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, Geochemical information for P and T. a) Quartz geothermobarometer based on 757, Figure 5

S. Foustoukos, Points represent Si measured in fluids with calculated 758 temperature based on the Fe-Mn geothermometer. Grey dashed lines represent the "classical" 759 approach to evaluate P and T (see text for details). b) Fe and Mn concentrations on a logarithm 760 scale, 2007.

, P and T of some vents at equilibria with quartz are 764 presented. P and T were calculated using the Fe/Mn geothermometer of Pester, 765 quartz geothermobarometer (Foustoukos & Seyfried, 2007b) and NaCl-H2O solution properties 766, p.769, 2006.

. Combier, dotted 770 grey line correspond to F2. The blue line represents the inferred P-T path in the recharge zone 771 where cold seawater percolate through oceanic crusts and gradually interacts with rocks. Red 772 lines represent the inferred P-T path in the upflow zone, based on the conditions estimated from 773 fluid chemistry. The grey rectangle represents the phase separation zone estimated from the Si 774 and Cl concentrations in the low salinity fluids (Capelinhos, TE) using the geothermobarometer 775 proposed by, Grey lines represent fault labeled F1, F1b in Combier, 2009.

C. , F1, F1b and F2 from Combier et, 2013.

, Spatial Variations in Vent Chemistry at the Lucky Strike Hydrothermal Field, Mid 792 Atlantic Ridge (37°N): Updates for Subseafloor Flow Geometry from the Newly 793

, Discovered Capelinhos Vent

U. Geosciences-environnement-toulouse, . De-toulouse, . Cnrs, . Ird, and T. Ups, , p.798

, 799 Corresponding author : Valérie Chavagnac (valerie