Univ Camerino, Dipartimento Sci Terra, I-62032 Camerino, Italy
; Univ Camerino, INFM, I-62032 Camerino, Italy
; Chinese Acad Sci, Inst High Energy Phys, Beijing Synchrotron Radiat Facil, Beijing 100039, Peoples R China
; Univ Modena & Reggio Emilia, Dipartimento Sci Terra, I-41100 Modena, Italy
; Ist Nazl Fis Nucl, Lab Nazl Frascati, I-00044 Frascati, Italy
; Univ Roma Tre, Dip Sci Geol, I-00146 Rome, Italy
Article; Proceedings Paper
Experimental and theoretical EXAFS and XANES data on Fe coordination and bond distances have been obtained for a natural tetra-ferriphlogopite. XANES data show a predominance of trivalent iron in tetrahedral coordination. The use of theoretical multiple scattering calculations helps distinguish the contributions to the total spectrum coming from the different iron atoms. EXAFS spectra were reduced and analyzed using the GNXAS programs and Fe has been confirmed to be in tetrahedral coordination, with refined structural data Fe-O = 1.86 Angstrom, Fe-Si = 3.24 Angstrom, Fe-O-Si = 138 degrees. Moreover, a further contribution from Fe is detected corresponding to a Fe-O distance equal to 2.22 Angstrom. This latter contribution (20 mol % of the total Fe ca.) is interpreted to arise from divalent Fe in octahedral coordination, in excellent agreement with the structural and chemical data.