Measurements of H₂O content in granitic magma: A review

The H2O content in granular melts has an important influence on the physical-chemical properties of the melts, and thus it controls the crystallinity and emplacement depth of the granular magmas, and the migration and enrichment process of some metal elements. Therefore, it is of great geological significance to quantify the H2O contents in melt inclusions hosted in minerals of granite. At present, the quantification methods of H2O content in granitic magma include indirect estimation and direct measurement. The data accuracy for indirect estimating H2O contents depends on the granitic melt composition and temperature-pressure data of melt inclusions. The H2O contents of melt inclusion from granite could be measured through in-situ analysis techniques including FTIR, EPMA, and SIMS as well. However, these methods involve potential technique problems or limitations, such as the sample preparation being complicated, potential H2O leakage Upon homogenization of melt inclusions, and many other factors affecting the precision of H2O contents. Raman spectrum is characterized by simple samples preparation, in-situ and nondestructive analysis, that can determine H2O contents in melt inclusions. As a result, We propose that the Raman spectroscopy is useful and has a good potential in quantifying the H2O contents in granitic magmas. We can try to explore a new method which based on the Hydrothermal Diamond-anvil Cell+Raman Spectroscopy to in-situ test the H2O contents in granitic magma in the future.