Award Abstract # 1551054
Collaborative Research: Characterizing and Modeling Crustal Recycling

NSF Org: EAR
Division Of Earth Sciences
Recipient: UNIVERSITY OF CALIFORNIA, SANTA BARBARA
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: FY 2016 = $332,772.00
History of Investigator:
  • Bradley Hacker (Principal Investigator)
    hacker@geol.ucsb.edu
  • John Cottle (Co-Principal Investigator)
Recipient Sponsored Research Office: University of California-Santa Barbara
3227 CHEADLE HALL
SANTA BARBARA
CA  US  93106-0001
(805)893-4188
Sponsor Congressional District: 24
Primary Place of Performance: University of California-Santa Barbara
CA  US  93106-2050
Primary Place of Performance
Congressional District:
24
Unique Entity Identifier (UEI): G9QBQDH39DF4
Parent UEI:
NSF Program(s): Petrology and Geochemistry
Primary Program Source: 01001617DB NSF RESEARCH & RELATED ACTIVIT
Program Reference Code(s):
Program Element Code(s): 157300
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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Searle, MP, Hacker, B.R. "Structural and Metamorphic Evolution of the Karakoram and Pamir following India-Kohistan-Asia collision" Geological Society of London Special Publication , v.483 , 2018 doi.org/10.1144/SP483.6
Shaffer, M.E.F., Hacker, B R., Ratschbacher, L, Kylander-Clark, A.R.C "Foundering triggered by the collision of India and Asia captured in xenoliths" Tectonics , 2017 10.1002/2017TC004704
Shaffer, M.E.F., Hacker, B.R., Ratschbacher, L, Kylander-Clark, A.R.C "Foundering triggered by the collision of India and Asia captured in xenoliths" Tectonics , 2017 10.1002/2017TC004704

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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