Table of Contents for the Journal of GEOsciences. List of articles from the latest print issue.http://www.jgeosci.orgen-US http://www.jgeosci.org/jgeosci_cover.jpghttp://www.jgeosci.org Plášil J, Čejka J, Sejkora J, Hloušek J, Goliáš V; Vol. 54, issue 4, page: 373–384
Metakirchheimerite was found only on a few samples from the Jan Evangelista vein at the “Adit level” of the Svornost shaft, Jáchymov (St. Joachimsthal) ore district, Krušné Hory/Erzgebirge Mountains, Czech Republic. It forms rare crystalline aggregates consisting of fine tabular crystals which reach 0.1 mm in size, which are very brittle, having light pink to light orange colour, with a high vitreous lustre. Metakirchheimerite crystalline aggregates occur on carbonate gangue with disseminated primary minerals: arsenopyrite, uraninite and skutterudite. Studied metakirchheimerite is a (sub-)recent alteration product of the primary minerals, connected to the old open mine adit environment. According to electron microprobe analyses, the empirical formula of metakirchheimerite can be expressed, based on As + P = 2 apfu, as:
(Co_0.53Mg_0.25Ni_0.08Zn_0.07Fe_0.05Ca_0.03)_Σ1.01(UO₂)_2.07[(AsO₄)_1.99(PO₄)_0.01)]_Σ2.00.8H₂O.
Metakirchheimerite from Jáchymov exhibits an extensive cationic substitution trend of the metanováčekite component. The diffraction pattern of metakirchheimerite is consistent with a triclinic symmetry inferred from the single-crystal study of the synthetic metakirchheimerite analogue. Refined unit-cell parameters for the triclinic space group P-1 are a 7.210(4) Å, b 9.771(6) Å, c 13.252(9) Å, α 75.39(4)°, β 83.94(6)°, γ 81.88(6)° with unit-cell volume V 892(1) ų. Both infrared and Raman spectra of metakirchheimerite exhibited stretching and bending vibrations of (UO₂)²⁺, (AsO₄)^3-, (PO₄)^3- and H₂O groups. The vibration bands of all these units were tentatively assigned. The U-O bond lengths in uranyl and O-H…O hydrogen bond lengths, which were inferred from the spectra, are consistent with published crystal structure data for a synthetic analogue of metakirchheimerite. ]]> http://www.jgeosci.org/rss.php?ID=jgeosci.057_2009_4_plasil2.pdf Original Paper http://www.jgeosci.org/rss.php?ID=jgeosci.057_2009_4_plasil2.pdf Medaris G, Ackerman L, Jelínek E, Toy V, Siebel W, Tikoff B; Vol. 54, issue 4, page: 301–323
The Moldanubian Sklené garnet peridotite, which preserves mineralogical, geochemical, and structural evidence for a protracted mantle evolution, is a small boudin (˜1 m) enclosed by granulite of the Gföhl Assemblage. The peridotite has a porphyroclastic texture, in which large garnet and smaller olivine and pyroxene porphyroclasts (Stage 1) reside in a fine-grained, recrystallized matrix of olivine, pyroxene, and pargasitic amphibole (Stage 2). Garnet is surrounded by kelyphite, consisting of an outer zone of pargasite and an inner zone of spinel and pyroxene (Stage 3).
Lattice-preferred orientations (LPO) for olivine, orthopyroxene, and clinopyroxene were measured by electron backscatter diffraction. The LPO of olivine (mostly Stage 2) has an [010] maximum parallel to the Z fabric direction and [100] and [001] girdles in the X-Y fabric plane. Both orthopyroxene and clinopyroxene have [010] maxima parallel to Z and [001] girdles in the X-Y plane.
The Sklené peridotite is slightly depleted in incompatible major and minor elements relative to primitive mantle. Whole-rock REE contents are 0.3 to 0.8 times that of primitive mantle, with a convex upward pattern, and Rb, Th, U, Pb, and Sr show positive anomalies in an extended element plot. Among the highly siderophile elements, Os, Ir, Ru, and Pt are unfractionated, but Pd and Re are significantly depleted. A Sm-Nd garnet-whole rock-clinopyroxene isochron yields a cooling age of 338 ± 13 Ma, and ε_Nd and (⁸⁷Sr/⁸⁶Sr)_i values for clinopyroxene (at 335 Ma) are +4.5 and 0.7035, respectively.
By comparison with other Moldanubian garnet peridotites in the Czech Republic, the Sklené peridotite likely represents a fragment of subcontinental lithospheric mantle. It experienced early partial fusion and depletion of incompatible elements at moderate pressure in the spinel stability field, followed by transport to high-pressure conditions at 1230 °C and 50 kbar, where the Stage 1 garnet-bearing assemblage was stabilized. Subsequently, the depleted peridotite was metasomatized by transient, primitive basaltic melts, with the addition of Rb, Th, U, Pb, and Sr. Dynamic recrystallization, possibly with a progressive transition to grain size sensitive creep, occurred during Stage 2 at ˜915 °C and 24 kbar in a flattening-dominated, transpressive deformation regime. This event occurred prior to incorporation of the peridotite in granulite and may reflect the early stages of convergence between Brunia and Moldanubia. The static recrystallization and local growth of spinel within kelyphite at 900 °C and 17-21 kbar (Stage 3) probably took place after entrainment in granulite and was likely isofacial with granulite peak metamorphism. ]]> http://www.jgeosci.org/rss.php?ID=jgeosci.052_2009_4_medaris.pdf Original Paper http://www.jgeosci.org/rss.php?ID=jgeosci.052_2009_4_medaris.pdf Žáček V, Škoda R, Sulovský P; Vol. 54, issue 4, page: 343–354
A melasyenite porphyry from the vicinity of Kašperské Hory (the Šumava Mts., Moldanubian Zone) shows a high natural radioactivity (K = 4.4-6.1 wt. %, eU = 15-24 ppm, eTh = 38-49 ppm). The most important carriers of U and Th are zircon, thorite, allanite-(Ce) and scarce monazite. Most of the zircon and thorite grains are altered by post-magmatic processes due to which especially zircon shows a large degree of chemical variability. Primary magmatic zircon is nearly stoichiometric, poor in ThO₂ (up to 0.13 wt. %) and UO₂ (up to 0.42 wt. %). It often encloses strongly altered U- and Th- rich cores. These cores show a conspicuous zoning in the BSE. The bright zones are enriched in UO₂ (0.66-1.36 wt. %) and ThO₂ (0.21-0.94 wt. %) whereas the darker zones are highly enriched in CaO (up to 5.19 wt. %), with UO₂ contents ranging between 0.95 and 2.15 wt. % and the ThO₂ between 0.99 and 1.67 wt. %. The first percolation point of zircon was estimated at 0.4 D_[dpa]. Thorite is also strongly altered, being depleted in Y,REE and Si in its more hydrated parts. A further consequence are strongly varying UO₂ contents (1.79-27.60 wt. %) and locally enriched ZrO₂ (up to 10.92 wt. %), P₂O₅ (0.22-6.39 wt. %) and Y,REE (0.73-12.81 wt. % of REE₂O₃ and Y₂O₃ combined). Elevated amounts of Fe, Ca, Pb, As, Al, S, and Ti were detected in the most hydrated parts. Allanite-(Ce) is weakly zoned with 0.20-1.22 wt. % ThO₂ and up to 0.11 wt. % UO₂. Scarce monazite-(Ce) has the ThO₂ contents (13.57-15.85 wt. %) strongly prevailing over UO₂ (1.51-1.91 wt. %). ]]> http://www.jgeosci.org/rss.php?ID=jgeosci.053_2009_4_zacek.pdf Original Paper http://www.jgeosci.org/rss.php?ID=jgeosci.053_2009_4_zacek.pdf Sedlák J, Gnojek I, Scheibe R, Zabadal S; Vol. 54, issue 4, page: 325–342
A new cross-border gravity map on the scale of 1:200,000 covering 14,900 km² of the SE Saxony and NW Bohemia was compiled. It is limited by the sites of Grimma (NW), Karlovy Vary (SW), Neratovice (SE) and Bautzen (NE). Three positive gravity regions - (a) Lusatian Anticline, (b) SE part of the North Saxon Syncline and (c) Teplá-Barrandian Unit were delimited. Separation of the Bouguer anomalies into the regional and residual components together with the Linsser filtering provided three types of derived gravity maps (regional, residual and density boundaries) for geological interpretation. Eighteen negative residual anomalies mostly pertaining to partially buried granite or acid volcanic bodies and ten positive residual anomalies mostly caused by metamorphic complexes were identified. The map of the Linsser indications showing the density boundaries at three depth levels (1, 3 and 6 km) introduces not only numerous disjunctions but also indicates an internal structure of the individual regions. A new cross-border magnetic map covering the same area is also presented.
A “central” circular gravity low (−61 mGal) delineates the Altenberg-Teplice Caldera extending to 10 km depth. Variscan igneous bodies produce only negative gravity anomalies regardless their size. Pre-Variscan igneous bodies cause either weak negative or positive anomalies. A chain of gravity and magnetic anomalies follows the Litoměřice Deep Fault and a large pronounced magnetic anomaly between Doupov volcanic complex (SW) and the Elbe Zone (NE) delineates the Saxothuringian/Teplá-Barrandian Suture Zone. ]]> http://www.jgeosci.org/rss.php?ID=jgeosci.054_2009_4_sedlak.pdf Original Paper http://www.jgeosci.org/rss.php?ID=jgeosci.054_2009_4_sedlak.pdf Sejkora J, Škovíra J, Čejka J, Plášil J; Vol. 54, issue 4, page: 355–371
Copper-rich members of the beudantite-segnitite series (belonging to the alunite supergroup) were found at the Krupka deposit, Krušné hory Mountains, Czech Republic. They form yellow-green irregular to botryoidal aggregates up to 5 mm in size. Well-formed trigonal crystals up to 15 μm in length are rare. Chemical analyses revealed elevated Cu contents up to 0.90 apfu. Comparably high Cu contents were known until now only in the plumbojarosite-beaverite series. The Cu²⁺ ion enters the B³⁺ position in the structure of the alunite supergroup minerals via the heterovalent substitution Fe³⁺Cu²⁺_-1 (AsO₄)^3-(SO₄)^2-_-1 . The unit-cell parameters (space group R-3m) a = 7.3265(7), c = 17.097(2) Å, V = 794.8(1) ų were determined for compositionally relatively homogeneous beudantite (0.35 - 0.60 apfu Cu) with the following average empirical formula:
Pb_1.00(Fe_2.46Cu_0.42Al_0.13Zn_0.01)_Ε3.02 [(SO₄)_0.89(AsO₃OH)_0.72(AsO₄)_0.34(PO₄)_0.05]_Ε2.00 [(OH)_6.19F_0.04]_Ε6.23 .
Interpretation of thermogravimetric and infrared vibrational data is also presented. The Cu-rich members of the beudantite-segnitite series are accompanied by mimetite, scorodite, pharmacosiderite, cesàrolite and carminite. These minerals are characterised by refined unit-cell parameters and by quantitative chemical analyses. The assemblage of supergene minerals corresponds to the following crystallization sequence: mimetite → beudantite-segnitite → pharmacosiderite, scorodite, cesàrolite, and carminite. ]]> http://www.jgeosci.org/rss.php?ID=jgeosci.055_2009_4_sejkora.pdf Original Paper http://www.jgeosci.org/rss.php?ID=jgeosci.055_2009_4_sejkora.pdf Plášil J, Čejka J, Sejkora J, Škácha P; Vol. 54, issue 4, page: 385–394
Strongly altered gangue, containing rich crystalline aggregates of parsonsite, was recently found at the outcrop parts of the Červené žíly vein system, the Jáchymov ore district, Czech Republic. Mineralogical research proved that in the crystal structure of parsonsite from Jáchymov is present a higher content of molecular water than expected. This conclusion is supported by the results of thermogravimetric analysis and infrared spectroscopy. The weight loss obtained from TG curve is 3.70 wt. %, corresponding to 1.93 mols of H₂O. The presence of a broad vibration band reflecting the O-H stretching vibrations of molecular water was ascertained in the infrared spectrum of studied parsonsite sample, suggesting that H₂O molecules are involved in the hydrogen-bonding network in the crystal structure of studied parsonsite. Inferred hydrogen bond lengths can vary in the range 2.6-3.0 Å, which is consistent with the distance between possible position of the molecular water and nearest neighbouring oxygen atom in the crystal structure of the synthetic parsonsite given in literature. The chemical composition of the studied parsonsite from Jáchymov, 47.27 PbO, 13.38 P₂O₅, 1.60 As₂O₅, 0.16 SiO₂, 32.61 UO₃, 3.70 H₂O, total 98.71 wt. %, can be expressed as Pb_1.99(UO₂)_1.07 [(PO₄)_1.77(AsO₄)_0.13(SiO₄)_0.03]_Σ1.93^.1.93 H₂O, based on electron microprobe and thermal analyses. Its refined unit-cell parameters for triclinic space group P-1, a 6.860(2), b 10.404(3), c 6.665(3) Å, α 101.46(3)O, β 98.30(3)^o, γ 86.29(2)^o, V 461.0(3) ų agree very well with the published data. ]]> http://www.jgeosci.org/rss.php?ID=jgeosci.056_2009_4_plasil1.pdf Original Paper http://www.jgeosci.org/rss.php?ID=jgeosci.056_2009_4_plasil1.pdf