Deciphering ore formation and guiding ore exploration for antimony within the North Himalayan Metallogenic Belt, southern Xizang (Tibet): Insights from antimony isotopic fingerprints

The North Himalayan Metallogenic Belt (NHMB) hosts a series of Sb, Sb-Au, and Sb-Pb-Zn-Ag deposits, yet the genetic association for these deposits remains poorly understood. Herein, we examine the Sb isotopic compositions of these Sb-bearing deposits to gain insights into regional Sb mineralization processes and guide ore exploration. The measured δ123Sb values (relative to the NIST 3102a standard) of the stibnite range from −0.16‰ to +2.06‰, with the Mazhala deposit exhibiting the lightest Sb isotopic compositions (−0.16‰ to +0.15‰), followed by the Shalagang (+0.09‰ to +0.35‰) and Cheqiongzhuobu (−0.11‰ to +0.45‰) deposits. Meanwhile, the Taga deposit displays the heaviest Sb isotopic compositions (+1.89‰ to +2.06‰) observed to date. Rayleigh distillation is inferred as the primary mechanism driving Sb isotopic variation during ore formation. With the support of S-Pb isotopic data and geological evidence, a Rayleigh distillation model was established. This model, together with the negative correlation between Sb isotopic compositions and ore-forming paleodepths, indicates that the studied Sb-bearing deposits in the NHMB share a common dominant Sb source (Precambrian metamorphic basement). These Sb-bearing deposits are products of a large-scale regional Sb-bearing hydrothermal system that precipitated ores at different positions or paleodepths within the shallow crust. Subsequently, these ores underwent differential erosion. Additionally, the regional differential erosion coupled with the Rayleigh distillation model indicate that the deeper parts of these deposits still hold significant potential for Sb-Au exploration. These findings provide new insights into the role of Sb isotopes in tracing hydrothermal mineralization processes and guiding regional exploration strategies.