New Potential Barite Reference Materials for LA-MC-ICP-MS Sulfur Isotope Analysis with Application to Hydrothermal Barite in the Huayangchuan Deposit, Western China
摘要
Sulfur isotopes of S-bearing materials are powerful tools to trace various geological processes and sulfur sources in earth sciences, especially in ore deposits where sulfide-sulfate pair coprecipitates widely. However, in-situ S isotope determination of barite is challenging without natural matrix-matched reference material. In this study, we present two natural barite reference materials (1-YS and 294-YS) for in-situ sulfur isotopic analysis. Independent LA-MC-ICP-MS laboratories were utilized to test the δ34S micron-scale homogeneity of 1-YS and 294-YS barites that have 2s re-peatabilities of better than ±0.45‰ and ±0.41‰, respectively. Meanwhile, the in-situ analysis results are consistent with the results of the bulk analysis by GS-IRMS within uncertainty. The grand mean δ34S values of 1-YS (13.37‰ ± 0.42‰, 2s) and 294-YS (14.38‰ ± 0.44‰, 2s) are the final recommended values obtained from four independent laboratories. All the results confirm the suitability of 1-YS and 294-YS barite used as calibration materials with respect to in-situ S isotopic analysis. Moreover, the new developed barite reference materials were used as matrix-matched standard to calibrate the barite samples from the Huayangchuan carbonatite-hosted U-polymetallic deposit (Qinling orogenic belt, western China) to obtain δ34S values. Utilizing the temperature-dependent δ34S fractionation of barite-pyrite pair, we calculate the formation temperature of barite (i.e., 506 to 537 °C) and the δ34S value of mineralizing fluid (i.e., −7.11‰ to −7.59‰) in the Huayangchuan deposit. The results indicate an involvement of sedimentary sulfur, presumably acting as a potential uranium source (e.g., upper crustal materials) for the giant Huayangchuan deposit.