将从远征364号岩芯获得的一维结构信息与类地行星上大型撞击坑的更全面结构框架联系起来。

Crater floors of large terrestrial impact structures, also known as impact basins, are largely flat and dissected by two or more morphological rings. The formation of the innermost ring, the so-called peak ring, and causes of target rock weakening leading to flat crater floors are still unknown. Unravelling these mechanisms are the prime structural geological objectives of Expedition 364 Drilling the K-Pg Impact Crater and this proposal using the Chicxulub impact structure, Mexico, as a terrestrial analogue for the formation of planetary impact basins. Specifically, drill core will be analysed in terms of (1) impact-induced deformation mechanisms, (2) kinematics of deformation, (3) weakening of target rock during cratering and (4) structural evidence of long-term relaxation of crust underlying the crater floor. This will be accomplished by microfabric analysis applying quantitative image analysis using an in-house work flow, electron microprobe analysis, televiewer data and high-resolution 3D volumetric imaging by means of X-ray-computed microtomography. The structural data will be compared to equivalent data from the Sudbury impact structure, Canada, to relate the 1D structural information gained from Expedition 364 drill core to a more comprehensive structural framework of large impact cratering on terrestrial planets.