SUMARRY

Petrographical, geochemical composition and formation pressure - temperature of Chiêm Hóa granites, Tuyên Quang province

Phạm Thị Dung, Trần Trọng Hòa, Trần Quốc Công, Trần Hồng Lam,
Đào Thái Bắc, Phạm Ngọc Cẩn, Bùi Ấn Niên, Phạm Thị Phương Liên

Chiem Hóa granites are exposed as small bodies in the Chiêm Hóa district, Tuyên Quang province. Their petrographical composition includs light colored, small - to medium - grained size biotite granite and two - mica granite, and aplite. The crystallization temperature of granites calculated based on zircon saturation and chemical composition of granites is 787 to 740^o C, coreponding to the forming - pressure and depth of <5 Kbar and 15 km, respectively. The rocks have high aluminum content with ASI> 1.1. The results of calculating the temperature by the method of zircon saturation and the main element for the forming temperature fluctuate in a wide range from about 787 to 740oC; The forming pressure is calculated based on the main element, fluctuating in the range <5 Kbar (corresponding to the forming depth of <15 km). Petrographic composition and geochemistry indicate that Chiêm Hóa granite is characterized by S-type granite, originated from the crust and formed at medium to shallow depth, similar to Phia Bioc granite.

Keywords: Chiêm Hóa granite, pressure, temperature, Permian - Triassic.