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Analogue models of lithospheric-scale rifting monitored in an X-ray CT scanner
  • Frank Zwaan,
  • Guido Schreurs
Frank Zwaan
Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences

Corresponding Author:frank.zwaan@geo.unibe.ch

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Guido Schreurs
University of Bern
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Rifting and continental break-up are fundamental tectonic processes, the understanding of which is of prime importance. However, the vast temporal and spatial scales involved pose major limitations to researchers. Analogue tectonic modelling represents a great means to mitigate these limitations, but studying internal deformation in lithospheric-scale models remains a challenge. We therefore present a novel method for lithospheric-scale rifting models that are uniquely monitored in an X-ray CT-scanner. CT-scanning, combined with digital image correlation (DIC) techniques, provides unparalleled insights into model deformation. Our models show that the degree of coupling between competent lithospheric layers, which are separated by a weak lower crustal layer, strongly impacts rift system development. Low coupling isolates the upper crust from the upper lithospheric mantle layer below, preventing an efficient transfer of deformation between both layers. By contrast, fast rifting increases coupling, so that deformation in the mantle is efficiently transferred to the upper crust, inducing either a symmetric or asymmetric (double) rift system. The observation that asymmetric deformation can initiate during the earliest rifting stages challenges the two-phase scenario involving initial symmetric rifting, prior to subsequent asymmetric rifting. Oblique divergence leads to en echelon graben arrangements, and seemingly delays break-up, somewhat in contradiction to concepts of oblique divergence promoting break-up. These insights provide an incentive to further run lithsospheric-scale rifting models, and to apply advanced monitoring techniques to extract as much information as possible from these. There is indeed a broad range of opportunities for follow-up studies within and beyond the field of rift tectonics.