TRACE-METALS IN HYDROTHERMAL SOLUTIONS FROM CLEFT SEGMENT ON THE SOUTHERN JUAN-DE-FUCA RIDGE

Concentrations of trace metals in Fe- and Cl-rich hydrothermal solutio ns from the southern Juan de Fuca Ridge (SJFR) have been determined an d corrected for residual precipitates formed in the sampler. Precipita te corrections for Ag, Cd, Cu, Mo, Pb, Sb, and Zn were variable, contr ibuting an average of 20% to total solution concentrations whereas cor rections for Co averaged less than 5% and essentially no corrections w ere required for Fe and Mn. Values for Cu, Co, and Mo in these solutio ns showed a strong dependence on temperature with sharp decreases in c oncentrations as temperatures decreased to less than 320-degrees-C. In addition, and unlike most other metals studied, all vent fluids from the SJFR were almost completely depleted in Mo relative to seawater va lues of about 110 nmol kg-1. In contrast to the Cu-Co-Mo group, concen trations of Ag, Cd, Sb, and Pb correlated well with those for Zn and a re presumed to follow a distribution that is influenced less by temper ature over the 246 to 332-degrees-C range encountered in this study an d more by the combined chemical processes that control Zn levels along the transport pathway from the deep reaction zone to the vent orifice .