| NSF Org: |
EAR Division Of Earth Sciences |
| Recipient: |
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| Initial Amendment Date: | February 1, 2019 |
| Latest Amendment Date: | December 4, 2020 |
| Award Number: | 1906305 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Jennifer Wade
jwade@nsf.gov (703)292-4739 EAR Division Of Earth Sciences GEO Directorate for Geosciences |
| Start Date: | May 1, 2019 |
| End Date: | December 31, 2021 (Estimated) |
| Total Intended Award Amount: | $60,001.00 |
| Total Awarded Amount to Date: | $60,001.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
5801 S ELLIS AVE CHICAGO IL US 60637-5418 (773)702-8669 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
5734 S. Ellis Avenue Chicago IL US 60637-2612 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | Petrology and Geochemistry |
| Primary Program Source: |
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| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
Volcanic activities release elements from magma at depth into shallow underground fluids which seep as hot springs. Helium is an element highly enriched in magma, thus it can be easily detected as magmatic isotope signal in the hot spring water. The magmatic helium signal appears to respond to eruption cycles at some volcanos, but the association between its variation and observed volcanic activities is often indecisive, making it difficult to use as an eruption forecasting tool. In those studies, the temporal variations of the volcanic signals from hot springs were compared with the volcanic activities of time that the samples were collected. However, the volcanic signal may travel for substantial time period underground before seeping from the springs so that the volcanic signature we detect could reflect the magmatic activity of tens of years ago. In order to evaluate the time scale of the possible delay, the proposed project will determine the travel time of the shallow subsurface fluids that carry the magmatic helium signals using radioisotopes of Kr and Ar.
Ontake and Unzen volcanos, Japan, were selected as candidate sites because of their relatively recent volcanic activities and abundant helium monitoring records. Radioisotopes of Kr and Ar will be analyzed by Atom Trap Trace Analysis (ATTA) at Argonne National Laboratory and by low level decay counting at University of Bern. The chronological information will be used for re-interpreting the relationship between local geotectonic activities and He isotope records as well as for assessing the possibility of recovering 'fossil' magmatic signatures. This is the first application of these novel tools to a volcanic aquifer system. This work will provide fundamental knowledge to evaluate the feasibility of forecasting volcanic eruptions using geochemical tracers including helium. Two students will be trained in the international fieldwork and laboratory work.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Since the 1960s, it has been known that meteoric water circulates in geothermal systems. However, the exact time scale of this process has not been well determined. A complicating factor is that the circulating fluid often comes into contact with shallow, young meteoric water flowing underground as groundwater before samples can be collected. Some geothermal fluids have been found to contain tritium, an indicator of young groundwater contribution from the nuclear bomb test period. However, it has remained unclear whether this tritium represents a small fraction of young meteoric water mixed with old meteoric water. Additionally, there have been reports of deep subduction and recycling of meteoric-related elements through volcanoes. To address the time scales of meteoric water circulation in geothermal systems, we conducted a study at Ontake volcano in Japan using radioactive tools such as tritium, krypton-85 and krypton-81, which have different time sensitivities. By measuring the tracers of young meteoric water, we can estimate the age and mixing fraction of the young water. The results showed that the circulating time scale of meteoric water in geothermal systems is significantly longer than the lifetime of these tracers, which is on the order of 50 years. Furthermore, the presence of krypton-81 at levels similar to modern atmospheric abundance suggests that there is minimal contribution from the deep subduction and recycling of meteoric-related elements via the volcano.
Last Modified: 05/31/2023
Modified by: Reika Yokochi
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