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

Abstract

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.

Early Paleozoic or Early-Middle Triassic collision between the South China and Indochina Blocks: The controversy resolved? Structural insights from the Kon Tum massif (Central Vietnam)

“…The top-to-the-NW sense of shear might be 583 a consequence of the N-dipping Early Paleozoic inherited crustal structure. The importance of 584 a mantle source for the heat flux required to produce the UHT metamorphism of the Kon Tum 585 massif was also documented by petrography and geochemistry (Owada et al, 2006(Owada et al, , 2016586 Osanai et al, 2008). Thus, the role of the Emeishan-Song Da LIP, related to a mantle plume, 587 as a possible heat source for the melting of the continental crust in the Kon Tum massif must 588 be seriously considered.…”

K–Ar geochronology of orogenic gold mineralization in the Vangtat gold belt, southeastern Laos: Effect of excess argon in hydrothermal quartz

“…A 206 Ma age for the Thongkai‐Ok orogenic gold deposit of southeast Laos is consistent with regional geological and geochronological data and indicates a post‐collisional, post‐peak metamorphism hydrothermal gold event that is potentially younger than much of the orogenic gold mineralization in nearby Vietnam, as follows: Regional magmatism and metamorphism in the Kontum Massif associated with the collision between the South China and Indochina terranes have been dated at 270–230 Ma (zircon U–Pb data; Lepvrier et al ., 2004; Owada et al ., 2016). Late‐stage metamorphism in the Kontum Massif was dated by Osanai et al .…”

Neoproterozoic to Early Triassic tectono-stratigraphic evolution of Indochina and adjacent areas: A review with new data

“…The Late Permian-Early Triassic event, which is also characterized by HT (even UHT) conditions, took place between 250 and 236 Ma (Lepvrier et al, 2004(Lepvrier et al, , 2008 in a retrograde decompression setting (Nakano et al, 2013;Osanai et al, 2008). More recently Faure et al (2018) and Owada et al (2016) argued that the HT metamorphism represented an intraplate event.…”

“…et al, 2016 (Figure 11) are consistent with this tectonic setting in the Late Permian. In addition, the 250 Ma gabbro from the Kon Tum terrane (sample OG9, Figure 11) might be due to plume-related magmatism in the Late Permian (Nakano et al, 2013;Owada et al, 2016). This mantle heat source may play a key role in the Late Permian-Early Triassic tectonic exhumation and metamorphic core complex formation over the Kon Tum terrane that overprinted the earlier Ordovician metamorphic event (Faure et al 2018).…”

“…polycyclic high grade metamorphism including at least an Early Paleozoic and a Late Permian-Early Triassic event (Faure et al, 2018;Nakano et al, 2007Nakano et al, , 2013Osanai, 2004;Osanai et al, 2008;Owada et al, 2016Owada et al, , 2006Roger et al, 2007;Usuki et al, 2009Usuki et al, , 2013Vu et al, 2013).…”