Geochronology of Triassic-Jurassic Granitoids in the Southern Framing of the Mongol-Okhotsk Foldbelt and the Problem of Early Mesozoic Granite Formation in Central and Eastern Asia

摘要

Early Mesozoic geological events played an important role in the structural evolution of Eastern and Central Asia. They involved collision between Siberia and Sino-Korean continents. This was accompanied by the closure of the Solonker paleocean in Early Triassic and Mongol-Okhotsk paleocean no later than in Middle Jurassic and formation of a convergent boundary along the Pacific margin. These events generated large-scale granitoid magmatism. However, existing concepts of the relation between tectonic and magmatic processes in the evolution of the considered region are not always supported by geological and geochronolog-ical data. Scales and distribution of Early Mesozoic magmatism related to the formation of the Mongol-Okhotsk foldbelt were recently established from geo-chronological data only for the western pinchout of this structure. For the eastern segment, such models are hypothetical because of the absence of geochrono-logical data. Therefore, the identification and study of Early Mesozoic magmatic complexes in this area are crucial for reconstruction of one of the final evolution stages of the Mongol-Okhotsk foldbelt, in particular, and the eastern margin of Asia, in general.