Insights into ore genesis of the Beishan Pb–Zn deposit in Guangxi, South China: Evidence from Rb–Sr dating and in-situ S–Pb isotopes

Abstract

The Beishan Pb–Zn deposit, situated in the transitional zone between the Yangtze Block and Cathaysia Block, is a significant source of non-ferrous metal ore in Guangxi, China. The orebodies are hosted within distinct fine- and coarse-grained dolomites, exhibiting layered and lenticular shapes controlled by stratigraphy and structural factors, demonstrating good continuity. No evidence of magmatic activity has been observed in the Beishan deposit. To ascertain the sources of ore-forming materials, age of formation, and genesis of the Beishan deposit, this study employed a systematic approach involving trace element analysis, Rb–Sr dating, and in-situ S–Pb isotope analysis of representative sulfide minerals, namely, sphalerite, pyrite, and galena. The sphalerite within the Beishan deposit displayed enrichment of Cd, Ga, and Ge, while exhibiting depletion of Fe, Mn, and In, indicating a medium–low formation temperature. An in situ S isotope study suggests that sulfur primarily originates from seawater sulfate, with bacterial sulfate reduction (BSR) and thermochemical sulfate reduction (TSR) processes playing a crucial role in mineral deposition. In-situ Pb isotope analysis indicated that Pb was derived from a combination of crustal and mantle sources. Multiple geochemical findings indicate that the Beishan deposit is a typical Mississippi Valley Type (MVT) Pb–Zn deposit. Furthermore, the obtained Rb–Sr isochron age of 330 ± 12 Ma (1σ) indicates that the Beishan deposit was formed during the Hercynian orogeny, aligning with the formation timing of the Siding Pb–Zn deposit in northwestern Guangxi.