The first MEMIN shock recovery experiments at low shock pressure (5–12.5 GPa) with dry, porous sandstone
The first MEMIN shock recovery experiments at low shock pressure (5–12.5 GPa) with dry, porous sandstone
复制标题
首次在低冲击压力 (5–12.5 GPa) 下使用干燥多孔砂岩进行 MEMIN 冲击恢复实验
DOI：
10.1111/maps.12030
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发表时间：
2013
影响因子：
2.2
通讯作者：
U. Hornemann
中科院分区：
文献类型：
--
作者：
A. Kowitz;R. Schmitt;W. Uwe Reimold;U. Hornemann
摘要：作为 MEMIN 研究计划的一部分，该项目的重点是在 5 至 12.5 GPa 的低冲击压力范围内，在干燥、多孔 Seeberger 砂岩中实验产生冲击变形。特别关注孔隙度对渐进激变质作用的影响。冲击恢复实验是使用产生平面冲击波的高爆炸装置并使用冲击阻抗法进行的。平均粒度为 0.17mm、孔隙率为约 19 vol%、含有约 96 wt% SiO2 的砂岩柱体发生冲击变形。随着冲击压力增加而引起的冲击效应包括： (1) 在 5 GPa 时，整个孔隙空间已经封闭；石英颗粒显示出波动性消光。平均每毫米观察到 134 条裂缝。该砂岩的蒙脱石层状硅酸盐成分的暗色泡状熔体（玻璃）的平均含量为 1.6 vol%。 (2) 在7.5GPa压力下，石英颗粒表现出较弱但显着的镶嵌现象，裂缝数量增加至每毫米171条。可以观察到另外两种熔体，均基于页硅酸盐前体：浅色、多孔熔体和含有大铁颗粒的熔体。本实验中熔体总量（所有类型）增加至 2.4 vol%。拉曼光谱证实了表面附近存在冲击变形的石英颗粒。 (3)在10和12.5GPa压力下，石英颗粒也表现出较弱但显着的镶嵌现象，每毫米裂缝数已达到约200条的平台值，不同熔体类型的总量增加至4.8vol%。在受影响的表面附近可以局部观察到介电石英玻璃。此外，局部冲击效应（很可能是由砂岩-容器界面处的多次冲击波反射引起）发生在整个样品圆柱体中，包括局部增强的 PDF 形成，以及与碎裂微角砾岩、介电石英玻璃和 SiO2 熔体相关的剪切带。这些初步实验的总体结果表明，用于确认冲击结构并适合冲击压力校准的特征冲击效应诊断很少见。到目前为止，它们仅限于在 10GPa 及以上的冲击压力下有限形成 PDF 和介电石英玻璃。
Abstract– As part of the MEMIN research program this project is focused on shock deformation experimentally generated in dry, porous Seeberger sandstone in the low shock pressure range from 5 to 12.5 GPa. Special attention is paid to the influence of porosity on progressive shock metamorphism. Shock recovery experiments were carried out with a high‐explosive set‐up that generates a planar shock wave, and using the shock impedance method. Cylinders of sandstone of average grain size of 0.17 mm and porosity of about 19 vol%, and containing some 96 wt% SiO2, were shock deformed. Shock effects induced with increasing shock pressure include: (1) Already at 5 GPa the entire pore space is closed; quartz grains show undulatory extinction. On average, 134 fractures per mm are observed. Dark vesicular melt (glass) of the composition of the montmorillonitic phyllosilicate component of this sandstone occurs at an average amount of 1.6 vol%. (2) At 7.5 GPa, quartz grains show weak but prominent mosaicism and the number of fractures increases to 171 per millimeter. Two additional kinds of melt, both based on phyllosilicate precursor, could be observed: a light colored, vesicular melt and a melt containing large iron particles. The total amount of melt (all types) increased in this experiment to 2.4 vol%. Raman spectroscopy confirmed the presence of shock‐deformed quartz grains near the surface. (3) At 10 and 12.5 GPa, quartz grains also show weak but prominent mosaicism, the number of fractures per mm has reached a plateau value of approximately 200, and the total amount of the different melt types has increased to 4.8 vol%. Diaplectic quartz glass could be observed locally near the impacted surface. In addition, local shock effects, most likely caused by multiple shock wave reflections at sandstone‐container interfaces, occur throughout the sample cylinders and include locally enhanced formation of PDF, as well as shear zones associated with cataclastic microbreccia, diaplectic quartz glass, and SiO2 melt. Overall findings from these first experiments have demonstrated that characteristic shock effects diagnostic for the confirmation of impact structures and suitable for shock pressure calibration are rare. So far, they are restricted to the limited formation of PDF and diaplectic quartz glass at shock pressures of 10 GPa and above.