Yttrium in the Vigo Ria (NW Iberian Peninsula): Sources, distribution, and background levels

Abstract

Certain heavy minerals enriched in yttrium, such as monazite and xenotime, have previously been indexed in the Vigo area. The levels and spatial distribution of this element were studied in 50 surface sediment samples from the Vigo Ria. The highest levels were found along the southern margin in the middle of the ria, coinciding with the geological source of the Galiñeiro Complex. From this zone, a dilution of yttrium in the sediments was observed seaward due to the presence of calcium carbonate (outer ria) and upstream due to the input of migmatites, anatexites, and two-mica granites (inner ria). The estimated background concentration in the Vigo Ria was 14.6 ± 2.6 mg kg-1 (Sc normalized), which is close to the average concentration found in surface sediments (13.4 ± 5.4 mg kg-1). This suggests that yttrium in the Vigo Ria sediments is mainly of lithogenic origin.

Factors driving sediment compositional change in the distal area of the Ria de Vigo (NW Spain): oceanographic processes vs. paleopollution

“…This would be expected since, according to Turekian and Wedepohl (1961), the worldwide sands have higher mean concentrations of Y (40 mg kg −1 ) than shale (26 mg kg −1 ). In surface sediments of the Ria de Vigo, the enrichment of this element is mostly observed in its middle zone and is also related to sands (Marmolejo-Rodríguez et al 2008). The PCA results (Fig.…”

“…The Malpica-Tui unit (Gil-Ibarguchi and Ortega 1985) and the Galiñeiro Complex (Montero et al 1998), which cross the Ria de Vigo, have abundant bastnasite, parisite, xenotime, thalenite, and yttrialite (Marmolejo-Rodríguez et al 2008). Yttrium is a trace element in the Earth's crust (mean 33 mg kg −1 ; Taylor 1964) but is concentrated in some minerals, especially xenotime and monazite (Montero et al 1998), which are present as accessory phases in granitic gneiss, igneous, and metamorphic rocks that occur around the Ria de Vigo (Evans et al 2003;Nombela et al 1995).…”

“…Yttrium is also considered to have little involvement in diagenetic processes. Therefore, it has been used to relate the sediments to the source rocks (Murad 1978), and the concentrations of this element provide insights into the weathering of the rocks surrounding the Ria de Vigo and the transport of sediments from this coastal system toward the adjacent continental shelf (Marmolejo-Rodríguez et al 2008).…”

Ressources en terres rares de l’Europe et du Groenland : potentiel minier et enjeux

“…La diminution de l'activité du fluor avec la baisse de température et la cristallisation de minéraux fluorés ont remobilisé les complexes précédemment créés pour conduire à la formation de minéraux riches en REE. En outre, le complexe de Galiñeiro après altération et érosion serait la source des minéraux à REE qui constituent les placers alluviaux et côtiers de la vallée de Ría Vigo (Marmolejo-Rodríguez et al, 2008).…”

“…Les placers sont en général datés du Cénozoïque et du Quaternaire et contiennent aussi du xénotime, ainsi que des minéraux à Ti-Zr-Sn-(W)-Nb-Ta (ilménite, zircon, rutile, columbo-tantalite, wolframite et scheelite). Des analyses récentes ont montré des teneurs en Y intéressantes (0,3-23,1 mg/kg, moyenne de 14,5 ± 3,5 mg/kg) au sein des sédiments de Ría Vigo (Marmolejo-Rodríguez et al, 2008 ;Prego et al, 2009). L'origine de l'yttrium serait liée au complexe de Galiñeiro.…”