We propose a structural evolutionary model for deformation band (DB) development via microcrack propagation and coalescence process in a normal fault zone affecting arkosic sandstones. Based on structural analysis and reconstruction of the paleostress, we infer that a sub-horizontal minimum principal stress (σ3) in the NNW-SSE direction controlled the multiscalar evolution of microcracks and DBs. Two main sets of coalesced microcracks and DBs are recognized: (1) NE-SW and (2) E-W, in which the coalescence pattern of microcracks is also observed among the DBs at meso-scale. Our results suggest that the DBs develop during three deformation stages: (1) pore collapse followed by initial grain breakage and the formation of NE-SW tensile microcracks favoured by cleavage planes in feldspars. These microcracks coalesce through linking NW-SE shear microcracks to form intermediary microplanes. An intense microcracking crush the grains, enhancing the cataclastic process. The further coalescence of these intermediary microplanes with other intermediary microplanes and/or microcracks might generate through-going microplanes inside the band, causing the formation of E-W DBs; (2) the E-W structures coalesce through NE-SW hard-linking DBs, which corresponds to the DBs clusters, generating NE-SW intermediary planes at meso-scale; (3) the NE-SW intermediary planes coalesce through an E-W hard-linking structure, which results in the DB fault zone.
Growth of cataclastic bands into a fault zone: A multiscalar process by microcrack coalescence in sandstones of Rio do Peixe Basin, NE Brazil / de Souza, D. H. S.; Nogueira, F. C. C.; Vasconcelos, D. L.; Torabi, A.; Souza, J. A. B. D.; Nicchio, M. A.; Perez, Y. A. R.; Balsamo, F.. - In: JOURNAL OF STRUCTURAL GEOLOGY. - ISSN 0191-8141. - 146(2021), p. 104315.104315. [10.1016/j.jsg.2021.104315]
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