Geoquímica deis sediments de la xarxa de drenatge del riu Garona a la Val d'Aran

Abstract

The geochemíca! baseline levéis were established for 48 ma]or and trace elements in stream sediments of the Garonne fííver watershed in the Valley of Aran in the Central Pyrenees, We used samptes collected in 1981 in a pilot project ofstream sediment geochemistry. We have analysed the grain síze fractíon íower than 180 mícrons by HR-ICPMS usíng a multiacíd digestión to establísh the quashtotal concentration of the elements. The results of nitríc acid leachates were used to model the environmentaily avaHabte fraction and the erosión rates ofsuch etements. The results define three lithogeochemical uníts consísting ofthe Maladeta-Marímanya granitoids, the metasedíments occumngin an extensivo área of the basin, and the btack shales, whích are present in Sfnaller áreas.