FTIR data of the article entitled "CO2-induced a small water solubility in orthopyroxene and its implications for water storage in the upper mantle"

The data are the polarized FTIR spectra of the article entitled "CO₂-induced a small water solubility in orthopyroxene and its implications for water storage in the upper mantle". To investigate the water solubility of orthopyroxene as functions of water fugacity, temperature, and pressure, single crystalline orthopyroxene was sintered in coexisting with H₂O-CO₂ fluids in a closed system under high P-T conditions. After quenching the experiments, we measured the polarized FTIR spectra of the recovered samples at ambient conditions.

The water content of orthopyroxene, an anisotropic mineral, can be determined from the polarized spectra of three random (x, y, z) but orthogonal sections of the crystal. The total thickness-normalized integral absorbance (Abs_tot) can be expressed as:

Abs_tot = Abs_x + Abs_y + Abs_z

with

Abs_x = (Abs_max,x + Abs_min,x) / 2 ,                    

Abs_y = (Abs_max,y + Abs_min,y) / 2 ,                  

and

Abs_z = (Abs_max,z + Abs_min,z) / 2 .

The water content (C_w, in ppm) can be determined by the Beer–Lambert law, C_w = Abs_tot / I, where Abs_max and Abs_min represent the maximum and minimum values on each axis, I is the mineral-specific integral molar absorption coefficient (ppm⁻¹·cm⁻²).