Geochemical Study of the My Duc Pb-Zn Deposits in Vietnam

This study presents a comprehensive geochemical investigation of the undeveloped Pb-Zn mineral deposits in the My Duc area of Quang Binh Province, central Vietnam. The regional geology includes the upper Silurian to lower Devonian Dai Giang Formation (limestone, mudstone, sandstone, and schist), the upper Devonian Co Bai Formation, the lower Carboniferous La Khe Formation (limestone), and the upper Carboniferous to lower Permian Muong Long Formation (recrystallized limestone), with Cretaceous lamprophyre intrusions. The Pb-Zn ore bodies are primarily hosted in dolomitized and recrystallized limestone and are classified into primary and oxidized zones. The main ore minerals are sphalerite, galena, smithsonite, and associated sulfide and carbonate minerals. A total of 31 rock and ore samples were collected from ore bodies and surrounding rocks, followed by X-ray diffraction (XRD), electron probe micro analysis (EPMA), and chemical analyses. Sphalerite from Dong Tri Mountain shows high Zn contents (64.5-67.7 wt.%), low Fe, and moderate Cd concentrations, indicating high purity. The average Zn and Pb concentrations in ore bodies were 1,230 ppm and 27,700 ppm, respectively, with Zn reaching up to 16,000 ppm in high-grade ores. Geochemical anomalies of Cd, Sb, As, and Ag were also detected. Additionally, a regional geochemical survey was conducted over an area of 180 km<sup>2</sup>, using 90 stream sediment and 90 heavy mineral samples. Anomalous zones were identified near the Tau A and Len Dong Areas, where multielement enrichment indicates hydrothermal vein-type mineralization. These zones are considered promising targets for future exploration. The findings suggest that the My Duc Pb- Zn deposits exhibit strong geochemical signatures typical of epithermal processes, and further trenching, drilling, and geophysical surveys are recommended to define economically viable ore zones.