Extraordinary rocks from the peak ring of the Chicxulub impact crater: P-wave velocity, density, and porosity measurements from IODP/ICDP Expedition 364
Extraordinary rocks from the peak ring of the Chicxulub impact crater: P-wave velocity, density, and porosity measurements from IODP/ICDP Expedition 364
复制标题
DOI：
10.1016/j.epsl.2018.05.013
复制
发表时间：
2018-08-01
影响因子：
5.3
通讯作者：
Yamaguchi, K. E.
中科院分区：
文献类型：
--
作者：
Christeson, G. L.;Gulick, S. P. S.;Yamaguchi, K. E.
联合国际海洋发现计划和国际大陆科学钻探计划第364远征队钻到了希克苏鲁伯陨石坑的峰环。我们展示了M0077A孔的纵波速度、密度和孔隙度测量结果，揭示了峰环岩石的不同寻常的物理性质。在撞击后沉积岩和浮岩（含撞击熔体角砾岩）之间的边界，我们测量到速度和密度急剧下降，孔隙度增加。苏威石的速度值为2900 ~ 3700 m/s，密度值为2.06 ~ 2.37 g/cm(3)，孔隙度值为20 ~ 35%。软岩下薄层（25 m）冲击熔融岩单元的速度测量值为3650-4350 m/s，密度测量值为2.26-2.37 g/cm(3)，孔隙度测量值为19-22%。我们将速溶岩和冲击熔融岩的低速度、低密度和高孔隙度与快速侵位、热液蚀变产物以及孔隙空间、孔洞和囊泡的观察联系起来。隆起的花岗岩峰环物质的速度、密度和孔隙度分别为4000 ~ 4200 m/s、2.39 ~ 2.44 g/cm(3)和8 ~ 13%；这些数值明显不同于典型的未蚀变花岗岩，后者具有更高的速度和密度，以及更低的孔隙度。M0077A井峰环速度、密度和孔隙度的大部分测量结果表明，岩石受到了相当大的破坏，这与峰环形成的数值模型预测相一致，峰环内的岩性代表了撞击盆地中一些最受冲击和破坏的岩石。我们将我们的结果与以前的地震数据集结合起来，绘制了井眼附近的岩石图。我们在环槽、峰环和盆地中央的古近系沉积岩下方绘制了苏威石图，这表明，在撞击后，苏威石覆盖了整个撞击盆地。峰环顶部的细砾石厚度为100 ~ 165 m，而盆地中部的细砾石厚度为200 m，说明在峰环形成期间及之后，细砾石从崩塌的中央隆起向下坡流动，并优先在盆地中部聚集。(C) 2018 Elsevier B.V.版权所有
Joint International Ocean Discovery Program and International Continental Scientific Drilling Program Expedition 364 drilled into the peak ring of the Chicxulub impact crater. We present P-wave velocity, density, and porosity measurements from Hole M0077A that reveal unusual physical properties of the peak-ring rocks. Across the boundary between post-impact sedimentary rock and suevite (impact melt bearing breccia) we measure a sharp decrease in velocity and density, and an increase in porosity. Velocity, density, and porosity values for the suevite are 2900-3700 m/s, 2.06-2.37 g/cm(3), and 20-35%, respectively. The thin (25 m) impact melt rock unit below the suevite has velocity measurements of 3650-4350 m/s, density measurements of 2.26-2.37 g/cm(3), and porosity measurements of 19-22%. We associate the low velocity, low density, and high porosity of suevite and impact melt rock with rapid emplacement, hydrothermal alteration products, and observations of pore space, vugs, and vesicles. The uplifted granitic peak ring materials have values of 4000-4200 m/s, 2.39-2.44 g/cm(3), and 8-13% for velocity, density, and porosity, respectively; these values differ significantly from typical unaltered granite which has higher velocity and density, and lower porosity. The majority of Hole M0077A peak-ring velocity, density, and porosity measurements indicate considerable rock damage, and are consistent with numerical model predictions for peak-ring formation where the lithologies present within the peak ring represent some of the most shocked and damaged rocks in an impact basin. We integrate our results with previous seismic datasets to map the suevite near the borehole. We map suevite below the Paleogene sedimentary rock in the annular trough, on the peak ring, and in the central basin, implying that, post impact, suevite covered the entire floor of the impact basin. Suevite thickness is 100-165 m on the top of the peak ring but 200 m in the central basin, suggesting that suevite flowed downslope from the collapsing central uplift during and after peak-ring formation, accumulating preferentially within the central basin. (C) 2018 Elsevier B.V. All rights reserved.