Texture development in naturally compacted and experimentally deformed silty clay sediments from the Nankai Trench and Forearc, Japan
Texture development in naturally compacted and experimentally deformed silty clay sediments from the Nankai Trench and Forearc, Japan
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DOI：
10.1016/j.tecto.2014.08.005
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发表时间：
2014-12
期刊：
影响因子：
2.9
通讯作者：
K. Schumann;M. Stipp;B. Leiss;J. Behrmann
中科院分区：
文献类型：
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作者：
K. Schumann;M. Stipp;B. Leiss;J. Behrmann
细粒海洋沉积物的岩石物理性质在很大程度上取决于微观结构和晶体择优取向（CPO）。在这篇文章中，我们表明基于 Rietveld 的同步加速器纹理分析是一种新的有价值的工具，可以量化水饱和的细粒富含页硅酸盐沉积物的纹理，并评估压实和构造变形的影响。我们研究了来自南海增生棱镜斜坡和日本西南近海菲律宾海板块的成分几乎均质的粉质粘土钻芯样品的 CPO。页硅酸盐的底面显示出层理平行排列随着钻孔深度的增加而增加，从而反映了渐进的埋藏和压实。在一些样品中，方解石和钠长石由于晶体学控制的非等距晶粒形状或超微化石测试而显示出 CPO。来自棱柱坡度的一组十三个样品的固结不排水实验变形表明，页硅酸盐和方解石基面的 CPO 垂直于实验缩短轴发展。 CPO 强度和应变大小之间至少存在定性关系。扫描电子显微照片显示微孔和碎屑伊利石片垂直于轴向缩短的优选方向同时演化。这表明微织物是敏感的应变计，并与 CPO 一起产生各向异性物理特性。
The petrophysical properties of fine-grained marine sediments to a large extent depend on the microstructure and crystallographic preferred orientations (CPOs). In this contribution we show that Rietveld-based synchrotron texture analysis is a new and valuable tool to quantify textures of water-saturated fine-grained phyllosilicate-rich sediments, and assess the effects of compaction and tectonic deformation. We studied the CPO of compositionally almost homogeneous silty clay drillcore samples from the Nankai Accretionary Prism slope and the incoming Philippine Sea plate, offshore SW Japan. Basal planes of phyllosilicates show bedding-parallel alignment increasing with drillhole depth, thus reflecting progressive burial and compaction. In some samples calcite and albite display a CPO due to crystallographically controlled non-isometric grain shapes, or nannofossil tests. Consolidated-undrained experimental deformation of a suite of thirteen samples from the prism slope shows that the CPOs of phyllosilicate and calcite basal planes develop normal to the experimental shortening axis. There is at least a qualitative relation between CPO intensity and strain magnitude. Scanning electron micrographs show concurrent evolution of preferred orientations of micropores and detrital illite flakes normal to axial shortening. This indicates that the microfabrics are sensitive strain gauges, and contribute to anisotropic physical properties along with the CPO.