Sr and Nd isotopic study and Rb-Sr geochronology of the Bejar granites, Iberian Massif, Spain

The Spanish Central Massif (SCM) is a major granitoid complex in the southern Central-Iberian Zone of the Hercynian Iberian belt. Its western part consists of mafic enclave bearing porphyritic biotite monzogranite-granodiorites (BG) with minor cordierite ± muscovite-bearing granites (CMG). The BG and the CMG are geochemically similar, though the latter have higher Sr contents. Both are moderately peraluminous. The Rb/Sr biotite ages from both granite types are consistent with each other, and range between 295 ± 4 and 307 ± 5 Ma. The isotopic data presented here, and the close association of the granites with gabbroic rocks of mantle origin, rule out a purely crustal source, rather suggesting a mantle-crust mixed origin. A two-stage petrogenetic process is envisaged. -from Authors