Nanodiamond Formation at the Lithogenesis and Low-Stages of Regional Metamorphism

Resumo

Samples of gilsonite from Adzharia, anthraxolite and graphite of coal from Taimyr, shungite from Karelia, and anthracite from Donbass are studied using Raman spectroscopy. Peaks at 1600 cm⁻¹, indicating the presence of nanographite, are recorded in all samples. The anthracite sample from Donbass, 1330 cm⁻¹, corresponds to the sp³-line of carbon hybridization conforming to a nanodiamond. It is concluded that in nature diamonds can be formed at late stages of lithogenesis (catagensis, metagenesis), and for coals, it can occur at the zeolite stage of regional metamorphism of rocks, before the green schist stage.