2016 Fiscal Year Annual Research Report
Creating glass standards for SIMS analysis of H2O and CO2 in rhyolite glass
Project/Area Number |
16H07491
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Research Institution | Japan Agency for Marine-Earth Science and Technology |
Principal Investigator |
McIntosh Iona 国立研究開発法人海洋研究開発機構, 地球内部物質循環研究分野, ポストドクトラル研究員 (70780899)
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Project Period (FY) |
2016-08-26 – 2018-03-31
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Keywords | glass / standards / SIMS / water / carbon dioxide / rhyolite / volcanology |
Outline of Annual Research Achievements |
The necessary materials have been acquired to conduct the high pressure, high temperature synthesis of water-rich and carbon-dioxide-rich glasses in the coming financial year. A preliminary test SIMS analysis of existing rhyolite glasses with independently known volatile contents revealed important issues to consider in future work. First, the best method for preparing sample surfaces for SIMS analysis was determined. Second, comparison of SIMS and FTIR data for the same glasses show increasing offset with the amount of water and, particularly, the amount of molecular water in the glass. Experimental conditions for future glass synthesis will be chosen to investigate this apparent trend, and to test the importance of water speciation of glass standards for SIMS calibration.
Concurrently, work continued using FTIR analysis to examine so-called 'silicate peaks' in transmission spectra and to evaluate how they vary with glass composition. A manuscript draft is being prepared on the use of the 1830 cm-1 silicate peak to find glass thickness and the potential for the ~1600 cm-1 silicate peak to interfere with the 1630 cm-1 H2Om peak, with implications for accuracy of H2O measurement by FTIR in the mid-IR range.
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Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
The somewhat-unexpected finding during the preliminary SIMS analysis of an apparent speciation-controlled mismatch between SIMS and FTIR data led to a slight delay as different possibilities for the offset were tested and ruled out. The outcome is a refined set of experimental conditions for the glass synthesis work, and the deferment of planned fieldwork to collect natural samples to FY2017.
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Strategy for Future Research Activity |
Synthesis of high pressure and temperature rhyolitic glasses with a wide range of H2O speciation and CO2 contents will take place early in FY2017. Glasses will then be prepared for FTIR analysis to constrain volatile contents and 'silicate peaks' and then prepared for SIMS analysis and calibration testing. Findings will be presented at the American Geophysical Union Fall Meeting in December.
Fieldwork in New Zealand is planned for winter 2017 (southern hemisphere summer) to sample rhyolitic and high-alkali rhyolitic glasses. These will add to the range of glass standards with low volatile contents and test the impact of alkali concentration on the choice of standards for SIMS. It is also expected that some of these natural glasses will have experienced varying amounts of secondary hydration. Natural glasses that are found to have homogeneous volatile concentrations will be used as standards; these standards will then be used to calibrate analyses of glasses found to have varying volatile concentrations in order to investigate magmatic degassing, emplacement and subsequent hydration processes.
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