| Título: | Heterogeneous metasomatism in cumulate xenoliths from theSpanish Central System: implications for percolative fractionalcrystallization of lamprophyric melts |
| Autores: | Orejana García, David ; Villaseca González, Carlos |
| Tipo de documento: | texto impreso |
| Editorial: | Geological Society of London, 2008 |
| Dimensiones: | application/pdf |
| Nota general: | info:eu-repo/semantics/openAccess |
| Idiomas: | |
| Palabras clave: | Estado = Publicado , Materia = Ciencias: Geología: Petrología , Tipo = Artículo |
| Resumen: |
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. |
| En línea: | https://eprints.ucm.es/id/eprint/12371/1/GSLSPMetasomatism_01_08.pdf |
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