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Lookup NU author(s): Dr Mohamed Rouainia, Dr Mark IrelandORCiD
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
© 2023, The Author(s).Microscale diagenetic changes that occur during burial exert a profound influence on the elastic and mechanical properties of sediments—but are poorly quantified. The focus here is on how diagenesis influences the elastic properties of carbonate-rich mudstones, which are subject to a wide range of physical and chemical changes. Nanoindentation data for gas-window (180 ∘ C) Eagle Ford formation samples give intrinsic indentation moduli of the clay-sized calcite matrix of M= 40–50 GPa, which contrasts with M= 60–77 GPa for diagenetic calcite fills of foraminifera tests, closer to values for highly crystalline calcite. The matrix calcite is weakly anisotropic. Inverse analysis of immature (< 70 ∘ C) organic-rich chalks gives much lower intrinsic indentation moduli for biogenic calcite, between 17 and 30 GPa; the calcite is also more anisotropic, with values of M1/ M3∼ 1.3. Diagenesis, which includes recrystallisation and pore-filling cementation, results in calcite becoming elastically stiffer and behaving in an increasingly isotropic manner, in agreement with grain scale studies using atomic force microscopy. The results demonstrate that nanoindentation can resolve diagenetic contributions to the mechanical response of mudstones, and suggest intrinsic structural changes to calcite, in addition to diagenetic cementation, need to be accounted for in rock-physics models of mud-rich sediments.
Author(s): Graham SP, Aplin AC, Rouainia M, Ireland MT, Armitage PJ
Publication type: Article
Publication status: Published
Journal: Geomechanics and Geophysics for Geo-Energy and Geo-Resources
Year: 2023
Volume: 9
Issue: 1
Print publication date: 01/12/2023
Online publication date: 26/08/2023
Acceptance date: 27/06/2023
Date deposited: 11/09/2023
ISSN (print): 2363-8419
ISSN (electronic): 2363-8427
Publisher: Springer Science and Business Media Deutschland GmbH
URL: https://doi.org/10.1007/s40948-023-00634-z
DOI: 10.1007/s40948-023-00634-z
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