Temporal and spatial variations in hydrothermal budgets of degassing metals across a full eruptive cycle: 9 degrees 46 '-9 degrees 50 ' N East Pacific Rise


The influence of eruptive activity in fluid trace metal abundances, especially those that have been shown to degas from shallow magma bodies (1) is not fully quantified. Accordingly new metal abundance data across a full eruptive cycle will provide insight into links between crustal and magmatic processes and contribute to improved approximations of element cycling in the oceans and the significance of these metals in hydrothermal ecosystems. Recent analytical developments have enhanced the capability to determine hydrothermal metal concentrations in spite of their low abundances and the difficulty in quantifying their sinks and sources. During the last decade, frequent sampling of hydrothermal vents at the Ridge2000 Integrated Study Site (ISS) has provided a spatially diverse range of samples to characterize the evolution of vent fluid chemistry throughout the eruption cycle (1991-2006). This unique sample set includes particulate, precipitate and dissolved hydrothermal fluid samples collected in a time window ranging from just after the first eruption at the site (April 1991) through late 2007, following the 2005-6 eruption. The sample subset also includes brine and vapor fluid samples as well as fluids with a large CO2 range(2). Samples have been analyzed for complete trace metal budgets of 210Pb, Pb and Cd which have degassing potential in magmatic and hydrothermal systems (1). Preliminary results show that vapor phase vent sites located at the maximum of the CO2 degassing signal (9°50.3í-50.8íN) contain elevated 210Pb/Pb ratios relative to vent sites south of the degassing maximum (9°46.3í-47.2íN). Furthermore, high levels of CO2 are associated with increasing concentrations of Cd as well as 210Pb. The metal contents of fluids associated with lower CO2 generally do not correlate well with CO2 but contain relatively higher metal abundances, consistent with their high chlorinities and longer fluid residence time in the crust (3).


Earth Sciences, Earth Systems Research Center

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