Abstract
Research subject. The object of the study is the Ulyuk-Bar gold deposit ore-bearing rocks, located in the Bashkir meganticlinorium (the Southern Urals). Methods. The article presents the first data on the distribution of rare earth elements (REE), platinum group elements (PGE) and Au, obtained by inductively coupled plasma mass spectrometry (ICP-MS) on “ELAN- 6100 DRC” and “Agilent 7700” with the use of the computer data processing program “TOTALQUANT”, which includes automatic accounting of isotopic and molecular overlays on the mass spectral analytical lines of the determined elements. The chemical composition of ore minerals (native gold, pyrite, pyrrhotite, gersdorfite, chalcopyrite, arsenopyrite, and galena) was determined using an REMMA-202M scanning electron microscope with an LZ-5 X-ray energy-dispersive spectrometer and detectors for secondary and reflected electrons. Results. As a result of the studies, the enrichment of heavy lanthanides from ore-bearing rocks of the Ulyuk-Bar deposit in comparison with the sandstones and shales of the Bolshoi Inzer Formation outside of the ore field was established. It is shown that the noble-metal geochemical specialization of ore-bearing sediments of the Bolshoi Inzer Formation of the Ulyuk-Bar deposit is similar in a number of parameters to rocks of the Mashak Formation of the Shatak complex, formed under the influence of Middle Riphean magmatism on sedimentary rocks of the upper layers of the earth’s crust. Based on the calculation of the age of the minerals thorium and uranium, according to the isotopic studies of Rb-Sr (996 ± 26 Ma) and K-Ar (676–706 Ma) methods and galena by the Pb-Pb method (950 Ma), it was established that mineralization was formed in two stages. The first of which is associated with tectono-thermal activation at the border of the Middle and Late Riphean, and the second was realized about 600 Ma ago. Conclusions. It is concluded that the REE-EPG-Au taxonomy of ore-bearing deposits of the Ulyuk-Bar deposit is due to the polychrony and polygenicity of ore formation processes associated with the Middle Riphean plume magmatism, manifested over a vast territory, and the Late Vendian dynamothermal collisional metamorphism.
Highlights
На основе расчета возраста минералов тория и урана, а также по данным изотопных исследований Rb-Sr (996 ± 26 млн лет) и K-Ar (676–706 млн лет) методами, а также Pb-Pb методом по галенитам (950 млн лет) установлено, что оруденение сформировалось в два этапа, первый из которых связан с тектоно-термальной активизацией на границе среднего и позднего рифея, а второй реализовался около 600 млн лет назад
The article presents the first data on the distribution of rare earth elements (REE), platinum group elements (PGE) and Au, obtained by inductively coupled plasma mass spectrometry (ICP-MS) on “ELAN- 6100 DRC” and “Agilent 7700” with the use of the computer data processing program “TOTALQUANT”, which includes automatic accounting of isotopic and molecular overlays on the mass spectral analytical lines of the determined
It is shown that the noble-metal geochemical specialization of ore-bearing sediments of the Bolshoi Inzer Formation of the Ulyuk-Bar deposit is similar in a number of parameters to rocks of the Mashak Formation of the Shatak complex, formed under the influence of Middle Riphean magmatism on sedimentary rocks of the upper layers of the earth’s crust
Summary
Определение в образцах песчаников, алевролитов, сланцев и терригенно-карбонатных пород, отобранных из керна скв. На графиках содержаний РЗЭ в рудоносных породах месторождения Улюк-Бар, а также в фоновых глинистых сланцах и песчаниках большеинзерской свиты, нормированных по верхней континентальной коре (McDonough, Sun, 1995) В фоновых глинистых сланцах большеинзерской свиты величина Uср равна 2.28 (0.74–3.15) г/т, что близко к значениям, характерным для рудоносных пород месторождения Улюк-Бар, в то время как Thср составляет 12.27 (1.09–20.59) г/т. 3. Графики нормализованных по верхней континентальной коре (McDonough, Sun, 1995) средних содержаний РЗЭ и элементов-примесей в рудоносных отложениях месторождения УлюкБар (1), а также в фоновых глинистых сланцах (2) и песчаниках (3) большеинзерской свиты. 4. Диаграммы ∑РЗЭ–∑ТРЗЭ и Th–U для рудоносных пород месторождения Улюк-Бар (1), а также фоновых глинистых сланцев (2) и песчаников (3) большеинзерской свиты. 5. График нормированных по континентальной коре (Wedepohl, 1995) содержаний благородных металлов (а) и диаграмма Au-Pt/Pd (б) для рудоносных пород месторождения Улюк-Бар и средних составов осадочных образований Башкирского мегантиклинория. Такое распределение имеет принципиальное значение, так как определяет генетические условия формирования геохимической ЭПГспециализации рудоносных пород месторождения Улюк-Бар
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