Oxygen isotope study of the highly fractionated Podlesí granite system, Krušné hory Mts., Czech Republic


Authors: Žák K, Pudilová M, Breiter K

Published in: Bulletin of Geosciences, volume 80, issue 2; pages: 139 - 143; Received 28 June 2004; Accepted in revised form 7 April 2005;

Keywords: Krušné hory/Erzgebirge Mts., granite, oxygen isotopes, isotope thermometry,

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The extremely fractionated, Li-, P- and F-rich, and Sn-, W-, Nb-, and Ta-bearing minor granite stock cropping out near Podlesí east of Potůčky, western Krušné hory/Erzgebirge Mts., was studied using oxygen isotope geochemistry of quartz and other silicate minerals. A total of 39 monomineral analyses were taken from 13 rock samples. delta;18O values were obtained from quartz (9.2 to 11.6‰), feldspar (7.1 to 10.6‰), and mica of protolithionite and zinnwaldite composition (5.8 to 8.6‰, SMOW). The delta;18O relationships among minerals indicate the influence of hydrothermal processes in sub-solidus conditions, which especially affected the feldspars. The oxygen isotope systematics of these rocks results from the activity of high- delta;18O fluids, while no major involvement of low- delta;18O fluids was evident. Whole-rock delta;18O data, estimated based on mineral delta;18O data and modal composition, range between 9.5 and 10.5‰ SMOW, which demonstrate the limited effect of hydrothermal activity and point to a crustal origin of the Podlesí granite.