Iron Isotope Compositions of Coexisting Sulfide and Silicate Minerals in Sudbury-Type Ores from the Jinchuan Ni-Cu Sulfide Deposit: A Perspective on Possible Core-Mantle Iron Isotope Fractionation

Many studies have shown that the average iron (Fe) isotope compositions of mantle-derived rocks, mantle peridotite and model are close to those chondrites. Therefore, it is considered chondrite values represent bulk Earth Fe composition. However, this a brave assumption because nearly 90% in core, where its composition unknown, but required construct We approach problem by assuming Earth’s core separation can be approximated terms Sudbury-type Ni-Cu sulfide mineralization, sulfide-saturated mafic magmas segregate into immiscible liquid silicate liquid. Their density/buoyancy controlled stratification solidification produced net-textured ores above massive below disseminated ores. The coexisting minerals (pyrrhotite (Po) > pentlandite (Pn) chalcopyrite (Cp)) (olivine (Ol) orthopyroxene (Opx) clinopyroxene (Cpx)) expected hold messages on fractionation between two liquids before their solidification. studied Jinchuan deposit. show varying δ56Fe (−1.37–−0.74‰ < 0.09–0.56‰ (Cp) 0.53–1.05‰ (Pn)), (Ol, Opx, Cpx) chondrites (δ56Fe = −0.01 ± 0.01‰). heavy value (0.52–0.60‰) serpentines may reflect isotopes exchange with pyrrhotite light δ56Fe. obtained an equilibrium factor Δ56Fesilicate-sulfide ≈ 0.51‰ reconstructed 0.21‰) −0.30‰), or 0.36‰ weighted mean bulk-silicate (δ56Fe[0.70ol,0.25opx,0.05cpx] 0.06‰) bulk-sulfide −0.30‰). Our study indicates significant does take place during mineralization. hypothesize must taken core–mantle segregation, lighter than although analysis experimental sulfide-silicate under depth conditions needed test our results. advocate importance further research subject. Given Fe-Ni association magmatic mineralization majority Ni also we infer needs attention.