NSF Org:	EAR Division Of Earth Sciences
Recipient:	MASSACHUSETTS INSTITUTE OF TECHNOLOGY
Initial Amendment Date:	November 19, 2009
Latest Amendment Date:	December 19, 2011
Award Number:	0944122
Award Instrument:	Continuing Grant
Program Manager:	Robin Reichlin EAR  Division Of Earth Sciences GEO  Directorate for Geosciences
Start Date:	December 15, 2009
End Date:	March 31, 2013 (Estimated)
Total Intended Award Amount:	$360,280.00
Total Awarded Amount to Date:	$360,280.00
Funds Obligated to Date:	FY 2010 = $153,474.00 FY 2011 = $119,627.00 FY 2012 = $28,713.00
History of Investigator:	Sang-Heon Shim (Principal Investigator) SHDShim@gmail.com
Recipient Sponsored Research Office:	Massachusetts Institute of Technology 77 MASSACHUSETTS AVE CAMBRIDGE MA  US  02139-4301 (617)253-1000
Sponsor Congressional District:	07
Primary Place of Performance:	Massachusetts Institute of Technology 77 MASSACHUSETTS AVE CAMBRIDGE MA  US  02139-4301
Primary Place of Performance Congressional District:	07
Unique Entity Identifier (UEI):	E2NYLCDML6V1
Parent UEI:	E2NYLCDML6V1
NSF Program(s):	Petrology and Geochemistry, Geophysics
Primary Program Source:	01001112DB NSF RESEARCH & RELATED ACTIVIT 01001011DB NSF RESEARCH & RELATED ACTIVIT 01001213DB NSF RESEARCH & RELATED ACTIVIT
Program Reference Code(s):	1031, OTHR, 0000
Program Element Code(s):	157300, 157400
Award Agency Code:	4900
Fund Agency Code:	4900
Assistance Listing Number(s):	47.050

ABSTRACT

The mantle represents 70% of the Earth's volume, and therefore plays a key role in the evolution of the Earth. Since early 20th century, a seismic discontinuity at 660-km depth in the mantle has been believed to be an important filter for material exchange (including water and carbon-dioxide) between the upper and lower mantle. Laboratory measurements have shown that the phase transitions in the dominant mantle minerals explain this 660-km discontinuity. However, there exist multiple phase transitions near this depth and the interactions among these phase transitions are not well understood. Recent high-resolution seismology studies reveal complex structures near the discontinuity and strong lateral variations in the properties of the discontinuity, suggesting interaction between mineral phase transitions occur in the mantle and providing motivation for high-resolution laboratory measurements.

In order to measure the interactions among different phase transitions near the 660-km discontinuity, the investigators will take full advantage of recent developments in (1) the diamond-anvil cell (a high pressure device) technique, which allows fine control of pressure, (2) the laser levitation synthesis technique, which allows the investigators to engineer the compositions of starting materials similar to those expected for mantle rocks, and (3) high-resolution synchrotron X-ray diffraction techniques, which allow detection of the phase transitions unambiguously. The results from this study will help geophysicists to understand the role of the 660-km discontinuity in mantle convection and chemical differentiation. Ths proposed work is timely because huge seismic datasets available from large digital seismic networks, such as USARRAY, are beginning to provide high-resolution images to resolve fine-scale structures near the 660-km discontinuity.

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