Quantitative analysis of H2O and CO2 in cordierite using polarized FTIR spectroscopy |
| |
Authors: | Giancarlo Della Ventura Francesco Radica Fabio Bellatreccia Andrea Cavallo Francesco Capitelli Simon Harley |
| |
Institution: | 1. Dipartimento di Scienze Geologiche, Università Roma Tre, Largo S. Leonardo Murialdo 1, 00146, Rome, Italy 2. LNF-INFN, Via E. Fermi 40, Frascati (Roma), Italy 3. INGV, Via di Vigna Murata 605, Rome, Italy 4. Institute of Crystallography, CNR, Via Salaria Km 29,300, 00016, Monterotondo, Roma, Italy 5. School of GeoSciences, University of Edinburgh, Kings Buildings, West Mains Road, Edinburgh, EH9 3JW, Scotland, UK
|
| |
Abstract: | We report a FTIR (Fourier transform infrared) study of a set of cordierite samples from different occurrence and with different H2O/CO2 content. The specimens were fully characterized by a combination of techniques including optical microscopy, single-crystal X-ray diffraction, EMPA (electron microprobe analysis), SIMS (secondary ion mass spectrometry), and FTIR spectroscopy. All cordierites are orthorhombic Ccmm. According to the EMPA data, the Si/Al ratio is always close to 5:4; X Mg ranges from 76.31 to 96.63, and additional octahedral constituents occur in very small amounts. Extraframework K and Ca are negligible, while Na reaches the values up to 0.84 apfu. SIMS shows H2O up to 1.52 and CO2 up to 1.11 wt%. Optically transparent single crystals were oriented using the spindle stage and examined by FTIR micro-spectroscopy under polarized light. On the basis of the polarizing behaviour, the observed bands were assigned to water molecules in two different orientations and to CO2 molecules in the structural channels. The IR spectra also show the presence of small amounts of CO in the samples. Refined integrated molar absorption coefficients were calibrated for the quantitative microanalysis of both H2O and CO2 in cordierite based on single-crystal polarized-light FTIR spectroscopy. For H2O the integrated molar coefficients for type I and type II water molecules (ν3 modes) were calculated separately and are I]ε?=?5,200?±?700?l?mol?1?cm?2 and II]ε?=?13,000?±?3,000?l?mol?1?cm?2, respectively. For CO2 the integrated coefficient is $ \varepsilon_{{{\text{CO}}_{ 2} }} $ ?=?19,000?±?2,000?l?mol?1?cm?2. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|