ALBERT

Description: Oxy-schorl (IMA 2011-011), ideally Na(Fe 2+ 2 Al)Al 6 Si 6 O1 8 (BO 3 ) 3 (OH) 3 O, a new mineral species of the tourmaline supergroup, is described. In Zlatá Idka, Slovak Republic (type locality), fan-shaped aggregates of greenish black acicular crystals ranging up to 2 cm in size, forming aggregates up to 3.5 cm thick were found in extensively metasomatically altered metarhyolite pyroclastics with Qtz+Ab+Ms. In Pribyslavice, Czech Republic (co-type locality), abundant brownish black subhedral, columnar crystals of oxy-schorl, up to 1 cm in size, arranged in thin layers, or irregular clusters up to 5 cm in diameter, occur in a foliated muscovite-tourmaline orthogneiss associated with Kfs+Ab+Qtz+Ms+Bt+Grt. Oxy-schorl from both localities has a Mohs hardness of 7 with no observable cleavage and parting. The measured and calculated densities are 3.17(2) and 3.208 g/cm 3 (Zlatá Idka) and 3.19(1) and 3.198 g/cm 3 (Pribyslavice), respectively. In plane-polarized light, oxy-schorl is pleochroic; O = green to bluish-green, E = pale yellowish to nearly colorless (Zlatá Idka) and O = dark grayish-green, E = pale brown (Pribyslavice), uniaxial negative, = 1.663(2), = 1.641(2) (Zlatá Idka) and = 1.662(2), = 1.637(2) (Pribyslavice). Oxy-schorl is trigonal, space group R 3 m , Z = 3, a = 15.916(3) Å, c = 7.107(1) Å, V = 1559.1(4) Å 3 (Zlatá Idka) and a = 15.985(1) Å, c = 7.154(1) Å, V = 1583.1(2) Å 3 (Pribyslavice). The composition (average of 5 electron microprobe analyses from Zlatá Idka and 5 from Pribyslavice) is (in wt%): SiO 2 33.85 (34.57), TiO 2 〈0.05 (0.72), Al 2 O 3 39.08 (33.55), Fe 2 O 3 not determined (0.61), FeO 11.59 (13.07), MnO 〈0.06 (0.10), MgO 0.04 (0.74), CaO 0.30 (0.09), Na 2 O 1.67 (1.76), K 2 O 〈0.02 (0.03), F 0.26 (0.56), Cl 0.01 (〈0.01), B 2 O 3 (calc.) 10.39 (10.11), H 2 O (from the crystal-structure refinement) 2.92 (2.72), sum 99.29 (98.41) for Zlatá Idka and Pribyslavice (in parentheses). A combination of EMPA, Mössbauer spectroscopy, and crystal-structure refinement yields empirical formulas (Na 0.591 Ca 0.103 0.306 ) 1.000 (Al 1.885 Fe 2+ 1.108 Mn 0.005 Ti 0.002 ) 3.000 (Al 5.428 Mg 0.572 ) 6.000 (Si 5.506 Al 0.494 ) 6.000 O 18 (BO 3 ) 3 (OH) 3 (O 0.625 OH 0236 F 0.136 Cl 0.003 ) 1000 for Zlatá Idka, and (Na 0.586 Ca 0.017 K 0.0060.391 ) 1.000 (Fe 2+ 1.879 Mn 0.015 Al 1.013 Ti 0.093 ) 3.00 (Al 5.732 Mg 0.190 Fe 3+ 0.078 ) 6.000 (Si 5.944 Al 0.056 ) 6.000 O 18 (BO 3 ) 3 (OH) 3 (O 0.579 F 0.307 OH 0.115 ) 1.000 for Pribyslavice. Oxy-schorl is derived from schorl end-member by the AlOFe –1 (OH) –1 substitution. The studied crystals of oxy-schorl represent two distinct ordering mechanisms: disorder of R 2+ and R 3+ cations in octahedral sites and all O ordered in the W site (Zlatá Idka), and R 2+ and R 3+ cations ordered in the Y and Z sites and O disordered in the V and W sites (Pribyslavice).

Description: The Moldanubian domain of the Variscan Bohemian Massif is characterized by a large number of rare-element pegmatites, which are of possible economic importance. In order to investigate timing relationships between emplacements of Li-bearing rare-element pegmatites and the tectonometamorphic and magmatic evolution of this domain, 10 in situ U–Pb dates of minerals of the columbite–tantalite group from eight rare-element pegmatites, belonging to different pegmatite fields, have been obtained by the LA–SF–ICP–MS technique. As in former studies, our results suggest that assimilation of common Pb is very limited, and diffusion of radiogenic Pb is of minimal importance in columbite. Two ages of emplacement have been obtained. An older episode at ~333 ± 3 Ma follows closely the generalized melting event that occurred at the end of the Moravo–Moldanubian phase, during exhumation of high-pressure rocks. The younger episode, at ~325 ± 4 Ma, seems to have been contemporaneous with the beginning of the Bavarian phase. The emplacement of Li-bearing rare-element pegmatites in the Moldanubian domain is the oldest known magmatic event involving rare-element-enriched melts during the Variscan orogeny. Our results show that the emplacement of Li-bearing rare-element pegmatites is not genetically related with the granulite-facies metamorphism of the lower crust. Rather, the magmas could have originated directly by partial melting linked to the formation of migmatites contemporaneous with the exhumation of high-pressure rocks.

Description: The composition of topaz from different granites and greisen in the Krusné Hory/Erzgebirge area was investigated using electron microprobe analysis (EMPA) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). All topaz grains are rich in F (17.9–19.8 wt.%, 1.73–1.90 a.p.f.u.) and the most important minor/trace elements are P, Ge and Ga. Contents of P up to 1 wt.% P 2 O 5 (0.025 a.p.f.u.) were found in topaz from the strongly peraluminous P-rich magmatic systems at Podlesí. Regardless of genetic type, topaz from granites typically contains 50–100 ppm Ge. The greatest amounts (up to 204 ppm Ge) were found in topaz from quartz-topaz-apatite greisen in Krásno. In fractionated granites and greisens, topaz is calculated to contain 23–87% of the bulk Ge content in the rock. In contrast, topaz does not concentrate Ga. The Ga content of topaz (typically 5–35 ppm in S-type granites, 〈10 ppm Ga in A-type granites) is usually smaller than the bulk Ga content of the rock. In addition, up to 16 ppm Sc, 23 ppm Sn and 〉400 ppm Fe may be present.

Description: 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 Cínovec (Zinnwald) granite cupola containing a well-known Sn–W–Li deposit. The Cínovec 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.

Description: The evolution of the trace-element patterns of quartz during crystallization of pegmatite melt was investigated using laser ablation inductively coupled plasma mass spectrometry. The contents of Al, B, Ba, Be, Cr, Fe, Ge, Li, Mn, P, Rb, Sn, Sr and Ti were analysed in quartz from the border, intermediate and core zones of four granitic pegmatites differing in degree of fractionation and origin. The material investigated originates from the pegmatite district of the Strážek Unit, Moldanubian Zone, Bohemian Massif, Czech Republic and includes: lepidolite LCT (Li-Cs-Ta) pegmatite from Rožná; beryl-columbite LCT pegmatite from Věžná; anatectic pegmatite from Znětínek; and intragranitic NYF (Nb-Y-F) pegmatite Vladislav from the Třebíč Pluton. The abundances of the elements analysed varied over wide intervals: 〈1 to 32 ppm Li, 0.5 to 6 ppm B, 〈1 to 10 ppm Ge, 1 to 10 ppm P, 10 to 450 ppm Al, 1 to 45 ppm Ti and 〈1 to 40 ppm Fe (average sample contents). Concentrations of Be, Rb, Sr, Sn, Ba, Cr and Mn are usually 〈1 ppm. Quartz from LCT pegmatites exhibits a distinct evolutionary trend with a decrease in Ti and an increase in Al, Li and Ge from the pegmatite border to the core. In comparison with the most fractionated rare-metal granites, pegmatitic quartz is relatively depleted in Al and Li, but strongly enriched in Ge. Quartz from simple anatectic and NYF pegmatites is poor in all trace elements with their evolution marked by a decrease in Ti and a small increase in Ge. There is little Al or Li and neither shows any systematic change with pegmatite evolution. Using the Ti-in-quartz thermo-barometer, the outer zones of the Znětínek and Vladislav pegmatites crystallized at ~670°C, whereas the border zone in the Rožná pegmatite yields a temperature near 610°C.

Description: An extensive set of porosity, , effective diffusion coefficient, D e , and hydraulic conductivity, K , data were obtained from 45 granitic samples from the Bohemian Massif, Czech Republic. The measured dataset can be used to define parameter ranges for data to be used in safety assessment calculations for a deep (〉400 m) radioactive waste repository, even though the samples originated from shallower depths (〈108 m). The dataset can also be used for other purposes, such as evaluating the migration of contaminants in granitic rock (e.g. from shallow intermediate-level radioactive waste repositories and chemical waste repositories). Sample relaxation and ageing processes should be taken into account in research otherwise migration parameters might be overestimated in comparisons between lab results and those determined in situ .

Description: Zircon from 14 representative granite samples of the late-Variscan Cornubian Batholith in SW England was analysed for W, P, As, Nb, Ta, Si, Ti, Zr, Hf, Th, U, Y, La, Ce, Pr, Nd, Sm, Gd, Dy, Er, Yb, Al, Sc, Bi, Mn, Fe, Ca, Pb, Cu, S and F using electron probe microanalyses. Zircons from the biotite and tourmaline granites are poor in minor and trace elements, usually containing 1.0–1.5 wt.% HfO 2 , 〈0.5 wt.% UO 2 and P 2 O 5 , 〈0.25 wt.% Y 2 O 3 , 〈0.2 wt.% Sc 2 O 3 and Bi 2 O 3 and 〈0.1 wt.% ThO 2 . Zircon from topaz granites from the St. Austell Pluton, Meldon Aplite and Megiliggar Rocks are slightly enriched in Hf (up to 4 wt.% HfO 2 ), U (1– 3.5 wt.% UO 2 ) and Sc (0.5–1 wt.% Sc 2 O 3 ). Scarce metamictized zircon grains are somewhat enriched in Al, Ca, Fe and Mn. The decrease of the zircon Zr/Hf ratio, a reliable magma fractionation index, from 110–60 in the biotite granites to 30–10 in the most evolved topaz granites (Meldon Aplite and Megiliggar Rocks), supports a comagmatic origin of the biotite and topaz granites via long-lasting fractionation of common peraluminous crustal magma. In comparison with other European rare-metal provinces, the overall contents of trace elements in Cornubian zircons are low and the Zr/Hf and U/Th ratios show lower degrees of fractionation of the parental melt.

Description: 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, 〈0.1 Li atoms per formula unit [apfu] and Mg/(Mg + Fe) = 0.4–0.8. The biotites from the S-type granites usually contain 5.3–5.7 Si, 3.2–3.6 Al, 0.1–0.3 Li apfu and Mg/(Mg + Fe) = 0.15–0.4. The annites and zinnwaldites from the rare-metal granites contain 5.7–6.8 Si, 3.2–3.8 Al, 0.6–2.6 Li apfu and Mg/(Mg + Fe) 〈 0.1. The concentrations of F, Rb, Cs and Tl increase from the phlogopites and biotites to zinnwaldites: F 0.1 -〉 8 wt.%, Rb 2 O 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 〈5 W. The highest concentrations were found in the Li-annites in the relatively early facies of rare-metal granites (in ppm): 250–600 Sn, 400–600 Nb, 60–120 Ta and 50–120 W. The zinnwaldites in the late rare-metal granites facies are impoverished in these elements, which is explained by contemporaneous crystallization of cassiterite and columbite. Lithium enters the crystal lattice of trioctahedral micas via the exchange vector Li 3 Si 3 Fe –6 Al –1 up to concentrations of ~2.5 wt.% Li 2 O (1.5 apfu Li). At higher Li concentrations, Li is incorporated through the exchange vector Li 3 Si 1 –1 Fe –2 Al –1 .