P–T CONDITIONS, U/Pb AND 40Ar/39Ar ISOTOPIC AGES OF UHT GRANULITES FROM CAPE KALTYGEI, WESTERN BAIKAL REGION

• Published in: Geodinamika i tektonofizika Vol. 12; no. 2; pp. 310 - 331
• Main Authors: Volkova, N. I., Mikheev, E. I., Travin, A. V., Vladimirov, A. G., Mekhonoshin, A. S., Khlestov, V. V.
• Format: Journal Article
• Language: English
• Published: Russian Academy of Sciences, Siberian Branch, Institute of the Earth's crust 23.06.2021
• Subjects: cape kaltygei; p–t pseudosections; u-pb and ar-ar geochronology; uht granulites; western baikal region
• ISSN: 2078-502X; 2078-502X
• DOI: 10.5800/GT-2021-12-2-0526

The study is focused on metapelitic granulites of Cape Kaltygei (Western Baikal region) that contain a diagnostic mineral assemblage of ultrahigh temperature (UHT) metamorphic rocks (orthopyroxene+sillimanite+quartz). The pseudosection-based thermobarometry yields peak metamorphic temperature and pressure values (T=950 °C, P=~9 kbar) and suggests near-isobaric cooling (IBC) conditions during the retrograde evolution of the granulites. The U/Pb zircon age estimates for metamorphism (~1.87 Ga) support the data published by other researchers. The SHRIMP-II U-Pb dating of zircon cores yields a minimum protolith age of 1.94–1.91 Ga. Biotites and amphiboles from granulites of Cape Kaltygei show the 40 Ar/ 39 Ar isotopic ages that are close to the Early Paleozoic accretion-collision system of the Western Baikal region.