Controlling factors and impacts of river-borne neodymium isotope signatures and rare earth element concentrations supplied to the Canadian Arctic Archipelago

• Published in: Earth and Planetary Science Letters
• Main Authors: Grenier, Mélanie, Brown, K.A., Colombo, M., Belhadj, M., Baconnais, I., Pham, V., Soon, M., Myers, P.G., Jeandel, C., François, R.
• Other Authors: Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Centre National de la Recherche Scientifique (CNRS), Institute of Ocean Sciences Sidney (IOS), Fisheries and Oceans Canada (DFO), University of British Columbia (UBC), University of Saskatchewan Saskatoon (U of S), University of Alberta
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2022
• Subjects: Rare Earth Elements; neodymium isotopes; bedrock geology; dissolved riverine inputs; Canadian Arctic Archipelago; river geochemistry; [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; Arctic; Arctic Archipelago
• Online Access: https://hal.science/hal-03805808; https://hal.science/hal-03805808/document; https://hal.science/hal-03805808/file/Grenier-etal_eNd-REE-CAArivers_EPSL_22.pdf; https://doi.org/10.1016/j.epsl.2021.117341

International audience Determining the factors controlling the neodymium (Nd) isotopic compositions (expressed as ε Nd) and rare earth element (REE) concentrations of rivers is imperative to improve our understanding of the distribution of these water mass tracers in the ocean. Here we present the first measurements of <0.45 μm-filtrate REE concentrations (i.e., the concentration of truly dissolved, nano-particulate and colloidal REEs passing through a 0.45 μm filter, hereafter referred to as dissolved) and ε Nd in rivers draining into the Canadian Arctic Archipelago (CAA). Results show a large variation in both REE concentrations (Nd = [8; 37, 260] pmol/kg) and ε Nd ([−32.1; −15.1]) in the thirteen rivers sampled. Dissolved REE concentrations increase with increasing fractions of metamorphic rocks and ice cover in the rivers' watersheds, while ε Nd and PAAS-normalized REE patterns are inherited from the watershed's bedrock lithology. The four rivers draining watersheds composed of Precambrian metamorphic rocks exhibit the highest REE concentrations, the least radiogenic ε Nd , and shale-normalized patterns enriched in light REEs. The remaining nine rivers drain mainly or exclusively sedimentary bedrock and have lower REE concentrations, more radiogenic ε Nd and generally show heavy REE enrichment, with variable negative cerium (Ce) anomalies. The presence of ice sheets in the drainage area, and the ionic strength, pH, and dissolved organic carbon concentration of river water are the main factors determining riverine dissolved REE concentrations by controlling the formation and stabilization of colloids. We estimate a flow of dissolved Nd transported by Arctic rivers discharging into the CAA equivalent to the Nd flux of seawater entering the CAA. Depending on the percentage of Nd removal during mixing with seawater, the impact of river water on the ε Nd of seawater exiting the CAA could be modest (if 90% removal) or more significant (if 90% removal). This riverine contribution could potentially impart a ...