Duration of the young (Pliocene) plutonic magmatism in Tyrnyauz ore field, Northern Caucasus: New K-Ar and Rb-Sr data

Isotope-geochronologic investigation of Tyrnyauz rhyolites and vitrophyres was conducted on all available for isolation and further analysis monomineral fractions of these rocks. The dating results show that magmatism in the considered region was completed 1.90-1.95 mln years ago with vitrophyre dike intrusion. The dikes aren't associated with the Elbrus Center volcanism, as was suggested before, since volcanic activity in Elbrus region began near 900 thousand years ago, and the volcano appeared nor earlier than 250 thousand years ago. Formation of granite Eldjurtinskii massif as well as breaking through it subvolcanic rhyolite substances and, in its turn, crossing them vitrophyre dikes proceeded without considerable pauses in the time range 2.5-1.9 mln years, that is, total duration of these processes was not higher than 600 thousand years. The narrow formation time range, similar chemical composition and also equal initial isotope ratios 87Sr/S+86S/Sr (reflecting existing of common magmatic source for all young Tyrnyauz rocks) enable to consider these rocks as integral Late-Pliocene volcano-plutonic complex

Contribution of crustal and mantle sources to genesis of Sn, B and Pb-Zn deposits in South Sikhote-Alin subprovince (Russian Far East): Evidence from high–precision MC-ICP-MS lead isotope study

© 2020 Elsevier B.V. South Sikhote-Alin metallogenic subprovince (SSAP) is located in the southern part of the Sikhote-Alin orogenic belt. It encompasses more than one hundred well-known deposits and occurrences of boron, tin, lead, and zinc. These deposits have been genetically related to the Late Cretaceous and Paleocene granitoid magmatism. Pb isotope composition was measured using the MC-ICP-MS method in 20 SSAP deposits. Pb isotope ratios (48 samples of galena) vary within narrow limits: 206Pb/204Pb ranges from 18.321 to 18.474, 207Pb/204Pb − 15.608–15.655, and 208Pb/204Pb 38.601–38.796. The high degree of homogeneity of the Pb isotope composition and absence of correlations between the lead isotope characteristics of the deposits, on the one hand, and the age and type of ore mineralization, on the other, indicate the presence of a regional uniform Pb source for all the SSAP deposits. The results of Pb-Pb studies of the different rocks of the SSAP suggest that the source was most likely the Mesozoic sedimentary sequences of the Sikhote-Alin accretionary complexes. In turn, individual lead isotope characteristics of the SSAP deposits are caused by varibale contribution of mantle source to the overall balance of lead

Duration of the young (Pliocene) plutonic magmatism in Tyrnyauz ore field, Northern Caucasus: New K-Ar and Rb-Sr data

Isotope-geochronologic investigation of Tyrnyauz rhyolites and vitrophyres was conducted on all available for isolation and further analysis monomineral fractions of these rocks. The dating results show that magmatism in the considered region was completed 1.90-1.95 mln years ago with vitrophyre dike intrusion. The dikes aren't associated with the Elbrus Center volcanism, as was suggested before, since volcanic activity in Elbrus region began near 900 thousand years ago, and the volcano appeared nor earlier than 250 thousand years ago. Formation of granite Eldjurtinskii massif as well as breaking through it subvolcanic rhyolite substances and, in its turn, crossing them vitrophyre dikes proceeded without considerable pauses in the time range 2.5-1.9 mln years, that is, total duration of these processes was not higher than 600 thousand years. The narrow formation time range, similar chemical composition and also equal initial isotope ratios 87Sr/S+86S/Sr (reflecting existing of common magmatic source for all young Tyrnyauz rocks) enable to consider these rocks as integral Late-Pliocene volcano-plutonic complex

Magmatic-related ore systems of volcanogenic massive sulphide deposits of the Urals, Russia: fluid inclusion and isotope data

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Crustal Source of Pb and S at the Yubileynoe Porphyry Gold Deposit (Southern Urals, Kazakhstan): High Precision Pb–Pb and δ³⁴S Data

Abstract: The Yubileinoe large gold deposit, located at the southern end of the Magnitogorsk megazone, is the only known representative of the Au–porphyry systems in the Southern Urals. It is genetically related to granitoids formed in a suprasubduction setting under mature oceanic island arc environment/setting. The obtained isotope (Pb–Pb and δ34S) data indicate the input of mineral-forming components into the Au–porphyry system of the deposit, mainly from granitoid melts, confirming a common source of ore material and ore-bearing granitoids. The geochemical and isotopic characteristics of granitoids indicate the leading role in their genesis of the crustal source, which is considered Late Precambrian continental crust

Vorontsovka Carlin-style gold deposit in the North Urals: Mineralogy, fluid inclusion and isotope data for genetic model

The Vorontsovka gold deposit in the Tagil zone, North Urals, hosts 101 t Au, averaging 7 g/t Au and including 30 t Au in the regolith, and 120 t Ag, averaging 8 g/t Ag. Early skarn-magnetite mineralisation related to a dioritic intrusion of the shoshonitic series was formed in the Late Emsian. Water and volatiles (mainly CO2) released from host metapelites and limestones were mixed with the metalliferous magmatic fluid during catagenesis to contact metamorphism. The modified fluid extracted ore components from host rocks and syn-volcanic stratiform mineralisation and became enriched in Fe, Mn, Ba, Zn, Pb, Au, Ag and S to deposit these components as sulphide dissemination in the footwall of siliciclastic unit and underlying limestone both brecciated along the trust. At the final Early Eifelian stage, there was an additional inflow of deep mantle/magmatic fluid, enriched in Au, Hg, As, Sb and Tl. The mixing of this fluid with metamorphic water resulted in Carlin-style gold-realgar-stibnite (+Tl minerals) mineralisation mainly in carbonate breccia. The main gold endowment associates with gold‑arsenic ores located in brecciated silicified limestone (jasperoid) and argillised tuff-siltstone. Early ore assemblages were formed at 510–240 °C (including magnetite skarn), whereas overprinting Carlin-style gold-(Fe, As, Sb, Hg, Tl) sulphide mineralisation was deposited at decreasing temperatures mainly from 260 to 110 °C. Fluid inclusion data revealed aqueous‑carbonic, Ca-, Na-, Mg- and K-chloride compositions of ore-bearing fluid of 4.8–9.3 wt% eq. NaCl. Changing fluid pressure corresponded to near lithostatic (0.5–0.6 kb) to hydrostatic (0.15–0.2 kb) conditions. Based on the δ34S ranges of sulphides determined for siliciclastic rocks (−2.3 … +1.8‰) and skarns (−2 … +1.6‰) it is assumed that most of the sulphur derived from magmatic reservoir associated with the mantle. The lead isotopic compositions of sulphides show a relatively narrow range and continue the linear trend of the Early Silurian VMS deposits corresponding to the mixing line of mantle and crustal lead sources. Model Pb–Pb ages for the Vorontsovka sulphides are grouped into two clusters: 425–416 and 398–388 Ma. The second period is close to the U–Pb isotope age of the final stage of the Auerbakh pluton as well as in a good agreement with the Ar–Ar isotope age of 391.1 ± 4.9 Ma of hydromica from the late gold-arsenopyrite assemblage. The specific features of the Vorontsovka deposit indicative of the Carlin-style mineralisation are as follows: the paleo-continental margin and trust-related position; causing high-K/shoshonitic igneous activity; the fine-disseminated sulphide mineralisation in the highly brecciated carbonate-clastic sequence; jasperoid and argillic alteration accompanying gold orebodies with assay boundaries; multiple fluid source; Au-As-Hg-Tl geochemical association; the abundance of As- and As-Fe-sulphides and As–Sb sulphosalts; the occurrence of Hg-, Tl-sulphides and sulphosalts; the association of gold with arsenian pyrite and arsenopyrite overgrowing previously forming pyrite; and the predominance of submicroscopic gold in the ores. A LA-ICP-MS analysis of pyrite confirms that elevated concentrations of Au regularly correlate with higher contents of As, Ag, Sb or Tl. © 201

Erratum to: Crustal Source of Pb and S at the Yubileynoe Porphyry Gold Deposit (Southern Urals, Kazakhstan): High Precision Pb–Pb and δ³⁴S Data (Geology of Ore Deposits, (2021), 63, 3, (173-184), 10.1134/S107570152103003X)

An Erratum to this paper has been published: https://doi.org/10.1134/S1075701521300012