Metaluminous pyroxene-bearing granulite xenoliths from the lower continental crust in central Spain: their role in the genesis of Hercynian I-type granites

Abstract

Basic and intermediate meta-igneous xenoliths are very scarce within the granulite population transported by the Permian
alkaline lamprophyric dyke swarmof the Spanish Central System(SCS). These xenoliths aremetaluminous pyroxene-bearing
charnockites (sensu lato). They show LREE-poor plagioclase and orthopyroxene-clinopyroxene. Crystallization conditions were
estimated at about 850 to 1000 ◦C and 9 to 11 kbar, a slightly higher range than that estimated for the associated peraluminous
granulites, but indicating derivation from the lowermost crust.
Whole-rock geochemistry suggests that the charnockite samples are not a cogenetic suite. The more basic varieties have affinities
with cumulates from previous calc-alkaline underplated protoliths, whereas intermediate charnockites have a restitic origin. The
similarity in Sr-Nd-Pb isotopic signatures between these restitic charnockites and some SCS I-type granites suggests a genetic
relationship. This study, including Pb isotopic data from the whole granulite xenolith suite, reinforces the lower-crustal derivation
of the SCS Hercynian granitic batholith.