Geochemical Features of Early Mesozoic Metabasalts of the Western Part of the Tukuringra Terrane, Mongol–Okhotsk fold belt

Abstract

The paper presents the results of geochemical and Sm–Nd isotope study of the metavolcanic rocks of the western part of the Tukuringra Terrane, one of the largest terranes of the Mongol–Okhotsk fold belt. It is shown that among the metavolcanics of the Teplokluchevskaya, Garmakan, and Algaja formations there are varieties similar to OIB and N-MORB, yet no rocks revealing features characteristic of the subduction origin are found. Being of Early Mesozoic age, the studied metabasalts are the youngest rocks within the Mongol–Okhotsk belt. The Lower Mesozoic deposits of the western part of the Tukuringra Terrane, including the volcanics of the OIB and N-MORB types, may have been relics of the residual ocean basin. The data obtained reflect the absence of subduction processes in the Late Triassic–Middle Jurassic at the final stages of the formation of the Mongol–Okhotsk fold belt. The closure of the Early Mesozoic basin was probably due to large-scale shear displacements.