Journal of GEOsciences Table of Contents for the Journal of GEOsciences. List of articles from the latest print issue.http://www.jgeosci.orgen-US Journal of GEOsciences <![CDATA[ An open access-journal with a difference ]]> Janoušek V; Vol. 64, issue 1, page: 1
I have the great honour of kicking off the already 64thvolume of Journal of Geosciences (counting the predecessors also published by the Czech Geological Society, of course). I think we can be happy about the current Journal’s performance and can only promise to carry on in our mission of bringing you scientifically sound, process-oriented and though-provoking reading from various branches of mineralogy, geophysics, hard-rock geology, petrology and geochemistry. We aim to do so under the open-access model but with a difference. Unlike the numerous publishers, ranging from honest to predatory, we do not take the open access as an excuse to maximize our profits. We try to keep nil to minimal costs to the authors, gratefully accepting the kind financial and logistic support from the Czech Geological Society, Council of Scientific Societies of the Czech Republic, Czech Geological Survey, Institute of Petrology and Structural Geology (Charles University in Prague) and Czech Literary Fund Foundation. Clearly, we could not do so without the tireless work and enthusiasm of our editorial board, as well as guest editors and reviewers, to whom I would like to extend my sincere thanks. Last but not least, I am indebted to our staff (executive editor M. Vaněček, web editor V. Erban, technical redactor I. Sedláčková and secretary T. Sidorinová) for their diligent work and patience with the impulsive and aging editor in chief.
This issue is very special because it opens with the last paper by Stanislav Vrána, valued colleague, friend and former editor-in-chief of our predecessor, Journal of the Czech Geological Society (1992-2006).Stanislav passed away more than a year ago, aged 82 years. But we need not to be sad - I can guarantee that also the current paper bears the typical imprint of Stanislav’s work. Namely, it shows his deep knowledge of mineralogy and petrology, innovative thinking and thought-provoking ideas - for which we will Stanislav always remember! ]]> Editorial
<![CDATA[ Zalužany - a circular structure in the Czech Republic accompanied by glass of granodiorite composition ]]> Vrána S, Mrlina J, Škoda R, Halodová P; Vol. 64, issue 1, pages 3 - 18
The Hejný Pond, 500 × 400 m, southeast of the Zalužany village in central Bohemia, attracted attention as a possible impact structure. The pond has a notable bilateral symmetry with an axis oriented NW-SE, indicating a significant subhorizontal vector in the overall deformation pattern. A negative gravity anomaly elongated in the same direction (600 × 300 m) with the amplitude of -0.35 mGal was disclosed by detailed gravity survey. The incomplete ring of elevations suggests slightly uplifted basement segments with a diameter of 1 km. Search for glass and other possible indicators of shock metamorphism resulted in a find of glass fragments 22 to 37 mm across. The glass has composition comparable to the local Kozárovice hornblende-biotite granodiorite of the Central Bohemian Plutonic Complex. Unusual features include locally high contamination by iron (up to 10-13 wt. % FeOt) and abundant cristobalite. The absence of planar deformation features in quartz and feldspars together with the absence of platinum-group elements and Ni enrichment in local glass may be considered as obstacles in defining Zalužany as an impact structure. Although glass fragments are rare at the locality, and the considerable Quaternary erosion, the occurrence of rock inclusions in two of the fragments makes the Zalužany structure a promising object for future study. ]]> Original paper
<![CDATA[ Trace-element chemistry of barren and ore-bearing quartz of selected Au, Au-Ag and Sb-Au deposits from the Bohemian Massif ]]> Pacák K, Zachariáš J, Strnad L; Vol. 64, issue 1, pages 19 - 35
The trace-element contents in gold-bearing and barren quartz veins from eight Au, Au-Ag and Sb-Au Variscan deposits in the Bohemian Massif have been determined in situ in order to evaluate the differences between the various types of gold deposits and discuss trace-element variations in the successive generations of quartz veins. The variability of Ti, Al, Ge, Li and Sb abundances obtained by Laser-Ablation Inductively-Coupled Plasma Mass Spectrometry (LA-ICP-MS) roughly correlates with the origin and the temperature of the mineralizing fluids. The Al content ranges up to 4020 ppm (median value 230 ppm), while the Li content is generally low (< 4 ppm). The elevated Sb content (30-360 ppm Sb) is only related to quartz that immediately preceded deposition of Sb-rich phases. The titanium content of the ore-bearing vein quartz follows bimodal distribution: gold deposits with assumed higher-temperature (> 450 °C) formation exhibit higher median values (˜10 ppm Ti) than medium-to-low (< 300 °C) temperature deposits (˜2 ppm Ti). A statistically significant threshold value (8 ppm Ti) has been recognized as an empirical tool for discriminating between them. In terms of the Ti and Al contents, the studied Bohemian gold deposits fall within and in between fields of orogenic gold and porphyry deposit types. ]]> Original paper
<![CDATA[ Anorogenic Early Permian dykes in the western Mongolian Altai - petrography, geochemistry and K-Ar geochronology ]]> Žáček V, Buriánek D, Pécskay Z, Škoda R; Vol. 64, issue 1, pages 37 - 58
A variety of felsic and mafic dykes grouped into swarms intruded the Lower Palaeozoic volcano-sedimentary sequences (flysch) and Late Devonian to Early Carboniferous plutonic rocks in the Hovd and Altai zones of the Central Asian Orogenic Belt (CAOB), western Mongolian Altai. The dykes reach a thickness of 0.5-20 m, length of approximately 50-2,500 m and strike mostly SW-NE or E-W. The felsic rocks chemically correspond to high-K calc-alkaline to alkaline rhyolites. Compositional trends of mafic rocks pass from alkaline- and calc-alkaline basalts to trachyandesite. The bimodal nature of the association and the transitional calc-alkaline to alkaline character of the dykes indicate magma production through partial melting of the mantle and continental crust in an intra-plate (rift) geodynamic setting.
The new conventional whole-rock K-Ar dating of mafic and felsic dykes yielded ages ranging from 300 ± 9 to 281 ± 9 Ma (1σ). This indicates anorogenic volcanic activity associated with Late Carboniferous to Early Permian extension coeval with magmatism in the Gobi-Altai Rift and in the adjacent parts of the Chinese Altai. The calculated crystallization pressures of 1-2 kbar and 0.3-0.4 kbar for felsic and mafic rocks, respectively, indicate emplacement at shallow levels. ]]> Original paper
<![CDATA[ Octahedral substitution in beryl from weakly fractionated intragranitic pegmatite Predné Solisko, Tatry Mountains (Slovakia): the indicator of genetic conditions ]]> Bačík P, Fridrichová J, Uher P, Rybár S, Bizovská V, Luptáková J, Vrábliková D, Pukančík L, Vaculovič T; Vol. 64, issue 1, pages 59 - 72
Crystal-chemical properties, and octahedral substitution role in particular, of beryl from weakly fractionated intragranitic pegmatite Predné Solisko, Vysoké Tatry Mts. (Slovakia) is described in detail. The studied beryl was found in granitic pegmatite derived from biotite I-type granodiorite. It has a weakly zoned core with variable Fe and Mg contents but constantly high Na. The rim zone shows weak irregular chemical zoning with low Na and Mg, the latter dominating over Fe. The total Al content varies between 1.77 and 1.87 apfu; Al is substituted by Fe (0.03-0.07 apfu) and mostly by Mg (0.02-0.13 apfu). The decrease in octahedral site charge is mostly balanced by Na (0.05-0.30 apfu). However, the Na content in the rim is insufficient for balancing octahedral Fe + Mg, implying that at least a part of Fe is ferric. The c/a ratio is typical of “normal” beryl but its low value suggests dominant octahedral substitution. The 2b channel site is occupied by Na, Ca, REE and Sr. At the larger 2a site, Cs is clearly the most abundant (up to 3919 ppm). Water is present as both type I and type II but with large dominance of doubly coordinating H2O type II suggesting relatively fluid-rich genetic environment. The composition of beryl reflects the source rock of pegmatitic melt; I-type granitoids are generally enriched in Mg compared to S-type ones and consequently, the CNaOMgC-1OAl-1 substitution may play a more important role in beryl from I-type derived pegmatites such as Predné Solisko. The geological position of the studied intragranitic pegmatite excludes the possibility of contamination from the host rock and the beryl chemistry, therefore, reflects faithfully the pegmatitic melt composition. ]]> Original paper
<![CDATA[ Giftgrubeite, CaMn2Ca2(AsO4)2(AsO3OH)2·4H2O, a new member of the hureaulite group from Sainte-Marie-aux-Mines, Haut-Rhin Department, Vosges, France ]]> Meisser N, Plášil J, Brunsperger T, Lheur C, Škoda R; Vol. 64, issue 1, pages 73 - 80
Giftgrubeite, ideally CaMn2Ca2(AsO4)2(AsO3OH)2·4H2O, is a new mineral occurring at the Giftgrube Mine, St Jacques vein, Rauenthal, Sainte-Marie-aux-Mines, Haut-Rhin Department, Grand Est, France and named after the type-locality. Giftgrubeite is mostly associated with Mn-bearing calcite, native arsenic, löllingite, and picropharmacolite. It is a recent secondary mineral, formed by alteration of the arsenical vein minerals after mining. Giftgrubeite occurs in colorless, rarely pearl white to pale yellow rosettes of brittle tabular crystals flattened on {1 0 0} and up to 0.2 mm in size. Hardness (Mohs) is 3 ½, Dmeas is 3.23(2) g·cm-3, Dcalc is 3.24 g·cm-3. The new mineral is biaxial negative without pleochroism. Measured 2V angle is ~72° and calculated 2V angle is 75.1°; the refractive indices measured in white light are: α = 1.630(2), β= 1.640(2) and γ = 1.646(2). The most prominent Raman bands are at 902, 885, 864, 851, 824, 797 and 759 cm-1. The empirical chemical formula is (Ca3.04Mn1.30Mg0.38Fe0.28)Σ5.00(AsO4)1.99(AsO3OH)2·4H2O. Giftgrubeite is monoclinic, C2/c, Z = 4, with a = 18.495(7) Å, b = 9.475(4) Å, c = 9.986(4) Å, β = 96.79(3)° and V = 1737.7(12) Å3. The six strongest lines in the X-ray powder diffraction pattern are [d in Å (I)(hkl)]: 3.33 (100)(-2 2 2), 3.18 (80)(2 2 2), 2.414 (60)(7 1 1), 4.80 (50)(-3 1 1), 4.65 (50)(-2 0 2) and 3.05 (50)(1 1 3). The structure of giftgrubeite was solved from the crystal retrieved from the type specimen by the charge-flipping algorithm. Giftgrubeite contains a well-known structure type parent to the hureaulite group of minerals, which is based upon an octahedral edge-sharing pentamers of M2+-polyhedra; pentamers linked into a loose framework by sharing corners with octahedra in adjacent pentamers and further by AsO4 and AsO3OH tetrahedra. There are three distinct octahedral sites: M1, M2, and M3. In the case of giftgrubeite, two of the M sites were found to be fully occupied by Ca; namely M1 and M3. The M2 site was then found to contain Mg besides dominant Mn. Considering the refined site occupancies, the structural formula for giftgrubeite is Ca3Mn1.30Mg0.70(AsO4)2(AsO3OH)2(H2O)4. Giftgrubeite is an ordered intermediate member between villyaellenite, MnMn2Ca2(AsO3OH)2(AsO4)2·4H2O and sainfeldite, CaCa2Ca2(AsO4)2(AsO3OH)2·4H2O. ]]> Original paper