Ar-Ar age of metamorphic and mylonitic rocks in northern part of the Kon Tum massif: evidence for the Indosinian movement along shear zones between Kon Tum massif and Truong Son belt

Abstract

The studied area is situated in the easternmost of Indochina (south of Central Vietnam), covers the boundary between Kon Tum massif and Truong Son belt, where exposed a lot of intensively deformed ductile shear zones. The study result shows that those shear zones have undergone strong deformation with mylonites in high temperature metamorphism accompanied. The kinematic criteria observed in field indicate that they are suffered from a dextral strike-slip shear with sub-vertical foliation and sub-horizontal stretching lineation. Mineral assemblages of metamorphism associated with the deformation show that metamorphism of the shearing attaint amphibolitic facies. Age of this deformation took place at c.a 240 Ma for metamorphism of the shear zone and of 230 Ma for mylonite related to ending of ductile deformation. The obtained results evidence that both Truong Son belt and Kon Tum massif had been affected by Indosinian movement.