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In this study, we present the first systematic dataset on natural variations of OH defect and trace element contents in quartz within igneous bodies. Samples were derived from bore holes of two plutonic bodies from the Krušné Hory/Erzgebirge (German–Czech border), representing typical A-type (Cínovec/Zinnwald granite cupola) and S-type (Podlesí Stock) granite intrusions. Fourier Transform Infrared spectroscopy of quartz was used to investigate the sample set with regard to its OH defect speciation and content. For Zinnwald quartz, IR absorption spectra reveal different lithologies due to changes of the OH defect inventory, enabling a subdivision of the granitic body: (1) hydrothermal greisen quartz of the uppermost part of the intrusion have low OH defect contents (average of 15 µg/g H2O); (2) zinnwaldite granite quartz vary strongly in defect content and show the highest content of the dataset (10–70 µg/g H2O); (3) quartz from an underlying biotite granite have slightly lower, but very uniform contents down to the bottom of the borehole at 1600 m (average 20 µg/g H2O). Infrared spectra of Podlesí quartz reveal a gradual increase in total defect water content with increasing depth over 350 m (30–55 µg/g H2O). Lithium contents in quartz samples from the uppermost part of the Zinnwald intrusion correlate with the occurrence of Li-specific OH defects, while cathodoluminescence (CL) images do not show specific differences. Our findings evidence the potential of OH defects in quartz as a tool to decipher differentiation trends in igneous bodies, and the application of their eroded material for provenance analyses. [ABSTRACT FROM AUTHOR]

Hafnium contents and Zr/Hf ratios were studied in zircons and their parent rocks from three magmatic suites associated with the Teplice caldera, Eastern Erzgebirge: rhyolite and dacite from the peraluminous Schönfeld Unit, relatively younger A-type Teplice rhyolite, and post-caldera A-type biotite and zinnwaldite granite and greisen. New data suggest that zircon crystallizing from a geochemically less evolved volatile- and water-poor melt is, compared to the host rock, relatively Hf-depleted, while zircon crystallizing from an evolved volatile- and water-rich melt has a Zr/Hf value approximately identical to that of the parental melt. Zr/Hf values in zircon did not change substantially either during greisenization, or during low-temperature alteration after metamictization. Zr/Hf values in the whole rock may serve as a sensitive indicator of magmatic fractionation of evolved granitic melts, as they are only negligibly influenced by the following hydrothermal processes. Zr/Hf values in individual cogenetic zircon grains are scattered but their general evolution trend in the rock series is consistent with the evolution of the whole-rock Zr/Hf values. [ABSTRACT FROM AUTHOR]

Molybdenite is a common mineral accompanying Sn-W, Au, and base metal mineralizations located in different geotectonic units of the Bohemian Massif, but it is also widespread in granitoids and/or related quartz veins/pegmatites forming disseminated Mo mineralization. Thirty Re-Os ages were obtained for molybdenite samples from the Bohemian Massif to provide constraints on the timing and duration of mineralization event(s) within the framework of previously published geochronological data for the host and/or associated rocks. The obtained data for Sn-W-(Li) deposits in the Erzgebirge metallogenetic province indicate the predominance of one and/or multiple short-time mineralization events taking place between ∼319 and 323 Ma, with the exception of the Krupka deposit associated with the Altenberg-Teplice caldera where the data may suggest prolonged activity until ∼315 Ma. The ages of the Pb-Zn-(Au-Mo) Hůrky u Rakovníka and Fe-Cu-As Obří důl mineralizations from the exocontacts of the Čistá pluton and Krkonoše-Jizera Plutonic Complex, respectively, provide evidence for synchronous emplacement of the ore and the associated granitic rocks. In contrast, the Padrť Fe-As-Mo mineralization postdates the age of the associated Padrť granite. Disseminated Mo mineralization in Cadomian and Variscan granitoids and/or related to quartz veins/pegmatites provides Re-Os ages that overlap with the previously published geochronological data for the host rocks, suggesting coeval evolution. Molybdenite samples from the Sázava suite granites of the Central Bohemian Plutonic Complex (CBPC) have resolvable younger ages than their host granites, but similar to the age of spatially related Au mineralization which is associated with the latest evolution of the CBPC. [ABSTRACT FROM AUTHOR]

The chemical compositions of zircon and monazite and the relationships between the contents of Th, U, Y, and REE in both minerals and in the bulk samples of their parental rocks were studied in three Variscan composite peraluminous granite plutons in the Bohemian Massif. It was established that granites of similar bulk composition contain zircon and monazite of significantly different chemistry. Monazite typically contains 5-13 wt% (rarely up to 28 wt%) ThO, 0.4-2 wt% (up to 8.2 wt%) UO, and 0.5-2 wt% (up to 5 wt%) YO, whereas zircon typically contains less than 0.1 wt% (rarely up to 1.7 wt%) ThO, less than 1 wt% UO (in the Plechý/Plockenstein granite, commonly, 1-2 wt% and scarcely up to 4.8 wt% UO), and less than 1 wt% YO (in the Nejdek pluton often 2-5, maximally 7 wt% YO). Monazite is an essential carrier of thorium, hosting more than 80 % of Th in all studied granites. Monazite also appears to be an important carrier of Y (typically 14-16 %, and in the Melechov pluton, up to 81 % of the total rock content) and U (typically 18-35 % and occasionally 6-60 % of the total rock budget). The importance of zircon for the rock budget of all the investigated elements in granites is lower: 4-26 % U, 5-17 % Y, and less than 5 % Th. [ABSTRACT FROM AUTHOR]

Nine SHRIMP U/Pb ages on zircon and two Pb/Pb single zircon ages have been determined from Late Paleozoic volcanic rocks from Saxony and northern Bohemia. Samples came from the Teplice-Altenberg Volcanic Complex, the Meissen Volcanic Complex, the Chemnitz Basin, the Döhlen Basin, the Brandov-Olbernhau Basin, and the North Saxon Volcanic Complex. The Teplice-Altenberg Volcanic Complex is subdivided into an early Namurian phase (Mikulov Ignimbrite, 326.8 ± 4.3 Ma), thus older than assumed by previous studies, and a late caldera-forming phase (Teplice Ignimbrite, 308.8 ± 4.9 Ma). The age of the latter, however, is not well constrained due to a large population of inherited zircon and possible hydrothermal overprint. The Leutewitz Ignimbrite, product of an early explosive volcanic episode of the Meissen Volcanic Complex yielded an age of 302.9 ± 2.5 Ma (Stephanian A). Volcanic rocks intercalated in the Brandov-Olbernhau Basin (BOB, 302 ± 2.8 Ma), Chemnitz Basin (CB, 296.6 ± 3.0 Ma), Döhlen Basin (DB, 296 ± 3.0 Ma), and the North Saxon Volcanic Complex (NSVC, c. 300-290 Ma) yielded well-constrained Stephanian to Sakmarian ages. The largest Late Paleozoic ignimbrite-forming eruption in Central Europe, the Rochlitz Ignimbrite, has a well-defined middle Asselian age of 294.4 ± 1.8 Ma. Ages of palingenic zircon revealed that the Namurian-Westphalian magmatism assimilated larger amounts of crystalline basement that formed during previous Paleozoic geodynamic phases. The Precambrian inherited ages support the chronostratigraphic structure assumed for the Saxo-Thuringian Zone of the Variscan Orogen. The present results help to improve the chronostratigraphic allocation of the Late Paleozoic volcanic zones in Central Europe. At the same time, the radiometric ages have implications for the interbasinal correlation and for the geodynamic evolution of the Variscan Orogeny. [ABSTRACT FROM AUTHOR]

The lattice-preferred orientation (LPOs) of two late-Variscan granitoids, the Meissen monzonite and the Podlesí dyke granite, were determined from high-resolution time-of-flight neutron diffraction patterns gained at the diffractometer SKAT in Dubna, Russia. The results demonstrate that the method is suitable for the LPO analysis of polyphase, relatively coarse-grained (0.1-6 mm) rocks. The Meissen monzonite has a prominent shape-preferred orientation (SPO) of the non-equidimensional minerals feldspar, mica and amphibole, whereas SPO of the Podlesí granite is unapparent at the hand-specimen scale. The neutron diffraction data revealed distinct LPOs in both granitoids. The LPO of the non-equidimensional minerals feldspar, mica and amphibole developed mainly during magmatic flow. In the case of the Meissen monzonite, the magmatic flow was superimposed by regional shear tectonics, which, however, had no significant effect on the LPOs. In both samples, quartz shows a weak but distinct LPO, which is atypical for plastic deformation and different in the syn-kinematic Meissen monzonite and the post-kinematic Podlesí granite. We suggest that, first of all, the quartz LPO of the Meissen monzonite is the result of oriented growth in an anisotropic stress field. The quartz LPO of the Podlesí granite, which more or less resembles a deformational LPO in the flattening field of the local strain field, developed during magmatic flow, whereby the rhombohedral faces of the quartz crystals adhered to the (010) faces of aligned albite and to the (001) faces of zinnwaldite. Due to shape anisotropy of their attachments, the quartz crystals were passively aligned by magmatic flow. Thus, magmatic flow and oriented crystal growth are the major LPO-forming processes in both granitoids. For the Meissen monzonite, the solid-state flow was too weak to cause significant crystallographic re-orientation of the minerals aligned by magmatic flow. Finally, the significance of our results for the evaluation of the regional tectonic environment during magma emplacement is discussed. The discussion on the regional implications of the more methodologically oriented results provides the basis for future, more regionally aimed studies in view of the fabric characteristics of such plutons and their developing mechanisms. [ABSTRACT FROM AUTHOR]

Verner and co-authors (Int J Earth Sci (2009) 98:517-532) published geological and structural model of evolution and emplacement of the Plöckenstein pluton in the border area of Austria, Germany and Czech Republic. They used data of other authors, giving no reference as to their source, for interpretations without any discussion of the already published results. [ABSTRACT FROM AUTHOR]