资源环境科技发展态势分析平台

Olivine ([Mg,Fe]₂SiO₄) has been remotely detected on numerous Solar System bodies, but its composition has been only partially constrained using visible‐near infrared (VNIR, 0.5‐3 μm) and mid‐infrared (MIR, 8‐15 μm) spectra. Meanwhile, the spectral character of olivine in the “cross‐over” region of the infrared (4‐8 μm) remains generally unexplored. We examine the relationship between olivine Mg# (molar Mg/[Mg+Fe] x 100) and the wavelength‐positions of two strong, discrete overtone‐combination bands at ~5.6 and ~6.0 μm. In reflectance and thermal emission spectra measured for 47 synthetic and natural olivine samples that span the Mg‐Fe solid solution, we find that the 5.6 and 6.0 μm bands shift systematically to longer wavelengths by 0.11 μm and 0.10 μm, respectively, with increasing Fe content. Our results indicate that olivine Mg# may be determined within ±10 mol% forsterite using the positions of these two bands, making “cross‐over” region spectroscopy a potentially powerful remote sensing tool.