Tracing magma sources of three different S-type peraluminous granitoid series by in situ U–Pb geochronology and Hf isotope zircon composition: The Variscan Montes de Toledo batholith (central Spain)

Three distinct S-type peraluminous granitoid types have been identified within the Variscan Montes de Toledo batholith, located in the Central Iberian Zone (SW European Variscides): type-1, extremely high peraluminous restite-rich granitoids; type-2, highly peraluminous restite-bearing granitoids; and type-3, moderately peraluminous granitoids with mafic microgranular enclaves. Type-1 and type-2 granitoids are restricted to the western part of the batholith, whereas type-3 granites are mostly restricted to the eastern segment. There is a sequential youngering of emplacement age from type-1 (late-tectonic) to type-2 and type-3 granitoids (post-tectonic), extending the timing of the batholith formation for about 19 Ma between 316 and 297 Ma. Although the degree of peraluminousity of the different series could be related to different partial melting conditions or to the variable entrainment of restitic components (including the peritectic mineral assemblage of the melting reactions), whole-rock geochemical signatures and isotope zircon composition of the peraluminous granitoid types suggest contribution of different crustal sources. There is no evidence for the direct mantle-derived material contribution in the genesis of these peraluminous melts. Type-1 and type-2 granitoids contain mostly Archean to Neoproterozoic inherited zircons, whereas type-3 granites show preferentially Neoproterozoic (up to late Cryogenian) and Ordovician inheritance. The wide range of initial Hf isotope composition, ranging to highly radiogenic values (ƐHf up to + 10), of Neoproterozoic zircon inheritances in type-1 and type-2 granitoids suggests derivation from heterogeneous Neoproterozoic metasedimentary sources composed of both juveline and recycled crustal materials, similar in composition to the host Schist–Greywacke Complex metasediments. Trace-element modelling clearly suggests the involvement of metasediments similar to those mentioned from the southern part of the Central Iberian Zon
Ministerio de Economía y Competitividad (MINECO)
Universidad Complutense de Madrid
Depto. de Mineralogía y Petrología
Fac. de Ciencias Geológicas
TRUE
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