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Histogram of Os isotopic compositions of the Ru-Os-Ir alloys from (a) Kunar and Unga (this study, n = 32), (b) Unga (LA MC-ICP-MS data from this study and N-TIMS data from [17], n = 46), and (c) Kunar and Unga (data from this and [17] studies, n = 60).
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In order to provide further insights into the origin of Ru-Os-Ir alloys, this study presents new highly siderophile element (HSE: Re, Os, Ir, Ru, Pt, and Pd) abundance and 187Re-187Os and 190Pt-186Os isotope data for detrital grains of native Ru-Os-Ir alloys in placer deposits of the Kunar and Unga Rivers, which display a close spatial association...
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Context 1
... LA MC-ICP-MS data from this study show similar average initial 187 Os/ 188 Os values for both PGM assemblages at Kunar and Unga (0.1218 ± 0.0010, γOs(740 Ma) = -0.18 ± 0.84, and 0.1222 ± 0.0025, γOs(740 Ma) = +0.10 ± 2.1, respectively, Table 3, Figure 7a). These values are identical, within uncertainty, to the initial 187 Os/ 188 Os value for the Ru-Os-Ir alloy obtained by N-TIMS (0.1218463 ± 0.0000015, γOs(740 Ma) = −0.1500 ...
Context 2
... combined average initial 187 Os/ 188 Os ratio for all grains analyzed in this study is 0.1220 ± 0.0020 (γ 187 Os(740 Ma) = −0.02 ± 1.6, 2SD), which is identical to that for Ru-Os-Ir alloys from the Unga deposit studied previously [0.1220 ± 0.0054, n = 28, Figure 7b]. No correlation between the chemical and Os isotopic composition of the PGM was found. ...
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... Details of the analytical procedures are described elsewhere (González-Jiménez et al., 2015;Malitch et al., 2017b). In addition, the precise 186 Os/ 188 Os and 187 Os/ 188 Os isotope compositions in the samples of chromitite (G-40) and osmium minerals (67 and 7-71) were determined by N-TIMS (Creaser et al., 1991) using a ThermoFisher Triton mass spectrometer at the IGL, following the analytical techniques detailed previously Malitch et al., 2022b). A total of 20 Os isotope analyses were carried out. ...
... In this context, the lighter Cu isotope composition in the secondary Cu-con- Os values (expressed as γ 187 Os) for chromitite and osmium minerals from the Guli massif (this study), Precambrian mafic-ultramafic rocks, and present-day abyssal peridotites vs. their age. The diagram shows data for komatiites from Lapland , Vetrenyi Belt (Puchtel et al., 2016b), Belingwe (Puchtel et al., 2009b), Pike Hill (Puchtel et al., 2004(Puchtel et al., , 2009b, Boston Creek (Puchtel et al., 2018), Kostomuksha , Volotsk Formation (Puchtel et al., 2007), Weltevreden and Komati (Puchtel et al., 2014), Schapenburg (Puchtel et al., 2009a, 2016a), Kelly, Ruth Well, and Regal (Puchtel et al., 2022, and Sum-Kenozero (Puchtel, 2022) and for PGM from the Kunar River (Malitch et al., 2022b). Dark-blue vertical band marks the present-day Bulk Silicate Earth (BSE) (Meisel et al., 2001b;Day et al., 2017). ...
... (b) Initial 186 Os/ 188 Os values (expressed as μ 186 Os(T) for chromitite and osmium minerals from the Guli massif (this study), Precambrian maficultramafic rocks, and present-day abyssal peridotites vs. their age. The diagram shows data for komatiites from Lapland , Vetrenyi Belt (Puchtel et al., 2016b), Belingwe (Puchtel et al., 2009b), Boston Creek (Puchtel et al., 2018), Kostomuksha , and Weltevreden and Komati (Puchtel et al., 2014), for PGM from the Kunar River (Malitch et al., 2022b), and for chondritic meteorites, abyssal peridotites (AP), and bulk silicate earth (BSE) (Brandon et al., 2000(Brandon et al., , 2006Fischer-Gödde et al., 2010;Day et al., 2017). All errors are at the 2SD level. ...
Understanding the main events of platinum-group element (PGE) ore formation is impossible without analysis of the sources and behavior of major ore-forming components, namely, platinum, osmium, sulfur, and copper, which are important indicators of magmatic and hydrothermal processes. In contrast to the Re–Os isotope system, the radiogenic Pt–Os isotope system, as well as stable isotopes of Cu and S in PGE deposits, are still relatively understudied. Our comprehensive research is aimed at filling this gap. The article presents data for the Guli massif of ultramafic and alkaline rocks and carbonatites in Polar Siberia and for the zoned-type Nizhny Tagil and Svetly Bor clinopyroxenite–dunite massifs in the Middle Urals, which include: (1) the contents of the highly siderophile elements (HSE) in whole-rocks and platinum-group minerals (PGM), (2) the Re–Os and Pt–Os isotope systematics of chromitite, Os–Ir alloys, and Ru–Os sulfides, (3) the sulfur isotope composition in Ru–Os and Ir–Rh sulfides in primary and secondary PGM assemblages, and (4) the copper isotope composition of Pt–Fe minerals from chromitites and placers. The research was performed using scanning electron microscopy, electron probe microanalysis, and high-precision isotope-geochemical analysis. The high-precision Re–Os and Pt–Os isotope data show that the HSE contents in chromitites and PGM of the Guli massif were controlled by the composition of the mantle source that evolved with near-chondritic time-integrated Re/Os and Pt/Os ratios, which are also typical of the sources of most komatiites and abyssal peridotites. The δ65Cu values of the studied samples of ferroan platinum and isoferroplatinum are identical within the analytical uncertainty and are close to 0‰, which is typical of high-temperature Cu-containing minerals. The sulfur isotope compositions of the Ir–Rh sulfides of the kashinite–bowieite series and of the Ru–Os sulfides of the laurite–erlichmanite series in the primary PGM assemblages indicate that the source of sulfur has a chondritic isotope composition, which is in agreement with the osmium isotope composition of the Ru–Os sulfides and Os–Ir alloys. The heavy sulfur isotope composition (δ34S = 5.6 ± 1.5‰) of As-containing erlichmanite is consistent with its secondary origin. The new data on the isotope compositions of osmium, copper, and sulfur can be used as new important parameters that characterize the sources of PGE mineralization.
... Исследования химического состава МПГ выполнены с использованием рентгеноспектрального микроанализа (ARL-SEMQ с четырьмя волновыми спектрометрами, оснащенными энергодисперсионным анализатором LINK, Горный университет Леобена; CAMECA SX 100 c пятью волновыми спектрометрами, ЦКП УрО РАН «Геоаналитик», Екатеринбург). Re-Os и Pt-Os изотопные данные для хромититов и минералов осмия получены с помощью термоионизационной массспектрометрии в отрицательных ионах (negative thermal ionization mass spectrometry, N-TIMS [Creaser et al., 1991]) на многоколлекторном масс-спектрометре ThermoFisher Triton Plus в лаборатории изотопной геохимии Государственного университета штата Мэрилэнд (США), следуя аналитическим процедурам, охарактеризованным в работах [4][5][6]. Особенности начального изотопного состава осмия в Os-Ir сплавах и Ru-Os сульфидах определены с помощью лазерной абляции и масс-спектрометрии с ионизацией пробы в индуктивно-связанной плазме (LA MC-ICP-MS) на многоколлекторном массспектрометре Nu-Plasma с системой лазерного пробоотбора LUV213 (λ=213 нм) New Wave/Merchantek в Университете Макуори (Сидней, Австралия) по методике, приведенной в работе [7]. Изотопный состав серы в Ru-Os сульфидах изучен с помощью системы лазерной фемтосекундной абляции (NWR Femtosecond UC with laser Pharos 2mJ-200-PPam and harmonics module HE-4Hi-A) и масс-спектрометра МАТ-253 «Thermo Fisher Scientific» в ЦКП «Приморский центр локального элементного и изотопного анализа» ДВГИ ДВО РАН (Владивосток) по методике, приведенной в работе [8]. ...
To gain insight into the source of ore material, this study presents new Re–Os and Pt–Os isotopic and highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, Re) abundance data for chromitite and native osmium from the Guli massif of ultramafic alkaline rocks and carbonatites located in the Maimecha–Kotui province, Polar Siberia. The study utilized a number of analytical techniques, including electron probe microanalysis (EPMA), negative thermal ionization mass spectrometry (N-TIMS), and high pressure asher
digestion and isotope dilution inductively-coupled plasma mass-spectrometry (ID ICP-MS). The HSE concentrations in chromitite samples range from 191 to 866 ppb with a predominance of Ir-group platinum-group elements (PGE) (Os, Ir, and Ru) over Pt-group PGE (Rh, Pt, and Pd) and Re, which is consistent with
the platinum-group mineral control (i.e., Os–Ir alloys and laurite, RuS2) within the chromitite. The Re–Os and Pt–Os isotope data indicate that the HSE budget of the chromitite and native osmium from the Guli massif was largely controlled by that of their mantle source, which evolved with long-term near-chondritic Re/Os and Pt/Os ratios; this source had time-integrated Re/Os and Pt/Os within the range of those for the majority of komatiites and abyssal peridotites worldwide.
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