VALIDACE TERÉNNÍHO RENTGEN-FLUORESCENČNÍHO SPEKTROMETRU PRO POTŘEBY ANALÝZ PŮD, ŘÍČNÍCH SEDIMENTŮ A SUSPENDOVANÉ HMOTY

The portable X-ray-fluorescence analyser is being used for Ag, As, Ba, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Rb, Sb, Se, Sn, Sr, Ti, U, V, Zn a Zr. There is an Alpha model (Innov-X Systems, Inc) used at the Czech Geological Survey for geological mapping, contamination of the soil, stream sediment or vegetation and for geochemical purposes and environmental mapping. For the measurement the total amount of sample with 10–30 g of material was used, it means such amount of material which can cover in large measure the window of the instrument. The thickness of the measured layer varies from 3 to 20 mm. For the study purposes 100 samples was analyzed including 20 reference laboratory samples. Its specification is presented in Table 1. To compare both sets of samples the whole rock analysis of duplicate samples has to be mesasured and this kind of analysis was provided by Acme Analytical Laboratories (Vancouver) Ltd., Canada. The results shows that correlation between measurement based on XRF method and reference materials or classic laboratory measurements corresponds in a good way. The most of the evaluated components reaches acceptable relative errors by precision of the measurement. Using this instrument makes the process of samples selection for the regional environmental research or core samples measurement much easier. In a short period we can analyze the wide spectrum of components under the low cost budget

Comparison of the results of classical analytical methods with a portable X-ray fluorescence spectrometer in the map sheets 1 : 25 000 Brno-North and Mokrá-Horákov

New subchapter Geochemistry of soil cover in the chapter of the Geochemistry examines geochemical character of the forestry soils or soils that are not agriculturally used. For displaying of the results of the geochemical character of soils is best to use contour maps. For creating of contour maps is need for a large number of samples. The conventional laboratory methods of analysis are very expensive and consumed time. In addition to analysis performed conventionally laboratory methods FAAS, HGAAS and stationary XRF, these samples were analysed by the portable XRF spectrometer Alpha 4000 too. An accuracy of the portable XRF measurement was verified in five geo-referenced materials. Method of the portable XRF against to conventional laboratory methods is quick and cheap. Creating of the geochemical maps of soils 1 : 25,000 is needed to cover the whole map sheet regular grid sampling points. The results show that not all elements are measured with the same reliability. Therefore, it is appropriate to measure of the portable XRF to analyse by conventional laboratory methods about 10% of the total number of samples collected to evaluate the reliability the results.New subchapter Geochemistry of soil cover in the chapter of the Geochemistry examines geochemical character of the forestry soils or soils that are not agriculturally used. For displaying of the results of the geochemical character of soils is best to use contour maps. For creating of contour maps is need for a large number of samples. The conventional laboratory methods of analysis are very expensive and consumed time. In addition to analysis performed conventionally laboratory methods FAAS, HGAAS and stationary XRF, these samples were analysed by the portable XRF spectrometer Alpha 4000 too. An accuracy of the portable XRF measurement was verified in five geo-referenced materials. Method of the portable XRF against to conventional laboratory methods is quick and cheap. Creating of the geochemical maps of soils 1 : 25,000 is needed to cover the whole map sheet regular grid sampling points. The results show that not all elements are measured with the same reliability. Therefore, it is appropriate to measure of the portable XRF to analyse by conventional laboratory methods about 10% of the total number of samples collected to evaluate the reliability the results

Geochemistry and mineralogy of platinum-group elements (PGE) in chromites from Centralnoye I, Polar Urals, Russia

The Polar Urals region of northern Russia is well known for large chromium (Cr)-bearing massifs with major chromite orebodies, including the Centralnoye I deposit in the Ray-Iz ultramafic massif of the Ural ophiolite belt. New data on platinum (Pt)-group elements (PGE), geochemistry and mineralogy of the host dunite shows that the deposit has anomalous iridium (Ir) values. These values indicate the predominance of ruthenium–osmium–iridium (Ru–Os–Ir)-bearing phases among the platinum-group mineral (PGM) assemblage that is typical of mantle-hosted chromite ores. Low Pt values in chromites and increased Pt values in host dunites might reflect the presence of cumulus PGM grains. The most abundant PGM found in the chromite is erlichmanite (up to 15 μm). Less common are cuproiridsite (up to 5 μm), irarsite (up to 4–5 μm), and laurite (up to 4 μm). The predominant sulfide is heazlewoodite, in intergrowth with Ni–Fe alloys, sporadically with pentlandite, and rarely with pure nickel. Based on the average PGE values and estimated Cr-ore resources, the Centralnoye I deposit can be considered as an important resource of PGE

The Origin of Synchysite-(Ce) and Sources of Rare Earth Elements in the Rožná Uranium Deposit, Czech Republic

Synchysite was identified in the Rožná uranium deposit in a quartz–carbonate–sulfide vein, which is a part of the late (post-uranium and, post-Variscan) stage of the development of the hydrothermal system. The synchysite forms needles or lamellae, which are almost exclusively bound to the quartz filling of the veins. The structure of the quartz vein-filling, i.e., the preserved tubular syneresis crack pattern, Liesegang bands formed by hematite, chaotic grain size distribution of quartz grains, and ribbons of fibrous SiO2 grains, indicate that the synchysite crystallized in a silica gel. Its formation may be explained by the reaction of hydrothermal acid fluids rich in Fe2+ and rare earth elements (REEs) with alkaline Ca2+ HCO3− and F-rich fluids expelled from the gel during syneresis, or by its ageing. The subsequent recrystallization of the gel to form euhedral quartz grains was accompanied by the deformation of previously formed Liesegang rings, and the development of quartz rosettes. The study of fluid inclusions indicated that the silica gel originated at a very low temperature. The temperatures of the homogenization of two-phase inclusions in carbonate and quartz vein-filling varied between 38 and 74 °C, and the salinity ranged between 4 and 10 wt.% NaCl equiv. The δ13C carbonate values (from −4.65 to −5.21‰, PDB) indicate the deep-seated source of CO2, and δ18O values (from 14.76 to 18.22‰, SMOW) show that the source of the hydrothermal fluids was mainly surface water, with a possible admixture of fossil saline brines. The main sources of REEs are thought to have predominantly been uranium minerals (coffinitized uraninite and coffinite) that form a part of the breccia fragments embedded in the vein filling. The results illustrate the significant mobility of REEs in the late, low-temperature hydrothermal system, and they indicate the multiple remobilizations of REEs in the uranium deposits in general