Isotopic analyses of DSDP Hole 45-395A samples from veins containing gypsum (Table 1)

Gypsum and halite crystals, together with saponite and phillipsite, were found in a vein in a basalt sill 625 m below the sea floor at DSDP Site 395A, located 190 km west of the crest of the Mid-Atlantic Ridge. The delta34S value of the gypsum (+19.4‰) indicates a seawater source for the sulfate. The delta18O values of the saponite (+19.9‰) and phillipsite (+18.1‰) indicate either formation from normal seawater at about 55°C or formation from delta18O-depleted seawater at a lower temperature. […]