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Abstract— <p>Svyatonosites, which are intermediate moderately alkaline to alkaline andradite rocks, were found for the first time on the Svyatoi Nos Peninsula at the beginning of the 20th century. One of the discussible questions is related to their age, which has not precisely been determined by isotopic methods. The results of U/Pb dating of accessory zircon from svyatonosites and leucosyenite showed the Late Paleozoic age for the Markov (310‒297 Ma) and Eskola (317‒312 Ma) plutons of the Svyatoi Nos Peninsula, which is synchronous with the formation of granitoids of the Barguzin complex (330‒290 Ma). Zircon from leucosyenite of the Markov pluton has a typical magmatic structure, which is in agreement with a Th/U ratio of &gt;0.3. Anhedral zircon grains from svaytonosites together with the Th/U ratio of &lt;0.1 indicates the recrystallization processes at the origination stage of the Markov and Eskola plutons. The slightly older <sup>40</sup>Ar/<sup>39</sup>Ar age of amphibole from svyatonosites of the Markov pluton (360‒336 Ma) is related to the presence of excessive <sup>40</sup>Ar, which can be sourced from the Early Paleozoic metamorphic rocks.</p>

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Age of Formation of Svyatonosites of the Svyatoi Nos Peninsula, Lake Baikal (U/Pb and 40Ar/39Ar Data)

  • 期刊论文

  • 发表日期：

    2025年3月1日

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  • E. I. Mikheev,
  • A. V. Travin,
  • A. S. Mekhonoshin,
  • Ya. Yu. Shelepov,
  • N. N. Kruk,
  • A. A. Tsygankov,
  • E. N. Moroz

摘要

Abstract—

Svyatonosites, which are intermediate moderately alkaline to alkaline andradite rocks, were found for the first time on the Svyatoi Nos Peninsula at the beginning of the 20th century. One of the discussible questions is related to their age, which has not precisely been determined by isotopic methods. The results of U/Pb dating of accessory zircon from svyatonosites and leucosyenite showed the Late Paleozoic age for the Markov (310‒297 Ma) and Eskola (317‒312 Ma) plutons of the Svyatoi Nos Peninsula, which is synchronous with the formation of granitoids of the Barguzin complex (330‒290 Ma). Zircon from leucosyenite of the Markov pluton has a typical magmatic structure, which is in agreement with a Th/U ratio of >0.3. Anhedral zircon grains from svaytonosites together with the Th/U ratio of <0.1 indicates the recrystallization processes at the origination stage of the Markov and Eskola plutons. The slightly older 40Ar/39Ar age of amphibole from svyatonosites of the Markov pluton (360‒336 Ma) is related to the presence of excessive 40Ar, which can be sourced from the Early Paleozoic metamorphic rocks.