The duration of hydrothermal activity is key to understanding the genesis of hydrothermal deposits, yet dating low-temperature systems is difficult due to the scarcity of suitable minerals. The Youjiang Basin in the western South China Antimony Metallogenic Belt (SCAMB) hosts several giant Sb deposits and represents the largest lowtemperature (<250 ◦C) Au-As-Sb-Hg mineralization domain in China. Although previous studies have reported mineralization ages of 148–101 Ma for regional Sb deposits, the duration of hydrothermal activity for a single deposit remains unclear. The Nadan Sb deposit in the southwestern Youjiang Basin contains three generations of stibnite-associated calcite (Cal-I, II, III), providing an ideal case for investigation. LA-ICPMS analyses show decreasing Fe-Mn contents (5330–3760, 3291–1537, and 1764–566 ppm) and increasing total REE concentrations (1.57, 10.7, and 12.1 ppm) from Cal-I to Cal-III. U-Pb dating yields ages of 81.6 ± 1.7 Ma, 77.6 ± 1.1 Ma, and 69.8 ± 1.7 Ma, suggesting that the Nadan deposit is the youngest Sb deposit in the SCAMB. The ~ 10 Myr age span indicates prolonged hydrothermal activity. δ13CPDB (􀀀 0.10‰ to + 0.75‰) and δ18OSMOW (+10.71‰ to + 12.72‰) values suggest calcite precipitation from magmatic-hydrothermal fluids. These results indicate that sustained magmatic heat and fluid input enabled the long-lived hydrothermal system and played a key role in Sb mineralization in the SCAMB.