Table S3 - Magma reservoir formation and evolution at a slow-spreading center (Atlantis Bank, Southwest Indian Ridge)

In situ trace elements concentrations in ppm of 24 samples analyzed with a ThermoFinnigan Element2 XR (eXtended Range - ICP-MS) coupled with a laser ablation (LA) system Téledyne G2 at Géosciences Montpellier (AETE-ISO regional facility of the OSU OREME, Montpellier University, France). Signal acquisition was made in Time Resolved Acquisition, counting 120 s for the background, and 60 s for the sample measurement. The frequency of the laser was of 10 Hz, with an energy density 174 of ~6.2 J.cm². Ablation experiments were conducted under helium which was mixed with argon before entering the plasma. Clinopyroxenes (Cpx) were analyzed with a laser spot size of 77 μm, while a spot size of 102 μm was used for olivines (Ol) and plagioclases (Pl). Data were processed using the GLITTER software (Van Achterberg et al., 2001). All measured concentrations were calibrated using the synthetic glass NIST 612 with the values of Pearce et al. (1997). The internal standards used for the minerals are 43Ca for Cpx, and 29180 Si for Pl and Ol, with the values previously analyzed in the same minerals by EPMA. An average of the values analyzed by LA-ICP-MS for the standard reference basalt BIR-1G is available at the end of the table.