Abstract

The Kon Tum Block, located in central Vietnam, is made up of Pre-Cambrian metamorphic rocks, Early Paleozoic metamorphic rocks, Paleozoic and Early Mesozoic magmatic formations and sedimentary rocks of different ages. Based on the petrographic composition and metamorphic degree of rocks, the Kontum Block is divided into three metamorphic rock complexes: the Kannak complex (granulite facies), the Ngoc Linh complex (amphibolite to granulite facies) and the Kham Duc complex (greenschists, quartz schists and two mica schists). The granulite and enderbit-charnockite magmatic complexes accompanying the Kannack series were previously considered to be Archean age, mainly based on the metamorphic degree, petrographic characteristics and comparative relationship with the Archean metamorphic series, which distributed in India. and shields Aldan, Okhot, Khankai (Russian Federation). The analytical results of detrital zircon U-Pb ages obtained by single laser ablation method (LA-ICP-MS) for quartz-schist of the Kham Duc Complex showing a wide range of ²⁰⁶Pb/²³⁸U ages, from 1242 to 2382 Ma. But mostly concentrated in the period of 1390-1430 Ma. This indicated that the Kham Duc Complex was formed as early as perhaps in the Mesoproterozoic period. Among the analysis results, there is no indicator for Arkean age, the oldest age detected in this study is ²⁰⁶Pb/²³⁸U=2382 Ma and there is only one analytical point. From the new results presented in this paper, combined with the previously reported data, it can be said that the period of 1400-1430 Ma is an early and intensively developed stage of the crustal formation in the Kontum Block in particular and in the Indosinian Block in general.