Large selenium isotopic variations and its implication in the Yutangba Se deposit, Hubei Province, China

The selenium isotopic ratios have been measured in the Yutangba Se deposit, Hubei Province, China. The results show that the delta Se-82/76(NIST) values vary from -12.77 parts per thousand to 4.93 parts per thousand, which is the largest Se isotopic variation found so far in natural terrestrial samples. The sample Ytb-5 of high-selenium carbonaceous shale has the lightest Se isotopic composition with a delta Se-82/76(NIST) value of -12.77 parts per thousand. On the basis of variations of Se isotope in the deposit along with other geological and geochemical evidence, the "redox model" is suggested to favor the explanation of the occurrence of native Se in the deposit. The application to the Yutangba Se deposit with the discovery of large Se isotopic fractionation for natural samples indicates the potential of Se isotope as a new geochemical tracer.