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Processes driving iron and manganese dispersal from the TAG hydrothermal plume (Mid-Atlantic Ridge): results from a GEOTRACES process study

Citation

Gonzalez-Santana, D and Planquette, H and Cheize, M and Whitby, H and Gourain, A and Holmes, T and Guyader, V and Cathalot, C and Pelleter, E and Fouquet, Y and Sarthou, G, Processes driving iron and manganese dispersal from the TAG hydrothermal plume (Mid-Atlantic Ridge): results from a GEOTRACES process study, Frontiers in Marine Science, 7, (JULY) Article 568. ISSN 2296-7745 (2020) [Refereed Article]


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DOI: doi:10.3389/fmars.2020.00568

Abstract

Hydrothermal vents are a recognized source of trace elements to the ocean inventory. Nevertheless, the contribution of slow-spreading ridges remains poorly resolved. To address this, high-resolution dissolved (<0.45 μm) iron (dFe) and manganese (dMn) samples were collected during the GEOTRACES HERMINE GApr07 process study at the Mid Atlantic Ridge. Samples were collected at nine stations, from the TAG vent site to 75 km south-southwest following the neutrally buoyant plume. Concentrations of dMn and dFe ranged from 71 6 and 51 2 nmol kg1 right above the vent site to 0.43 0.01 and 1.56 0.02 nmol kg1 at the most distal station, respectively. Using a 5-box model coupled with our data, we show that as the plume traveled away from the vent, aggregation processes controlled dFe concentrations in the first 2 km, with an aggregation rate averaging between 8.0 0.6 and 0.11 0.04 nmol L1 d1, respectively in the first and second kilometer. Aggregation, likely of small colloidal particles, led to partitioning of the size fractionated Fe pool, as 6% of the dFe was moved into the particulate size fraction. Further away, disaggregation processes became more prevalent, with rates ranging from 0.27 0.02 to 0.008 0.001 nmol L1 d1, enriching the dFe pool by 10%. The computed decrease of hydrothermal Fe within the neutrally buoyant plume was likely caused by flocculation of small Fe oxyhydroxide particles. This process resulted in Fe aggregate formation with radii estimated to range between 14 and 20 μm in the first km from TAG. Between 2 and 30 km from the vent site, the radii ranged between 2 and 4 μm.

Item Details

Item Type:Refereed Article
Keywords:iron, manganese, hydrothermal, TAG, Mid Atlantic Ridge, GEOTRACES
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Chemical oceanography
Objective Division:Environmental Management
Objective Group:Marine systems and management
Objective Field:Oceanic processes (excl. in the Antarctic and Southern Ocean)
UTAS Author:Holmes, T (Dr Thomas Holmes)
ID Code:143470
Year Published:2020
Deposited By:Oceans and Cryosphere
Deposited On:2021-03-19
Last Modified:2021-03-23
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