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Detailed Reference Information |
Schleicher, A.M., van der Pluijm, B.A., Solum, J.G. and Warr, L.N. (2006). Origin and significance of clay-coated fractures in mudrock fragments of the SAFOD borehole (Parkfield, California). Geophysical Research Letters 33: doi: 10.1029/2006GL026505. issn: 0094-8276. |
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The clay mineralogy and texture of rock fragments from the SAFOD borehole at 3067 m and 3436 m measured depth (MD) was investigated by electron microscopy (SEM, TEM) and X-ray-diffraction (XRD). The washed and ultrasonically cleaned samples show slickenfiber striations and thin films of Ca-K bearing smectite that are formed on polished fault surfaces, along freshly opened fractures and within adjacent mineralized veins. The cation composition and hydration behavior of these films differ from the Na-montmorillonite of the fresh bentonite drilling mud, although there is more similarity with circulated mud recovered from 3479 m MD. We propose that these thin film smectite precipitates formed by natural nucleation and crystal growth during fault creep, probably associated with the shallow circulation of low temperature aqueous fluids along this shallow portion of the San Andreas Fault. |
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Abstract |
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Keywords
Mineralogy and Petrology, Petrography, microstructures, and textures, Mineralogy and Petrology, Instruments and techniques, Structural Geology, Fractures and faults, Structural Geology, Rheology and friction of fault zones, Tectonophysics, Dynamics and mechanics of faulting |
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Publisher
American Geophysical Union 2000 Florida Avenue N.W. Washington, D.C. 20009-1277 USA 1-202-462-6900 1-202-328-0566 service@agu.org |
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