To assess the ability of densimetry for CO 2 fluid in CO 2 inclusions, we compare two methods, microthermometry and Raman microspectroscopic densimetry for CO 2. The comparative experiment was performed for nine CO 2 inclusions in three mantle xenoliths. The results are as follows: (1) microthermometry precisely determines CO 2 density with the range of 0.65 to 1.18 g/cm 3 compared with Raman microspectroscopic densimetry; (2) CO 2 density obtained by Raman microspectroscopic densimetry is fairly consistent with that by microthermometry; (3) it is hard to determine CO 2 density in CO 2 inclusion with diameter of less than around 3 μm using microthermometry; and (4) microthermometry can be applied only to the CO 2 inclusion whose CO 2 density ranges from around 0.65 to 1.18 g/cm 3, whereas the Raman microspectroscopic densimetry is applicable to CO 2 density ranging from 0.1 to 1.24 g/cm 3. The above features carry the potential for estimation of depth origin of mantle-derived rocks. The depth where the rocks were trapped by host magma can be estimated using both geothermometric data and CO 2 fluid density in CO 2 inclusions in the rocks. Typical precisions of density of CO 2 in CO 2 inclusions obtained by the Raman microspectroscopic densimetry (∼0.01 g/cm 3) and by the microthermometry (< 0.001 g/cm 3) correspond to uncertainties in the depth origin of 2.4 km and < 1.7 km, respectively, at 1000 ± 50 °C. In case of the mantle under 750-1250 °C and 1 GPa, the CO 2 fluid has a density ranging from 1.06 g/cm 3 to 1.21 g/cm 3, which are well measured by the Raman microspectroscopic densimetry. Combination of both densimetries for CO 2 in mantle minerals elucidates the deep structure of the Earth.
All Science Journal Classification (ASJC) codes
- Materials Science(all)