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 GEOscienceshttp://www.jgeosci.org/img-system/jgeosci_cover.jpghttp://www.jgeosci.org <![CDATA[ Geological interpretation of a seismic reflection profile in the eastern part of the Bohemian Cretaceous Basin ]]> Skácelová Z, Mlčoch B, Čech S; Vol. 67, issue 1, pages 1 - 17
A seismic reflection profile was realized in the eastern part of the Bohemian Cretaceous Basin in the years 2013-2015. Seismic research was supported by a detailed gravity and geoelectric survey. The profile crossed three significant hydrogeological structures or districts: Vysoké Mýto, Ústí and Kyšperk synclines. Interpretation of geophysical data enabled a determination of the Cretaceous sediments with a thickness of up to 250 m and Permian sediments even with a thickness of 2000 m. The seismic reflectors and gravity effect, together with the boreholes and geological mapping, were used to compile the uncovered geological map. ]]>
http://www.jgeosci.org/rss.php?ID=jgeosci.339 Original paper http://www.jgeosci.org/rss.php?ID=jgeosci.339
<![CDATA[ Titanium-oxide activity during the formation of gold-bearing quartz veins: evidence for closed system behavior ]]> Pacák K, Zachariáš J, Němec M; Vol. 67, issue 1, pages 19 - 32
Titanium contents of both vein and magmatic quartz from five Bohemian gold deposits with known P-T history were used to calculate/discuss the titanium oxide activities ( ) of natural quartz formed in the absence of Ti-buffering phases at 250-550 °C and 0.1-4 kbar.
Data suggest significant variations in during vein quartz formation, due to variation of P, T, growth rate and . Negative correlation between and quartz formation temperature was documented for intrusion-related gold deposits, implying quartz precipitation under closed-system conditions (i.e., without substantial equilibration of the ascending fluid with surrounding rocks). We propose a relationship for quantifying disequilibrium quartz formation that can be readily applied to quartz with known P-T history. The relationship was tested on natural samples exhibiting both rapid and slow crystallization. An example of extreme Ti enrichment (up to ˜30 ×) in quartz, associated with its rapid growth, is described and discussed. ]]>
http://www.jgeosci.org/rss.php?ID=jgeosci.340 Original paper http://www.jgeosci.org/rss.php?ID=jgeosci.340
<![CDATA[ Michalskiite, Cu2+Mg3Fe3+3.33(VO4)6, an Mg analogue of lyonsite, from the Ronneburg uranium deposit, Thuringia, Germany ]]> Kampf AR, Plášil J, Škoda R, Čejka J; Vol. 67, issue 1, pages 33 - 40
Michalskiite (IMA2019-162), Cu2+Mg3Fe3+3.33(VO4)6, is a new mineral found on specimens from the dump of the Lichtenberg open pit, Ronneburg uranium mining district, Thuringia, Germany. It is a secondary mineral occurring with arcanite, epsomite, hematite and syngenite on matrix consisting of fine-grained quartz, K-feldspar and mica. It forms striated prisms and needles, elongated on [001], up to about 0.2 mm long. Crystals are brown-red with a light orange streak. They are transparent and have adamantine lustre. The mineral is brittle with curved fracture, very good {001} cleavage and a Mohs hardness of ˜3½. The calculated density is 3.848 g.cm-3 based on the empirical formula. The new mineral is biaxial (-), with 2Vmeas = 49(1)°. No pleochroism was observed. Optical orientation is X = c. The empirical formula of michalskiite (on the basis of 24 O apfu) is (Cu2+1.31Mg2.76Fe3+2.75Al0.21Ni0.16Ti4+0.14Mn3+0.06Zn0.01)Σ7.40(V5+5.96Si0.02)Σ5.98O24. The Raman spectrum is dominated by the vibrations of VO43- units. Michalskiite is orthorhombic, Pmcn, a = 10.2356(9), b = 17. 3689(16), c = 4.9406(4) Å, V = 878.35(13) Å3 and Z = 2. The five strongest powder X-ray diffraction lines are [dobs, Å (I, %) (hkl) ]: 3.27 (100) (221,150), 2.74 (40) (241,151), 2.52 (50) (331), 1.55 (30) (282), 1.42 (25) (063). The crystal structure of michalskiite was refined from the single-crystal X-ray data to R = 0.0386 for 888 independent observed reflections, with Iobs > 2σ(I). Michalskiite is isostructural with lyonsite; however, the Cu2 site in the lyonsite structure is split into M2 and M2’ sites in the michalskiite structure with Mg occupying the M2’ site. The new mineral name honours German mineral collector and dealer Dipl. Min. Steffen Michalski, who discovered this mineral. ]]>
http://www.jgeosci.org/rss.php?ID=jgeosci.341 Original paper http://www.jgeosci.org/rss.php?ID=jgeosci.341
<![CDATA[ Pokhodyashinite, CuTlSb2(Sb1-xTlx)AsS7-x, a new thallium sulfosalt from the Vorontsovskoe gold deposit, Northern Urals, Russia ]]> Kasatkin AV, Plášil J, Makovicky E, Škoda R, Agakhanov AA, Tsyganko MV; Vol. 67, issue 1, pages 41 - 51
Pokhodyashinite CuTlSb2(Sb1-xTlx)AsS7-x, is a new sulfosalt from the Vorontsovskoe gold deposit, Sverdlovsk Oblast’, Northern Urals, Russia. It forms anhedral grains up to 0.1 × 0.05 mm in size in calcite and is associated with major orpiment, pyrite, realgar and minor baryte, clinochlore, As-bearing fluorapatite, harmotome, prehnite, native gold and a rich spectrum of sulfosalts. Pokhodyashinite is black, opaque, and has a metallic luster and a black streak. It is brittle, with an uneven fracture and poor cleavage on {010}. The Vickers hardness (VHN, 20 g load) is 55 kg/mm2, corresponding to a Mohs hardness of 2. The calculated density is 5.169 g/cm3. In reflected light, pokhodyashinite is grayish-white, bireflectance is distinct. In crossed polars, it is strongly anisotropic; rotation tints vary from dark brownish gray to light bluish-gray. No internal reflections are observed. The reflectance values for wavelengths recommended by the Commission on Ore Mineralogy of the IMA are (Rmin/Rmax, %): 28.9/34.6 (470 nm), 27.6/33.4 (546 nm), 26.7/32.4 (589 nm), 26.1/31.1 (650 nm). The empirical formula of pokhodyashinite based on ΣMe = 6 apfu is Cu0.700Ag0.340Tl1.320Pb0.020Sb2.630As0.990S6.625.
Pokhodyashinite is monoclinic, space group C2/m, a = 23.431(5), b = 3.996(2), c = 14.070(3) Å, β = 110.23(3)°, V = 1236.1(8) Å3 and Z = 4. Its structure can be described as wavy slabs of a complex structure based on double-rods of Sb-coordination pyramids and lone-electron-pair interspaces/micelles, separated by wavy interlayers consisting of paired columns of Tl and rods of paired Cu-coordination polyhedra. A small amount of Tl-for-Sb substitution results in partial anion vacancies in one sulfur site. The new mineral is named in honor of Maxim Mikhailovitch Pokhodyashin, a pioneer of mining engineering and smelting works in the Northern Urals of the 18th century. ]]>
http://www.jgeosci.org/rss.php?ID=jgeosci.342 Original paper http://www.jgeosci.org/rss.php?ID=jgeosci.342
<![CDATA[ Ar-Ar Geochronology and Sr-Nd-Pb-O Isotopic Systematics of the Post-collisional Volcanic Rocks from the Karapınar-Karacadağ Area (Central Anatolia, Turkey): An Alternative Model for Orogenic Geochemical Signature in Sodic Alkali Basalts ]]> Gençoğlu Korkmaz G, Kurt H, Asan K, Leybourne M; Vol. 67, issue 1, pages 53 - 69
The Plio-Quaternary post-collisional volcanism in the Karapınar area is represented by two occurrences: (1) Karacadağ Volcanic Complex (KCVC) and (2) Karapınar Volcanic Field (KPVF). The investigated volcanic units are the southwestern part of the Neogene to Quaternary Cappadocia Volcanic Province (CVP) in Central Anatolia. The CVP generally displays calc-alkaline affinity in the Late Miocene to Pliocene rocks, but both calc-alkaline and sodic alkaline affinity in the Plio-Quaternary rocks, all of which have an orogenic geochemical signature. Such a volcanic activity contradicts the Western and Eastern Anatolian volcanism characterized by anorogenic OIB-like sodic alkaline volcanic rocks postdating early orogenic calc-alkaline ones. We hypothesize that such temporal and geochemical variations in the investigated rocks result from crustal contamination and present major and trace element chemistry and Sr-Nd-Pb-O isotope geochemistry, coupled with 40Ar/39Ar geochronology data to restrict the genesis and evolution of the rocks. The Neogene Karacadağ volcanic rocks are represented by lava flows, domes and their pyroclastic equivalents constituting a stratovolcano, and dated by new 40Ar/39Ar ages of 5.65 to 5.43 Ma. They are mainly composed of andesitic, rarely basaltic, dacitic and trachytic rocks and have a calc-alkaline character. Constituting a monogenetic volcanic field, the Quaternary Karapınar volcanic rocks are typically formed by cinder cones, maars and associated lavas, including xenoliths and xenocrysts plucked from the Karacadağ rocks. They comprise basaltic to andesitic rocks with a transitional affinity, from sodic alkaline to calc-alkaline. Both the Karacadağ and Karapınar volcanic rocks display incompatible trace element patterns rather characteristic for orogenic volcanic rocks. The Sr, Nd and Pb isotopic systematics of both units show a relatively narrow range, but their δ18O values are markedly different. The Karacadag volcanic rocks have δ18O values ranging from 7.5 to 8.9 ‰, resembling those of subduction-related basalts, but the Karapınar volcanics have δ18O ratios between 5.7 and 6.5 ‰ corresponding to OIB-like rocks. Additionally, δ18O values and 87Sr/86Sr ratios correlate positively with SiO2 in the rocks, indicating that contamination played an important role during differentiation processes. All the data obtained suggest that the Karacadağ basaltic rocks stemmed from a subduction-modified lithospheric mantle source. On the other hand, the origin of the Karapınar basaltic rocks can be explained in terms of OIB-like melts contaminated with the Karacadağ volcanic rocks to gain orogenic geochemical signature, which may be an alternative model for the origin of the CVP sodic alkali basalts. ]]>
http://www.jgeosci.org/rss.php?ID=jgeosci.343 Original paper http://www.jgeosci.org/rss.php?ID=jgeosci.343