Oxygen isotope study on origin of ore-forming fluid responsible for skarn-type W deposit: Example at the Date-Nagai deposit

Abstract

Oxygen isotopic compositions of skarn minerals were analyzed. Garnet and scheelite have variable δ¹⁸O, 4.6-8.2 per mil and 0.8-2.9 per mil, respectively. Temperature of skarn formation was calculated using oxygen isotope fractionation factor between quartz and scheelite, and T= 277°C was obtained. δ¹⁸O of skarn-forming solution was calculated. Early stage solution had δ¹⁸O values of 6-8 per mil and most garnet precipitated from this solution. While later stage solution had δ¹⁸O values 1-5 per mil, and this solution was responsible for precipitation of scheelite and quartz.