| NSF Org: |
OCE Division Of Ocean Sciences |
| Recipient: |
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| Initial Amendment Date: | March 2, 2022 |
| Latest Amendment Date: | July 25, 2024 |
| Award Number: | 2146911 |
| Award Instrument: | Continuing Grant |
| Program Manager: |
Gail Christeson
gchriste@nsf.gov (703)292-2952 OCE Division Of Ocean Sciences GEO Directorate for Geosciences |
| Start Date: | September 1, 2022 |
| End Date: | August 31, 2026 (Estimated) |
| Total Intended Award Amount: | $472,786.00 |
| Total Awarded Amount to Date: | $287,935.00 |
| Funds Obligated to Date: |
FY 2023 = $72,503.00 FY 2024 = $202,541.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
601 S KNOLES DR RM 220 FLAGSTAFF AZ US 86011 (928)523-0886 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
AZ US 86011-0001 |
| 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: |
01002324DB NSF RESEARCH & RELATED ACTIVIT 01002425DB NSF RESEARCH & RELATED ACTIVIT 01002526DB NSF RESEARCH & RELATED ACTIVIT |
| Program Reference Code(s): | |
| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
The existence of a weak, ductile asthenosphere, the upper layer of Earth?s mantle below the lithosphere, is fundamental for the operation of plate tectonics on Earth since it enables the motion of the overlying mobile lithospheric plates. Since the discovery of plate tectonics more than 50 years ago, the dominant mechanism responsible for this weakening remains unresolved. Debate centers on two competing mechanisms: partial melting and hydration of the mantle. In theory, geophysical imaging of seismic velocity and electrical resistivity could distinguish between these competing mechanisms, but inherent trade-offs and uncertainties associated with inferring physical properties from the field observations result in significant ambiguity. This project will image the seismic and electric structure of the mantle beneath a portion of the Cocos Plate in the eastern equatorial Pacific Ocean, where the presence of asthenospheric melt is confidently known. The new observations will provide an independent calibration for the effect of asthenospheric melt on seismic and electric properties and constrain the regional extent and geometry of the melt. This will in turn enable improved understanding of the source of abundant and anomalous volcanism in the region. The project will support the research activities of four graduate students and several undergraduate students, as well as data sharing and collaboration with partners in the neighboring countries of Nicaragua, El Salvador, and Costa Rica. More than 20 cruise participants will be trained in geophysical data acquisition during two research expeditions, including students, international partners, and community participants.
This project will utilize passive-source seismic and magnetotelluric imaging to quantify the seismic velocity and electrical resistivity structure of the Cocos Plate lithosphere and asthenosphere. A co-located array of ocean-bottom seismic and electromagnetic receivers will be deployed over a 500 km by 500 km section of the Cocos Plate on both sides of the Nicaragua Fracture Zone (NFZ). The seafloor in the survey area shows abundant evidence of past intraplate magmatism, including elevated seafloor bathymetry, numerous seamounts significantly younger than the plate age, and prominent volcanic sills within the sediment column. The presence of a partial melt channel at the lithosphere-asthenosphere boundary is clearly imaged by a previous small-scale magnetotelluric profile. Observations from this study will provide new insights on the dominant controls on asthenosphere rheology and the mechanisms that produce intraplate magmatism by addressing the following key questions: (1) What is the spatial and depth extent of the high-melt region? Does the bathymetry contrast across the NFZ reflect a change in melt content and/or volcanic productivity? (2) What is the seismic signature of the previously inferred melt-rich channel? Are seismic observations consistent with magnetotelluric results and how can they be calibrated to each other? Given this calibration between melt content and velocity, what does it imply for the weakening mechanisms in the asthenosphere globally? (3) Does the mantle fabric change across the NFZ, both within and below the lithosphere? Does the implied flow field suggest a Galápagos plume influence on past seafloor spreading, and/or recent melt productivity beneath the plate?
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.
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