A new approach to develop the Raman carbonaceous material geothermometer for low-grade metamorphism using peak width
A new approach to develop the Raman carbonaceous material geothermometer for low-grade metamorphism using peak width
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DOI：
10.1111/iar.12057
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发表时间：
2014-03-01
期刊：
影响因子：
1.5
通讯作者：
Wallis, Simon
中科院分区：
文献类型：
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作者：
Kouketsu, Yui;Mizukami, Tomoyuki;Wallis, Simon
采集于日本西南部6个相距较远地区的19个变质沉积样品，其拉曼光谱显示出随变质温度的系统变化，可分为四种类型：低级碳质(C.150-280°C)、中级碳质(C.280-400°C)、高级碳质(C.400-650°C)和结晶良好的石墨(>；约650°C)。低级CM的拉曼光谱表现出典型的无定形碳的特征，在一阶区出现了几个无序带(D带)。在中级CM的拉曼光谱中，可以识别出石墨带(G带)，并且在几个带参数的趋势上发生了突变。观察到的变化表明，CM在280°C左右开始从无定形碳向结晶石墨转变，并持续到400℃。在CM高品位时，G带成为最显著的峰，这表明CM结构接近于结晶良好的石墨。在最高温度为655℃的样品中，CM的拉曼光谱显示出一个很强的G带，但几乎没有可识别的D带，这意味着CM的颗粒是结晶良好的石墨。在低至中级CM的拉曼光谱中，几个谱带参数与已知的变质温度的比较表明，变质温度与D_1和D_2带的半高全宽(FWHM)呈负相关。这些关联式被校准为新的拉曼CM地温计，适用于约150-400°C的范围。本文还讨论了从低到中温范围的拉曼光谱峰分解方法的细节，目的是建立一个坚固耐用和用户友好的地温计。
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 ofc.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.