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Earth Institute Research Projects

Collaborative Research: Plutons as Ingredients for Continental Crust: Pilot Study of the Differences between intermediate plutons and lavas in the intra-oceanic Aleutian arc

Lead PI: Prof. Peter B. Kelemen , Dr. Steven Lloyd Goldstein , Sidney Rasbury Hemming

Unit Affiliation: Geochemistry, Lamont-Doherty Earth Observatory (LDEO)

February 2012 - July 2014
Inactive
Pacific Ocean ; Aleutian Islands
Project Type: Research

DESCRIPTION: Felsic plutonic rocks formed in arcs are buoyant with respect to mantle peridotite over the entire range of relevant pressures and temperatures. They tend to remain at the Earth?s surface, to form the fundamental building blocks of continental crust. In the Aleutians, most felsic plutonic rocks have compositions that overlap estimates for the bulk composition of the continental crust, and that are distinctly different from spatially associated lavas. Understanding the genesis of Aleutian felsic plutonic rocks is a key to understanding continental genesis and evolution via arc magmatism, a key science goal for the MARGINS and GeoPRISMS Initiatives. The PIs will address the following questions: (1) Do Aleutian plutonic rocks have an isotopically distinct source composition, compared to nearby lavas? If they do, this is vitally important since it is commonly assumed that erupted basalts are representative of the magmatic flux from the mantle into arc crust. If not, we will evaluate how they can be explained as the result of different differentiation processes operating on the same parental melt. (2) Has there been compositional variation in the Aleutian arc over time? Do differences between plutonic and volcanic rocks represent temporal evolution of the arc, or different modes of magma transport and emplacement for different magma compositions? And (3) are high viscosity felsic magmas preferentially emplaced in plutons, while low viscosity, mafic magmas preferentially form lavas? What biases does this introduce, when lavas are presumed to be representative of arc magmatic processes and compositions?

SPONSOR:

National Science Foundation (NSF)

FUNDED AMOUNT:

$99,105

EXTERNAL COLLABORATORS:

University of California Santa Barbara

WEBSITE:

https://www.nsf.gov/awardsearch/showAward?AWD_ID=1144759&HistoricalAwards=false

PUBLICATIONS:

Peter Kelemen; Mark D. Behn; Oliver Jagoutz. "Rethinking Recycling in Arcs," presented at 2012 Fall Meeting, AGU, San Francisco, Calif., 3-7 Dec., v.AGU abs, 2012, p. V31E-04.

Thomas W. Sisson; Peter B. Kelemen; Jorge A. Vazquez. "Near-solidus rhyolitic melts of MORB+4 wt% H2O from base-of- crust through shallow subducted slab pressures," presented at 2012 Fall Meeting, AGU, San Francisco, Calif., 3-7 Dec., v.AGU abs, 2012, p. V21D-08 (.

PETER B. KELEMEN, BRADLEY R. HACKER, MARK D. BEHN AND OLIVER E. JAGOUTZ. "Ongoing Formation of Continental Crust: Batholiths Are Forever," Goldschmidt Conference abstracts (invited), Mineralogical Magazine, v.76(6), 2012, p. 1926.

Shillington, D.J., H.J.A. Van Avendonk, M.D. Behn, P.B. Kelemen, and O. Jagoutz. "Constraints on the composition of the Aleutian arc lower crust from Vp/Vs," Geophys. Res. Lett., 2013, p. 2579. doi:10.1002/grl.50375

Marc Spiegelman; Cian R. Wilson; Peter van Keken; Peter B. Kelemen; Bradley R. Hacker. "Hot 'nough for ya?: Controls and Constraints on modeling flux melting in subduction zones," presented at 2012 Fall Meeting, AGU, San Francisco, Calif., 3-7 Dec., v.AGU abs, 2012, p. V21C-02 (.

Gordon, S.M., P. Luffi, B. Hacker, J. Valley, M. Spicuzza, R. Kozdon, P. Kelemen, L. Ratshbacher and D.V. Minaev. "The thermal structure of continental crust in active orogens: Insight from Miocene eclogite and granulite xenoliths of the Pamir Mountains," J. Met. Geol., v.30, 2012, p. 413.

KEYWORDS

continental crust magma lava plutons seismology geology and tectonics seismology