Rare earth elements in mud volcano sediments from the Gulf of Cadiz, South Iberian Peninsula

Lina Carvalho; Rui Monteiro; Paula Figueira; Cláudia Mieiro; Eduarda Pereira; Vítor Magalhães; Luís Pinheiro; Carlos Vale

doi:10.1016/j.scitotenv.2018.10.227

Rare earth elements in mud volcano sediments from the Gulf of Cadiz, South Iberian Peninsula

Sci Total Environ. 2019 Feb 20:652:869-879. doi: 10.1016/j.scitotenv.2018.10.227. Epub 2018 Oct 17.

Authors

Lina Carvalho¹, Rui Monteiro², Paula Figueira³, Cláudia Mieiro⁴, Eduarda Pereira⁵, Vítor Magalhães⁶, Luís Pinheiro⁷, Carlos Vale⁸

Affiliations

¹ Central Laboratory of Analysis (LCA), University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal.
² CESAM and Chemistry Department, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal; Interdisciplinary Centre of Marine and Environmental Research (CIIMAR), University of Porto, Avenida Norton de Matos, 4450-208 Matosinhos, Portugal.
³ Central Laboratory of Analysis (LCA), University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal; CICECO (Aveiro Institute of Materials) and Chemistry Department, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal. Electronic address: paulafigueira@ua.pt.
⁴ CESAM and Chemistry Department, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal.
⁵ Central Laboratory of Analysis (LCA), University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal; CESAM and Chemistry Department, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal.
⁶ Marine Geology and Georesources Division (DivGM), Portuguese Institute for the Ocean and Atmosphere (IPMA), Rua C ao Aeroporto, 1749-077 Lisboa, Portugal.
⁷ CESAM and Geosciences Department, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal.
⁸ Interdisciplinary Centre of Marine and Environmental Research (CIIMAR), University of Porto, Avenida Norton de Matos, 4450-208 Matosinhos, Portugal.

PMID: 30380493
DOI: 10.1016/j.scitotenv.2018.10.227

Abstract

Eight gravity cores (GC) were retrieved from the deep mud volcanoes Sagres, Bonjardim, Soloviev and Porto in the Gulf of Cadiz. Cores with 137 to 317 cm long were sliced in intervals of 15 to 20 cm thickness, and 46 samples were analyzed for grain size distribution, loss on ignition, Al, Fe, Ca, Mg, Mn, Sr, Ba and the rare earth elements (REE) La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu. REE profile normalized to Post-Archean Australian Average Shale (PAAS) was dominated by a mid-REE bulge with a pronounced Eu enhancement. Sediment reducing conditions resulting from the anaerobic oxidation of methane probably contributed to the positive-Eu anomaly (1.18-2.19, PAAS normalization). Most likely, reactions near the sulfate-methane transition zone such as the precipitation of barium sulfate found at layers around 50-cm depth explain the enhancement of Eu/Eu* ratios. The Ce anomalies (0.93-1.09) were almost absent.

Keywords: Anaerobic oxidation of methane; Eu anomaly; Gulf of Cadiz; Mud volcanoes; REE composition; Sediment cores.