%0 Journal Article
%T Geological position, mineral assemblages and contamination of granitic pegmatites in the Moldanubian Zone, Czech Republic; examples from the Vlast¨§jovice region
%A Nov¨˘k M
%A Kadlec T
%A Gadas P
%J Journal of Geosciences
%D 2013
%I 
%R 10.3190/jgeosci.132
%X Three groups of pegmatites distinct in their geological position, age, internal structure, mineral assemblages and chemical composition of minerals (tourmaline, amphibole, garnet, and biotite) were distinguished in the Vlast¨§jovice region, Moldanubian Zone: a) tourmaline-bearing pegmatites (Qz + Kfs + Pl + Bt + Ms + Tur) enclosed in the pre-Variscan orthogneiss, b) contaminated amphibole-bearing pegmatites (Pl + Qz + Amp + Kfs + fluorite + allanite) hosted by the Fe-skarn, and c) tourmaline-bearing pegmatites cutting paragneisses (Qz + Kfs + Pl + Bt + Ms + Ab + Tur + Grt) and the Fe-skarn (Qz + Kfs + Pl + Bt + Tur ˇŔ Ab, Amp, Grt, elbaite). The pegmatites enclosed in the orthogneiss show simple internal structure and mineral assemblages, low degree of tectonometamorphic overprint. The amphibole-bearing pegmatites, likely anatectic and related to the Variscan MP-HT regional metamorphism, are spatially restricted to the Fe-skarn body and highly variable in shape, size, effects of in situ contamination by Ca, Fe ˇŔ F and REE from the host Fe-skarn, and degree of hydrothermal overprint. The tourmaline-bearing pegmatites related to the Variscan magmatic event cut different rocks (paragneisses, Fe-skarn bodies) and belong to the Moldanubian rare-element pegmatite province. They show distinct degree of textural differentiation, geochemical fractionation and external contamination by Ca and/or Fe (Ca,Fe-rich Al-poor tourmalines) higher in the less evolved pegmatite bodies in the Fe-skarn. The tourmaline-bearing pegmatites were evidently generated from the granite-pegmatite body in the footwall contact of the Fe-skarn. Degrees of the textural differentiation and geochemical fractionation of the individual tourmaline-bearing pegmatites are comparable to those of the respective parts of the parental footwall granite-pegmatite body. This observation seems consistent with the model of sequential derivation of pegmatite melts from evolving parental granite. Primitive to highly evolved and usually B-rich pegmatites originated during the Variscan orogeny from the MP ( 0.6-0.7 GPa) to the LP conditions ( 0.2 GPa), and manifest that formation of various granitic pegmatites was an integral part of the tectonomagmatic evolution of the region.
%K tourmaline
%K granitic pegmatites
%K Fe-skarn
%K Vlast¨§jovice
%K Moldanubian Zone
%U http://www.jgeosci.org/content/jgeosci.132_novak.pdf