The gangue sponge: implications for in-situ/heap leaching of chalcopyrite

(Partial) dissolution of reactive aluminosilicate gangue minerals increase the complexity of chalcopyrite leaching by forming an amorphous, porous silica residue that interacts with the leaching solution to form local non-equilibirum microenvironments. Reactive phyllosilicates chamosite and kaolinite minerals berthierine and greenalite sample mineralogy and bulk chemistry is determined by XRD, XRF, Moessbauer Spectroscopy and OES. After leaching, the leaching solution chemistry was analysed via OES and UV-VIS. The leaching residue textures, chemistry and cpy S-oxidation state was analysed using SEM, FIB, uXRF and uXANES. Heterogeneous element distribution in the porous textures and leaching solution, as well as chalcopyrite and pyrite textures reveal incongruent dissolution of reactive gangue minerals that form a porous amorphous silica residue that can entrap and penetrate Cu sulfides. The pores of the ASR form local microreactors with variable non equilibium conditions of the lixiviant, that lead to larger variety and more complex S oxidation states on chalcopyrite grains. Gangue mineral dissolution hence influences chalcopyrite leaching reactions and Cu recovery.