The Permo-Carboniferous Graissessac–Lodève Basin (France): new insights into Variscan exhumation processes revealed by detrital zircon and apatite

The use of detrital zircon U–Pb geochronology is a well-established tool for provenance analysis. Yet, considering solely U–Pb data results in fundamental shortcomings, such as zircon grain recycling and the underrepresentation of particular age populations due to different magmatic zircon crystallization intensities. This study presents for the first time an integrated provenance approach combining detrital zircon U–Pb geochronology, zircon morphology, Lu–Hf isotopes, and detrital apatite U–Pb thermochronology applied to a Permo-Carboniferous intramontane basin. This multi-proxy approach allows us to better distinguish between primary source signals and sediment recycling, thereby providing improved constraints on source-to-sink relationships and tectonic processes during late Variscan basin evolution. Detrital zircon age populations reveal a dominant Neoproterozoic to Cambrian group sourced from the surrounding Paleozoic metasedimentary cover of the Montagne Noire, an Ordovician group likely derived from regional orthogneisses, and a prominent Late Devonian to Early Carboniferous population interpreted as derived from syn-orogenic intrusives and volcanic rocks. Rounded zircon grains and apatite cooling ages indicate significant sediment recycling and exhumation during late Variscan extension. Lu–Hf data point to heterogeneous crustal sources with both juvenile and evolved signatures. These results support a model of synchronous unroofing of the Montagne Noire dome and reworking of nearby Variscan units during post-orogenic collapse. The combination of heavy mineral provenance patterns and deduced thermal histories provides a yet rarely used approach on sediment routing, basin development, and the tectonic evolution of Central European Carboniferous-Permian strata. Graphical abstract