A second track of the Réunion hotspot in the Mascarene Basin

Hotspots are generally interpreted as the surface expression of lithospheric plates moving over mantle plumes, progressively forming volcanic chains aligned with plate motion. However, it is increasingly recognized that hotspots—such as Hawaii, Samoa, and Tristan–Gough— can exhibit two volcanic lineaments that are not necessarily parallel and display distinct geochemical characteristics.Here we report the discovery of a previously unrecognized volcanic chain related to the Réunion hotspot in the Mascarene Basin (western Indian Ocean), which we term the Mascarene Chain (MASC). This chain extends from the Seychelles across the seafloor through a series of seamounts and records a southward progression of volcanism from ca. 67 to 6 Ma. This age progression is constrained by multi-technique geochronology (⁴⁰Ar/³⁹Ar on biotite; U–Pb on zircon; (U–Th)/He on zircon and apatite) performed on dredged volcanic samples. Petrology, whole-rock major and trace elements and Sr–Nd–Pb isotopes, as well as zircon trace elements and δ¹⁸O–Hf isotopes, indicate that these volcanoes formed from extremely low (