| NSF Org: |
OCE Division Of Ocean Sciences |
| Recipient: |
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| Initial Amendment Date: | February 26, 2015 |
| Latest Amendment Date: | February 26, 2015 |
| Award Number: | 1459433 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Deborah K. Smith
OCE Division Of Ocean Sciences GEO Directorate for Geosciences |
| Start Date: | March 1, 2015 |
| End Date: | February 28, 2019 (Estimated) |
| Total Intended Award Amount: | $316,200.00 |
| Total Awarded Amount to Date: | $316,200.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
300 TURNER ST NW BLACKSBURG VA US 24060-3359 (540)231-5281 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
1405 Perry Street Blacksburg VA US 24061-0001 |
| 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): | Marine Geology and Geophysics |
| 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
Few techniques exist where visual observations and compositional measurements can be made of mineral reactions inside natural host minerals in real-time. This research by two investigators at Virginia Tech, one of whom is early career, explores an exciting and potentially transformative new experimental method by which synthetic fluid inclusions, filled with fluids of seawater-like composition, are grown in the laboratory and then held at temperatures and pressures at which important geological mineral reactions occur. In these reactions, secondary minerals precipitate inside the inclusion due to the reaction between the fluid and host mineral. This research targets serpentinization of the ocean crust, which involves the formation of serpentine, a hydrous mineral, and other secondary phases from anhydrous magnesium-rich silicate minerals (olivine, pyroxene,and garnet) that are the primary constituents of seafloor lavas. Serpentinization of ocean crust releases H2O into the mantle which can trigger melting and arc volcanism. It is also linked to the generation of abiotic organic compounds due to the release of hydrogen during mineral reaction. These organic molecules can form the base of the food chain for microbes living in in the ocean crust. Broader impacts of the work include (1) developing new experimental methods and demonstrating their utility, (2) developing the Raman spectroscopic identification of hydrous minerals associated with serpentinization reactions, (3) support of an early career female scientist and a minority graduate student; and (4) creation of podcasts on science in Spanish to inform and excite Hispanic audiences about science and the proposed research.
This experimental program will react fluids in minerals at ~280 degrees C for a number of weeks and monitor the dissolution and precipitation reactions that take place in the fluid inclusions as a function of time, temperature, fluid composition, and host mineral composition using a variety of state-ot-the-art analytical techniques that include: microthermometry, Raman spectroscopy, laser ablation inductively coupled plasma mass spectrometry, micro-FTIR (Fourier Transform Infrared) spectroscopy, and FIB-SEM (focused ion beam scanning electron microscopy). An additional research goal is to develop Raman spectroscopy as a tool for the identification of phases associated with serpentinization, including the identification of chrysotile, lizardite, antigorite, and magnetite, as well as the protolith phases undergoing reaction. Results of the experiments will be compared with predictions from thermodynamic models. Successful development of this experimental technique and demonstation of its applicabilty has the potential to impact other fields of science such as pharmachology and materials science where the ability to observe chemical reactions and their rates of reaction in host crystals in real-time may lead to breakthroughs in understanding.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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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.
The interaction of seawater with rocks in the ocean basins, including at mid-ocean ridge spreading centers and in subduction environments where oceanic lithosphere is subducted back into the deep Earth, is one of the major controls on ocean chemistry and the cycling of water back into the mantle. The dominant process involves the conversion of peridotite minerals olivine and pyroxene into the hydrous phases serpentine and brucite, and also generates the mineral magnetite and hydrogen gas. The serpentinization process also generates a reducing environment in which carbon dioxide may be converted into methane and other hydrocarbons that serve as the basic building blocks of life.
In this project we have conducted experiments in which tiny droplets of aqueous fluid were isolated by healing fractures in olivine at high temperature and pressure. These synthetic fluid inclusion micro-reactors were then held at PT conditions at which the trapped fluid interacted with the olivine host to produce serpentine and related phases. The reaction progress was monitored by measuring the change in fluid salinity with time, as water molecules were removed from the fluid and transferred into the newly-forming hydrous phases during serpentinization. These data were then used to estimate rates of reaction for the serpentinization process. A major and significant finding is that the rate of serpentinization is highly dependent on the activity of H2O in the fluid, and that as water is removed from the fluid and transferred into hydrous phases, the fluid salinity increases and the reaction shuts down. These results suggest that complete serpentinization of oceanic lithosphere requires a dynamic system in which new fractures are continuously being opened to allow low salinity seawater (or meteoric water) to enter the rocks and dilute the salinity of fluid remaining after reactions have progressed. In a closed system the serpentinization process will cease after some small amount of rock has been altered and the fluid salinity has increased.
Last Modified: 09/16/2019
Modified by: Robert J Bodnar
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