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Nutrient Fluxes Associated With Submarine Groundwater Discharge From Karstic Coastal Aquifers (Côte Bleue, French Mediterranean Coastline) ArchiMer
Bejannin, Simon; Tamborski, Joseph James; Van Beek, Pieter; Souhaut, Marc; Stieglitz, Thomas; Radakovitch, Olivier; Claude, Christelle; Conan, Pascal; Pujo-pay, Mireille; Crispi, Olivier; Le Roy, Emilie; Estournel, Claude.
Determination of submarine groundwater discharge (SGD) from karstic coastal aquifers is important to constrain hydrological and biogeochemical cycles. However, SGD quantification using commonly employed geochemical methods can be difficult to constrain under the presence of large riverine inputs, and is further complicated by the determination of the karstic groundwater endmember. Here, we investigated a coastal region where groundwater discharges from a karstic aquifer system using airborne thermal infrared mapping and geochemical sampling conducted along offshore transects. We report radium data (223Ra, 224Ra, 228Ra) that we used to derive fluxes (water, nutrients) associated with terrestrial groundwater discharge and/or seawater circulation through the...
Tipo: Text Palavras-chave: Submarine groundwater discharge; Mediterranean sea; Radium isotopes; Thermal infrared remote sensing; Nutrient fluxes; GEOTRACES.
Ano: 2020 URL: https://archimer.ifremer.fr/doc/00610/72171/70945.pdf
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Origin of the Oligocene manganese deposit at Obrochishte (Bulgaria): Insights from C, O, Fe, Sr, Nd, and Pb isotopes ArchiMer
Dekov, Vesselin M.; Barry Maynard, J.; Kamenov, George D.; Rouxel, Olivier; Lalonde, Stefan; Juranov, Sava.
The large manganese (Mn) deposit at Obrochishte (NE Bulgaria) is part of a cluster of similar Early Oligocene deposits located around present-day Black Sea. They collectively constitute the Earth’s second largest endowment of Mn, after the Kalahari Manganese Field in Africa. We have employed a battery of isotopic techniques (C, O, Fe, Sr, Nd, Pb) to help understand the genesis of this deposit. Carbon isotope data indicates that some sections of the Mn-ore layer have diagenetic MnCO3 mineralization, formed by reaction of Mn oxides with organic carbon (Corg), whereas other sections have MnCO3 precipitated directly from the seawater column. Oxygen isotopes show that the high-grade Mn mineralization had seawater as the fluid source, whereas some lower-grade...
Tipo: Text Palavras-chave: Mn metallogenesis; C-O-Fe-Sr-Nd-Pb isotopes; Early Oligocene; Submarine groundwater discharge; Water column anoxia; Proto-Black Sea geochemistry.
Ano: 2020 URL: https://archimer.ifremer.fr/doc/00624/73591/73025.pdf
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Authigenic carbonate mounds from active methane seeps on the southern Aquitaine Shelf (Bay of Biscay, France): evidence for anaerobic oxidation of biogenic methane and submarine groundwater discharge during formation ArchiMer
Pierre, Catherine; Demange, Jerome; Blanc-valleron, Marie-madeleine; Dupre, Stephanie.
The widespread methane emissions that were discovered in 2013 on the Aquitaine Shelf at water depth between 140 and 220 m are associated with authigenic carbonate crusts that cover meter-high subcircular reliefs of 10 to 100 m in diameter. These authigenic carbonates are primarily aragonite plus calcite and dolomite, which cement the fine- to medium-grained sandy sediment. The carbonate cement is often pierced by numerous circular cavities of 5 to 10 µm in diameter that are considered to be moulds of gas bubbles. Conversely, micron-sized cavities in the aragonite crystals are attributed to dissolution features, in relation to the production of CO2 during the aerobic oxidation of methane. The oxygen isotopic compositions of bulk carbonate (+1.7 to +3.7‰)...
Tipo: Text Palavras-chave: Aquitaine Shelf; Methane-derived authigenic carbonates; Oxygen isotopes; Carbon isotopes; Submarine groundwater discharge; Anaerobic oxidation of methane; Aerobic oxidation of methane.
Ano: 2017 URL: http://archimer.ifremer.fr/doc/00361/47209/47164.pdf
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