Tracing the thermal evolution of the Corsican lower crust during Tethyan rifting

Abstract

Continental rifting requires thinning the continental lithosphere from ~120 km to <20 km by a series of processes which each impart a characteristic thermal signature to the extending lithosphere. Here high‐resolution thermochronology is used to trace the synrift thermal evolution within a lower crustal section of an upper plate hyperextended margin sampled in Corsica. Novel zircon, rutile, and apatite 206Pb/238U depth profiling coupled with garnet trace element diffusion modeling provide compelling evidence for rift‐related crustal reheating. A Jurassic thermal pulse is recorded in the footwall of the Belli Piani Shear Zone (BPSZ), where 200–180 Ma zircon 206Pb/238U overgrowth ages on Permian core populations and the preservation of stranded diffusion profiles in resorbed garnets implies the dominant footwall fabric formed as a result of high‐temperature (T ~ 800°C) ductile thinning of the lower crust. Conductive reheating of middle crustal rocks in the immediate BPSZ hanging wall, demonstrated by Jurassic apatite 206Pb/238U ages, was likely achieved by synkinematic juxtaposition against the hot footwall and wholesale conductive steepening of geothermal gradients. Subsequent rapid cooling from 180 to 160 Ma, coeval with extensional unroofing of the footwall, underscores the importance of extreme ductile thinning during crustal hyperextension. The results of this study suggest that early lithospheric‐scale depth‐dependent thinning follows an early phase of diffuse rifting and tectonic subsidence and triggers crustal reheating during early hyperextension. Continued extension results in rapid exhumation and cooling of the lower crust, extreme crustal attenuation, and mantle exhumation followed by relaxation to a steady state thermal field coeval with the start of seafloor spreading.

Detrital zircon age patterns from turbidites of the Balagne and Piedmont nappes of Alpine Corsica (France): Evidence for an European margin source

“…This distribution supports the previously proposed paleogeographic location of the Santa-Lucia nappe in a para-autochthonous position to the East of the granitic batholith (Durand-Delga, 1984); or on the Ocean-Continent Transition (Fig. 14;Rossi et al, 2006;Beltrando et al, 2013;Seymour et al, 2016).…”

Controls on the Thermomechanical Evolution of Hyperextended Lithosphere at Magma‐Poor Rifted Margins: The Example of Espirito Santo and the Kwanza Basins

“…The modeled thermal history is broadly consistent with recent thermochronological work that show that DDT is accompanied by an increase in thermal gradient in H-Block and hyperextension by an increase in thermal gradient in the sediments (Beltrando et al, 2015;Hart et al, 2017;Seymour et al, 2016;Smye et al, 2019;Smye & Stockli, 2014). While current seismic images and interpretations in Angola do not resolve the underplated magmatic additions, we do interpret a thickened oceanic crust and also magmatic additions at the OCT.…”

“…Understanding the factors controlling decoupling, coupling and hyperextension should provide critical information on the mechanics of lithospheric necking and breakup. This exercise is critical at a time when new thermochronological data of fossil magma‐poor margins in the Alps and the Pyrenees have shown that reheating of the crust and the sediments occurs during lithospheric necking (thinning; Smye & Stockli, ; Beltrando et al, ; Seymour et al, ; Hart et al, ; Smye et al, ). Some authors suggest that these thermal events can be explained by rapid, active mantle upwelling during necking (Smye et al, ) and suggest that structures coupling fault in the crust and mantle are linked to both hyperextension and an actively upwelling mantle that could increase heat flow at the base of the extending crust and mantle lithosphere (Chenin et al, ; Gallacher et al, ; Hart et al, ; Huismans & Beaumont, , ; Royden & Keen, ; Svartman Dias et al, , ).…”

Thermotectonic Evolution of the North Pyrenean Agly Massif During Early Cretaceous Hyperextension Using Multi‐mineral U‐Pb Thermochronometry

“…Intragrain apatite U‐Pb increments were plotted as age spectra similar to data using Isoplot (Ludwig, ). Individual age spectra were stacked to examine overall U‐Pb topology within samples and to evaluate the thermal history of samples (Seymour et al, ).…”