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Browse MARGINS-related
awards in reverse chronological order after start
date (most recent first):
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Collaborative Research: Melting and Mass Transfer in the Central American
Arc From Pa-231, Th-230, and Ra-226 Systematics
| MARGINS Focus Area |
Subduction Factory |
| NSF Org |
EAR |
| Latest Amendment Date |
May 5, 1999 |
| Award Number |
9814805 |
| Award Instrument |
Standard Grant |
| Program Manager |
Glen S. Mattioli
EAR DIVISION OF EARTH SCIENCES
GEO DIRECTORATE FOR GEOSCIENCES |
| Start Date |
February 1, 1999 |
| Expires |
January 31, 2002 (Estimated) |
| Expected Total Amount |
$158,157 (Estimated) |
| Investigator |
Marc M. Hirschmann
(Principal Investigator current)
R. Lawrence Edwards (Co-Principal Investigator current) |
| Sponsor |
U of Minnesota-Twin Cities
450 University Gateway
Minneapolis, MN 55415 |
| NSF Program |
1573 PETROLOGY AND GEOCHEMISTRY |
| Field Application |
0000099 Other Applications NEC |
| Abstract |
The mechanism and timing of partial melting and melt extraction
in the mantle beneath arcs constitutes one of the key unresolved
questions regarding arc magmatism. This collaboration between researchers
at the Universities of Minnesota and Iowa will use analyses of U-series
nuclides and particularly of 231Pa in young volcanic rocks to better
understand the melting process beneath the Central American arc
and to determine how this process is affected by fluxes of components
from the subducting slab. Preliminary studies show that 231Pa is
strongly fractionated from U in the sub-arc mantle prior to eruption
on a time scale similar to or less than the half life of 231Pa (33
kyr), strongly suggesting that 231Pa is a sensitive indicator of
the timing and mechanism of melting and melt extraction. Measurements
of (231Pa)/(235U) and (230Th)/(238U) activity ratios using thermal
ionization mass spectrometry and (226Ra)/(230Th) ratios using alpha
counting techniques will be made for an along-arc suite of young
volcanic rocks from the southern Central American arc in Costa Rica
and Nicaragua. The southern Central American arc is an ideal location
for studying melting and mass transfer processes using U-series
isotopes because many of the parameters affecting arc volcanism,
such as the composition of the mantle and the mass flux of components
from the subducting slab, vary across the region in a systematic
and well-characterized fashion. The resulting data set will be to
our knowledge the most complete study of U-series isotopes associated
with an arc province, and combined with the trace element and long-lived
isotopic data will yield a unique body of data against which hypotheses
for melting and mass transfer in arcs can be tested. |
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