Vertical distribution of major, minor and trace elements in sediments from mud volcanoes of the Gulf of Cadiz: evidence of Cd, As and Ba fronts in upper layers
authors Carvalho, L; Monteiro, R; Figueira, P; Mieiro, C; Almeida, J; Pereira, E; Magalhaes, V; Pinheiro, L; Vale, C
nationality International
journal DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS
author keywords Cadiz mud volcanoes; Sediment elemental composition; Depth profiles; Ba, Cd and As fronts
keywords EASTERN MEDITERRANEAN SEA; CONTINENTAL-MARGIN SEDIMENTS; GAS HYDRATE; COLD SEEPS; AUTHIGENIC CARBONATES; SULFATE REDUCTION; SUBDUCTION ZONES; DISSOLVED BARIUM; BLAKE RIDGE; OF-MEXICO
abstract Mud volcanoes are feature of the coastal margins where anaerobic oxidation of methane triggers geochemical signals. Elemental composition, percentage of fine particles and loss on ignition were determined in sediment layers of eleven gravity cores retrieved from four mud volcanoes (Sagres, Bonjardim, Soloviev and Porto) and three undefined structures located on the deep Portuguese margin of the Gulf of Cadiz. Calcium was positively correlated to Sr and inversely to Al as well as to most of the trace elements. Vertical profiles of Ba, Cd and As concentrations, and their ratios to Al, in Porto and Soloviev showed pronounced enhancements in the top 50-cm depth. Sub-surface enhancements were less pronounced in other mud volcanoes and were absent in sediments from the structures. These profiles were interpreted as diagenetic enrichments related to the anaerobic oxidation of methane originated from upward methane-rich fluxes. The observed barium fronts were most likely caused by the presence of barite which precipitated at the sulphate-methane transition zone. Cd and As enrichments have probably resulted from successive dissolution/precipitation of sulphides in response to vertical shifts of redox boundaries.
publisher PERGAMON-ELSEVIER SCIENCE LTD
issn 0967-0637
year published 2018
volume 131
beginning page 133
ending page 143
digital object identifier (doi) 10.1016/j.dsr.2017.12.003
web of science category Oceanography
subject category Oceanography
unique article identifier WOS:000425203300012
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5 year journal impact factor (jcr 2016): 2.735
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