Edad y contexto geodinámico del magmatismo básico Ordovícico del Sistema Central Español
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2016
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Sociedad Geológica de España.
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Abstract
Nuevos datos geoquímicos (elementos mayores, traza e isótopos) y geocronológicos obtenidos en metabasitas intrusivas en las series metasedimentarias y metaígneas pre-Arenigienses del Sistema Central Español confirman la heterogeneidad composicional de estos materiales. Su evolución es de afinidad toleítica, pero con unos contenidos en elementos incompatibles relativamente elevados, lo que las diferencia de magmas tipo N-MORB. Se pueden distinguir dos grupos: 1) uno isotópicamente empobrecido y más diferenciado, y 2) otro isotópicamente más enriquecido, pero que representa líquidos más primitivos y con mayores contenidos de metales (Cr, Ni) y LILE. Estos datos apuntan a la participación de varias fuentes de manto, incluyendo sectores litosféricos con una impronta cortical. Dos muestras han aportado edades U-Pb en circones entre 473 y 453 Ma, lo que las relaciona con el contexto de rifting asociado a la apertura del océano Rheico. En la Zona Centro-Ibérica no hay magmatismo básico Cambro-Ordovícico anterior al que se describe en este trabajo, lo cual podría indicar que el rifting sería un fenómeno más tardío en este sector, en comparación con lo que se observa en otros terrenos del Macizo Ibérico.
New geochemical (major, trace and isotopic) and geochronological data obtained on metabasites intrusive into pre-Arenig metasedimentary and metaigneous rocks of the Spanish Central System confirm their heterogeneous composition. They exhibit a tholeiitic affinity, but show relatively high incompatible element contents, contrary to NMORB magmas. Two groups can be distinguished: 1) one isotopically depleted and more evolved and 2) one isotopically enriched, representing more primitive liquids with higher metal (Cr, Ni) and LILE contents. These data point to the involvement of several mantle sources, including lithospheric sections with a crustal imprint. Two samples have provided U-Pb zircon ages in the range 473- 453 Ma, thus related to the rifting context associated with the Rheic ocean opening. The absence of basic magmatism in the Central-Iberian Zone prior to that described in this work, might indicate that rifting was a late event in this region when compared to other terranes from the Iberian Massif.
New geochemical (major, trace and isotopic) and geochronological data obtained on metabasites intrusive into pre-Arenig metasedimentary and metaigneous rocks of the Spanish Central System confirm their heterogeneous composition. They exhibit a tholeiitic affinity, but show relatively high incompatible element contents, contrary to NMORB magmas. Two groups can be distinguished: 1) one isotopically depleted and more evolved and 2) one isotopically enriched, representing more primitive liquids with higher metal (Cr, Ni) and LILE contents. These data point to the involvement of several mantle sources, including lithospheric sections with a crustal imprint. Two samples have provided U-Pb zircon ages in the range 473- 453 Ma, thus related to the rifting context associated with the Rheic ocean opening. The absence of basic magmatism in the Central-Iberian Zone prior to that described in this work, might indicate that rifting was a late event in this region when compared to other terranes from the Iberian Massif.