Impact‐Induced Porosity and Microfracturing at the Chicxulub Impact Structure
Impact‐Induced Porosity and Microfracturing at the Chicxulub Impact Structure
复制标题
希克苏鲁伯冲击结构的冲击诱发孔隙度和微裂缝
DOI：
10.1029/2019je005929
复制
发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Riller, Ulrich
中科院分区：
文献类型：
--
作者：
Rae, Auriol S. P.;Collins, Gareth S.;Morgan, Joanna V.;Salge, Tobias;Christeson, Gail L.;Leung, Jody;Lofi, Johanna;Gulick, Sean P. S.;Poelchau, Michael;Riller, Ulrich
孔隙度及其在撞击坑中的分布对冲击岩的岩石物理性质有重要影响：地震波速和反射率、岩石渗透率、强度和密度。这些特性对于识别潜在的陨石坑以及了解陨石坑形成的过程和后果很重要。国际海洋发现计划和国际大陆科学钻探计划探险364联合计划最近钻探的希克苏鲁布撞击结构提供了一个独特的机会，可以将撞击岩的直接观测与地球物理观测和模型进行比较。在这里，我们结合了小尺度的岩石学和岩石物理测量，以及大尺度的地球物理测量和希克苏鲁布撞击结构的数值模拟。我们的目标是评估Chixulub峰环内异常高的孔隙率的原因，以及数值撞击模拟预测重力特征以及陨石坑内孔隙度的分布和结构的能力。我们发现，奇克苏鲁布峰环内的高孔隙率主要是由冲击诱导的微破裂引起的。这些裂缝具有较好的取向，可以通过考虑冲击期间主应力的取向和峰环形成期间的后续变形来预测。结果表明，数值撞击模拟实现了峰环形成的动态坍塌模型，可以准确地预测大型陨石坑中撞击引起的微裂缝的分布和方向，这对撞击结构的地球物理特征起着重要的作用。
Porosity and its distribution in impact craters has an important effect on the petrophysical properties of impactites: seismic wave speeds and reflectivity, rock permeability, strength, and density. These properties are important for the identification of potential craters and the understanding of the process and consequences of cratering. The Chicxulub impact structure, recently drilled by the joint International Ocean Discovery Program and International Continental scientific Drilling Program Expedition 364, provides a unique opportunity to compare direct observations of impactites with geophysical observations and models. Here, we combine small‐scale petrographic and petrophysical measurements with larger‐scale geophysical measurements and numerical simulations of the Chicxulub impact structure. Our aim is to assess the cause of unusually high porosities within the Chicxulub peak ring and the capability of numerical impact simulations to predict the gravity signature and the distribution and texture of porosity within craters. We show that high porosities within the Chicxulub peak ring are primarily caused by shock‐induced microfracturing. These fractures have preferred orientations, which can be predicted by considering the orientations of principal stresses during shock, and subsequent deformation during peak ring formation. Our results demonstrate that numerical impact simulations, implementing the Dynamic Collapse Model of peak ring formation, can accurately predict the distribution and orientation of impact‐induced microfractures in large craters, which plays an important role in the geophysical signature of impact structures.