Quantification of Solute Composition in H 2 O-NaCl–CaCl 2 Solutions Using Cryogenic 2D Raman Mapping
Various analytical techniques have been developed to determine the solution composition of fluid inclusions, including destructive, non-destructive, single-inclusion, and bulk-inclusion methods. Cryogenic Raman spectroscopy, as a non-destructive and single-inclusion method, has emerged as a potentia...
| Published in: | Minerals |
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| Main Authors: | , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
MDPI AG
2020
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| Subjects: | |
| Online Access: | https://doi.org/10.3390/min10111043 https://doaj.org/article/9af9d38e554a4c48b0f47fa73b4a1553 |
| Summary: | Various analytical techniques have been developed to determine the solution composition of fluid inclusions, including destructive, non-destructive, single-inclusion, and bulk-inclusion methods. Cryogenic Raman spectroscopy, as a non-destructive and single-inclusion method, has emerged as a potentially powerful tool of quantitative analysis of fluid inclusion composition. A method of point analysis using cryogenic Raman spectroscopy has been previously proposed to quantitatively estimate the solute composition of H 2 O-NaCl-CaCl 2 solutions, but there are uncertainties related to heterogeneity of frozen fluid inclusions and potential bias in the processing of Raman spectra. A new method of quantitative analysis of solute composition of H 2 O-NaCl-CaCl 2 solutions using Raman mapping technology is proposed in this study, which can overcome the problems encountered in the point analysis. It is shown that the NaCl/(NaCl + CaCl 2 ) molar ratio of the solution, X( NaCl, m ), can be related to the area fraction of hydrohalite over hydrohalite plus antarcticite, F hydrohalite , by the equation X( NaCl, m ) = 1.1435 F hydrohalite − 0.0884, where F hydrohalite = hydrohalite area/(hydrohalite area + antarcticite area). This equation suggests that the molar fraction of a salt component may be estimated from the fraction of the Raman peak area of the relevant hydrate. This study has established a new way of estimating solute composition of fluid inclusions using cryogenic Raman mapping technique, which may be extended to other solutions. |
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