%0 Journal Article
%A Orejana García, David
%A Villaseca González, Carlos
%T Heterogeneous metasomatism in cumulate xenoliths from theSpanish Central System: implications for percolative fractionalcrystallization of lamprophyric melts
%D 2008
%@ 0305-8719
%U https://hdl.handle.net/20.500.14352/49601
%X The alkaline lamprophyres and diabases from the Spanish Central System carry aheterogeneous suite of xenoliths including a group of highly altered ultramafic pyroxenites thatcontain Cr–Mg-rich high-T hydrous minerals (Ti-phlogopite and pargasitic to kaersutitic amphibole),indicative of modal metasomatism. The trace element mineral compositions of these xenolithsshow three patterns: type A xenoliths, with light rare earth element enriched clinopyroxeneswith high field strength element (HFSE) negative anomalies; type B xenoliths, with clinopyroxenesand amphiboles with high incompatible trace element contents (large ion lithophile elements(LILE), HFSE and REE); type C xenoliths, with relatively REE- and HFSE-poor clinopyroxenesand amphiboles. These metasomatic signatures suggest the involvement of three different metasomaticagents: carbonate, silicate and hydrous fluids or melts, respectively. These agents couldhave been derived from the progressive differentiation of a CO2–H2O-rich highly alkaline magma,genetically related to the Late Permian alkaline magmatism. Because of the original sub-alkalinenature of the pyroxenite xenoliths, theymight have been formed originally as pyroxene-rich cumulatesassociated with underplated Hercynian calc-alkaline basic magmas. Metasomatism as a result ofthe infiltration of alkalinemagmaswithin these cumulatesmight explain the relatively high radiogenicNd composition of the altered ultramafic xenoliths.
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