Fig. S2.
Plot of measured Mg vs. measured (A) H2, (B) C2H6, (C) C3H8, and (D) Cl. Conservative behavior in Cl, C2H6, and C3H8 as well as CH4 in mixed fluids (green symbols; in the text) during mixing between near-endmember fluid (blue circles) and seawater (yellow stars) suggests that the Von Damm vent field is fed by a single-source fluid originating in the high-temperature reaction zone below the seafloor. Nonconservative H2 behavior occurs at two mixed fluid vents: Old Man Tree (115 °C) and Shrimp Hole (21 °C). Uncertainties (2σ) not shown are smaller than symbols.