Geology applications of Fourier transform infrared spectroscopy

Fourier transform infrared spectroscopy (FTIR) is a spectroscopic technique that has been used for analyzing the fundamental molecular structure of geological samples in recent decades. As in other infrared spectroscopy, the molecules in the sample are excited to a higher energy state due to the absorption of infrared (IR) radiation emitted from the IR source in the instrument, which results in vibrations of molecular bonds. The intrinsic physicochemical property of each particular molecule determines its corresponding IR absorbance peak, and therefore can provide characteristic fingerprints of functional groups (e.g. C-H, O-H, C=O, etc.).

In geosciences research, FTIR is applied extensively in the following applications:

• Analysing the trace amount of water content in Nominally anhydrous minerals (NAMs)
• Measuring volatile inclusions in glass and minerals
• Estimating the explosion potential in volcanic setting.
• Analysing chemotaxonomy of early life on earth
• Linking biological affinities of both microfossils and macrofossils

These applications are discussed in details in the later sections. Most of the geology applications of FTIR focus on the mid-infrared range, which is approximately 4000 to 400 cm⁻¹.