This study is aimed to determine the Fe content in natural epidote from Varan area (Urumieh-Dokhtar Magmatic Arc, Iran) by using vibrational FTIR and Raman spectroscopy and EPMA analyses. Fe3+ concentration calculated from FTIR spectroscopic data is in the range of 0.96 to 1 apfu. The results are in complete agreement with EPMA data. The comparison between obtained Raman spectra of studied epidote grains and those from the RRUFF database suggest that epidote from Varan area is rich in Fe3+. High Fe3+ content might reflect moderate to high oxygen fugacity during the crystallization of epidote. This short paper demonstrates that the quantification of the Fe content in epidote via FTIR method is as good as EPMA, whereas the utilization of a low-cost Raman spectrometer helps in quickly distinguishing between Fe-rich and Fe-poor epidote, which even could be useful in the case of field studies.Key-words: Epidote, FTIR, Raman spectroscopy, Iron content, Urumieh-Dokhtar Magmatic Arc, Iran. پرونده مقاله

Mineralogical studies play a key role in deciphering mineral’s formation and associated geochemical processes in geosciences. This paper presents the application of Raman spectroscopy to the characterization of actinolite in rock samples. The studied actinolite was formed as the pseudomorph of primary pyroxene in gabbrodiorite intrusive rock sample collected from Varan area, Urumieh-Dokhtar Magmatic Arc of Iran. The Raman spectra of micrometer-sized actinolite grains embedded in a crude rock sample are compared with the corresponding literature data for actinolite and tremolite in range of 200-1200 cm-1 and 3600-3700 cm-1 region. The results show that the quantitative estimation of Mg# = Mg/(Mg+Fe2+) can be obtained from the fractional intensities of the OH-stretching bands by applying Raman spectroscopy to micrometer-sized actinolite grains in a crude rough rock sample, which is in good agreement with the results from EMPA. The Raman spectroscopy is a fast method and low-cost for quantitative estimation of Mg# in actinolite. پرونده مقاله