Diffusive transfer of oxygen from seamount basaltic crust into overlying sediments: An example from the Clarion–Clipperton Fracture Zone.

Mewes, K., Mogollón, J.M., Picard, A., Rühlemann, C., Eisenhauer, Anton , Kuhn, T., Ziebis, W. and Kasten, S. (2016) Diffusive transfer of oxygen from seamount basaltic crust into overlying sediments: An example from the Clarion–Clipperton Fracture Zone. Earth and Planetary Science Letters, 433 . pp. 215-225. DOI 10.1016/j.epsl.2015.10.028.

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[img] Text (MMC 1. Lithology description of piston and gravity cores (site BIO12-60PC, SO205-59GC and BIO12-53PC) and nomenclature used in the reaction-transport model with respective fundamental units.)
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Abstract

Highlights

• Geochemical evidence confirms exchange between sediments and the basaltic crust fluids.
• O2 exchange between the sediment and the basaltic crust produces a fully oxic sediment column.
• Transport-reaction modeling was performed to quantify the exchange of O2 and nutrients.

Abstract

The Clarion–Clipperton Fracture Zone (CCFZ) in the Pacific Ocean is characterized by organic carbon-starved sediments and meter-scale oxygen penetration into the sediment. Furthermore, numerous seamounts occur throughout its deep-sea plain, which may serve as conduits for low-temperature hydrothermal seawater circulation through the oceanic crust. Recent studies in deep-sea environments of the Pacific and Atlantic Oceans have suggested and presented evidence of dissolved constituent exchange between the seawater flowing in the basaltic crust and the pore water of the overlying sediments. Through high-resolution pore-water oxygen and nutrient measurements, we examined fluxes and geochemical interactions between the seamount basaltic basement and pore waters of the overlying sediments at three sites located on a radial transect from the foot of Teddy Bare, a small seamount in the CCFZ. At three sites, located 1000, 700 and 400 m away from the foot of the seamount, we found that oxygen concentrations initially decrease with sediment depth but start to increase at depths of 3 and 7 m toward the basaltic basement. Nitrate (View the MathML sourceNO3−) concentrations mirror the oxygen concentration profiles, as they increase with sediment depth but decrease towards the basement. These profiles suggest an upward diffusion of oxygen from seawater circulating within the seamount crust into the overlying basal sediments and a downward diffusion of View the MathML sourceNO32− from sediment pore water into the basaltic crust. At one site, we determined that the 87Sr/86Sr ratios of the bottom water and of the deep sediment near the basaltic crust are similar, further supporting diffusive exchange between basaltic crust fluids and sediment pore water.
Transport-reaction modeling performed at two of the study sites revealed that (1) the diffusive flux of oxygen from the basaltic basement outpaces the oxygen consumption through organic matter oxidation and nitrification in the basal sediments and (2) the nutrient exchange between the sediment and the underlying basaltic crust occurs at orders-of-magnitude lower rates than between the upper sediment and the overlying bottom water. These results further show that the diffusion of oxygen from the seamount basaltic basement into the overlying pore waters affects the preservation of organic compounds and helps to maintain a completely oxygenated sedimentary column at all 3 sites near the seamount.

Document Type: Article
Funder compliance: info:eu-repo/grantAgreement/EC/H2020/661163
Additional Information: WOS:000367120300022
Keywords: deep-sea sediments; eastern equatorial Pacific; redox zonation; basement–sediment interactions; seamounts; oxygen; RV Sonne; SO205; RV L’ATALANTE cruise BIONOD
Research affiliation: MARUM
Kiel University
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
AWI
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1016/j.epsl.2015.10.028
ISSN: 0012-821X
Expeditions/Models/Experiments:
Date Deposited: 08 Jan 2016 13:35
Last Modified: 23 Sep 2019 21:52
URI: http://oceanrep.geomar.de/id/eprint/30936

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