Abstract
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.