Ages from the “Mogod Formation” of the Permian–Triassic igneous rocks in the Sayan–Baikal belt, northern Mongolia

Late Paleozoic–Early Mesozoic volcano-plutonic rock unit at the southern margin of the Sayan–Baikal belt, Mongolia is a significant factor in understanding the Paleozoic–Mesozoic arc system along the Siberian continental margin. The Permian–Triassic igneous rocks have been divided into the Lower–Middle Permian Khanui Group, Late Permian–Early Triassic Selenge plutonic rock complex, Permian?–Middle Triassic Erdenet plutonic rock complex, and Upper Triassic– Lower Jurassic Mogod Formation. However, a U-Pb age pointing latest Permian was recently reported from the Khanui Group, and stratigraphy of the Permian–Triassic igneous rocks is required to be reexamined. This paper describes zircon U-Pb age of 257.6 ± 3.6 Ma (Late Permian) and hornblende K-Ar age of 292.9 ± 14.1 Ma (Early Permian) from the Mogod Formation, which has previously been assigned to Upper Triassic–Lower Jurassic, and presents a possibility that the stratigraphic division of the Permian–Triassic igneous rocks is revised.