Study on the Occurrence States and Enrichment Mechanisms of the Dispersed Elements Ga, Ge, and In in the Chipu Pb-Zn Deposit, Sichuan Province, China

The dispersed elements Ga, Ge, and In are crucial strategic mineral resources often enriched in Pb-Zn deposits. The Chipu Pb-Zn deposit, located on the western edge of the Yangtze Block, lies to the north of the Sichuan-Yunnan-Guizhou (SYG) Pb-Zn metallogenic province with large amounts of Emeishan basalt. Based on trace element and in situ sulfur isotope analyses by (LA)-ICP-MS, sphalerite is the main carrier mineral for Ga (17~420 ppm), Ge (3.87~444 ppm), and In (31~720 ppm). Ga or Ge correlate significantly with Cu, while In substitutes for Zn in sphalerite alongside Fe. Key substitution reactions include Ga3+ + Cu+ ↔ 2Zn2+, Ge4+ + 2Cu+ ↔ 3Zn2+, and 2In3+ + Fe2+ ↔ 4Zn2+. Sphalerite crystallized at medium to low temperatures (114–195 °C). Sulfide δ34S values (+3.48 to +24.74‰) suggest sulfur mainly originated from Dengying Formation marine sulfates via thermochemical sulfate reduction (TSR). Metal-bearing fluid release at 30 Ma post-Emeishan mantle plume activity (261–257 Ma) coincides with the Chipu deposit’s mineralization period (230–200 Ma), suggesting the Chipu deposit is associated with Emeishan plume activity. The magmatic activity drove basinal brine circulation, extracting In from intermediate-felsic igneous rocks and metamorphic basement. Elevated temperatures promoted the coupling of Fe and In into sphalerite, causing anomalous In enrichment.