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Date submitted2020-05-28
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Date accepted2020-05-28
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Date published2020-06-30
The age of mineralization of Mayskoe gold ore deposit (Central Chukotka): results of Re-Os isotopic dating
The article presents the results of the sulfide mineralization dating of the Mayskoe gold ore deposit using the Re-Os isotope system and isochron age estimation method of the main sulfide minerals: arsenopyrite, pyrite, and antimonite. The complex multistage formation of the studied sulfides, as well as the close intergrowths of genetically different mineral phases, did not allow obtaining a single rhenium-osmium isochron corresponding to the formation time of sulfide mineralization. Isochrones for single minerals, collected from each sulfide sample, turned out to be the result of isotopically distinct components mixture (radiogenic crustal and non-radiogenic mantle) and do not make sense from the geochronological point of view. In terms of geology, the most significant result of the study is an age estimation of 128.8 ± 4.4 Ma, obtained for the sulfide mineralization of Mayskoe deposit using Re-Os isotope dating of single fractions of pyrite and antimonite of the ore mineralization stage. While arsenopyrite is most closely associated with gold mineralization, one of the arsenopyrite varieties corrodes framboidal pyrite of the pre-ore stage, has a maximum of the crust component in the osmium isotopic composition and forms a mixing line in the isochron diagram with an apparent formation age of 458 ± 18 Ma. The initial osmium isotopic composition of the studied sulfides indicates a mixed mantle-crust source of sulfide mineralization. The issue of simultaneous ore genesis and granitoid magmatism in the Mayskoe deposit remained unresolved (the age of granitoids according to the U-Pb zircon system is 108 Ma). However, a possible solution could be the further determination of the Re-Os isochron age of the ore mineralization sulphides from the single paragenesis of a specific sample containing both arsenopyrite and pyrite (+ antimonite) with gold.
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Date submitted2008-10-05
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Date accepted2008-12-30
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Date published2009-12-11
Thermobaric granite crystallization conditions of the severniy massif (the Chukotka) in accordance with the feldspars study data
- Authors:
- V. I. Alekseev
The Kamentsev I.E. and Sorokin N.D. method is used to investigate the dependence of Al-Si-ordering and structure of alkaline feldspars decomposition in different granites from the Severny massif (Chukotka) under thermobaric conditions of their crystallization. The temperature and pressure on the granite system in the initial period of feldspars ordering are determined quantitatively for the first time for the region. Progressive pressure change which exceeds lithostatic load by 750 МPа at the late stage of lithium-fluoride granites formation is revealed. It is hypothesized that the deposits similar to explosive ore-bearing breccia can be discovered in the Chukotka. The conclusion on possibility to apply the Sobolev-Dobretsov concept of superpressure to interpret the process of rare-metal magmatism is drawn.