Establishment of High Precision Cd Isotope Analysis Method and Its Geological Application

Cadmium (Cd) has eight stable isotopes and is highly volatile (semi-condensed temperature Tc=430 K, 1 Pa), resulting in low abundance in the earth and meteorites, which makes it very difficult to accurately measure Cd isotopes. In recent years, with the wide application of multi-receiver inductively coupled plasma mass spectrometry (MC-ICP MS), it is possible to accurately determine the isotope ratio of Cd. In this paper, the separation and purification steps of Cd were optimized, and a high precision Cd isotope measurement method with double diluent correction was established. By optimizing the acid system, resin volume, eluent concentration and eluent volume, the recovery rate of Cd is 99.5%, and the residual element/Cd ratio & lt≤0.07%, which can effectively realize the separation of Cd from matrix elements (Zn, Ga, Ge, Zr, Nb, Mo, Pd, Ag, In, Sn, Sm, Pb) and better meet the requirements of Cd isotope determination. Previous studies have shown that geological processes in hydrothermal systems, such as sulfide precipitation, fluid migration and temperature changes, will lead to Cd isotope fractionation, especially in low temperature systems, while in high temperature systems, fractionation is weak. Cd isotope data are of great significance in the discrimination of genetic types of lead-zinc deposits, the evolution of ore-forming fluids and the tracing of ore-forming material sources. Using the new method established in this paper, we have tested the sphalerite samples from Xinqiao and Hehuashan mining areas in Tongling area. The measured Cd isotope data indicate the geological problems such as genetic type discrimination, ore-forming fluid evolution and ore-forming material sources of lead-zinc deposits.