REE Geochemistry of Neogene–Holocene Sediments of La Fontanilla Cove (Tinto Estuary, SW Spain)

Abstract

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 ∑ 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.

Análisis geológico multidisciplinar de la Unidad Arenas de Trigueros (Formación Arcillas de Gibraleón, S.O. de España)

“…Algo similar puede apreciarse en las tierras raras (Tabla 2), cuyos valores suelen ser inferiores a la mayoría de las medidas indicadas en otras investigaciones de esta formación (Abad, 2007;González de Canales, 2017;Prudencio et al, 2022). El mayor tamaño de grano de la UAT explicaría esta disminución, ya que estos elementos tienden a concentrarse en los sedimentos más finos de los fondos ma-Tabla 2.…”

“…Geoquímica de la FAG. Datos procedentes de Abad (2008), González de Canales (2017), Prudencio et al (2022), Arroyo (com. pers.…”

“…) rinos actuales (Prego et al, 2012;Ge et al, 2020;Wu et al, 2020). Por otro lado, el enriquecimiento relativo de tierras raras medias es común en los sedimentos fluviales actuales y holocenos de esta región (López-González et al, 2005, Prudencio et al, 2022, lo que podría avalar la presencia de una componente fluvial importante en la dinámica sedimentaria que dio lugar al depósito de la UAT, ya indicada por otros autores (Toscano et al, 2013).…”