Raman spectroscopic measurements of CO₂ density: Experimental calibration with high-pressure optical cell (HPOC) and fused silica capillary capsule (FSCC) with application to fluid inclusion observations

详细信息    查看全文

• 作者：Xiaolin Wang^a ; ^{xl.wang.geo@gmail.com"" rel=""nofollow} ; I.-Ming Chou^b ; Wenxuan Hu^a ; Robert C. Burruss^c ; Qiang Sun^d ; Yucai Song^e
• 刊名：Geochimica et Cosmochimica Acta
• 出版年：2011
• 出版时间：15 July 2011
• 年：2011
• 卷：75
• 期：14
• 页码：4080-4093
• 全文大小：1093 K

文摘

Raman spectroscopy is a powerful method for the determination of CO₂ densities in fluid inclusions, especially for those with small size and/or low fluid density. The relationship between CO₂ Fermi diad split (Δ, cm⁻¹) and CO₂ density (ρ, g/cm³) has been documented by several previous studies. However, significant discrepancies exist among these studies mainly because of inconsistent calibration procedures and lack of measurements for CO₂ fluids having densities between 0.21 and 0.75 g/cm³, where liquid and vapor phases coexist near room temperature.

In this study, a high-pressure optical cell and fused silica capillary capsules were used to prepare pure CO₂ samples with densities between 0.0472 and 1.0060 g/cm³. The measured CO₂ Fermi diad splits were calibrated with two well established Raman bands of benzonitrile at 1192.6 and 1598.9 cm⁻¹. The relationship between the CO₂ Fermi diad split and density can be represented by: ρ = 47513.64243 − 1374.824414 × Δ + 13.25586152 × Δ² − 0.04258891551 × Δ³ (r² = 0.99835, σ = 0.0253 g/cm³), and this relationship was tested by synthetic fluid inclusions and natural CO₂-rich fluid inclusions. The effects of temperature and the presence of H₂O and CH₄ on this relationship were also examined.