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[ Editorial ]]> Plášil J; Vol. 67, issue 4, page: 287
Times they are a-changin’…to be said with Bob Dylan. Nevertheless, we are here to deliver you the best we can do. The end of the year is a period to reconsider and reflect on what happened. The last two years were difficult for our Journal due to Covid-period, which, unfortunately, is still not over as we hoped and, most probably, many things have changed forever. What the upcoming year will bring is in the wind, but we can try our best and continue providing the scientific community with a high-standard platform for publishing. Several changes are on the horizon. We expect, finally, the online submission system to be started during the next year. Also, the editorial structure will change as I resign from the position of Editor-in-Chief starting on 3/2023.
I wish you a Merry Christmas and all the best for 2023!
In Prague, December 6, 2022
Jakub K. Plášil ]]> Editorial
<![CDATA[ Stibioústalečite, Cu6Cu6(Sb2Te2)Se13, the first Te-Se member of tetrahedrite group, from the Ústaleč, Czech Republic ]]> Sejkora J, Plášil J, Makovicky E; Vol. 67, issue 4, pages 289 - 297
Stibioústalečite, Cu12(Sb2Te2)Se13, was approved as a new mineral species from the Ústaleč mine, 15 km west of Horažďovice, SW Bohemia, Czech Republic. It occurs as metallic anhedral grains up to 0.1-0.3 mm in size, dark grey in color, in a calcite gangue. It is directly associated with hakite-(Hg), berzelianite, the not-yet approved phase Cu12(As2Te2)Se13 and uraninite. Stibioústalečite is brittle, with an indistinct cleavage and a conchoidal fracture; the calculated density is 5.676 g/cm3. In reflected light, stibioústalečite is isotropic, and grey in color; internal reflections were not observed. Reflectance data for the four COM wavelengths in air are [λ (nm): R (%)]: 470: 33.3; 546: 33.2; 589: 33.1; 650: 33.0. Electron microprobe analysis for holotype material (grain used for single-crystal X-ray study) gave (in wt. % - average of 7 spot analyses): Cu 34.10, Ag 1.22, Fe 0.04, Zn 0.09, Hg 0.33, Sb 9.39, As 0.70, Te 12.41, S 3.76, Se 37.59, total 99.63. On the basis of (As + Sb + Te) = 4 atoms per formula unit (apfu), the empirical formula of stibioústalečite is M(2)(Cu5.75Ag0.25)Σ6M(1)(Cu5.93Hg0.04Zn0.03Fe0.02)Σ6.02X(3)(Te2.12Sb1.68As0.20)Σ4(Se10.36S2.55)Σ12.91. The ideal formula is Cu6Cu6(Sb2Te2)Se13, which requires Cu 33.33, Sb 10.64 Te 11.16 Se 44.87, total 100 wt. %. Stibioústalečite is cubic, I 3m, with unit-cell parameters a = 10.828(4) Å, V = 1269.6(9) Å3, Z = 2. The crystal structure of stibioústalečite was studied by single-crystal X-ray diffraction data and it is isotypic with other members of the tetrahedrite group. The mineral is named after its type locality Ústaleč and its chemical composition, being the (Sb/Te) end-member in the possible ústalečite series. ]]> Original paper
<![CDATA[ Chemical composition and Raman spectroscopy of aerugite, xanthiosite, and a natural analog of KNi3(AsO4)(As2O7) from Johanngeorgenstadt, Germany ]]> Korybska-Sadło I, Szuszkiewicz A, Prell M, Gunia P; Vol. 67, issue 4, pages 299 - 310
Aerugite Ni8.5(AsO4)2As5+O8 and xanthiosite Ni3(AsO4)2, two rare anhydrous arsenates, have been identified in a historic sample from Johanngeorgenstadt, Saxony, Germany. The minerals have been characterized through scanning electron microscopy, electron microprobe analysis and Raman spectroscopy for the first time. They are mostly dark-green (aerugite) to light-green (xanthiosite) fine-grained or microcrystalline crusts on a quartz matrix in association with barite, bunsenite, dolomite, and rooseveltite. Aerugite forms up to 200 μm large pseudo-hexagonal platy crystals, whereas xanthiosite forms short prisms to nearly equant forms, often with indistinct, poorly-developed and rounded faces. The chemical composition of the two minerals can be expressed by the empirical formulas: (Ni7.92Co0.52Cu0.06)Σ8.50 (As1.00O4)2 As1.00O8 with traces of Bi (aerugite, mean of 4 analyses, based on 32 oxygens) and (Ni2.85Co0.12Cu0.03)Σ3.00 (As1.00O4)2 (xanthiosite, mean of 5 analyses, based on 32 oxygens). The Raman spectra of both minerals lack bands related to OH stretching vibrations and are dominated by antisymmetric ν3 and symmetric ν1 As-O vibrations in AsO4 polyhedra centered at 817, 846 and 886 cm-1 in the case of aerugite and at 786, 808, 826 and 843 cm-1 in xanthiosite. Bands from stretching vibrations As-O in AsO4 polyhedra are located at 728 and 735 cm-1 in aerugite and are slightly displaced to 726 and 747 cm-1 in xanthiosite. The Raman spectrum of aerugite also contains well-defined 692, 675 and 658 cm-1 bands due to the stretching mode of NiO6 octahedra, a broad feature at 576 cm-1 probably from a number of modes connected with AsO6 octahedra. On the other hand, the xanthiosite spectrum displays a number of low-intensity, well-defined bands related to antisymmetric ν4 and ν2 symmetric bending vibrations in AsO4 below 700 cm-1 as well as to lattice vibrational modes and Ni-O interactions below 250 cm-1. Locally, the interstices between xanthiosite grains are filled with cryptocrystalline mass with the mean chemical composition of (K0.90Ba0.01)Σ0.91 (Ni2.86Co0.11Cu0.05)Σ3.02 (As1.00O4)(As2.1O7) with traces of Na (mean of 7 analyses, based on 11 oxygens). The recorded Raman spectrum, with a strongly overlapping xanthiosite-related signal, lacks bands of water molecules or OH groups and contains bands related to the As-O-As vibration modes attributed to pyroarsenate As2O7 groups. Although it was impossible to obtain more detailed data on crystal structure, we suggest this is the first reported natural occurrence of KNi3(AsO4)(As2O7) phase. ]]> Original paper
<![CDATA[ The role of peridotite and pyroxenite melts in the origin of the Karapınar basalts, Cappadocia Volcanic Province, Central Anatolia ]]> Gençoğlu Korkmaz G, Kurt H, Asan Kş, Petrelli M, Leybourne M; Vol. 67, issue 4, pages 311 - 329
This study investigates the mantle source characteristics of the Quaternary Karapınar Basalts from the southwestern part of the Cappadocia Volcanic Province (CVP) in Central Anatolia using a combination of whole-rock and olivine major- and trace-element geochemistry as well as olivine oxygen isotope composition. Petrographic features and trace element distributions demonstrate that the Karapınar basalts can be classified into two sub-groups as basalt-1 (KB1/alkaline-calc-alkaline) and basalt-2 (KB2/calc-alkaline). Although these two types of basalts are petrographically, texturally and geochemically different, they exhibit similar “orogenic type” incompatible trace element patterns in MORB-normalized diagrams. KB1 basalts are relatively primitive (e.g., up to 12 wt. % MgO) and calc-alkaline to mildly alkaline (Ne-normative content up to 5 %) in character, whereas KB2 basalts are enclave-bearing, calc-alkaline (hypersthene-normative plus quartz or olivine) ones with the more evolved composition. The most primitive olivine from the KB1 exhibits normal zoning, from core compositions of Fo89 to rim compositions of Fo86, with a concomitant decreasing in Ni and increasing MnO and CaO contents. On the contrary, the KB2 olivines show both inverse and normal zoning in terms of CaO and MnO contents. Moreover, the studied olivine phenocrysts have enriched rims and/or growth zones in Li, Zn, Cr, Ti, Sc, and V contents, which indicates a source containing recycled continental crust and/or magma recharging processes. The olivine from the most primitive samples (KB1; MgO > 10 wt. %) has high Zn/Fe, Fe/Mn, Co, Zn, Ni, Ca, and low Mn/Zn, Co/Fe values indicating melt addition from a pyroxenitic source. Calculations based on the olivine chemistry indicate that the most primitive nepheline normative KB1 rocks originated from the melting of mixed pyroxenitic-peridotitic source that shows the average proportion of ˜70 % and ˜30 %, respectively. The mean δ18O values of olivine phenocrysts (+6.4 ‰; n = 8) from the Karapınar basaltic rocks are higher than typical mantle olivine (+5.1-5.4 ‰) but overlap known OIB-EMII sources (+5.4-6.1 ‰). Collected data indicate that the Karapınar basalts are the mixing products of partial melts from mantle peridotite and metasomatic pyroxenite generated by the reaction of the subducted oceanic slab-derived melts with the surrounding peridotite, related to the convergence system of the Eurasian and Afro-Arabian plates. ]]> Original paper
<![CDATA[ Molybdenum isotopic composition of molybdenite and the fertility potential of the Ekomédion U–Mo prospect, SW Cameroon ]]> Fonabe Embui V, Emmanuel Suh C, Lehmann B, Ackerman L; Vol. 67, issue 4, pages 331 - 344
We present Mo isotope data for molybdenite from the Ekomédion U-Mo prospect, SW Cameroon, a Late Neoproterozoic granite-pegmatite-quartz vein system. Disseminated and veinlet-controlled molybdenite in granite and pegmatitic pods yields a narrow range of δ98Mo values from -0.06 to +0.24 ‰, with two overlapping populations of +0.03 ± 0.07 ‰ (n = 4) in granite, and slightly heavier of +0.11 ± 0.10 ‰ (n = 5) in pegmatite. By contrast, molybdenite from a quartz-muscovite vein has an isotopically heavy δ98Mo value of +1.61 ‰. We interpret this trend from granite through pegmatite to vein system towards isotopically heavy Mo to reflect the fractionation of an evolving magmatic-hydrothermal system. Furthermore, the LREE-enriched bulk-rock patterns with largely negative Eu anomalies and the overall enrichment of HREE in zircon indicate plagioclase fractionation as the dominant petrogenetic process during melt evolution. Furthermore, the presence of accessory ilmenite indicates relatively reducing conditions of the melt system, unfavorable for significant Mo accumulation. Therefore, the Ekomédion granite system seems to have limited economic potential for molybdenum despite the advanced degree of magmatic evolution. ]]> Original paper