Ocean resurge-induced impact melt dynamics on the peak-ring of the Chicxulub impact structure, Mexico
Ocean resurge-induced impact melt dynamics on the peak-ring of the Chicxulub impact structure, Mexico
复制标题
墨西哥希克苏鲁伯撞击结构峰环上海洋复苏引起的撞击融化动力学
DOI：
10.1007/s00531-021-02008-w
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发表时间：
2021
影响因子：
2.3
通讯作者：
Riller, Ulrich
中科院分区：
文献类型：
--
作者：
Schulte, Felix M.;Wittmann, Axel;Jung, Stefan;Morgan, Joanna V.;Gulick, Sean P.;Kring, David A.;Grieve, Richard A.;Osinski, Gordon R.;Riller, Ulrich
来自IODP/ICDP第364次考察的M0077孔岩心为在一次大型陨石撞击尤卡坦大陆架沃茨后，撞击熔融物与岩石碎片海水相互作用期间发生的物理过程提供了前所未有的证据。这种相互作用的证据是基于46.37米厚的冲击熔融岩序列的岩相学、显微结构和化学检查，该序列覆盖在希克苏鲁布冲击结构峰环的受冲击花岗岩类目标岩上。熔融岩序列由两个视觉上明显不同的相组成，一个是黑色，另一个是绿色。黑色相的成分是隐晶质和粗安岩，与撞击构造内其他地点的熔融岩石相似。绿色相主要由粘土矿物和亮晶方解石组成，可能是在热液条件下由固化的水-岩屑混合物形成的。我们认为，熔融岩序列的分层和内部结构是由一个单一的过程，即，最初过热的硅酸盐冲击熔体与海洋复苏引起的水-岩石混合物的剧烈接触覆盖了冲击熔体。在密度，温度，粘度和速度的差异，这种混合物和冲击熔体触发开尔文-亥姆霍兹和瑞利-泰勒不稳定性在其相边界。因此，在边界处的剪切扰动，因此，混合两个不混溶相，并伴随着phreatomagmatic过程。这些过程导致了冲击熔融岩序列顶部的角砾岩化。海水对该角砾岩的淬火阻止了随后沉积苏镁石时凝固角砾岩层的重新加工。固态变形，特别是在最上面的角砾化的冲击熔融岩层，证明了长期的重力沉降的峰值环。
Core from Hole M0077 from IODP/ICDP Expedition 364 provides unprecedented evidence for the physical processes in effect during the interaction of impact melt with rock-debris-laden seawater, following a large meteorite impact into waters of the Yucatán shelf. Evidence for this interaction is based on petrographic, microstructural and chemical examination of the 46.37-m-thick impact melt rock sequence, which overlies shocked granitoid target rock of the peak ring of the Chicxulub impact structure. The melt rock sequence consists of two visually distinct phases, one is black and the other is green in colour. The black phase is aphanitic and trachyandesitic in composition and similar to melt rock from other sites within the impact structure. The green phase consists chiefly of clay minerals and sparitic calcite, which likely formed from a solidified water–rock debris mixture under hydrothermal conditions. We suggest that the layering and internal structure of the melt rock sequence resulted from a single process, i.e., violent contact of initially superheated silicate impact melt with the ocean resurge-induced water–rock mixture overriding the impact melt. Differences in density, temperature, viscosity, and velocity of this mixture and impact melt triggered Kelvin–Helmholtz and Rayleigh–Taylor instabilities at their phase boundary. As a consequence, shearing at the boundary perturbed and, thus, mingled both immiscible phases, and was accompanied by phreatomagmatic processes. These processes led to the brecciation at the top of the impact melt rock sequence. Quenching of this breccia by the seawater prevented reworking of the solidified breccia layers upon subsequent deposition of suevite. Solid-state deformation, notably in the uppermost brecciated impact melt rock layers, attests to long-term gravitational settling of the peak ring.