WHOLE-ROCK CHEMISTRY AND GENETIC TYPOLOGY OF THE WEST-CARPATHIAN VARISCAN GRANITES

Rok, strany: 2001, 79 - 90

The geochemistry of 166 new whole-rock analyses from West-Carpathian Variscan granitic rocks are presented on the basis of their division into four principal groups: S-, I-, A- and specialized S-type (S_S). The contribution shows some discrimination diagrams which are useful for the recognition of these principal granite groups and also give a possible outline of the geodynamic scenario of their origin. All studied groups belong to mainly crustal aluminic (S_S-, S-type) and aluminocafemic (I-, A-, partly S-type) associations, mantle-derived cafemic dioritic rocks are rare. Generally, the S- and I-type groups show predominantly Na₂O/K₂O ratio > 1, whereas A- and S_S-type granites usually exhibit Na₂O/K₂O < 1. I-types are more Si-poor and Fe, P-rich than other groups, however, a part of the S_S-type group belongs to the P-rich evolved granites (>0.2 wt. % P₂O₅) and the A-types are generally very poor in P. The Zr vs. SiO₂ diagram clearly discriminates Zr and Si-rich hypersolvus A-type from other groups, similarly the A-types show the highest Zr/Hf-ratio and Y contents (>20 ppm). Ba-Sr and Sr-Rb diagrams successfully divide plagioclase-rich I-type from S,A-type and especially from K,Na-feldspar-rich S_S-type. The newly modified Rb-Ba-Sr diagram reliably discriminates the groups: poorly (I, S), mildly (S, A, rarely I) and strongly evolved granites (S_S, rarely S and A) were recognized. REE rock/chondrite normalized diagram discriminate all groups: REE-rich I-type without Eu-anomaly, from REE-rich A-type with negative Eu-anomaly and REE-poor S- and especially S_S-type with pronounced negative Eu-anomaly. In this sense of the geotectonic position, the S- and I-type can be considered as orogenic granites, in contrast, the A-type and S_S type granites are post-orogenic members.

ISO 690:

Broska, I., Uher, P. 2001. WHOLE-ROCK CHEMISTRY AND GENETIC TYPOLOGY OF THE WEST-CARPATHIAN VARISCAN GRANITES. In Geologica Carpathica, vol. 52, no.2, pp. 79-90. 1335-0552.

APA:

Broska, I., Uher, P. (2001). WHOLE-ROCK CHEMISTRY AND GENETIC TYPOLOGY OF THE WEST-CARPATHIAN VARISCAN GRANITES. Geologica Carpathica, 52(2), 79-90. 1335-0552.