Permo–Triassic Barrovian‐type metamorphism in the ultrahigh‐temperature Kontum Massif, central Vietnam: Constraints on continental collision tectonics in Southeast Asia

Abstract

AbstractThe Kontum Massif in central Vietnam is composed of various metamorphic complexes including a high‐temperature southern part (Kannak and Ngoc Linh complexes) and a low‐ to medium‐temperature northern part (Kham Duc complex). The Kham Duc complex exhibits Barrovian‐type medium‐pressure metamorphism evidenced by kyanite‐ and/or staurolite‐bearing metapelites. The garnet–gedrite–kyanite gneiss, which is the focus of the present study, preserves several mineral parageneses formed during a prograde and retrograde metamorphic history: staurolite + quartz in gedrite, garnet + gedrite + kyanite in the matrix, and spinel + cordierite symplectite between gedrite and sillimanite. The calculated semiquantitative petrogenetic grid reveals peak pressure conditions of 620–650°C at 1.1–1.2 GPa and peak temperature conditions of 730–750°C at 0.7–0.8 GPa. The monazite U–Th–Pb electron microprobe ages of the garnet–gedrite–kyanite gneiss and associated gneisses yield 246 ± 3 Ma for the Kham Duc complex, which is similar to the age of the high‐ to ultrahigh‐temperature metamorphism in the adjacent Kannak and Ngoc Linh complexes of the southern Kontum Massif. The present results indicate that both the Barrovian‐type and ultrahigh‐temperature metamorphism occurred simultaneously in the Kontum Massif during an event strongly related to Permo–Triassic microcontinental collision tectonics in Asia.