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. (C) 2018 Elsevier B.V. All rights reserved.
keywords
AUTHIGENIC CARBONATES; PORE WATERS; COLD-SEEP; MARINE-SEDIMENTS; SALT-MARSHES; ICP-MS; METHANE; TRACE; GEOCHEMISTRY; RIDGE
subject category
Environmental Sciences & Ecology
authors
Carvalho, L; Monteiro, R; Figueira, P; Mieiro, C; Pereira, E; Magalhaes, V; Pinheiro, L; Vale, C
our authors
Paula Figueira
Laboratory Officeracknowledgements
This work was supported by the Strategic Funding of CESAM, Portugal (UID/AMB/50017/2013), CIIMAR, Portugal (CORAL project), CICECO, Portugal (UID/CTM/50011/2013), Euromargins MVSeis Project (01-LEC-EMA24F) and through national funds provided by FCT/MEC and the co-funding by the FEDER, within the PT2020 Partnership Agreement and Compete 2020. Rui Monteiro (SFRH/BD/108535/2015) and Claudia Mieiro (SFRH/BPD/100740/2014) acknowledge their grants to FCT. The manuscript benefited from the comments and suggestions of three reviewers and the editor.