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A micromechanical investigation of diagenetically-induced changes to the anisotropic elastic properties of calcareous mudstones

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.

Publication metadata

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


DOI: 10.1007/s40948-023-00634-z


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Funder referenceFunder name
NE/R018057/1Natural Environment Research Council (NERC)