Particles were collected from the dilute portion of neutrally buoyant hydrothermal plumes from four Mid-Atlantic Ridge sites (MARK, 23°N; TAG, 26°N; Broken Spur, 29°N; Lucky Strike, 37°N). Comparison of data from proximal portions of the TAG (Atlantic) [German et al., 1991; this study] and North Cleft (Pacific) [Freely et al.,...