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Representative samples of high-Mg (picritic) rocks of Eocene to Oligocene age (38 to 21 Ma) from the Ceske středohoři Mts. (CSM) in the Ohře/Eger Rift were studied and compared with Cenozoic high-Mg rocks from the Bohemian Massif. The picritic rocks of the CSM correspond to picrite, meimechite and basanite to tephrite. Individual petrographic types are characterised by the association of mafic minerals: magnesian olivine (Fo86–80) + clinopyroxene (aluminian diopside) ± amphibole (pargasite/kaersutite) ± dark mica (ferroan phlogopite). The contents of incompatible elements, such as Nb, Ta, U, Th, the LaN/YbN ratios, and the overall Sr–Nd–Pb isotope signatures of the high-Mg rocks partly overlap the basanites of the Usti Formation, also showing a similar age (44–21 Ma). The Pb isotope signature for all recognised high-Mg rock types is compatible with a variable contribution from an inherited (Variscan) orogenic Pb component preserved in their lithospheric mantle source. Both the high-Mg volcanic rocks from the CSM and from other areas of the Bohemian Massif require the involvement of a heterogenous lithospheric source. Their parental melts were generated by variable degree of melting of an olivine-rich peridotitic mantle, containing clinopyroxene–amphibole (± phlogopite) vein assemblages with highly radiogenic Sr and Pb signatures.

The Li-Sn-W deposit Cinovec/Zinnwald in the eastern Erzgebirge (Czech Republic and Germany) represents one of the worldwide best known examples of complex rare-metal plutons with pervasive greisenization. Mica from altogether 38 samples representing all granite and greisen varieties from the present surface to the depth of 1596 m was analysed using electron microprobe (EMPA) and laser-ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) for major (including F, Rb) and trace (Li, Sc, Ga, Ge, Nb, In, Sn, Cs, Ta, Tl, W) elements, respectively. All primary micas at Cinovec are trioctahedral Li-Fe micas close to the annite–zinnwaldite–trilithionite series. Biotite from granites in the deeper part of the pluton (depth of 735–1596 m) contains 33.9–39.6 wt% SiO2, 19.6–23.8 wt% FeO, 0.5–0.7 wt% Rb2O, 0.9–1.8 wt% Li2O, 3.4–4.8 wt% F, 381–937 ppm Nb, 34–134 ppm Ta, 20–46 ppm W, and 93–617 ppm Sn. Zinnwaldite from granites in the upper part of the pluton (depth of 0–735 m) contains 41.2–48.5 wt% SiO2, 8.9–15.2 wt% FeO, 0.9–1.9 wt% MnO, 2.0–4.4 wt% Li2O, 0.8–1.9 wt% Rb2O, 7.0–8.6 wt% F, 43–464 ppm Nb, 101–213 ppm Sn, 6–80 ppm Ta, and 28–52 ppm W. Zinnwaldite from bodies of pervasive greisen and quartz-zinnwaldite veins is, compared to zinnwaldite from granites, relatively slightly enriched in Si, Mn and Ga, and depleted in Fe, F, Rb, Sn, W and Nb; Li and Ta contents are similar. Contents of Li, Rb and F, and the Fe/Mn and Nb/Ta values in mica closely positively correlate with those in the bulk rock, illustrating an upwards fractionation of parental melt. In contrast, the contents of high-field-strength elements in mica do not correspond to their contents in the bulk rock (melt): they were controlled by the order of crystallization of mica vs. accessory oxide minerals. Therefore, biotite generally contains distinctly higher Sn, Nb, Ta, and W than zinnwaldite. Dioctahedral micas of the muscovite–phengite series were found only as a late product of alteration of primary trioctahedral mica. Replacement of greisen-stage zinnwaldite by muscovite is chemically expressed in a strong depletion in Fe, F, and Li, and an enrichment in Sn. The share of trioctahedral mica in the bulk-rock budget of Sn decreases from 40–70% in biotite granite to less than 5% in greisen; in the case of Nb and Ta from 20–50% to less than 10%. The share of mica in the budget of W, mostly in the range of 2–15%, is stable through the whole pluton.

The genetic relationship between a granite pluton and adjacent complex of rare-metal pegmatite-aplite-banded sheets (Megiliggar Sheet Complex - MSC) has been studied at the border of the Tregonning topaz granite at Megiliggar Rocks, Cornwall, SW England. Similarities in whole-rock chemical and mineralogical compositions, together with a gradual change in textures away from the granite margin, provide strong evidence for a genetic link between the Tregonning Granite and MSC. The sheets are likely to represent apophyses of residual melt which escaped from the largely crystallized roof of the granite pluton. The escaping melt was peraluminous, had a composition near the F, B, Li slightly enriched granite minimum, and, in comparison with other Cornish granites, was enriched in F, Li, Rb, Cs, Sn, W, Nb, Ta, and U, and depleted in Fe, Mg, Ca, Sr, Th, Zr, and REE. With increasing distance from the Tregonning Granite, the silicate melt crystallized as homogeneous leucogranite sheets and banded complex sheets (i.e. combinations of bands with granitic, aplitic and pegmatitic textures), then layered aplite-pegmatites; this sequence becoming progressively more depleted in the fluxing and volatile elements F, Li, Rb, and Cs, but showing no change in Zr/Hf ratios. The fixed Zr/Hf ratio is interpreted as indicating a direct genetic link (parental melt) between all rock types, however the melt progressively lost fluxing and volatile elements with distance from the granite pluton, probably due to wall-rock reaction or fluid exsolution and migration via fractures. Differentiation of the primary melt into Na-Li-F-rich and separate K-B-rich domains was the dominant chemical process responsible for the textural and mineral diversity of the MSC. On a large (cliff-section) scale, the proximal Na-Li-F-rich leucogranite passes through complex sheets into K-B-rich aplite-pegmatites, whilst at a smaller (

The Cinovec rare-metal granite in the eastern segment of the Krusne Hory/Erzgebirge (Czech Republic/Germany) formed in the final stage of the magmatic evolution of the late Variscan volcano-plutonic system known as the Teplice caldera. The granite is slightly peraluminous; enriched in F, Li, Rb, Cs, Nb, Ta, Sn, W, Sc and U; and poor in P, Mg, Ti, Sr and Ba. The uppermost part of the granite cupola hosts a greisen-type Sn–W–Li deposit. Borehole CS-1 permits to study vertical evolution of the pluton to a depth of 1597 m. A combination of textural and chemical methods was applied to whole-rock and mineral samples to identify the extent of magmatic and metasomatic processes during the differentiation of the pluton and formation of the deposit. As indicated by textural and chemical data, the Cinovec pluton consists of two cogenetic intrusive bodies: a relatively homogeneous biotite granite at depths greater than 735 m, and a strongly differentiated zinnwaldite granite above this level. The pronounced differentiation of the zinnwaldite granite magma resulted in further increases in F, Li, Rb, Nb and Ta. A high degree of magmatic fractionation is documented by decreases in the K/Rb ratio from 25 to 15 and in the Zr/Hf ratio from 10 to 5. The increasing influence of the fluid is highlighted by a decrease in the Y/Ho ratio from 29 to 17. The following genetic scenario is proposed: the intrusion of the zinnwaldite granite magma reached subvolcanic conditions and a hem of fine-grained porphyritic granite crystallized along the upper contact. Separation of the first portion of fluid from the oversaturated melt promoted explosive degassing and the origin of breccia pipes. Subsequently, the zinnwaldite granite magma crystallized simultaneously from the upper contact and the footwall inwards. The residual melt between the two crystallizing fronts became enriched in water and volatiles to reach second saturation (“second boiling”). Segregated fluids escaped upwards, causing hydrofracturing of the overlying granite, while the water-poor residuum crystallized in situ in the form of mica-free granite. F- and Li-rich fluids invoked greisenization and created quartz–zinnwaldite veins. Alkalis liberated from feldspars destroyed during the greisenization induced local albitization in the uppermost part of the cupola and K-feldspathisation in its deeper part. The distribution of Sn and W was controlled by fluid processes, while Nb and Ta mainly crystallized from the melt. The results from Cinovec are universally applicable to shallow-intruded rare-metal granites regardless of A- or S-types of the primary magma.

The diversity of Ti–Sn–W–Nb–Ta oxide minerals within a complex granite-related magmatic–hydrothermal system was studied by electron microprobe on the example of the Cinovec (Zinnwald) granite cupola containing a well-known Sn–W–Li deposit. The Cinovec granite cupola is a late Variscan ( ca . 322 Ma), strongly fractionated A-type pluton composed of upper zinnwaldite granite and lower biotite granite. The zinnwaldite granite contains numerous subhorizontal quartz veins and greisen bodies, both composed of quartz, zinnwaldite and topaz and minor amounts of fluorite and Ti–Sn–W–Nb–Ta oxide minerals. Common Nb–Ta-rich rutile and rare cassiterite, columbite-(Fe) and -(Mn), and minerals of the pyrochlore-supergroup were found in biotite granite in deeper parts of the pluton, whereas common columbite occurs with rare W-rich ixiolite, qitianlingite, pyrochlores, and scheelite in some varieties of zinnwaldite granite. In the uppermost part of the cupola, Ta-rich cassiterite, microlite and pyrochlore are frequently observed. The greisens host predominantly wolframite, scheelite and Ta-poor cassiterite, which are accompanied by columbite-group minerals, rare W-rich ixiolite and qitianlingite. Throughout the pluton, the molar Mn/(Fe + Mn) ratio in columbite increases from 0.15–0.40 in the deeper part of the zinnwaldite granite (depths of 500–635 m) to 0.5–0.9 in granite and greisen in the uppermost part of the pluton (depths of 0–180 m), but no systematic changes in the Ta/(Nb + Ta) ratio were found. On the scale of individual zoned crystals, the rims are always Ta-enriched, whereas the Mn/(Fe + Mn) values in the rims are equal or lower. The Nb,Ta-rich rutile, interiors of the columbite crystals and Ta-rich cassiterite disseminated in the granites are interpreted as products of magmatic crystallization. The Ta-rich rims of columbite-(Fe) to -(Mn), Ta-poor cassiterite and all wolframite found in the greisen should be attributed to the early hydrothermal (greisenization) stage, whereas W-rich ixiolite, qitianlingite, and pyrochlore-supergroup minerals appear to belong to the later, hydrothermal event at comparatively lower temperature.

Quantification procedures based on the external calibration with total sum content standardization (ECTSCS) and the external calibration with internal standardization (ECIS) were compared in the analysis of glass materials by laser ablation inductively coupled plasma spectrometry (LA-ICP-MS) with a 213 nm Nd:YAG laser ablation device and a quadrupole mass spectrometer. Silicon was used as the internal reference element for ECIS. Applicability of these approaches was statistically tested using both homogeneous and inhomogeneous samples. The former type was represented by the standard reference material NIST 612 and an ancient glass bead (Early Bronze Age), while the latter was a mediaeval glass artefact (8th – 9th century). Homogeneity of samples was examined by EMP analysis. Identical results were obtained by both calibration methods for homogeneous samples, while underestimated contents resulted from quantification with ECIS method in comparison to EMP analyses of the same target area of inhomogeneous glass. Finally, elemental maps of zonal muscovite grain were recorded and quantified using ECTSCS method and verified by EMP analysis.

The compositions of trioctahedral micas from 51 samples of granitoids with different geochemical affiliations and grades of differentiation from the Bohemian Massif, Central Europe, were analysed using electron microprobe (major elements) and laser ablation inductively coupled plasma mass spectrometry (Li, Sc, Ga, Ge, Nb, In, Sn, Cs, Ta, W, Tl). The micas form a continuous evolutionary series from phlogopite to zinnwaldite. The phlogopites and biotites from the I-type rocks are characterized by 5.5–5.7 Si, 2.4–2.6 Al, 2O 0.05 → 1.7 wt.%, Tl 2 → 50 ppm and Cs 40 → 2000 ppm. The concentrations of Sn, Nb, Ta and W in phlogopites and biotites from the I- and S-type granitoids generally correlate with those of the parent rocks and reach values of (in ppm) 20–100 Sn, 20–250 Nb, 1–20 Ta and 3□Si3Fe–6Al–1up to concentrations of ∼2.5 wt.% Li2O (1.5 apfu Li). At higher Li concentrations, Li is incorporated through the exchange vector Li3Si1□–1Fe–2Al–1.

International audience; Effects of strongly radioactive primary minerals (mainly monazite) on the surroundings are compared in various rocks of similar chemical and mineral composition (mainly granites and paragneisses) of the Moldanubian area in the Bohemian massif. All these rocks cooled to ,150 C at similar time (300-250 Ma B.P.). Aureoles of secondary phases formed which extend up to 20 mm from the monazite surface (the thickness probably corresponds to the zone of most intense damage by a-particles). They mainly consist of low temperature clay minerals usually mixed with Fe-hydroxides; in some samples pyrite is common too. Pyrrhotite and pyrite also penetrate into the monazite and locally partly replace it. In a granite affected by strongly oxidizing alteration, monazite was finally replaced by a complicated hydrated phosphate. The halos of secondary phases most commonly occur around monazite in cordierite, but also in plagioclase and in quartz. It is unimportant if the monazite is included in one mineral grain or is located at grain boundaries. Compared to previous studies in similar rocks with similar cooling ages (e.g., in Erzgebirge and Massif Central, as documented in literature), quartz was destroyed relatively easily. In most cases the alteration of primary minerals close to radioactive grains cannot be explained in a conservative way that the radiation damage only helps to precipitation of secondary phases during a ''ubiquitous'' fluid alteration. It seems that the radioactivity promotes reactions of the primary minerals with fluid (fluid inclusions and H 2 O in channels of the cordierite structure) even at ''static'' conditions. The volume changes (caused by hydration or amorphization) make easier a later import of external fluid. The reason why these phenomena are observed in some regions and not in very similar rocks in other regions is not understood yet, but it is likely that the rocks of the Moldanubian area are mostly above-averagely rich in aqueous fluids. The frequent association of monazite with hydrated secondary phases may contribute significantly to resetting monazite ages during metamorphism and partial melting. In addition, the neglecting of the chemical transformation of the nuclear energy for the calculations of radioactive heat production and heat budgets of rocks is questioned.