SUMMARY

U-Pb zircon isotopic age of the Núi Pháo granite pluton in the Tam Đảo area
and its geological implications

Nguyễn Thị Bích Thủy, Phạm Văn Chung

The granites of Núi Pháo Pluton belong to the Núi Điệng Complex, exposed in the Tam Đảo area, Đại Từ District, Thái Nguyên Province. Petrographically, they are two mica granites of medium to coarse grains. The rocks are relatively light in colour and have porphyric texture. Formerly, the emplacement age of these granites was thought to be Middle-Late Triassic on the basis of their relationship with the country rocks. In order to elucidate the emplacement age of this pluton and its geological implication, zircons separated from the Nui Phao granites were dated by LA-ICP-MS U-Pb method, giving an average ²⁰⁶Pb/²³⁸U age of 248±9.9 Ma. This dating result pointed out the exsistence of the Indosinian tectonothermal event in the study area . Inherited zircon with ²⁰⁶Pb/²³⁸U ages of 840 and 447 Ma are also present in the sample indicating that the continental crust in the study area also contains Neoproterozoic and Paleozoic materials.

Người biên tập: PGS. TSKH Trần Trọng Hòa.