title: Ti and Fe speciation by X-ray photoelectron spectroscopy(XPS) and Mössbauer spectroscopy for a full crystal chemical characterisation of Ti-garnets from Colli Albani (Italy).
abstract: Different analytical and structural methods (Electron Probe Micro-Analysis, Single Crystal X-ray diffraction, X-ray Photoelectron Spectroscopy, Mössbauer spectroscopy) were combined to fully characterise the crystal chemistry of natural Ti-bearing garnets from Colli Albani (Lazio, Italy). The study of the relevant complex crystal chemistry ( large number of cation substitutions affecting the three independent X(8-fold), Y(6-fold) and Z(4-fold) crystallographic sites and Fe and Ti transition elements exhibiting several oxidation states and coordination environments) benefited from the multi-technique approach. Electron probe microanalysis provided elemental composition of the analysed samples, which have low Ti-content (TiO2 in the range 1.99 - 3.48 wt %) and slightly different Fe/Al ratios. For all samples, two doublets were fitted to room temperature Mössbauer spectra and assigned to Fe3+(Y) (approximately 95%) and Fe2+(X) (approximately 5%). Up to three doublets (Ti3+(Y), Ti4+(Y), Ti4+(Z)) were fitted to XPS spectra and yielded direct evaluation of Ti site population. XPS technique confirmed its potential for the study of speciation of Ti in minerals.
authors.affiliation: Dipartimento Geomineralogico, Universita' di Bari, via E. Orabona 4, 70125, Bari, Italy.
authors.forename: Emanuela
authors.initials: E
authors.lastname: Schingaro
authors.forename: Fernando
authors.initials: F
authors.lastname: Scordari
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Pedrazzi
authors.forename: Cosimino
authors.initials: C
authors.lastname: Malitesta
mesh_terms: D003460:Crystallization; D055593:Geological Phenomena; D005844:Geology; D007501:Iron / Q000032:analysis / Q000737:chemistry*; D007558:Italy; D017640:Silicates / Q000737:chemistry*; D013052:Spectrometry, X-Ray Emission; D014025:Titanium / Q000032:analysis / Q000737:chemistry*
chemical_list: D017640:Silicates; D014025:Titanium; D007501:Iron