Raman characteristics of Alpine–Himalayan serpentine polymorphs: A case study of Khankuie ultramafic complex, southeast of Iran
- 295 Downloads
Chrysotile, antigorite, and lizardite were analyzed to determine their chemical and structural properties as a function of Raman spectral patterns. Serpentine polymorph discrimination is a challenging issue as each polymorph represents different crystal structure and different thermodynamic phase situation of formation. Microtextural investigation, SEM (Scanning Electron Microscope), XRD (X-Ray Diffraction), and EMPA (Electron Microprobe Analysis) illustrate that there are some chemical and structural variations between our studied serpentine polymorphs. In the case of the three strongest Raman peaks at around 230, 390 and 690 cm−1, we obtained that antigorite tends to lower Raman Stoke lines, lizardite to moderate wavenumbers and the highest Raman Stoke lines belong to chrysotile. These main bands with principal peaks were used to find special spectral peak patterns of each polymorph, along with some other ‘weak’ peaks (around 350, 520, and 620 cm−1) with different behaviours. When Raman Stoke line shifts were plotted against each other, we reached to 25 scatter plots with different classified validation. The best 2d scatter discrimination diagrams are those of 230–390 cm−1 and 350–390 cm−1 with the overall accuracy rate of 94% and 98%, respectively. Also, there are proportional relations between chemical band vibrations of SiO4, MgO, and H2O, and Raman Stoke lines of 390, 620 and 230 cm−1, respectively. This information increases our ability to predict polymorph types and geochemical trends of serpentine group minerals just using the Raman spectra.
KeywordsSerpentine polymorphs Raman spectroscopy Raman Stoke line shifts chemical band vibrations discrimination diagrams
The authors are grateful to Prof. Rainer Abart and Prof. Fredrich Koller of the Department of Lithospheric Research and Prof. Luts Nasdala of Institut für Mineralogie und Kristallographie of the University of Vienna, who kindly provided the EMPA, XRF and Raman Spectrometer for our expensive analysis. Special thanks to Prof. Pier Paolo Lottici for his scientific leads based on other works (currently, preparing on surrounding area). Also thanks to Dr C Chanmuang for her kind cooperation while running Raman machine.
- Alavipanah S 2004 Application of remote sensing and spectroscopy in the earth sciences (soil); University of Tehran Press, ISBN, 117p.Google Scholar
- Bahrambeygi B and Moeinzadeh H 2017 Comparison of support vector machine and neutral network classification method in hyperspectral mapping of ophiolite mélanges – A case study of east of Iran; Egypt. J. Remote Sens. Space Sci. 20 1–10.Google Scholar
- Bahrambeygi B, Moeinzadeh H and Alavipanah S K 2019 Mineralogy, geochemistry and Raman Spectroscopy of multi-genesis serpentine polymorphs of Darepahn Ophiolites; J. Sci. I. R. Iran 30 251–269.Google Scholar
- Deer W A, Howie R A and Zussman J 2009 Rock forming minerals: Layered silicates excluding micas and clay minerals; Vol. 3B, Geological Society of London, 314p.Google Scholar
- Griffith W and Lesniak P 1969 Raman studies on species in aqueous solutions; Chem. Soc. Theor. 46 1066–1071.Google Scholar
- Iyer K 2007 Mechanisms of serpentinization and some geochemical effects; University of Oslo, 111p.Google Scholar
- Lazarev Y A 1962 Line Broadening in Rotational and Rotation – Vibrational Raman Spectra of Gases; Opt. Spectrosc. 13 373.Google Scholar
- O’Hanley D S and Wicks F J 1995 Conditions of formation of lizardite, chrysotile and antigorite, Cassiar, British Columbia; Can. Mineral. 33 753–773.Google Scholar
- Pasteris J D and Wopenka B 1987 Use of a laser Raman microprobe to trace geological reactions; Microbeam Analysis – Am. Mineral., 205p. Google Scholar
- Van Genderen J, Lock B and Vass P 1978 Remote sensing: Statistical testing of thematic map accuracy; Remote Sens. Environ. 7 3–14.Google Scholar