U-Th-He Geochronology of Pyrite from Alteration of the Au-Fe-Skarn Novogodnee-Monto Deposit (Polar Urals, Russia)—The Next Step in the Development of a New Approach for Direct Dating of Ore-Forming Processes
Olga Yakubovich,
Ilya Vikentyev,
Ekaterina Ivanova,
Mary Podolskaya,
Ivan Sobolev,
Eugenia Tyukova,
Alexander Kotov
Affiliations
Olga Yakubovich
Institute of Earth Sciences, Saint-Petersburg University, 199034 Saint-Petersburg, Russia
Ilya Vikentyev
Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry (IGEM), Russian Academy of Sciences, 119017 Moscow, Russia
Ekaterina Ivanova
Institute of Earth Sciences, Saint-Petersburg University, 199034 Saint-Petersburg, Russia
Mary Podolskaya
Vernadsky Institute of Geochemistry and Analytical Chemistry (GEOKHI), Russian Academy of Sciences, 119991 Moscow, Russia
Ivan Sobolev
Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry (IGEM), Russian Academy of Sciences, 119017 Moscow, Russia
Eugenia Tyukova
Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry (IGEM), Russian Academy of Sciences, 119017 Moscow, Russia
Alexander Kotov
Institute of Precambrian Geology and Geochronology (IPGG), Russian Academy of Sciences, 199034 Saint-Petersburg, Russia
We report on the application of the U-Th-He method for the direct dating of pyrite from the alteration halo of the Novogodnee-Monto Au-Fe-skarn deposit, Polar Urals. The deposit is genetically related to the formation of volcanogenic complexes of the Ural Paleozoic belt. A modification of the original methodology for measuring U, Th and He isotopes in a single grain allowed us to determine a U-Th-He age of 382 ± 8 Ma (2σ) based on six pyrite samples from the altered rocks of the deposit (U mass fraction ~0.2 mg/kg; Th/U ~3.5; 4He specific volume ~10−5 cm3·STP·g−1). This age is consistent with estimates of the age of ore formation and coeval with the end of the period of island arc magmatic activity. Our results indicate that U-Th-He dating for pyrite samples of ~1 mg in weight from the hydrothermal-metasomatic halo of ore bodies is possible, providing a crucial next step in the development of U-Th-He pyrite geochronology.
