VNIR spectra and statistical analysis of Fa₅₀ olivine under different shock pressures. (a) Average VNIR spectra of olivine under different shock pressures. (b) Normalized VNIR spectra at 700 nm with continuum removal across different shock pressures. Note that, at 31 GPa, two distinct regions, greenish white (powdered) and black (melted), were observed with the naked eye (Fig. A.1d). The spectra shown in blue represent the average of these two regions, while the insets in (a) and (b) display the VNIR spectra of these two regions separately, along with their averaged spectrum. (c) Point-line plot illustrating variations in absolute reflectance values, absorption depths, and spectral slopes of average olivine spectra under different shock pressures. Absolute reflectance and absorption depth correspond to the left y-axis, while spectral slope corresponds to the right y-axis. The band depth is defined as the minimum reflectance value at the absorption center near 1055 nm, determined from the continuum-removed reflectance curves. The slope is defined as the ratio of absolute reflectance at 1650 nm to that at 700 nm, calculated from reflectance spectra normalized at 700 nm. The dashed lines represent trend lines fitted using quadratic or cubic functions. The VNIR reflectance values and band depth of the shocked samples generally increased at lower shock pressure (18 GPa) but decreased at higher shock pressures. Additionally, the shocked olivine samples exhibited a blue shift at lower shock pressure (18 GPa), but a red shift at higher shock pressures.