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BIBTEX RIS

Growth of cataclastic bands into a fault zone: A multiscalar process by microcrack coalescence in sandstones of Rio do Peixe Basin, NE Brazil

2021; Elsevier BV; Volume: 146; Linguagem: Inglês

10.1016/j.jsg.2021.104315

1873-1201

Daniel Henrique Silva de Souza, Francisco C.C. Nogueira, David L. Vasconcelos, Anita Torabi, Jorge André Braz de Souza, Matheus Amador Nicchio, Yoe A. R. Perez, Fabrizio Balsamo,

Geological and Geochemical Analysis

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.