REE Geochemistry of Neogene–Holocene Sediments of La Fontanilla Cove (Tinto Estuary, SW Spain)
Prudencio, María Isabel; Ruiz Muñoz, Francisco; Rodríguez Vidal, Joaquín; Cáceres Puro, Luis Miguel; González-Regalado Montero, María Luz; Gómez Gutiérrez, Paula; Toscano Grande, Antonio; Arroyo, Marta; Romero Aguilar, Verónica; Gómez Álvarez, Gabriel
The Tinto and Odiel rivers (SW Spain) drain from a vast sulfide mining district and join at
a 20-km-long estuary that enters the Atlantic Ocean. In this work, the contents of rare earth elements
(REE) and fractionation in Neogene–Holocene sediment cores from La Fontanilla cove (Tinto estuary)
were studied. The sediments were collected from a depth of 18 m at different distances from the
recent river flow and were analyzed for new information on the temporal development of the REE
load in the sediment column. Results show that the å REE is higher in the finer sediments and
during periods of mining activity from prehistoric to recent times. Marine influence appears to
increase the light REE (LREE) relative to the heavy REE (HREE). The REE patterns of these estuarine
sediments show convex curvatures in the MREE relative to the LREE and HREE, indicating the
presence of acid-mixing processes between the fluvial waters affected by acid mine drainage (AMD)
and seawater, as well as the precipitation of poorly crystalline mineral phases. Significant positive Eu
anomalies were found in ebb-tide channels and marsh deposits, which can reflect the mineralogical
composition and/or a strong localized salinity gradient combined with organic matter degradation.
Sedimentological characteristics of the deposits appear to play the main role in accumulation and
fractionation of the REE
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