Relationship between pore water δ34S
and temperature. (a) δ34SSO4 decreases with increasing temperature across the hydrothermal sites Twinkie (+), Rocky Point (●), and Spiegelei (▲), relative to the Brine pool (×), background sediments (◇), and surface seawater sulfate (sw; ■). (b) A mass balance model suggests an increasing fraction of secondary sulfate (f
) in sites with elevated temperatures.