Late Permian plume-related magmatism and tectonothermal events in the Kontum Massif, central Vietnam

The Kontum Massif is situated in the southern part of Trans Vietnam Orogenic Belt (TVOB), central Vietnam, and contains various types of magmatic and metamorphic rocks, the latter including both ultrahigh-pressure and ultrahigh-temperature units. While geochronological data indicate the existence of two main tectonothermal events at 480-420 Ma and 270-240 Ma, the most intense metamorphic and magmatic activity occurred between the Late Permian and Early Triassic due to continental collision between the South China and Indochina cratons. In this study, U-Pb LA-ICP-MS geochronological analyses of zircon obtained from two samples of metagabbro and one sample of charnockite from the massif yielded a magmatic age range of 260-250 Ma for all three samples and an inherited age of ~ 1400 Ma for the charnockite. These magmatic ages overlap with those documented for peak metamorphism in the Kontum Massif. When combined with Nd isotopic data for granitic rocks and pelitic gneisses from the region, these data suggest that the massif may have been derived from reworked continental crust. Geochemical characteristics of metagabbros from the massif reveal that the parental basaltic magma can be correlated with the Song Da igneous suite situated in the northern part of the TVOB, and was assimilated by crustal materials. The Song Da igneous suite is a member of the Emeishan large igneous province and resulted from Late Permian mantle plume activity. We conclude that the plume-related magma intruded into the deeper part of Kontum Massif and induced ultrahigh-temperature metamorphism of the lower crust by acting as a heat source.