Award Abstract # 0620160
SGER: Chlorine Isotopes as Tracers of Subduction Zone Fluids

NSF Org: EAR
Division Of Earth Sciences
Recipient: UNIVERSITY OF NEW MEXICO
Initial Amendment Date: April 19, 2006
Latest Amendment Date: April 19, 2006
Award Number: 0620160
Award Instrument: Standard Grant
Program Manager: William P. Leeman
EAR
 Division Of Earth Sciences
GEO
 Directorate for Geosciences
Start Date: June 1, 2006
End Date: May 31, 2008 (Estimated)
Total Intended Award Amount: $82,163.00
Total Awarded Amount to Date: $82,163.00
Funds Obligated to Date: FY 2006 = $82,163.00
History of Investigator:
  • Zachary Sharp (Principal Investigator)
    zsharp@unm.edu
  • Tobias Fischer (Co-Principal Investigator)
Recipient Sponsored Research Office: University of New Mexico
1 UNIVERSITY OF NEW MEXICO
ALBUQUERQUE
NM  US  87131-0001
(505)277-4186
Sponsor Congressional District: 01
Primary Place of Performance: University of New Mexico
1 UNIVERSITY OF NEW MEXICO
ALBUQUERQUE
NM  US  87131-0001
Primary Place of Performance
Congressional District:
01
Unique Entity Identifier (UEI): F6XLTRUQJEN4
Parent UEI:
NSF Program(s): Marine Geology and Geophysics,
Petrology and Geochemistry,
International Research Collab
Primary Program Source: app-0106 
Program Reference Code(s): 9237, OTHR, 5977, 5926, 0000
Program Element Code(s): 162000, 157300, 729800
Award Agency Code: 4900
Fund Agency Code: 4900
Assistance Listing Number(s): 47.050

ABSTRACT

Intellectual merit. A proof-of-concept study is proposed to evaluate stable chlorine isotope abundances as a novel geochemical tracer of fluids derived in subduction zones. The PI has developed a robust analytical method for determination of delta37Cl values of different potential reservoirs - including sediments, pore waters, and serpentinites - all of which have distinct isotopic compositions. It is proposed that the Cl isotopic composition of fluids involved in arc magmatism should be faithfully recorded in either in volcanic gases (e.g., fumaroles) or glasses and ash. Contamination by surficial waters would have the effect of driving samples toward a near-zero delta37Cl value. The fact that preliminary data on fumarolic gases cover a range in excess of 10 permil demonstrates that this effect is minimal. Cl isotope systematics will be determined for already well characterized fumarolic gases, volcanic glasses and volcanic ash samples from the Central American volcanic arc, which is one of the MARGINS focal sites. All samples are in hand, the technique has been perfected and the postdoctoral student for whom funds are requested is an expert in the field of chlorine isotope geochemistry, thus almost no developmental time is required to carry out this pilot study. In addition, numerous tectonic forcing functions vary over the arc length - allowing relations to geochemical parameters to be evaluated. This study aims to determine whether or not there is sufficient variation in Cl isotopic composition in arcs to serve as a useful petrogenetic tool.

Broader impacts. This work will test the utility of using Cl isotopes for tracing fluids in subduction zone settings. It will take advantage of the well classified Central American arc, where samples are already in hand, and can be compared directly with other existing geochemical data (e.g., N and C isotopic composition, He/Ar). If successful, it should have wide applicability to other arc systems. The work will form the basis for a postdoctoral fellowship for J. Barnes, allowing her to expand her geochemical expertise into active volcanism/tectonism. In addition, an undergraduate student will undertake a subset of this work for an honors thesis and a minority high school student will be employed for the summer.

PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH

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Bao, H., Barnes, J.D., Sharp, Z.D., Marchant, D.R. "Two chloride sources in soils of the McMurdo Dry Valleys, Antarctica" J. Geophys. Res , 2008 10.1029/2007JD008703
Z. D. Sharp, J. D. Barnes, A. J. Brearley, M. Chaussidon, T. P. Fischer & V. S. Kamenetsky "Chlorine isotope homogeneity of the mantle, crustand carbonaceous chondrites" Nature , v.446 , 2007 , p.1062

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