Strontium geochemical evidence for the origin of the barite deposits from Sardinia, Italy

Sr content of 137 samples of barite, 81 samples of fluorite, and 65 samples of calcite from 27 post-Cambrian karst and hydrothermal deposits. Karst calcites have an average Sr content of 26 ppm, quite similar to that of the hydrothermal calcites. Hydrothermal fluorites show an average content of 56 ppm. Forty-five percent of the karst barites have an Sr content over 6,000 ppm, while as much as 83.8 percent of the hydrothermal barites contain more than 6,000 ppm Sr. The Sr isotope composition of the Cambrian stratiform barites (0.70867 + or - 3) is similar to that of Cambrian seawater, suggesting that the bulk of the Sr was provided by this source. The Sr isotope ratios of the karst barite (average ⁸⁷ Sr/ ⁸⁶ Sr = 0.70947 + or - 1) indicate that Sr was not only derived by recycling of the stratiform barite but was also provided by the noncarbonate fraction of the Cambrian wall rocks. The Sr isotope composition of the hydrothermal barites ranges from 0.70990 + or - 4 to 0.71837 + or - 4, suggesting that the Sr derived mainly from a high ⁸⁷ Sr/ ⁸⁶ Sr ratio source.--Modified journal abstract.