First Data on Permian Granitoids of Northeast Asia, Koni–Taigonos Arc.

The intrusions of Permian monzonites and granitoids exposed in the Koni–Taigonos arc, which composes the basement of the Uda–Murgal magmatic arc, are revealed for the first time in northeastern Asia. On the Taigonos Peninsula, a small Aichan pluton of Early Permian monzonitoids with an age of 297–290 ± 2 Ma (zircon, SHRIMP-II) intrudes the Permian sedimentary rocks, and, on the Koni-P'yagina Peninsula, two intrusions of leucocratic and porphyry granites with ages of 275 and 257 ± 2 Ma (zircon, LA-ICP-MS) are exposed in the basement blocks and are intruded by Early Cretaceous granitoids. The primary Sr and Nd isotope ratios of the Permian granitoids are close to the characteristics of the mantle (87Sr/86Sr = 0.07030‒0.07038, 143Nd/144Nd = 0.51245‒0.51270, εNd of +2 to +7.7). In the geochemical features, the rocks studied belong to type I aluminous granites of volcanic arcs of the shoshonite and high-K calc-alkaline series. These Permian granitoids are compared with those exposed in Japan (Maizuru belt) and Primor'e (Grodekovo batholith in the Khanka Block) and probably reflect the beginning of the most ancient subduction processes on the Pacific continental margin. [ABSTRACT FROM AUTHOR]