HR: 1340h
AN: B13A-0195    [Abstracts]
TI: Petrology and Geochemistry of the Eastern Lau Spreading Center
AU: * Bezos, A
EM: bezos@fas.harvard.edu
AF: Harvard University, Earth and Planetary Sciences 20 Oxford St, Cambridge, MA 02138 United States
AU: Langmuir, C
EM: langmuir@eps.harvard.edu
AF: Harvard University, Earth and Planetary Sciences 20 Oxford St, Cambridge, MA 02138 United States
AU: Michael, P
EM: pjm@utulsa.edu
AF: The University of Tulsa, Department of Geosciences 600 S. College Ave., Tulsa, OK 74104 United States
AU: Asimow, P
EM: asimow@gps.caltech.edu
AF: CALTECH, Div. of Geological Planetary Sci. 1200 E. California Blvd., Pasadena, CA 91125 United States
AU: Escrig, S
EM: escrig@eps.harvard.edu
AF: Harvard University, Earth and Planetary Sciences 20 Oxford St, Cambridge, MA 02138 United States
AU: Fornari, D J
EM: dfornari@whoi.edu
AF: Woods Hole Oceanographic Instituion, MS #22, Woods Hole, MA 02543 United States
AU: Gier, E
EM: ejgier@yahoo.com
AF: Harvard University, Earth and Planetary Sciences 20 Oxford St, Cambridge, MA 02138 United States
AU: Goddard, C
EM: cgoddard@coas.oregonstate.edu
AF: Oregon State University, College of Oceanic and Atmospheric Sciences 104 COAS Admin Bldg , Corvallis, OR 97331 United States
AU: Matzen, A
EM: andrew-matzen@utulsa.edu
AF: The University of Tulsa, Department of Geosciences 600 S. College Ave., Tulsa, OK 74104 United States
AU: Woods, S
EM: woods@eps.harvard.edu
AF: Harvard University, Earth and Planetary Sciences 20 Oxford St, Cambridge, MA 02138 United States
AU: TEAM, L
EM: langmuir@eps.harvard.edu
AF: Harvard University, Earth and Planetary Sciences 20 Oxford St, Cambridge, MA 02138 United States
AU: TEAM, L
EM: langmuir@eps.harvard.edu
AF: R/V Kilo Moana, Lau Basin , ELSC, 01234 Tonga
AB: The spreading centers of the southern Lau Basin lie at varying distances from the volcanic front of the Tongan arc. The Valu Fa spreading center in the south is only some tens of km from the arc volcanoes, while the Central Lau Spreading Center (CLSC) further north is much further from the arc. The Eastern Lau Spreading Center (ELSC) that links the two is at progressively varying distances from the arc. Previous studies have shown that lavas from the CLSC are similar to basalts from ordinary mid-ocean ridges, while Valu Fa lavas have higher water contents and distinctly higher SiO2, reflecting a greater influence of subduction components. Modeling of existing data from the ridges also shows a significant change in the background composition of the mantle wedge within the Lau Basin. Lavas from the south appear to be sampling a more depleted mantle, with lower Na2O and FeO contents than those further to the north. Making use of the new mapping results of Martinez and others (this meeting), we have undertaken an extensive sampling campaign focussed primarily on the Eastern Lau Spreading Center to investigate the transition from arc-like to MORB-like lavas. Sampling at steadily varying distances from the volcanic front should permit a clear definition of the subduction components influencing the mantle wedge, offer insight into the mechanisms by which subduction components affect the melting process, and possibly constrain the progressive evolution of slab components with increasing distance from the trench. All these issues are of importance to a broad range of convergent margin studies. The existence of this chemical transition also permits a better understanding of the relationship between ridge segmentation and mantle composition: are there abrupt changes across offsets, suggesting efficient focussing and mixing mechanisms within ridge segments, or are the transitions gradual along the ridge, indicating a more distributed delivery of magma to the crust? The major elements will also give indications of lava temperatures and the distribution of magma bodies in the crust, making it possible to investigate possible relationships with the distribution and intensity of the new hydrothermal activity discovered in this region. Samples will be obtained during the LauII cruise in September and October of this year. Planned shipboard analyses should permit a first-order investigation of these various questions.
DE: 1020 Composition of the crust
DE: 1025 Composition of the mantle
DE: 1050 Marine geochemistry (4835, 4850)
DE: 1206 Crustal movements--interplate (8155)
DE: 1645 Solid Earth
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting