Evolución contrastada de elementos trazas (Th-U-Y-HREE) entre granitos fraccionados de tipo-I y tipo-S de la Sierra de Guadarrama: reflejo en la quimica de minerales accesorios

Abstract

1- and 5-type granites from the Sierra de Guadarrama (Spanish Central System) display contrasting evolutionary patterns for Th, Y and REE. This chemical contrast is controlled by the behaviour of accessory phases. In felsic I-type granites the low fractionation of some phosphates (xenotime, monazite) permits the enrichment in the HFSE hosted in those accessories. Moreover, contrasts in trace element contents in accessory phases (zircon, xenotime, monazite) appear between 1- and S-type granites. Th, Y and HREE contents in monazite and xenotime are lower in S-type granites compared to those in less peraluminous ones. This is reflected in lower Th/U ratios in monazites and xenotimes from S-type granites.