Trace metal concentration and partitioning in the first 1.5 m of hydrothermal vent plumes along the Mid-Atlantic Ridge: TAG, Snakepit, and Rainbow

Abstract

Please cite this article as: Findlay, Alyssa J., Gartman, Amy, Shaw, Timothy J., Luther III, George W., Trace metal concentration and partitioning in the first 1.5 meters of hydrothermal vent plumes along the Mid-Atlantic Ridge: TAG, Snakepit, and Rainbow, AbstractTo determine the significance of metal fluxes from hydrothermal vents, understanding the speciation, reactivity, and possible transformations of metals and metal sulfides within the hydrothermal plume is critical. In this study, we measure the concentration and partitioning of trace metals (Fe, Mn, Cu, Cd, Co, Pb, Ni) and sulfide phases within the first 1.5 meters of the rising plume at three vent fields (TAG, Snakepit, and Rainbow) along the Mid-Atlantic Ridge. A combination HCl/HNO 3 leaching method was used to differentiate metals present in metal mono-sulfides from those in pyrite and chalcopyrite. At all three vent sites, Mn and Fe are primarily in the < 0.2 µm (filtered) portion, whereas Cu, Co, Cd, and Pb are mainly in the unfiltered fraction. Significant concentrations of HNO 3 -extractable metals were found in the < 0.2 µm fraction at all three vent sites, indicating that they likely exist in a recalcitrant nanoparticulate phase such as pyrite or chalcopyrite. At TAG and Snakepit, Cu is correlated with Co, as Co enters into chalcopyrite and other CuFeS phases and Zn is correlated with Cd and Pb as they form discrete metal sulfide phases. At Rainbow, Zn, Cd, and Pb are correlated, but Cu and Co are not correlated. The Rainbow data are consistent with the higher metal to sulfide ratio found at Rainbow. These speciation differences are significant as both A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT2 mineral type and size will affect the amount of metal transported from the vent site and its availability for biogeochemical processes.

The Size Fractionation and Speciation of Iron in the Longqi Hydrothermal Plumes on the Southwest Indian Ridge

“…It must be noted that Mn is not a strictly conservative element and Mn oxidation might be accelerated via microbial mediation (Cowen et al, ; Dick et al, ; Mandernack & Tebo, ). However, considering the hydrothermal plume can become a nonbuoyant plume in one hour generally (Lupton, ), the slow Mn oxidation rates do not significantly affect Mn distributions on the hours‐days timescale (Cowen et al, ; James & Elderfield, ; Findlay et al, ).…”

A Molecular Approach to Explore the Background Benthic Fauna Around a Hydrothermal Vent and Their Larvae: Implications for Future Mining of Deep-Sea SMS Deposits

“…plumes relatively rich in transition metals resulting in SMS deposits enriched in Cu, Zn, Co, and Ni (Charlou et al, 2002;Douville et al, 2002;Findlay et al, 2015). This plume could still be detected up to 50 km away from the vent site, moving predominantly to the north and east, following the contours of the Rainbow Ridge at ∼2,100 m depth (Severmann et al, 2004).…”

Impact of hydrothermalism on the ocean iron cycle

“…The prevalence of these potential stabilizing mechanisms is likely to vary between different hydrothermal sites, even within one ridge system. For example, for the well-studied MAR, there is a strong distinction in the sulfide concentrations between the high sulfide system of the TAG site when compared with the low sulfide Rainbow vent sites [39]. Wider afield, Fe(II) was a notable component of the plume signal at TAG [40], but not for the southern East Pacific Rise [24].…”