3.3. Fe K-edge XANES analysis
The Fe K-edge XANES spectra of standard compounds (pyrite (FeS), chalcopyrite (CuFeS2), jarosite (KFe3(SO4)2(OH)6) are shown in Fig. 4A. In the spectra of chalcopyrite, the strong pre-edge peak at 7111.9 eV indicates the tetrahedral structure of chalcopyrite, which allows 1s-3d transition ( Petiau et al., 1998). In the pyrite FeS2, iron is sixfold coordinated to the sulfur and forms an octahedral structure. The 1s-3d transition is dipolar forbidden for pure atomic states