Portal de Periódicos da CAPES

Graphite in rocks of the Popigai impact crater: residual or retrograde?

2019; Volume: 28; Issue: 3 Linguagem: Inglês

10.3906/yer-1808-6

1303-619X

Valentin Afanasiev, S. А. Gromilov, В. М. Сонин, Egor Egor, А. А. Чепуров,

Geology and Paleoclimatology Research

The concentration of diamond-bearing tagamite from the Popigai impact crater produces large amounts of graphite in addition to impact diamonds (1:100, respectively). The question arises of whether this is residual graphite not converted to diamond at the time of the Popigai impact or is a retrograde form resulting from back-conversion of impact diamond to graphite in a high-temperature tagamite melt. Experiments show that graphite from tagamite is a residual phase. Coexistence of lonsdaleite, cubic diamond, and single-crystal graphite within a limited volume may be due to different orientations of the graphite base plane relative to the impact stress direction. Thus, the diamond-bearing rocks may contain significant amounts of residual graphite, which is consistent with published evidence.