SUMARRY
U-Pb zircon
age of Diên B́nh granitoid pluton in Bờ Y, Kon Tum province and its
implications
Nguyễn Thị Bích Thủy, Nguyễn
Thị Xuân, Hồ Thị Thư,
Nguyễn Đức
Chính, Trần Đại Dũng, Bùi Thế Anh, Đặng
Văn Long
Diên B́nh complex is
made up of gabrodiorite, diorite, granodiorite and granite. Most of rocks are
medium to coarse grain and display gneissic texture. They are exposed under
small or elongated plutons along the Pô Cô Fault. In this study, two biotite
rich granodiorite samples were collected from one pluton, which assigned to
Diên B́nh complex, in the Bờ Y commune, Ngọc Hồi district,
Kon Tum province for age dating. The collected samples are strongly foliated.
Petrographically, the rocks are medium - to coarse-grained biotite rich granite
and display foliation texture with parallel alignment of biotite and feldspar.
The major rock forming minerals are Plagioclase; K-feldspar; Quartz and
Biotite. Acessory minerals are zircon, sphene, apatite and opaque minrals. Zircon
grains separated from two samples are mostly brown to colorless and
sub-transparent, containing black inclusions. They are prismatic in shape and
have the length and length/width ratios ranging from 100 to 200 μm and 2:1
to 1.5:1, respectively. All Th/U ratios of analyzed zircons (0.43-1.10) are
higher than 0.1 and cathodoluminescent images display oscillatory zoning,
indicating magmatic origin. The crystallization age of the granite was
determined by zircon U-Pb isotope using a laser beam and measured on an ICP-MS
machine and gave the mean 206Pb/238U age value of ca. 470 Ma. This age value of
granite indicated the existence of tectono-magmatism and crustal formation
during Early Paleozoic time in the study area
Keywords: Granitoid Diên B́nh, U-Pb zircon, Bờ
Y -Ngọc Hồi, Early Paleozoic