
NSF Org: |
EAR Division Of Earth Sciences |
Recipient: |
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Initial Amendment Date: | February 11, 2016 |
Latest Amendment Date: | February 11, 2016 |
Award Number: | 1551054 |
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: | February 15, 2016 |
End Date: | January 31, 2020 (Estimated) |
Total Intended Award Amount: | $332,772.00 |
Total Awarded Amount to Date: | $332,772.00 |
Funds Obligated to Date: |
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History of Investigator: |
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Recipient Sponsored Research Office: |
3227 CHEADLE HALL SANTA BARBARA CA US 93106-0001 (805)893-4188 |
Sponsor Congressional District: |
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Primary Place of Performance: |
CA US 93106-2050 |
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): | |
Program Element Code(s): |
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Award Agency Code: | 4900 |
Fund Agency Code: | 4900 |
Assistance Listing Number(s): | 47.050 |
ABSTRACT
Recycling of Earth's crust back down into the deep Earth has been invoked to explain a wide variety of Earth processes, including changes in the forces that move tectonic plates, and how the thickness and composition of Earth's crust evolved. All of these processes take place at depths inaccessible to humans. A volcanic eruption in the Pamir Mountains of Tajikistan has brought to light pieces of rock from 90 km deep in Earth that can be used to test recycling-related hypotheses. This project will provide training and research opportunities for graduate student Madeline Shaffer and several undergraduate students. Visits to local elementary schools will expose potential future scientists to Earth science. Continued development of the laser-ablation split-stream technique will benefit the broad range of visitors to their laboratory.
This collaborative US-Tajik-Romanian project has a two-pronged approach: 1) Laboratory geochronology and petrology that will constrain the timescale of recycling, and the compositions, densities and wavespeeds of the recycling materials. With some assumptions about protolith composition, the evolution in these physical properties can be calculated. 2) Geodynamic modeling of recycling crustal sections with different compositions and layers in different thermal gradients. The models will yield the calculated evolution of the physical properties of recycling crust and determine the types of crustal sections that may recycle. Because the Pamir-Tibetan Plateau is an archetypal continent-continent collision, ideas developed there can be applied globally.
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.
Volcanic rocks erupted in the Pamir mountains of Tajikistan contain tiny pieces of rock with a unique record of the rate of compression and heating experienced by the lower crust when it sinks into underlying mantle. We wrote a new petrological-thermal-mechanical computer code that tests various tectonic models that might account for the observed record. Most of our simulations fail to account for the observed record. One sequence of tectonic events does match the observed record, suggesting that those events did lead to the sinking of the lower crust: thickening of the Pamir crust from 40 to 20 million years ago, breakoff of the subducting Indian plate beneath the Pamir crust about 20 million years ago, upwelling of hot mantle to replace the missing Indian plate, heating of the lower Pamir crust, densification of the lower crust, sinking of the lower crust, melting of the lower crust and surrounding mantle by 11 million years ago, and eruption of volcanic rocks carrying small pieces of the sinking crust up to Earth's surface. Because the India-Asia collision zone is our archetype for continent collision zones, and because the Pamir has undergone much more rapid internal deformation than Tibet, this process of sinking of the lower crust into the mantle was likely a process central importance in forming the continent-collision zone exposed in the Pamir.
Last Modified: 03/04/2020
Modified by: Bradley R Hacker
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