Spatial trace element variations of stibnite in a world-class Sb deposit and their implications for ore genesis and exploration

Abstract Stibnite samples collected from a variety of depths in the world-class Xikuangshan Sb deposit in south China were analyzed to determine their trace element signatures and identify features that could be used in the exploration for similar deposits elsewhere. In situ LA-ICP-MS analyses revealed that trace elements such as Cu, Tl, Pb, and Hg are incorporated into the stibnite structure through complex substitution mechanisms. These include substitutions such as (Cu+ + Tl+) + (Pb2+ + Hg2+) ↔ 2Sb3+ + 2□ and Cu+ + Fe2+/Zn2+ ↔ Sb3+ + □, where □ denotes vacancies in the stibnite lattice. A key finding of the analyses is that the As, Zn and Tl contents of the stibnite vary systematically with depth in the deposit, i.e., the concentrations of As and Tl gradually increase with depth, whereas the Zn concentration decreases. These depth-related trends are interpreted to reflect the migration pathway of ore-forming fluids and the temperature evolution of the hydrothermal system. We, therefore, propose that these trace elements and their ratios (Tl/Zn and As/Zn) can serve to reconstruct the pathways of ore fluid migration and target the exploration for orebodies. In addition to our data for the Xikuangshan Sb deposit, we have compiled published data on the trace element compositions of stibnite from Sb, Sb-W, Au-Sb-W, and Au ore systems worldwide. The results show that trace elements involving Cu, Pb, Se, As, and Ag + Sn + In can be used to distinguish metal associations in natural hydrothermal ore systems. This study demonstrates that In situ LA-ICP-MS trace element for stibnite have the potential to be used to fingerprint fluid flow paths and provide a new tool for exploration.