Resumen de Evolución temporal del sistema de aguas ácidas del Arroyo del Val (Luesma, Zaragoza): influencia sobre el comportamiento geoquímico de los lantánidos
J.A. Orgaz Díaz, Luis Francisco Auqué Sanz, María José Gimeno Serrano, J. B. Gómez Jiménez, Juan Miguel A. Mandado Collado
Acidic waters of the Arroyo del Val (Zaragoza) are generated by oxidation of sulphide minerals dispersed in the Silurian shales (Bádenas Formation) of the drainage basin. Sulphate - rich waters (pH = 2-4) were compared from two different sampling campaigns (1992 and 2003) to evaluate the possible change in the Rare Earth Elements (REE) geochemistry behaviour due to modification of system conditions. Mixing of acidic waters with neutral tributaries generates amorphous solids (Al-hydroxisulfates and Fe-oxihydroxides) that precipitate at the confluences. The presence of more Fe-oxihydroxides than Al'-hydroxisulfate in the precipitates has changed the scavenging process of REE in the system. However basic properties of acidic waters are still preserved such as the high REE contents (REE = 80 - 320 ppb) and enrichment in intermediate REEs (MREE) which results in convex - upward NASC normalized patterns.