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/img-system/jgeosci_cover.jpghttp://www.jgeosci.org Yavuz F, Yavuz V; Vol. 68, issue 2, pages 95 - 110
A Microsoft^® Visual Basic software, called WinSpingc, has been developed to calculate and classify wet chemical and electron-microprobe spinel supergroup mineral analyses based on the New Minerals, Nomenclature and Classification (CNMMN) of the International Mineralogical Association (IMA-19) nomenclature scheme. The program evaluates the 60 approved species according to the dominant valance and constituents in the general AB₂X₄ formula for the spinel, ulvöspinel, carrollite, linnaeite, tyrellite and bornhardtite subgroups that belong to the oxyspinel, thiospinel and selenospinel groups. Mineral analyses of the oxyspinel group are calculated based on 3 cations and 4 oxygen atoms per formula unit, whereas the formulae of thiospinel and selenospinel analyses are on the basis of 7 atoms per formula unit. Employing the anions of spinel supergroup mineral analyses, the program first assigns three groups on the basis of dominant X anion, including O^2-, S^2- and Se^2-, determines subgroups according to the cation charge arrangement combinations and then defines the spinel species in each subgroup based on the dominant valance and constituents. The Fe³⁺ and Fe²⁺, as well as the Mn³⁺, Mn²⁺, Co³⁺ and Co²⁺ contents from microprobe-derived total FeO, MnO and CoO (wt. %) amounts, are estimated by stoichiometric constraints. WinSpingc allows the users to enter total 57 input variables for groups as well as to type and load the multiple spinel supergroup compositions in the data entry section, to edit and load the Microsoft^® Excel files in calculating, classifying and naming the spinel species, and to store all the calculated parameters in the Microsoft^® Excel file for further evaluations. The program is distributed as a self-extracting setup file, including the necessary support files used by the program, a help file, and representative sample data files. ]]> http://www.jgeosci.org/rss.php?ID=jgeosci.369 Original paper http://www.jgeosci.org/rss.php?ID=jgeosci.369 Novák M, Toman J, Škoda R, Šikola D, Mazuch J; Vol. 68, issue 2, pages 111 - 138
Geological position, mineral assemblages, and compositional evolution of several types of mostly hydrothermal zeolite mineralizations were examined in the easternmost part of the Moldanubian Zone (Strážek Unit), Czech Republic, using EPMA and Raman spectroscopy. The zeolite mineralizations are related to the following geological processes: (A1) late magmatic to (A2, A3) hydrothermal crystallization (pseudomorphs, brittle tectonic fractures) in granitic pegmatites; (B) retrograde stages of the Variscan metamorphism - (B1) Alpine-type hydrothermal veins on ductile to brittle fractures with epidote, prehnite and zeolites, (B2) laumontite and (B3) natrolite veinlets; the latter two on thin brittle fissures; (C) hydrothermal zeolite veins with dominant stilbite-(Ca) + heulandite-(Ca) and sulfides on ductile to brittle fractures, and (D) thin brittle fissure-filling veinlets lined with harmotome ± calcite. The zeolite mineralizations include pollucite (A), analcime (A, B), phillipsite-(Ca) (A), harmotome (A, D), chabazite-(Ca) and chabazite-(K) (A, B), thomsonite-(Ca) (A), natrolite (A, B), laumontite (A, B, C), stilbite-(Ca) (B, C), scolecite (B), and heulandite-(Ca) (B, C). The individual zeolite mineralizations differ significantly in their regional distribution: (B) Alpine-type hydrothermal veins and laumontite and natrolite veinlets are widespread within almost the whole region, whereas zeolites in (A) granitic pegmatites and in (C, D) hydrothermal veins are concentrated along the eastern border of the Strážek Unit, the latter two assemblages restricted to the Rožná-Olší ore field. Fluids with variable composition and origin facilitated the formation of individual zeolite mineralizations. They evolved from moderate-T (˜400 °C) to low-T (˜50 °C) conditions characterized by the following extra-framework cations ± volatiles with dominant H₂O: (A1) - Cs, Ba, Ca, Na ˃ K, (A2) - Ca, K, Ba ˃ Na, (A3) - Ca, Na, Ba (A: T ˜400-50 °C); (B1) - Ca ± B, (B2) - Ca, (B3) - Na, Ca (B: T ˜350-50 °C); (C) - Ca ˃ Na ± S, F (C: T ˜240-50 °C); (D) - Ba, Ca ± CO₂ (D: T ˜100-50 °C). Sources of fluids include - residual fluids exsolved from pegmatite melt (A1) and external fluids derived from host rock (A2, A3); fluids related to retrograde stages of the Variscan metamorphism (A3?, B1, B2, B3, C?); likely post-Variscan fluids of various origin (C, D). The zeolite assemblages demonstrate that the PTX conditions suitable for their origin were attained in the late stages of distinctive geological processes. Zeolites may be used as a valuable indicator of alkaline to neutral and low-T to very low-T hydrothermal fluids with high activity of Ca, K, Na and/or Ba, and variable aSiO₂ on tectonic fractures and fissures. ]]> http://www.jgeosci.org/rss.php?ID=jgeosci.370 Original paper http://www.jgeosci.org/rss.php?ID=jgeosci.370 Mederski S, Pršek J, Kołodziejczyk J, Kluza K, Melfos V, Adamek K, Dimitrova D; Vol. 68, issue 2, pages 139 - 162
This work presents a mineralogical and geochemical study of Cu-Bi-Ag±W ores from Janjevo in the Trepça Mineral Belt in Kosovo. This locality indicates a new type of Bi-Cu±Au mineralization within the Kizhnica-Hajvalia-Badovc ore field, including Cu-Bi±Ag±As sulfosalts paragenesis previously not described in Kosovo and in this part of the Vardar Zone. Chemical composition of Bi-Pb±Cu±Ag and Cu-Bi±Ag±As sulfosalts, sulfides, and associated minerals, as well as their paragenetic relationships and the distribution of minor and trace elements in main ore minerals, are discussed based on microscopy, microprobe, and laser ablation inductively coupled plasma mass spectrometry studies. The Cu-Bi-Ag±W hydrothermal mineralization in Janjevo was formed during four stages: (1) Early base metal stage, (2) Bismuth stage, (3) Main stage, and (4) Late stage. The Early base metal stage is represented by pyrite, sphalerite I, chalcopyrite I, galena I, bournonite I, tetrahedrite I, siderite, and quartz. The Bismuth stage includes arsenopyrite I, löllingite, native bismuth, galena II, chalcopyrite II, tetrahedrite II, quartz, siderite, and Bi-Pb±Cu±Ag sulfosalts: bismuthinite, aikinite, krupkaite, cosalite, and gustavite. The Main stage is represented by chalcopyrite III, tetrahedrite group minerals (tetrahedrite and tennantite) III, galena III, sphalerite II, arsenopyrite II, bournonite II, and siderite. The Cu-Bi±Ag±As sulfosalts (pearceite, cupropearceite, wittichenite, and an unknown phase: AgCuBiS₃) associated with galena IV, siderite, and quartz were formed in the final low-temperature Late stage. The application of GGIMFis geothermometry on sphalerite gives the following sphalerite precipitation temperatures: 220-272 °C for sphalerite I and 160-190 °C for sphalerite II. Presented results show that in addition to numerous Bi sulfosalts in Janjevo Cu-Bi-Ag±W ores, bismuth has been incorporated into base metal sulfides, as well as arsenopyrite. The main carrier of bismuth is arsenopyrite I, which has started the crystallization of the bismuth stage. ]]> http://www.jgeosci.org/rss.php?ID=jgeosci.371 Original paper http://www.jgeosci.org/rss.php?ID=jgeosci.371 Zhitova ES, Sheveleva RM, Zolotarev AA, Krivovichev SV, Shilovskikh VV, Nuzhdaev AA, Nazarova MA; Vol. 68, issue 2, pages 163 - 178
The crystal structure of magnesian halotrichite has been refined for two samples collected as white efflorescences from the surface of geothermal fields associated with the Koshelevsky (sample VK4-09) and Centralny Semyachik (sample SC2-20) volcanos (both Kamchatka peninsula, Russia). Halotrichite and its Mg-rich varieties are common products of the acid leaching of rocks, both volcanic and technogenic. The crystal structures of two halotrichite crystals were refined in the P2₁/n space group (vs. P2₁/c used previously) with the unit-cell parameters a = 6.1947(2)/ 6.1963(5) Å, b = 24.2966(8)/ 24.2821(14) Å, c = 21.0593(8)/ 21.063(2) Å, β = 96.512(4)/ 96.563(9) °, V = 3149.2(2)/ 3148.3(5) ų, Z = 4 to R₁ = 0.055 and 0.067 for 5673 and 3936 reflections with I > 2σI reflections, respectively. The crystal structure consists of isolated Al(H₂O)₆ octahedra, SO₄ tetrahedra, H₂O molecules and [X(SO₄)(H₂O)₅]⁰ clusters (X = Fe, Mg). The chemical analyses of both samples show their enrichment of Mg at the Fe²⁺ site. The analysis of geometrical parameters of the crystal structures of halotrichite and its Mg-analogue pickeringite suggests that the localization of O atoms carried out in this work is more accurate and the single-crystal X-ray diffraction data for the first time allowed localization of hydrogen atom positions. The refined number of H₂O molecules agrees with the ideal chemical formula. The crystal structure complexity of halotrichite is estimated as I_G,total = 2305 bits/cell, which belongs to the family of very complex mineral structures. The contribution of hydrogen bonding system plays a significant role in the overall bonding scheme and the overall complexity of the crystal structure, increasing the Shannon information amount more than twice from I_G,total(noH) = 988 bits/cell (no hydrogen atoms) to I_G,total = 2305 bits/cell (all atoms including hydrogen). The comparative distribution of halotrichite relative to other Fe-Al hydrated sulfates from the standpoint of structural complexity is considered. ]]> http://www.jgeosci.org/rss.php?ID=jgeosci.372 Original paper http://www.jgeosci.org/rss.php?ID=jgeosci.372