4-D architectural, kinematical and mechanical evolution of continental and oceanic low-angle normal faults and detachments

Co-organized by GD5

Convener: Costantino ZuccariECSECS | Co-conveners: Olivier Lacombe, Cristiano Collettini, Bernhard Grasemann, Geoffroy Mohn

Abstract submission

Crustal-scale low-angle normal faults (LANFs) and extensional detachments are dynamic structures, shaping the Earth’s crust over geological time intervals and potentially cumulating tens of kms of vertical and horizontal displacement. In the oceanic realm, they are also major players that accommodate (hyper) crustal extension and mantle exhumation at magma-poor passive margins and at slow to ultra-slow oceanic ridges, often linked to hydrothermal systems. Detachments testify thus to the past or ongoing crustal/lithospheric extension, where ductile and brittle deformation during strain localisation are characterised by (i) a progressive ductile-to-brittle transition during the shear zone evolution en route towards shallow crustal levels or (ii) can coexist at different structural levels, making the reconstruction of detachment evolution even more complex.
For this reason, constraints on brittle and ductile strain localisation and on their precise age of activation are increasingly relevant. This acquires a higher importance by looking at the architecture and mechanics of extensional detachments, where through-time superposed domains with different mineralogy and, thus, petrophysical properties, dramatically change the mechanical response of shear- and fault zones during progressive deformation. Coexisting or partitioned seismic vs. aseismic deformation, as well as repeated cycles of shear zone weakening/hardening and syn-tectonic fluid flow and fluid-rock interactions, might be governed by this through-time (and still partially underinvestigated) structural complexities.
- What guides this different deformation response of shear and fault zones?
- What allows the initiation and evolution of detachment zones, should they be continental or oceanic, and which processes act coevally or diachronously?
- What is the link between detachment formation and hydrothermal activity?
- What is the role of tectonic or thermal inheritance in the formation of LANFs and detachments?
All contributions fostering discussions on these points are welcome in this session, including comparisons between continental and oceanic systems. We encourage the submission of research based on a multidisciplinary and multiscale approach, encompassing, among others, field analysis, seismic and other geophysical investigations, numerical and laboratory modelling and absolute dating and petrological constraints of syn-kinematic fabrics and mineralisation.