Clay fabrics in SAFOD core samples
Clay fabrics in SAFOD core samples
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DOI：
10.1016/j.jsg.2012.07.004
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发表时间：
2012-10
影响因子：
3.1
通讯作者：
C. Janssen;W. Kanitpanyacharoen;H. Wenk;R. Wirth;L. Morales;E. Rybacki;M. Kienast;G. Dresen
中科院分区：
文献类型：
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作者：
C. Janssen;W. Kanitpanyacharoen;H. Wenk;R. Wirth;L. Morales;E. Rybacki;M. Kienast;G. Dresen
通过光学显微镜、扫描电子显微镜（SEM）、透射电子显微镜（TEM）和同步x射线衍射测量，我们分析了从圣安德烈亚斯断层观测站（SAFOD）主孔中获得的超碎屑/断层泥和碎裂岩心样品中的粘土微结构。分析揭示了在同步加速器x射线织物测量中观察到的弱粘土织物与光学显微镜记录的粘土颗粒的强优先排列程度之间的显着对比。透射电镜和扫描电镜观察也显示出明显的局部排列和随机定向的粘土矿物带。缺乏坚固的组构可能是由于断层岩中主要是随机取向的基片硅酸盐。强应变超碎屑岩/断层泥中弱织构的存在是由于：1)新形成的粘土矿物在许多方向上生长；2)折叠和扭结的粘土矿物；3)包裹在颗粒周围的粘土颗粒。此外，局部排列的粘土颗粒可能会成为流体流动的障碍，从而降低孔隙度，排出粒间孔隙流体，从而可能增加流体压力。
With optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and synchrotron X-ray diffraction measurements, we analyzed clay microfabrics in ultracataclastic/gouge and cataclastic core samples obtained from the main bore hole of the San Andreas Fault observatory at depth (SAFOD). The analysis reveals a significant contrast between weak clay fabrics observed in the core samples with synchrotron X-ray fabric measurements and strong degree of preferred alignment for clay particles documented with the optical microscope. TEM and SEM observations also show distinct zones of locally aligned and randomly oriented clay minerals. The lack of a strong fabric may be attributed to randomly oriented matrix sheet silicates dominating the fault rocks. The presence of weak fabrics in intensely strained ultracataclasites/fault gouges is attributed to 1) newly formed clay minerals that grew in many orientations, 2) folded and kinked clay minerals, and 3) clay particles that are wrapped around grains. In addition, the locally aligned clay particles may act as barriers to fluid flow, which in turn decrease porosity, expel intergranular pore fluids, and consequently, may increase fluid pressure.