The Meso-Cenozoic thermo-tectonic evolution of the Eastern Pyrenees: an 40Ar/39Ar fission track and (U–Th)/He thermochronological study of the Canigou and Mont-Louis massifs

Abstract

Vertical displacements on the SW-NE Têt fault (Eastern Pyrenees Axial Zone, France), which separates the Variscan Canigou-Carança and Mont-Louis massifs, were constrained using a thermochronologic multi-method approach. 40 Ar/ 39 Ar data from the granitic Mont-Louis massif record its Variscan cooling history and reveal no ages younger than Early Cretaceous, while the CanigouCarança gneiss massif records systematically younger 40 Ar/ 39 Ar ages. These younger 40 Ar/ 39 Ar ages in the Canigou-Carança gneiss massif are the result of partial to total rejuvenation of argon isotopic systems related to a thermal flow coeval with the Cretaceous HT-BP metamorphism in the North Pyrenean Zone. Only the deepest rocks from the Canigou-Carança suffered this extensive Mid-Cretaceous thermal overprint probably due to differential burial around 4 km at that time. The post Mid-Cretaceous vertical displacements along the Têt fault are recorded by ''low'' temperature thermochronology using K-feldspar 40 Ar/ 39 Ar, zircon and apatite fission track and (U-Th)/He datings. The Mont-Louis granite samples experienced a long period of protracted cooling reflecting a lack of thermo-tectonic activity in this area from Late Palaeozoic to Early Cenozoic, followed by cooling from 55-60 Ma to Late Eocene at a mean rate of 15-20°C/Ma in the final stage. This cooling stage corresponds to Têt fault reactivation with a reversed component, promoting exhumation of the Mont-Louis roof zone contemporaneously with the south-vergent Pyrenean thrusting. In the CanigouCarança massif, the main cooling event occurred from 32 to 18 Ma at a maximum rate of 30°C/Ma during Early Oligocene followed by a more moderate rate of 3°C/Ma from Late Oligocene to Early Burdigalian, coeval with the normal reactivation of the Têt fault in brittle conditions that accommodated the final exhumation of the massif during the opening of the Gulf of Lion.

Active Tectonics of the Pyrenees: A review

“…In the last decades, several works (Vanara et al, 1997;Vanara, 2000;Perez-Vila et al, 2001;Agustí et al, 2006;Calvet and Gunnell, 2008;Lacan, 2008;Ortuño, 2008;Suc and Fauquette, 2012;Ortuño et al, accepted) have reported postorogenic surface uplift > 0.5 km and up to 2 km since the late Miocene at several sites, all located at the High Chain. The same occurs with the data on post-orogenic enhanced exhumation (Fitzgeral et al, 1999;Calvet and Gunnell, 2008;Maurel et al, 2008;Gunnell et al, 2008;Metcalf et al, 2009;Méresse, 2010), which can be owed to the surface uplift and/or enhanced erosion.…”

“…This last event could be responsible from a rapid post-orogenic uplift of the Eastern Pyrenees reported by different authors (Pérez-Vila et al, 2001;Agustí et al, 2006;Suc and Fauquette, 2012) and possibly reflected in the exhumation history of the area Maurel et al, 2008).…”

“…Calvet (1999) has documented normal to strike-slip faulting only until the Early Pliocene. Maurel et al (2008) have relied in the exhumation history of the Canigó Massif derived from thermochronological data to discard any uplift related to the Conflent Fault after the Middle Miocene and Carozza and Delcaillau (2000) have assigned a sinistral strike-slip mouvement to the Conflent Fault during that period based on the analysis of the macrogeomorphology. Moreover, Carozza and Baize (2004) interpreted the faceted spurs of the fault as erosional-exhumed features, dating from the previous extensional period.…”

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

“…Time-temperature history (burial, heating and cooling) during the initial accretionary stage are therefore largely unknown. It may involve underestimated competing cooling processes such as syn-orogenic thermal relaxation or cooling by underthrusting as suggested recently in Taiwan (Mesalles et al, 2014).…”

Fault-Related Controls on Upward Hydrothermal Flow: An Integrated Geological Study of the Têt Fault System, Eastern Pyrénées (France)

“…Briais et al [59] and Calvet [60] attribute the triangular facets of the Têt fault scarp to its recent normal activity, while Petit and Mouthereau [61] suggest they are actually the morphological expression of the CMNC corroborating with the differential erosion of the hosting rocks. Authors agree that current displacements are low or nonexistent [56,57,60,[62][63][64]. The general tectonic regime seems to have changed during the Pliocene from normal [58,64,65] to reverse, but with no clear evidence about the compressive or strike-slip nature of the stress tensor [58].…”