Distribution of Sc, Cr, Co, Hf, Ta and Th in a weathering profile of gabbroic rocks (Serpa, Portugal)

Abstract: Trace element data (Sc, Cr, Co, Hf, Ta and Th) are reported for a weathering profile of gabbroic rocks located near Serpa, Portugal. The results obtained for the whole rock samples showed that: (i) Co and Sc contents decrease upwards the profile. Co appears to be mobilized in the soil probably as soluble cation; (ii) Cr tends to remain in the profile; and (iii) Hf and Th concentrate in the upper horizons. Trace element distribution in different size fractions of the upper horizons revealed: (i) Sc, Cr and Co have a more uniform distribution than Hf, Ta and Th; (ii) Hf and Ta are concentrated in the intermediate fractions; and (iii) Th is concentrated in the finer fractions, probably due to incorporation in weathering resistant minerals, specially in the initial stages of weathering.