Extensional detachments and low-angle normal faults (LANFs) are dynamic structures, shaping the Earth crust over geological time intervals and cumulating tens of km of vertical and horizontal displacement. In the oceanic realm, they are also major players accommodating (hyper-)extension, mantle exhumation and the development of oceanic core complexes at slow and ultra-slow spreading ridges and magma-poor passive margins, commonly associated with serpentinization, hydrothermal circulation and fluid-rock interactions. Detachments thus testify to past or ongoing crustal/lithospheric extension, where the localisation of ductile and brittle deformation is characterised by (i) a progressive ductile-to-brittle transition during 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 even greater importance when investigating the architecture and mechanics of extensional detachments, where through-time superposed domains with different mineralogy and petrophysical properties change the mechanical response of shear- and fault zones. Coexisting or partitioned seismic vs. aseismic deformation, repeated cycles of shear zone weakening/hardening, and syn-tectonic fluid flow and fluid-rock interactions may all be governed by these (still partially underinvestigated) structural complexities in both continental and oceanic settings.
- What allows the initiation and evolution of detachments, whether continental or oceanic, and which processes act coevally or diachronously?
- What is the link between detachment formation, mantle exhumation and hydrothermal activity?
- What is the role of tectonic or thermal inheritance in the formation of LANFs and continental/oceanic 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 multidisciplinary and multiscale approaches, encompassing, among others, field analysis, seismic and other geophysical investigations, numerical and laboratory modelling, ocean drilling, and absolute dating and petrological constraints on syn-kinematic fabrics and mineralisation.