Kinematics of peak-ring rock deformation during cratering

揭示大撞击坑和峰环形成过程中目标岩石变形的机制和运动学是IODP/ICDP 364考察队“钻探K-Pg撞击坑”的主要构造地质目标。在之前的项目中研究了变形机制，而本项目侧重于火山口形成过程中的变形运动学，特别是从声流化到固体变形的转变。该项目的最终目标将是重建陨石坑和峰环形成各个阶段的目标岩石旋转。这将通过识别应变分量来完成，特别是主应变轴的方向和在弹坑过程中连续形成的变形结构的剪切应变。构造为冲击诱发的微结构、平面碎裂岩和超碎裂岩带以及剪切断裂。对于后者，对M0077钻孔岩心602条前所未有的剪切断层及其相关滑动线的反演将提供有关陨石坑最新阶段变形非均质性的信息。碎裂岩和超碎裂岩带的运动学将通过使用SAGA GIS软件进行定量2D图像分析，并通过x射线计算机微断层扫描进行高分辨率3D体积成像。

Unravelling the mechanisms and kinematics of target rock deformation during large-impact cratering and peak-ring formation constitute the prime structural geological objectives of IODP/ICDP Expedition 364 “Drilling the K-Pg Impact Crater”.While deformation mechanisms were investigated in the previous project, the present project focuses on the kinematics of deformation during crater formation and in particular on the transition from acoustic fluidization to solid deformation. The ultimate goal of the project will be to reconstruct target rock rotation during individual stages of crater and peak-ring formation. This will be accomplished by identifying strain components, notably the orientations of principal strain axes and shear strains of deformation structures that formed consecutively during cratering. The structures are shock-induced microstructures, planar cataclasite and ultracataclasite zones, and shear faults. As to the latter, inversion of an unprecedented set of 602 shear faults and associated slip lineations of drill core M0077 will provide information on the heterogeneity of deformation during the latest stage of cratering. The kinematics of cataclasite and ultracataclasite zones will be examined by quantitative 2D image analysis using the software SAGA GIS and high-resolution 3D volumetric imaging through X-ray-computed microtomography.