A new approach to develop the Raman carbonaceous material geothermometer for low-grade metamorphism using peak width

Yui Kouketsu, Tomoyuki Mizukami, Hiroshi Mori, Shunsuke Endo, Mutsuki Aoya, Hidetoshi Hara, Daisuke Nakamura, Simon Wallis

Research output: Contribution to journalArticle

121 Citations (Scopus)

Abstract

The Raman spectra of carbonaceous material (CM) from 19 metasediment samples collected from six widely separated areas of Southwest Japan and metamorphosed at temperatures from 165 to 655°C show systematic changes with metamorphic temperature that can be classified into four types: low-grade CM (c. 150-280°C), medium-grade CM (c. 280-400°C), high-grade CM (c. 400-650°C), and well-crystallized graphite (>c. 650°C). The Raman spectra of low-grade CM exhibit features typical of amorphous carbon, in which several disordered bands (D-band) appear in the first-order region. In the Raman spectra of medium-grade CM, the graphite band (G-band) can be recognized and several abrupt changes occur in the trends for several band parameters. The observed changes indicate that CM starts to transform from amorphous carbon to crystallized graphite at around 280°C, and this transformation continues until 400°C. The G-band becomes the most prominent peak at high-grade CM suggesting that the CM structure is close to that of well-crystallized graphite. In the highest temperature sample of 655°C, the Raman spectra of CM show a strong G-band with almost no recognizable D-band, implying the CM grain is well-crystallized graphite. In the Raman spectra of low- to medium-grade CM, comparisons of several band parameters with the known metamorphic temperature show inverse correlations between metamorphic temperature and the full width at half maximum (FWHM) of the D1- and D2-bands. These correlations are calibrated as new Raman CM geothermometers, applicable in the range of c.150-400°C. Details of the methodology for peak decomposition of Raman spectra from the low to medium temperature range are also discussed with the aim of establishing a robust and user-friendly geothermometer.

Original languageEnglish
Pages (from-to)33-50
Number of pages18
JournalIsland Arc
Volume23
Issue number1
DOIs
Publication statusPublished - Jan 1 2014

Keywords

  • Carbonaceous material
  • FWHM
  • Geothermometer
  • Low temperature metamorphism
  • Raman spectroscopy

ASJC Scopus subject areas

  • Geology

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