We document the discovery of an active, shallow, seafloor hydrothermal system (known as the Seven Sisters Vent Field) hosted in mafic volcaniclasts at a mid-ocean ridge setting. The vent field is loca
Table S1: Locations and lithology of analyzed samples. Table S2: Calculated temperatures and pressures of augite and amphibole crystallization. Table S3: Major-element compositions of clinopyroxene. T
