Analogue modelling of brittle shear zone propagation across upper crustal morpho-rheological heterogeneities

• Published in: Journal of structural geology 2019-09, Vol.126, p.175-197
• Main Authors: Gomes, A.S., Rosas, F.M., Duarte, J.C., Schellart, W.P., Almeida, J., Tomás, R., Strak, V.
• Format: Article
• Language: English
• Subjects: Analogue modelling; Basement strike-slip fault; Brittle shear zone; Gloria transform fault; Pre-tectonic crustal viscous anomaly; Shear-zone structural pattern; Tore-Madeira rise tectono-magmatic interference
• ISSN: 0191-8141; 1873-1201
• DOI: 10.1016/j.jsg.2019.06.004

Crustal shearing of pre-tectonic weak bodies (e.g. salt pillows, igneous pockets) associated with basement strike-slip fault systems is common in nature. Yet the structural pattern arising from the interference between a brittle shear zone and such weak rheological heterogeneities is still not fully explained. In the present work, different sand-box analogue modelling experiments were carried out to better understand, not only the shear zone perturbation effect caused by a strictly rheologic (viscous-weak) anomaly, but also the one arising from a combined morphological perturbation (i.e. traverse topographic crest). Obtained results show that the development of different shear zone deformation patterns is in each case essentially determined by the interplay between: (i) ductile wrenching strain accommodation in the (viscous) weak body; and (ii) coincidence vs. mismatch between main brittle-viscous rheological boundaries and (crest-related) topographic steps. Comparison of the experimentally obtained results with complying natural examples is further discussed, and essentially focused on the NE Atlantic tectono-magmatic interference between the Gloria transform fault and the Tore-Madeira submarine ridge. •Analogue modelling of strike-slip brittle shear propagation across a pre-tectonic weak (viscous) anomaly.•Combined (morpho-rheologic) effect exerted by the viscous anomaly and by a (90° or 120°) trasverse topographic crest.•Coincidence vs. mismatch between rheological and morphological boundaries and its influence on the resulting structural pattern.•Control on the distribution of different structures around opposite quarters of the viscous anomaly.•The natural example of the transform Gloria fault - Tore Madeira rise tectono-magmatic interference in NE Atlantic.