Abstract
The pegmatites are widely distributed in Dak Rve, Kontum massif, and are characterized by large dykes from a few meters to a few ten meters in the northeast-southwest direction. They include two pegmatite series: the first pegmatite series contains quartz (40-45%) and feldspar (55-60%); and the second pegmatite series consists of feldspar (~70%), quartz (~ 25%), and a few muscovite and biotite. The formation age of pegmatite determined by the LA-ICP-MS U-Pb zircon method was a weighted average 206Pb/238U age of 448.2 ± 6.4 Ma and 271 ± 11 Ma, respectively. This age result shows that the study area exists two different magma-tectonic stages (1) Ordovician and (2) Permian in Phanerozoic. Ordovician pegmatite is close to the magmatic activities of the Chu Lai and Dai Loc complexes. Permian pegmatite is likely related to the Permian - Triassic magmatic activities of the Ben Giang - Que Son complex.