In:
Frontiers in Earth Science, Frontiers Media SA, Vol. 9 ( 2021-8-5)
Kurzfassung:
We present pore fluid geochemistry, including major ion and trace metal concentrations and the isotopic composition of pore fluid calcium and sulfate, from the uppermost meter of sediments from the Gulf of Aqaba (Northeast Red Sea) and the Iberian Margin (North Atlantic Ocean). In both the locations, we observe strong correlations among calcium, magnesium, strontium, and sulfate concentrations as well as the sulfur isotopic composition of sulfate and alkalinity, suggestive of active changes in the redox state and pH that should lead to carbonate mineral precipitation and dissolution. The calcium isotope composition of pore fluid calcium (δ 44 Ca) is, however, relatively invariant in our measured profiles, suggesting that carbonate mineral precipitation is not occurring within the boundary layer at these sites. We explore several reasons why the pore fluid δ 44 Ca might not be changing in the studied profiles, despite changes in other major ions and their isotopic composition, including mixing between the surface and deep precipitation of carbonate minerals below the boundary layer, the possibility that active iron and manganese cycling inhibits carbonate mineral precipitation, and that mineral precipitation may be slow enough to preclude calcium isotope fractionation during carbonate mineral precipitation. Our results suggest that active carbonate dissolution and precipitation, particularly in the diffusive boundary layer, may elicit a more complex response in the pore fluid δ 44 Ca than previously thought.
Materialart:
Online-Ressource
ISSN:
2296-6463
DOI:
10.3389/feart.2021.601194
DOI:
10.3389/feart.2021.601194.s001
DOI:
10.3389/feart.2021.601194.s002
DOI:
10.3389/feart.2021.601194.s003
DOI:
10.3389/feart.2021.601194.s004
DOI:
10.3389/feart.2021.601194.s005
Sprache:
Unbekannt
Verlag:
Frontiers Media SA
Publikationsdatum:
2021
ZDB Id:
2741235-0
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