CO_2 Density-Raman Shift Relation Derived from Synthetic Inclusions in Fused Silica Capillaries and Its Application

• Published in: 地质学报（英文版） Vol. 83; no. 5; pp. 932 - 938
• Main Authors: SONG Yucai, CHOU I'Ming, HU Wenxuan, Burruss ROBERT, LU Wanjun
• Format: Journal Article
• Language: English
• Published: Department of Earth Sciences, Nanjing University, Nanfing 210093, China%US Geological Survey, National Center, Reston, VA 20192, USA%Department of Earth Sciences, Nanjing University, Nanfing 210093, China%State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences,Wuhan 430074, China 2009; Institute of Geology, China Academy of Geological Sciences, Beifing 100037, China
• Subjects: synthetic fluid inclusion; CO_2 inclusion; Raman analysis; fused silica capillary; CO_2 density equation
• ISSN: 1000-9515; 1755-6724
• DOI: 10.3321/j.issn:1000-9515.2009.05.011

P5; The densities of CO_2 inclusions in minerals are commonly used to determine the crystallizing conditions of the host minerals. However, conventional microthermometry is difficult to apply for inclusions of small size (< 5-10 μm) or low density. Raman analysis is an alternative method for determining CO_2 density, provided that the CO_2 density-Raman shift relation is known. This study aims to establish this CO_2 deusity-Raman shift relation by using CO_2 inclusions synthesized in fused silica capillaries. By using this newly-developed synthetic technique, we formed pure CO_2 inclusions, and their densities were determined by microthermometry. The Raman analysis showed that the relation between CO_2 density (D in g/cm~3) and the separations (△ in cm~(-1)) between the two main bands (i.e. Fermi diad bands) in CO_2 Raman spectra can be represented by a cubic equation: D (g/cm~3)=0.74203(-0.019△~3+5.90332△~2-610.79472△+21050.30165)-3.54278 (r~2=0.99920). Our calculated D value for a given △ is between those obtained from two previously-reported equations, which were derived from different experimental methods. An example was given in this study to demonstrate that the densities of natural CO_2 inclusions that could not be derived from microthermometry could be determined by using our method.