New structural and RSCM thermometric data from the Variscan Orogen of Morocco: insight into the extension-to-compression transition

Abstract

International audienceThe Western Moroccan Meseta exposes in the Zaian region a pre-12 Visean, Eo-Variscan belt of inclined to recumbent folds detached from their 13 Precambrian basement and embedded in the Variscan Orogen. Using the Raman 14 Spectroscopy of Carbonaceous Material (RSCM) method, we obtained the first 15 quantitative thermometric characterization of the Cambro-Ordovician and un-16 conformable Upper Visean rocks in the area. The pre-Visean fold belt devel-17 oped in high-T conditions (mean value 323±23°C) contrary to the juxtaposed 18 Variscan folds that formed at lower T (209±37°C). The high geotherm of the 19 Paleozoic series during folding is likely inherited from the Late Devonian ex-20 tensional setting, but the fold belt emerged through compression, probably dur-21 ing the Devonian-Tournaisian transition. 2