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Fabric development and the smectite to illite transition in Gulf of Mexico mudstones: an image analysis approach

Lookup NU author(s): Professor Andrew Aplin

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Abstract

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.


Publication metadata

Author(s): Charpentier D, Worden RH, Dillon CG, Aplin AC

Publication type: Article

Publication status: Published

Journal: Journal of Geochemical Exploration

Year: 2003

Volume: 78-9

Pages: 459-463

ISSN (print): 0375-6742

ISSN (electronic):

URL: http://dx.doi.org/10.1016/S0375-6742(03)00073-6

DOI: 10.1016/S0375-6742(03)00073-6

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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