Multiple sources of the West-Carpathian Variscan granitoids: A review of Rb/Sr and Sm/Nd data

Detailed reviewing of several existing Rb/Sr datings from the West-Carpathi an granitic massifs shows that the Rb/Sr dates older than U/Pb zircon data are possibly caused by inclusion of high Rb/Sr samples in the sample collec tions. Such samples, usually occurring as leucocratic veins in metamorphic complexes, usually have higher initial Sr-87/Sr-86 ratios which results in generating pseudo-isochrons. Therefore, there is no need for an initial mix ing Line as suggested earlier. Some samples outlying both above and below i sochrons may be interpreted in terms of system opening at a time different from the initial closure. Depending on reconstructed Rb/Sr ratios late Vari scan to Early Alpine ages are obtained for the opening. In contrast to Rb/S r, previously published Sm/Nd data show that the initial Nd-143/Nd-144 rati os were not homogenized making it possible to suggest end-members responsib le for the observed variation. Such end-members are sought in (1) the peral uminous (leuco)granites that originated through dehydration melting of gnei sses with fairly high I-Sr and (2) gabbro/dioritic rocks occurring within g ranite massifs or as mafic enclaves. Assimilation of supracrustal rocks by the mafic magma could have produced either sub- to metaluminous I-type gran itoids or peraluminous S-type granites depending on proportions of the end- members. The varying proportions may also have been responsible for the min eralogical and petrological differences observed between the two groups. Se ven different sources are suggested for all the Variscan granitoids in the Western Carpathians.