THE GEOCHEMISTRY OF ATLANTIC HYDROTHERMAL PARTICLES

Particles were collected from the dilute portion of neutrally buoyant hydrothermal plumes from four Mid-Atlantic Ridge sites (MARK, 23 degre es N; TAG, 26 degrees N; Broken Spur, 29 degrees N; Lucky Strike, 37 d egrees N). Comparison of data from proximal portions of the TAG (Atlan tic) [German et al., 1991; this study] and North Cleft (Pacific) [Feel y et al., 1994] plumes show that oxyanion (e.g., V) scavenging is more efficient at TAG, possibly due to a higher proportion of Fe removed a s sulfides at North Cleft and/or the more vigorous mixing in the high energy TAG buoyant plume. Chalcophile elements (e.g., Cu) show two sta ge removal. They are precipitated as sulfides during initial mixing of vent fluids with seawater and are sedimented from the buoyant plume. In the dilute plume they are scavenged from seawater by Fe oxyhydroxid es. The REE show continued scavenging in the neutrally buoyant plume a nd lower levels in 1993 samples, compared to 1988 samples [German et a l., 1990] suggesting that the amount of scavenging is related to parti cle recycling.