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Lookup NU author(s): Professor Andrew Aplin
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Geostatistical image analysis of backscattered electron microscope (BSEM) images has been used to determine the degree of alignment (anisotropy) of clay minerals in late Tertiary mudstone samples from a range of depths from the Gulf of Mexico. This has been tied to mineral chemical analysis using secondary X-rays to determine whether fabric development is related to mineral diagenesis. Although compacted, mudstones at similar to 5100 m have isotropic clay fabrics. Thousands of meters of overburden and the resulting stress have not induced the development of aligned fabric in mudstones. Mudstones adopt a progressively more anisotropic fabric with increasing depth of burial to similar to 5600 m. Smectite is progressively replaced by illite with increasing depth over the same interval so there is a close correspondence between the illitization of smectite and fabric development. The fabric seems to be a consequence of mineral diagenesis. The kinetically controlled illitization of smectite has facilitated the development of fabric which is thus likely to be due to a dissolution and reprecipitation process rather than a solid-state process. Fabric development, with its consequences for porosity and permeability, is thus more likely to be a function of temperature and the thermal history rather than just depth and effective stress. (C) 2003 Elsevier Science B.V. All rights reserved.
Author(s): Charpentier D, Worden RH, Dillon CG, Aplin AC
Publication type: Article
Publication status: Published
Journal: Journal of Geochemical Exploration
ISSN (print): 0375-6742
Notes: Proceedings of Geofluids IV, Utrecht, The Netherlands, 12-16 May 2003
Edited by Verweij JM; Doust H; Peach CJ, Spiers CJ; Swennen RAJ
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