Cadmium isotope fractionation in a S-type granite related large magmatic-hydrothermal system

Granite -associated deposits are one of the important ore types in the Earth's crust and can dominantly be subdivided into S-, Iand A -type granite -related deposits with different mineralization elements and isotopic signatures (e.g., sulphur and boron). The object of this study is to investigate whether Cd isotopic difference exists between Iand S -type granite -related deposits, and to provide new insights on geochemical behavior of Cd in such systems that have not been well constrained. The Dulong deposit in southwest China is a world -class skarn -type polymetallic Zn-Sn-In deposit that is thought to be genetically related to the emplacement of the highly fractionated S -type Laojunshan granite. The extremely negative delta 114/110 Cd values of sulfides (-0.82 %. to -0.42 %.) within the Dulong deposit are all lower than those of sulfides from other Zn-Pb ore deposits globally. In comparison, representative sphalerites from Itype granite -related deposits yield heavier Cd isotopic compositions relative to the samples from the Dulong deposit. The Laojunshan granite samples are enriched in light Cd isotopes and have delta 114/110 Cd values that range from -0.73 %. to -0.40 %., overlapping with the delta 114/110 Cd values of sphalerite within the Dulong deposit and suggesting that the Cd in the deposit was derived from the Laojunshan granite. Similarly, I -type granite -related deposits elsewhere have Cd isotopic compositions that are similar to mafic-intermediate igneous rocks, suggesting little or no Cd isotopic fractionation took place during the magmatic-hydrothermal processes that formed these deposits. These results suggest that geochemical signatures of metal sources are the most likely control on Zn/Cd ratios and delta 114/110 Cd values of sulfides in these deposits, with different mineral deposit types having different Zn/Cd ratios and delta 114/110 Cd values. In summary, Cd isotopes provide a potentially effective tool for discriminating between different types of hydrothermal system and may also be useful in the investigation of granite petrogenesis. (c) 2024 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.