tailieunhanh - Báo cáo " 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 "

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 | VNU Journal of Science Earth Sciences 23 2007 253-264 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 Vu Van Tich Henri Maluski2 Nguyen Van Vuong1 1 College of Science VNU 2ISTEM University of Montpellier II France Received 4 October 2007 received in revised form 10 December 2007 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 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. Keywords Ar-Ar age Metamorphism Kon Tum Truong Son Indosini. 1. Introduction South East Asian geology was considered as an assemblage of different gondwanaphile fragments Sibumasu Indochina South-China blocks Fig. 1 during the Permo-Triassic time 11 6 . This tectonic event is nowaday well definded by metamorphic and magmatic activities in plural places 2 7-10 17 20 . The central part of Vietnam Truong Son belt which Corresponding author. Tel. 84-4-5587060. E-mail tichvv@ was characterized by a folded Paleozoic sedimentary strata covered place to place by Uper-Triassic red bed 3 . Numerous ductile shear zones such as the