U–Pb dating of carbonate gangue with associated As–Sb mineralization in the Matra Fault (Alpine Corsica, France): Constraints for the rifting stage in the Tyrrhenian Sea

Abstract

This paper presents results of the first attempt to date a normal fault system that affected the eastern side of the Alpine Corsica (France). The U–Pb method was employed to date carbonate material with associated As–Sb mineralization in the Matra Fault, a N–S striking normal fault located southward of the Castagniccia dome. This fault cuts the Alpine nappe stack, here consisting of two oceanic-derived tectonic units, including Middle–Late Jurassic metaophiolites and/or related Early Cretaceous metasediments. From the Late Cretaceous onward, these units were involved in subduction processes and record peak eclogite facies metamorphism. After a complex exhumation path to the surface, these units then experienced long-lasting extensional tectonics linked to the collapse of the Alpine wedge, followed by two rifting stages. The first rifting stage occurred in the Oligocene-Early Miocene and the second in the Middle Miocene to Quaternary that caused the opening of the Liguro–Provencal and the Tyrrhenian back-arc basins, respectively. The U–Pb dating of the Matra Fault yields a weighted age of 9.80 ± 0.37 Ma. Therefore, the Matra Fault developed, in association with syndeformational As–Sb–Fe sulfide mineralization, during the opening of the Tyrrhenian back-arc basin. This finding represents a significant advance in understanding the extensional tectonics in Corsica during the opening of the Tyrrhenian back-arc basin.