Della Ventura, G., Bellatreccia, F., Cámara, F., Oberti, R. (2014) Crystal-chemistry and short-range order of fluoro-edenite and fluoro-pargasite: a combined X-ray diffraction and FTIR spectroscopic approach. Mineralogical Magazine, 78 (2) 293-310 doi:10.1180/minmag.2014.078.2.05
| Reference Type | Journal (article/letter/editorial) | ||
|---|---|---|---|
| Title | Crystal-chemistry and short-range order of fluoro-edenite and fluoro-pargasite: a combined X-ray diffraction and FTIR spectroscopic approach | ||
| Journal | Mineralogical Magazine | ||
| Authors | Della Ventura, G. | Author | |
| Bellatreccia, F. | Author | ||
| Cámara, F. | Author | ||
| Oberti, R. | Author | ||
| Year | 2014 (April) | Volume | 78 |
| Issue | 2 | ||
| Publisher | Mineralogical Society | ||
| DOI | doi:10.1180/minmag.2014.078.2.05Search in ResearchGate | ||
| Generate Citation Formats | |||
| Mindat Ref. ID | 244502 | Long-form Identifier | mindat:1:5:244502:5 |
| GUID | 0 | ||
| Full Reference | Della Ventura, G., Bellatreccia, F., Cámara, F., Oberti, R. (2014) Crystal-chemistry and short-range order of fluoro-edenite and fluoro-pargasite: a combined X-ray diffraction and FTIR spectroscopic approach. Mineralogical Magazine, 78 (2) 293-310 doi:10.1180/minmag.2014.078.2.05 | ||
| Plain Text | Della Ventura, G., Bellatreccia, F., Cámara, F., Oberti, R. (2014) Crystal-chemistry and short-range order of fluoro-edenite and fluoro-pargasite: a combined X-ray diffraction and FTIR spectroscopic approach. Mineralogical Magazine, 78 (2) 293-310 doi:10.1180/minmag.2014.078.2.05 | ||
| Abstract/Notes | AbstractThis study addresses the crystal chemistry of a set of five samples of F-rich amphiboles from the Franklin marble (USA), using a combination of microchemical (Electron microprobe analysis (EMPA)), single-crystal refinement (SREF) and Fourier transform infrared (FTIR) spectroscopy methods. The EMPA data show that three samples fall into the compositional field of fluoro-edenite (Hawthorne et al., 2012), whereas two samples are enriched in high-charged C cations and – although very close to theCR3+boundary – must be classified as fluoro-pargasite. Magnesium is by far the dominant C cation, Ca is the dominant B cation (withBNa in the range 0.00−0.05 a.p.f.u., atoms per formula unit) and Na is the dominant A cation, withA☐ (vacancy) in the range 0.07−0.21 a.p.f.u.;WF is in the range 1.18−1.46 a.p.f.u. SREF data show that: TAl is completely ordered at the T(1) site; theM(1) site is occupied only by divalent cations (Mg and Fe2+);CAl is disordered between theM(2) andM(3) sites;ANa is ordered at the A(m) site, as expected in F-rich compositions. The FTIR spectra show a triplet of intense and sharp components at ~3690, 3675 and 3660 cm−1, which are assigned to the amphibole and the systematic presence of two very broad absorptions at 3560 and 3430 cm−1. These latter are assigned, on the basis of polarized measurements and FPA (focal plane array) imaging, to chlorite-type inclusions within the amphibole matrix. Up to eight components can be fitted to the spectra; band assignment based on previous literature on similar compositions shows thatCAl is disordered over theM(2) andM(3) sites, thus supporting the SREF conclusions based on the <M−O> bond distance analysis. The measured frequencies of all components are typical of O−H groups pointing towards Si−O(7)−Al tetrahedral linkages, thus allowing characterization of the SRO (shortrange- order) ofTAl in the double chain. Accordingly, the spectra show that in the fluoro-edenite/ pargasite structure, the T cations, Si and Al, are ordered in such a way that Si−O(7)−Si linkages regularly alternate with Si−O(7)−Al linkages along the double chain. | ||
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