Fe2+-Ti4+ charge-transfer in garnets from mantle eclogites
Platonov, Alexej N.; Langer, Klaus; Matsuk, Stanislas S.; Taran, Mikhail N.; Hu, Xiaorui
published: Feb 21, 1991
manuscript accepted: Jul 11, 1990
manuscript received: Feb 16, 1990
ArtNo. ESP147050301010, Price: 29.00 €
Abstract A broad band centred at 23500 cm-1 , with a half band width of 7000 cm-1 is observed in the optical absorption spectra of yellow to orange pyrope-almandine-grossular garnets from mantle-derived kyanite-eclogites or inclusions in diamonds from such rocks. This band is assigned to Fe2+-Ti4+ charge-transfer on the basis of its large half band width and the strong correlation with Fe2+-Ti4+ concentration product, α23500 = - 1235 + 901.78 • (XFe2+-XTi4+), with correlation coefficient r = 0.978 (X = no. of atoms per formula unit). The electronic transition involves edge sharing, Fe2+-centred triangular dodecahedra and Ti4+-centred octahedra of the garnet structure.