- Names
-
- Eric Quirico
- Lydie Bonal
- Gilles Montagnac
- Pierre Beck
- Bruno Reynard
- Title
- Precursor memory and maturation grade of coals, biotic and abiotic kerogens, as invetsgated by UV 244 nm Raman spectroscopy
- Abstract
- We report the characterization by 244 nm Raman spectroscopy of a series of coals, type II kerogens, Insoluble Organic Matter (IOM) extracted from primitive chondrites, and two stratospheric Interplanetary Dust Particles. We show that coals maturity can be rated through the first-order carbon bands, in the maturity range corresponding to a mean maximum vitrinite reflectance Ro > 1%. Several Raman parameters, such as the width of the G-band, the peak position of the D-band and the peak intensity ratio of the G and D-bands display fair linear correlations with vitrinite reflectance. No clear correlation with Raman parameters was observed in the maturity range Ro < 1%, but the data support the presence of an sp2 structural transition at Ro ~ 0.4%. Revisiting earlier published data collected with a 514 nm excitation confirms the existence of this structural transition, through the width and peak position of the G-band. UV Raman spectra also unambiguously distinguish coals and type II kerogens from chondritic IOM. An interesting application of this result is the determination of the biotic versus abiotic origin of kerogens, in the case of ancient terrestrial rocks on Earth, and of soils and rocks on Mars. Additionally, UV Raman data show that refractory carbonaceous matter in two stratospheric IDPs has a higher degree of disorder with respect to primitive chondrites. This supports the view that, more generally, the lower peak position and larger width of the G band in 514 nm spectra of some IDPs with respect to primitive chondrites point to a more disordered carbonaceous matter. Last, the 244 nm excitation provides stringent constraints on the relevancy of laboratory analogs of chondritic organic matter. In particular, materials formed in cold plasma reactors do not meet the structural characteristics of chondritic
- Keywords
- spectroscopy, Raman, data analysis
- Content
- spectral data, planetary sciences
- Year
- 2020
- Journal
- Geochimica et Cosmochimica Acta
- Volume
- 282
- Pages
- 156 - 176
- Document type
- article
- Publication state
- published