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  • Author: Nina Gardenová x
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Karel Breiter, Nina Gardenová, Viktor Kanický and Tomáš Vaculovič

Abstract

Contents of Ga and Ge in granites, rhyolites, orthogneisses and greisens of different geochemical types from the Bohemian Massif were studied using inductively coupled plasma mass spectrometry analysis of typical whole-rock samples. The contents of both elements generally increase during fractionation of granitic melts: Ga from 16 to 77 ppm and Ge from 1 to 5 ppm. The differences in Ge and Ga contents between strongly peraluminous (S-type) and slightly peraluminous (A-type) granites were negligible. The elemental ratios of Si/1000Ge and Al/1000Ga significantly decreased during magmatic fraction: from ca. 320 to 62 and from 4.6 to 1.2, respectively. During greisenization, Ge is enriched and hosted in newly formed hydrothermal topaz, while Ga is dispersed into fluid. The graph Al/Ga vs. Y/Ho seems to be useful tool for geochemical interpretation of highly evolved granitoids.