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Raman spectroscopic characterization of Phyllosilicates

Preparatory to identifying and characterize phyllosilicates on Mars, a Raman spectral database of phyllosilicates is under development in our laboratory. Phyllosilicates have complex structures and highly variable compositions. Although standard Raman spectra of major types will be included in the database, it is not possible to cover the entire range of compositions, especially those varieties from different types of alterations. Our approach is to:
(1) obtain high quality spectral data by using a state-of-the-art laboratory Raman spectrometer on pure mineral specimens previously characterized by other mineralogical techniques, and to match them with published data;
(2) look for systematics of spectral patterns for all major types of phyllosilicates through empirical observation of the spectral data, so these patterns can be used to classify the phyllosilicates encountered in rock measurements;
(3) develop an understanding of the structural and compositional causes for the major features (and differences) of these spectral patterns, and use this understanding to develop a rationale for identifying phyllosilicates not included in the current database.

 

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phyllo_2.jpg (562401 bytes) phyllo_3.jpg (337507 bytes)
typical di-octahedral phyllosilicates typical tri-octahedral phyllosilicates Spectral variation trend as Fe content change

Reference: Wang A, Freeman J., Kuebler K. E., Raman Spectroscopic Characterization of Phyllosilicates, Abstract #1374, 33th LPSc, 2002.

 

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