Evolution of the Raman spectrum of carbonaceous material in low-grade metasediments of the Glarus Alps (Switzerland)

Abstract

Terra Nova, 22, 354–360, 2010 Abstract The Raman spectrum of carbonaceous material (CM) from advanced diagenesis (∼200 °C) to low‐grade metamorphism (∼320 °C) is documented in the Helvetic flysch of the Glarus Alps (Switzerland). The spectrum is complex, with several defect bands at ∼1200 (D4), ∼1350 (D1), ∼1500 (D3) and ∼1620 (D2) cm−1. We document the evolution of these bands relative to the ‘graphite’ G band with increasing metamorphic grade, and we show that this qualitative evolution may be used as a proxy for temperature in the Glarus Alps. We develop a robust peak‐fitting method and propose quantitative parameters that may be used as proxies for thermal metamorphism in this region. Further work in other geological contexts is needed to assess whether the spectral evolution observed in the Glarus Alps may be generalized and to critically assess the potential for calibrating a general, empirical and quantitative thermometer based on the Raman spectrum of CM in low‐grade rocks.

Multiple Generations of Carbon in the Apex Chert and Implications for Preservation of Microfossils

“…Furthermore, Marshall et al (2001Marshall et al ( , 2007, and Lahfid et al (2010) demonstrated that Raman spectra acquired from CM thermally altered from 230°C to 300°C shows that the relative intensity of the D band progressively increases. Between temperatures of 300-350°C, the D band intensity is higher than the G band intensity (Marshall et al, 2001(Marshall et al, , 2007Lahfid et al, 2010). Additionally, there are several indicators that the CM in phase E1 must have been deposited before the less thermally mature CM in phase E3.…”

Assessment of Thermal Maturity Trends in Devonian–Mississippian Source Rocks Using Raman Spectroscopy: Limitations of Peak-Fitting Method

“…The two-peak fit led to four correlations with R 2 ≥ 0.79 with VRo, and five correlations with R 2 ≥ 0.90, even though this fitting strategy did not portray every vibrational mode. The literature reflects this conundrum, as peak-fitting protocols utilizing 2 to 10 peaks have been published (Quirico et al, 2005;Guedes et al, 2010Guedes et al, , 2012Lahfid et al, 2010;Hinrichs et al, 2014;Lünsdorf et al, 2014;Wilkins et al, 2014;Li et al, 2015;Lünsdorf, 2016;Schito , 2017). While more peaks can lead to reduced χ 2 values, how many peaks accurately represent the sample?…”

Thermal structure of the Kebara Formation and its proximal areas in the western Kii Peninsula, SW Japan: Application of the carbonaceous material Raman geothermometry

“…Recent progress on the Raman microscopy utilizes carbonaceous material (CM) as a convenient in situ temperature indicator (e.g., Beyssac et al, 2002). A variety of geologic situations become available for the application of Raman spectra of carbonaceous material (RSCM) geothermometer: regional metamorphism (Beyssac et al, 2002), contact metamorphism (Aoya et al, 2010), lowgrade metamorphism down to the zeolite-facies (Rahl et al, 2005;Lahfid et al, 2010;Kouketsu et al, 2014), and even for the extraterrestrial materials whose peak metamorphic temperature is below 100°C (Homma et al, 2015). Notably, the RSCM geothermometer is applicable for low-temperature conditions (approximately <400°C) where conventional thermodynamic approaches have difficulties due to the slow rate of metamorphic reactions (i.e., chemical equilibrium is not always attained: Cho and Liou, 1987).…”