Table of Contents for the Journal of GEOsciences. List of articles from the latest print issue.https://www.jgeosci.orgen-US https://www.jgeosci.org/img-system/jgeosci_cover.jpghttps://www.jgeosci.org Myšľan P, Ružička P, Števko M, Mikuš T; Vol. 70, issue 2, pages 53 - 69
The Čučma - Čierna baňa manganese deposit (Slovakia, Western Carpathians) hosts barium-rich mineralisation within the Early Paleozoic metacarbonate lenses associated with graphite-, quartz-muscovite phyllites and metalydites. The main metacarbonate mineral is represented by calcite containing up to 94.2 mol. % CaCO₃, with minor amounts of Mn, Fe and Mg constituents. The Ba-mineralisation consists of silicates such as cymrite, celsian, Ba-rich muscovite and baryte along with clinochlore, quartz, spessartine and accessory fluorapatite and rutile. Cymrite forms prismatic to tabular aggregates, commonly associated with celsian and Ba-rich muscovite, it displays a stable chemical composition close to the theoretical end-member formula. Celsian (89.0-97.3 mol. % Cls) with minor Na, K, Ca, and Sr contents typically occurs as anhedral grains and is overgrown by cymrite, indicating a possible hydration transformation. Ba-rich muscovite shows complex chemical zoning, suggesting variable Ba incorporation through multiple substitutions predominantly in Ba-enriched zones (up to 0.32 apfu Ba). Clinochlore lacks any Ba and is interpreted as a retrograde phase. Textural, chemical and structural evidence studied by optical microscopy, electron microprobe analyses (EPMA) and Raman spectroscopy indicates a multi-stage development involving baryte or barium enrichment during sedimentation influenced by submarine basic volcanism, subsequently followed by Variscan and Alpine metamorphic events. Metamorphic recrystallisation mobilised Ba, leading to the formation of Ba-rich silicates. The Ba-rich mineral assemblage and associated textures reflect the complex metamorphic evolution of the deposit and highlight cymrite and celsian as a key indicator of low-grade metamorphism in the studied Ba-rich environment. The presence of spessartine (up to 60.0 mol. % Sps) and other accessory phases further illustrates a close relation with associated manganese mineralisation. ]]> https://www.jgeosci.org/rss.php?ID=jgeosci.0032.25 Original Paper https://www.jgeosci.org/rss.php?ID=jgeosci.0032.25 Franěk J, Filippi M, Rapprich V; Vol. 70, issue 2, pages 71 - 86
Spatial distribution and mutual relations of large amygdales were studied in a texturally stratified basaltic lava flow in the Permian Krkonoše Piedmont Basin in northern part of the Czech Republic, Central Europe. Clusters of distinctively shaped large amygdales were observed in lensoidal domains of altered trachybasalt between massive, amygdale-free zones below and scoriaceous lava above. The shapes and orientations of amygdales - from vertically elongated forms in lower parts to horizontally flattened types near the base of the upper scoriaceous zone - indicate a progressive shape evolution influenced by cooling dynamics of the nearly static lava body. Fluids creating the large vesicles likely originated from underlying water-saturated older volcanic rocks or local sediments, while the alteration of surrounding trachybasalt is expected to proceed at least partly as higher-temperature processes in the cooling lava rather than purely by later stage percolation of meteoric groundwater. These results allow for a comprehensive model of formation of large vesicles and their possible immediate filling with agate, carbonates or goethite liberated by water-dominated fluids from cooling lava in their immediate surroundings, potentially explaining also meteoric isotopic signatures observed in amygdales elsewhere, without need for Si-rich nor vapour-rich parent magma. The implications are broadly relevant for studies of large agates, geodes and other amygdales in mafic lava flows in water-rich volcano-sedimentary environments within continental basins. ]]> https://www.jgeosci.org/rss.php?ID=jgeosci.0028.25 Original paper https://www.jgeosci.org/rss.php?ID=jgeosci.0028.25 Števko M, Rybárik M, Koděra P, Myšľan P, Prcúch J, Mikuš T; Vol. 70, issue 2, pages 87 - 104
An unusual hydrothermal Mn-Be mineralization was recently discovered at the Banská Hodruša intermediate-sulfidation epithermal deposit, Slovakia. Mn-Be mineralization occurs in dense stockwork of the stage 2 quartz-rhodonite-rhodochrosite veins (Karolína type) and it is represented by helvine, minerals of the rhodonite and epidote group, johannsenite-diopside series and axinite-(Mn) accompanied by minor Mn-rich clinochlore, adularia, pyrite, sphalerite, chalcopyrite, hematite as well as abundant younger Ca-rich rhodochrosite and calcite and rarely also anhydrite. Helvine from the Banská Hodruša deposit is compositionally close to the end member (content of Mn is between 3.50 to 3.98 apfu) with only minor presence of genthelvine (Zn up to 0.22 apfu) and danalite (Fe up to 0.20 apfu) constituents. Rare occurrence of hydrothermal axinite-(Mn) containing dominant Mn (1.83 to 2.10 apfu) and only subordinate amounts of Fe (up to 0.29 apfu) and Mg (0.11 apfu) is also notable. Beryllium and boron at the Banská Hodruša deposit were likely introduced by magmatic-hydrothermal fluids with increased activity of manganese. Homogenisation temperatures and salinities obtained from fluid inclusions hosted directly in helvine and associated quartz are typical for intermediate sulfidation epithermal deposits (259 to 309 °C, 1.9 to 6.3 wt. % NaCl eq.) with a slightly increased salinities compared to most fluid inclusions at the studied deposit. Persistent boiling is probably responsible for increased salinity of fluids and fractionation of Be and B in residual fluids which were trapped in cavities and fissures in veins. The resulting increased activities of Be and B along with cooling are probably responsible for the precipitation of helvine, axinite-(Mn) and associated minerals. ]]> https://www.jgeosci.org/rss.php?ID=jgeosci.0037.25 Original paper https://www.jgeosci.org/rss.php?ID=jgeosci.0037.25 Yavuz F; Vol. 70, issue 2, pages 105 - 116
A Microsoft^® Visual Basic software, WinGadclas, has been developed to calculate the chemical formulae of gadolinite-supergroup minerals based on data obtained from wet-chemical and electron-microprobe analyses. WinGadclas currently evaluates 13 valid mineral species using the Commission on New Minerals, Nomenclature and Classification (CNMNC) of the International Mineralogical Association (IMA) nomenclature scheme for the gadolinite-supergroup minerals in the general chemical formula A₂MQ₂T₂O₈φ₂. The program recalculates and estimates the chemical formulae of gadolinite-supergroup species based on 10 oxygen atoms, with the 2 T, 2 A, and T+Q = 4 atoms per formula unit normalization options. Mineral formulae of the gadolinite-supergroup minerals are calculated based on the occupancy of A, M, Q, T, and φ sites, as well as the application of the dominant-valency and dominant-constituent rules. WinGadclas operates in four stages: (1) it estimates cation and anion contents provided by input chemical data; (2) it determines the dominant cation and anion at the A, M, Q, T, and φ sites; (3) it assigns the gadolinite-supergroup minerals to one of the four subgroups, including datolite, gadolinite, herderite, and drugmanite; and (4) it classifies the gadolinite-supergroup species into appropriate groups, such as gadolinite and herderite. WinGadclas allows users to: (1) enter up to 46 input variables for mineral-chemical analyses; (2) type and load multiple gadolinite-supergroup mineral compositions in the data entry section; (3) edit and load the Microsoft^® Excel files used in calculating, classifying, and naming the gadolinite-supergroup minerals, and (4) store all the calculated parameters in the output of a Microsoft^® Excel file for further data evaluation. The program is distributed as a self-extracting setup file for Windows 7 or later operating system, including the necessary support files used by the program, a help file, and representative sample data files. ]]> https://www.jgeosci.org/rss.php?ID=jgeosci.404 Original paper https://www.jgeosci.org/rss.php?ID=jgeosci.404