Publication: The Variscan gabbros from the Spanish Central System: A case for crustal recycling in
the sub-continental lithospheric mantle?
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Publication Date
2009
Authors
Pérez-Soba Aguilar, Cecilia
Billstrom, Kjell
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Elsevier Science B.V., Amsterdam
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Abstract
The gabbroic intrusions that crop out along the Spanish Central System (SCS) are geochemically
heterogeneous, including primitive and evolved rocks. Differentiation is mainly related to fractionation of
Cr-spinel and olivine, but mixing with coeval granitic magmas or crustal assimilation may have also played a
role in the evolution of the most differentiated rocks. The most primitive uncontaminated gabbros show arclike
trace element chondrite and primitive-mantle normalised patterns, characterised by large ion lithophile
elements (LILE)-light rare earth elements (LREE) enrichment, Sr and Pb positive and Nb–Ta–Ti negative
anomalies. However, paleogeographic constraints suggest that the SCS was located far from subduction
zones, so these geochemical signatures could be better explained by a recycling of continental crustal
components within the mantle. The most primitive SCS gabbros expand the Sr–Nd isotopic compositional
range of the Variscan basic magmatism in the Central Iberian Zone to more depleted values. This reflects a
heterogeneous sub-continental lithospheric mantle under central Spain ranging from a depleted mantle
(εNd=+3.1, 87Sr/86Sr=0.704) towards an isotopically enriched component (εNd=−1.6, 87Sr/
86Sr=0.706). Geochemical modelling suggests that mantle enrichment could be explained by minor lower
crustal metapelitic granulite contamination (~2%). Additionally, the Sr–Nd–Pb isotopic ratios of the most
primitive gabbros match the composition of the European subcontinental lithospheric mantle recorded in
ultramafic xenoliths from western and central Europe.