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oai:docta.ucm.es:20.500.14352/496012023-08-26T05:58:32Zcom_20.500.14352_14col_20.500.14352_15

Orejana García, David Villaseca González, Carlos 2023-06-20T09:27:33Z 2023-06-20T09:27:33Z 2008 0305-8719 10.1144/SP293.6 https://hdl.handle.net/20.500.14352/49601 http://www.geolsoc.org.uk/gsl/op/%3C/publications/books/sp The alkaline lamprophyres and diabases from the Spanish Central System carry a heterogeneous suite of xenoliths including a group of highly altered ultramafic pyroxenites that contain 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 xenoliths show three patterns: type A xenoliths, with light rare earth element enriched clinopyroxenes with high field strength element (HFSE) negative anomalies; type B xenoliths, with clinopyroxenes and amphiboles with high incompatible trace element contents (large ion lithophile elements (LILE), HFSE and REE); type C xenoliths, with relatively REE- and HFSE-poor clinopyroxenes and amphiboles. These metasomatic signatures suggest the involvement of three different metasomatic agents: carbonate, silicate and hydrous fluids or melts, respectively. These agents could have 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-alkaline nature of the pyroxenite xenoliths, theymight have been formed originally as pyroxene-rich cumulates associated with underplated Hercynian calc-alkaline basic magmas. Metasomatism as a result of the infiltration of alkalinemagmaswithin these cumulatesmight explain the relatively high radiogenic Nd composition of the altered ultramafic xenoliths. eng open access Heterogeneous metasomatism in cumulate xenoliths from the Spanish Central System: implications for percolative fractional crystallization of lamprophyric melts journal article