Age Ranges of Zircons in the Kamchatka–Koryak Region (according to Zircon Geochronology)

Data on zircon crystallization times for igneous and metamorphic rocks of the Kamchatka–Koryak region based on isotope chronometry results of 430 zircon grains have been summarized. The geochronological data set an upper time limit to the Middle Eocene (40 Ma). The zircon formation intervals have the following values (Ma): 3200, 2700–2600, 2000–1800, 1600–1500, 1100–1050, 540–390, 350–180, and 100–48. Zircons with lower Th/U ratios characteristic of metamorphogenic mineral formation comprise the following clusters (Ma): 2700–2600, 1900–1800, 890–848, 343–320, 167–130, 79–73, and 54–49. The most ancient zircons with ages of 3.2, 2.7, 1.9, 1.6, and 0.5 Ga were identified among xenogenic zircons of Late Cretaceous gabbroic massifs of Central and East Kamchatka (Yurchiksky, Atvenayvayamsky, and Olenegorsky massifs), as well as among detrital zircons of Cretaceous–Lower Paleogene metasedimentary formations of the Sredinny and Ganalsky ranges (Central Kamchatka), Pensantine Ridge (West Kamchatka), Karaginsky Island (East Kamchatka), and terrigenous deposits of Ukelayat flysch (Central Koryakia).