Late Triassic 40Ar-39Ar ages of the Baga-Gazryn Chuluu granites (Central Mongolia)

New radiometric data have been obtained for two-mica granites from the Baga-Gazryn Chuluu Pluton in Central Mongolia, classified previously as A-type granites based on their geochemical characteristics and tectonic position. Three most common granite varieties were dated by 40Ar-39Ar method on separated biotite. The following ages were obtained: 201.0 ± 3.6 Ma (2σ) for the coarse-, 211.9 ± 4.0 Ma for the medium-, and 209.4 ± 3.2 Ma for the fine-grained granites. Such Late Triassic cooling ages agree well with the older assumptions on the time of emplacement of the Baga-Gazryn Chuluu Pluton, based on geological evidence and previous K-Ar dating. New geochronological data better constrain the age of granitic magmatism in post-collisional, extensional regime adjacent to the western part of the Mongol-Okhotsk suture zone in the Adaatsag area.