Spectral-compositional variations in the constituent minerals of mafic and ultramafic assemblages and remote sensing implications

Chemical compositions of the constituent minerals of 13 mafic and ultramafic assemblages containing from one to five mineral components were analyzed with an electron microprobe, and the compositions were correlated with the reflectance spectra of the samples to determine the spectral-compositional relationships of these assemblages. Results indicate that, as more components are added to a mixture, the quality and quantity of compositional information which can be derived from spectral analysis diminishes. It is shown that opaque minerals (such as magnetite for terrestrial occurrences and ilmenite in lunar assemblages) influence reflectance spectra out of proportion to their abundances, reducing overall reflectance and band depths of mafic silicates in small dispersed amounts.