Application of Raman spectroscopy to the study of graphitic carbons in the Earth Sciences

摘要

Graphitic (sp~2-bonded) carbons are widespread on Earth and throughout the Universe. They have a complex structural organization ranging from amorphous and turbostratic phases to perfectly crystallized graphite. Raman spectroscopy is used extensively to characterize graphitic carbon in the Earth Sciences. In this chapter, we first review the theoretical knowledge of the Raman spectrum of graphitic carbons with an emphasis on the defect-activated peaks. These peaks have unique specificities that are described and explained in terms of the double-resonance theory. More practically, we discuss in detail all the peaks, their attributions and spectral properties. A methodology section is dedicated to the review of all possible analytical artifacts when characterizing graphitic carbons by Raman spectroscopy. A reference protocol is proposed for proper analysis. The last section reviews the application of Raman spectroscopy in the study of graphitic carbons in the Earth Sciences along the following theme: graphitization during meta-morphism, fluid-rock interactions, fossils and traces of life in the geological record, cosmochemistry and Earth-surface processes.