Zircon U-Pb age of quartz-feldspar dykes and gold mineralization characteristics at Vai Dao mine, Song Da zone, Northwest Vietnam

The Vai Dao mine, located in Cao Ram Commune, Luong Son District, Hoa Binh Province, is situated within the Song Da structural zone. This zone is an active intracontinental rift that existed during the Indosinian period. The region shows significant potential for gold mineralization, particularly of the gold-quartz-sulfide ore formation, in Northwest Vietnam. To determine the origin of the gold mineralization, analyses were conducted including thin section, polished section, inclusion temperature, and U-Pb zircon isotope analysis. The research results indicate that the gold mineralization in the Vai Dao mine belongs to a medium-temperature hydrothermal gold-quartz-sulfide ore formation. The typical mineral assemblage includes gold-quartz-pyrite, arsenopyrite, and gold-quartz-polymetallic sulfides. In the research area, aplite dykes and quartz-feldspar dykes are also present. U-Pb isotope age analysis on zircon minerals from quartz-feldspar dykes (sample VD3021) using the LA-ICP-MS method yielded an age range of 251-259 Ma, with an average of 255.7±4.7 Ma. Based on petrological characteristics and distribution, these magmatic formations can be classified into acid effusive, sub-effusive, and sub-intrusive rock assemblages belonging to Episode 2 of the Vien Nam Formation (P3-T1vn2). Consequently, it can be concluded that the gold-quartz-sulfide mineralization is directly related to medium-temperature hydrothermal solutions associated with the magmatism of the Vien Nam formation. This research provides a foundation for the exploration and evaluation of gold-quartz-sulfide mineralization in areas with similar geological structures.