Genesis of celestine in the world-class Jinding Zn-Pb-Sr deposit, SW China: Constraints from field mapping, petrography, fluid inclusion, and elemental and S-O-Sr isotope geochemistry

The world-class Jinding deposit in SW China has ∼15 Mt combined Zn and Pb metals and 1.36 Mt SrSO4 in an evaporite dome created by the diapir of Late Triassic gypsum/anhydrite during Paleocene thrusting. The celestine genesis and its metallogenic link with Zn-Pb mineralization remain equivocal. The deposit contains non-economic pre-ore type I celestine, the economic type II celestine that has unclear paragenetic relationship to Zn and Pb sulfides, and sub-economic post-ore type III celestine. Type I was formed in low-temperature (<50 ℃) fluid and shows similar S-O isotope signature with that of the dissolved diapir gypsum/anhydrite. Type II was formed by replacing the diapir anhydrite in warm (70–90 ℃) and moderately saline (15–18 wt% NaCl equiv) fluid. It exhibits S-O isotope signature caused by the mixing of the remaining sulfate (after bacterial sulfate reduction) with minor reoxidized reduced sulfur. Type III was formed in hot (120–180 ℃) and highly saline (19–22 wt% NaCl equiv) fluid and has S-O isotopes reflecting the mixing of the remaining sulfate with appreciably more reoxidized reduced sulfur. The three types of celestine have consistent 87Sr/86Sr ratios (0.7100–0.7107), similar to the Cenozoic sedimentary gypsum and limestone in the region. Therefore, Sr in the Jinding celestine was mainly derived from sediment water expelled from the Cenozoic sedimentary packages. The celestine is suggested to be genetically unrelated to the Zn-Pb mineralization and however recorded multistage expelling of the Sr-rich sediment water and interactions with diapir gypsum/anhydrite and their variants in the Jinding evaporite dome.