Abstract

The work of "1:50,000 geological mapping and mineral survey of the Kon Plong sheet" have investigated in detail metamorphic rocks in Kon Plong and Dak Rong areas. Rocks of granulite facies are classified into Kan Nack complex and those of amphibolite facies are mainly classified into Kham Duc complex. The Kan Nack complex is widespread from the Kon Leng - Dek Pne - Kon Ka Kinh arc-shaped fault to the east, in Nam Xa Hieu region and to Dak Rong region (upstream of the Ba river) in the South. General structural strike is sub-latitudinal, northwest-southeast and sub-meridian. U-Pb zircon ages, recording metamorphic stage, are 253±3Ma and 252.3±7.5Ma, corresponding to Late Permian - Early Triassic belonging to Indosinian orogeny metamorphism. Kham Duc complex is widely exposed in Ngok Wang, Ngoc Reo, Dak Bla, Tan Lap, Dak Poe, Dak Pui, and small xenoliths in granitoid of the Hai Van and Ben Giang-Que Son complexes. Structural direction is mainly from Northeast-Southwest to sub-meridian and Northwest-Southeast in minor. U-Pb zircon ages, recording metamorphic stage, are 458.5±8.8Ma and 435.0±9.5Ma, corresponding to Middle-Late Ordovician to Early-Middle Silurian belonging to Central Vietnam Orogeny equivalent to Caledonian Orogeny in North Europe. In summary, the metamorphic rocks of studying areas are products of Central Vietnam Orogeny, when the major territory of Vietnam was a part of Gondwanaland in Southern hemisphere and Indosinian Orogeny when Vietnam territory has moved to Northern hemisphere.