Origin of the pegmatite veins within the skarn body at Vevčice near Znojmo (Gfohl Unit, Moldanubian Zone)

0475498 - GLÚ 2018 RIV CZ eng J - Journal Article
Buriánek, D. - Houzar, S. - Krmíček, Lukáš - Šmerda, J.
Origin of the pegmatite veins within the skarn body at Vevčice near Znojmo (Gfohl Unit, Moldanubian Zone).
Journal of Geosciences. Roč. 62, č. 1 (2017), s. 1-23. ISSN 1802-6222. E-ISSN 1803-1943
Institutional support: RVO:67985831
Keywords : diorite pegmatite * skarn * mineralogy * geochemistry * Moldanubian Zone * Bohemian Massif
OECD category: Geology
Impact factor: 1.415, year: 2017

The lower crustal Gfohl Unit (Moldanubian Zone of the Bohemian Massif) consists of various felsic orthogneisses to migmatites (the so-called Gfohl gneiss) that are conunonly associated with the high-pressure felsic granulites, serpentinized gamet/spinel peridotites, garnet pyroxenites, eclogites and skanis. The relatively small skarn bodies at Vevcice in southern Moravia have the prevailing assemblage of medium- to coarse-grained granoblastic clinopyroxene + garnet +/- amphibole +/- epidote. The skarn is cut by narrow veins of diorite pegmatite (SiO₂ = 46-56 wt. %) which is geochemically distinct from granitic melt generated by migmatization of surrounding orthogneisses. Major pegmatite minerals are plagioclase (An(15-14)), amphibole (K-rich hastingsite and potassic-hastingsite) and quartz, accompanied by minor K-feldspar, garnet, allanite-epidote, clinopyroxene, and accessory titanite. The pegmatites are characterized by high contents of Fe₂O_3tot, (11.2-17.5 wt. %), Ca₂O (7.5-10.11 wt. %), Na₂O (2.9-3.3 wt. %) and low contents of MgO (1.4-1.6 wt. %), K₂O (1.2-1.6 wt. %), Rb (43-86 ppm). Whole-rock and mineral chemistry of diorite pegmatites are consistent with their origin as a product of melt infiltration from surrounding migmatites and subsequent contamination by the country-rock skarn, with or without, fractional crystallization/crystal accumulation. Similarity in composition of amphiboles in the skarn and in the pegmatite can indicate formation under similar conditions, at c. 750 degrees C and 0.7-0.8 GPa.
Permanent Link: http://hdl.handle.net/11104/0272189