Abstract
Visible to near-infrared (VIS/NIR) reflectance spectra of natural pyroxenes have been measured since the Apollo projects. In general, several transition metals (Fe, Mn, Ti etc) are contained in natural samples, and these elements yield complex spectra because of the combination of absorption features from each transition-metal element. It is difficult to quantify the effects of these elements on the spectral reflectance of natural pyroxenes. For arguments of systematic spectral variations without effects of transition metals except iron, it would be useful to measure the reflectance spectra of synthesized pyroxenes. In this work, we measured the VIS/NIR reflectance spectra of pyroxenes synthesized in the MgO-FeO-CaO-SiO2 system, and compared the results with those of natural pyroxenes, in order to establish the new systematic compositional model. The all spectra show two absorption bands near 1 and 2um. We found the relations between the absorption wavelength and Fe#(=FeO/(MgO+FeO+CaO)) or Ca#(=CaO/(MgO+FeO+CaO)) and compared the results with those of natural pyroxenes (Cloutis & Gaffey (1991) and Schade et al. (2004)).
