2004 Volume 54 Issue 2 Pages 159-166
Contents of rare earth elements (REEs) and Sr isotopic composition of anhydrite sampled from Matsumine, Shakanai and Hanaoka Kuroko deposits are analyzed. Sr isotopic values of anhydrite samples (0.70772-0.708661) have the intermediate values between the values of Miocene seawater (0.7088) and the country rocks (0.7035-0.7050). Anhydrite in Kuroko deposits exhibits two chondrite-normalized REE patterns; a pattern containing a marked peak in Sm, and another exhibiting linear-pattern which decreases from light to heavy rare earth elements (REE).
Anhydrites from Kuroko deposits are similar to those from recent submarine hydrothermal systems (TAG and Grimisey Fields) in chondrite-normalized REE patterns and S and Sr isotope ratios. That indicates that these anhydrites would have similar formation mechanism, namely anhydrites from Kuroko deposits would have formed by the mixing of seawater and hydrothermal solution, similarly to those from TAG and Grimsey Fields. Further, variation of anhydrites from Kuroko deposits would be caused from the variation of seawater / hydrothermal solution ratios.
