Thermal imprint of rift-related processes in orogens as recorded in the Pyrenees

Abstract

International audience19 The extent to which heat recorded in orogens reflects thermal conditions inherited from 20 previous rift-related processes is still debated and poorly documented. As a case study, we 21 examine the Mauléon basin in the north-western Pyrenees that experienced both extreme 22 crustal thinning and tectonic inversion within a period of ~30 Myrs. To constrain the time-23 temperature history of the basin in such a scenario, we provide new detrital zircon fission-24 track and (U-Th-Sm)/He thermochronology data. The role of rift-related processes in 25 subsequent collision is captured by inverse modeling of our thermochronological data, using 26 relationships between zircon (U-Th-Sm)/He ages and uranium content, combined with 27 thermo-kinematic models of a rift-orogen cycle. We show that the basin recorded significant 28 heating at about 100 Ma characterized by high geothermal gradients (~80°C/km). Our 29 thermo-kinematic modeling and geological constraints support the view that subcontinental 30 lithospheric mantle was exhumed at that time below the Mauléon basin. Such a high 31 geothermal gradient lasted 30 Myr after onset of convergence at ~83 Ma and was relaxed 32 during the collision phase from ~50 Ma. This study suggests that heat needed for ductile 33 shortening during convergence, is primarily inherited from extension rather than being only 34 related to tectonic and/or sedimentary burial. This should have strong implications on tectonic 35 reconstructions in many collision belts that resulted from inversion of hyper-extended rift 36 basins

Constraints on the thermal evolution of the Adriatic margin during Jurassic continental break-up: U–Pb dating of rutile from the Ivrea–Verbano Zone, Italy

“…2), with only a minor role played by exhumation-related conductive cooling. A similar heating-cooling cycle broadly coeval with the rift-to-drift transition has recently been proposed for the hyper-extended Cretaceous margins now sampled in the Pyrenees (Vacherat et al 2014). The contemporaneity with the well-documented onset of mantle exhumation and extensive MORB magmatism in the Alpine Tethys (e.g.…”

Thermochronological Evidence of Early Orogenesis, Eastern Pyrenees, France

“…On the other hand, the Aptian–Cenomanian rifting generated a major thermal pulse that had not reequilibrated before the onset of convergence some 10 myrs later (Angrand et al, ). This inherited thermal perturbation may have been present during the first 30–35 myrs of orogenesis (Angrand et al, ; Vacherat et al, ), maintaining temperatures during early orogenesis above the sensitivity limit of low‐temperature thermochronometers (40–300 °C; e.g., Carrapa, 2010; Peyton & Carrapa, ) and thus delaying any cooling record until the main Eocene collision (Vacherat et al, ). However, previous limited low‐temperature thermochronology data (Yelland, ) indicate that the massifs at the eastern end of the external Pyrenean orogenic system, Agly‐Salvezines, record a Campanian–Maastrichtian cooling signal, synchronous with the first period of accelerating subsidence in the retroforeland (Ford et al, ).…”

Crustal structure and evolution of the Pyrenean-Cantabrian belt: A review and new interpretations from recent concepts and data

“…50 Ma (after data from Vacherat et al, 2014 andBosch et al, 2016). Vissers and Meijer (2012) added a 300 km-wide exhumed mantle domain to the scheme by Beaumont et al (2012), initiating convergence at 121 Ma and placing the collision in the ECORS-Pyrenees transect at 83 Ma.…”