Quantifying temperature for advanced diagenesis to low-grade metamorphism is critical to understand the formation and evolution of sedimentary basins and fold-and-thrust belts, or more generally, to understand the thermal evolution of the shallow part of the terrestrial crust. Numerous tools exist from thermochronology to isotopic (C, O) thermometry or thermo-chemistry of phyllosilicates. Each of these methods has specific contingences in terms of temperature range, mineralogy or methodological applicability. Among these methods, some largely used in the petroleum industry are based on the evolution of carbonaceous material (CM) with temperature and provides a maturity index or, even, quantitative thermal constraints (vitrinite reflectance, Rock Eval). Here, the potentiality of Raman spectroscopy for characterizing quantitatively the structural and chemical evolution of CM in the range 200-350°C is investigated. A set of samples from various geological settings has been selected to discuss the respective roles of temperature, geothermal gradient, lithology or organic precursor. The evolution of the Raman spectra in this temperature range is systematically described and quantitative parameters extracted after appropriate fitting are compared to the temperature history of the rocks. Altogether, the Raman spectroscopy of CM (RSCM) may provide a new, efficient, reliable and simple geothermometer for quantifying the peak metamorphic temperature of sediments in the range 200-350°C. Some potential application of this new geothermometer will be discussed.
Discipline Categories: Petrology, Metamorphic, Geochemistry, Geochemistry, OrganicPreferred Presentation Type: Either Oral or Poster