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dc.contributor.authorStandish, Jared J.  Concept link
dc.coverage.spatial9°-25°E
dc.coverage.spatialSouthwest Indian Ridge
dc.date.accessioned2007-02-15T16:25:21Z
dc.date.available2007-02-15T16:25:21Z
dc.date.issued2006-02
dc.identifier.urihttps://hdl.handle.net/1912/1508
dc.descriptionSubmitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2006en
dc.description.abstractBetween 9º-25º E on the ultraslow-spreading Southwest Indian Ridge lie two sharply contrasting supersegments. One 630 km long supersegment erupts N-MORB that is progressively enriched in incompatible element concentrations from east to west. The second 400 km long supersegment contains three separate volcanic centers erupting EMORB and connected by long amagmatic accretionary segments, where mantle is emplaced directly to the seafloor with only scattered N-MORB and E-MORB erupted. Rather than a major break in mantle composition at the discontinuity between the supersegments, this sharp contrast in geometry, physiography, and chemistry reflects “source” versus “process” dominated generation of basalt. Robust along-axis correlation of ridge characteristics (i.e. morphology, upwelling rate, lithospheric thickness), basalt chemistry, and crustal thickness (estimated from gravity) provides a unique opportunity to compare the influence of spreading geometry and rate on MORB generation. What had not been well established until now is the importance of melting processes rather than source at spreading rates < 20 mm/yr. Along the orthogonally spreading supersegment (14 mm/yr) moderate degrees of partial melting effectively sample the bulk mantle source, while on the obliquely spreading supersegment (7-14 mm/yr) suppression of mantle melting to low degrees means that the bulk source is not uniformly sampled, and thus “process” rather than “source” dominates melt chemistry.en
dc.description.sponsorshipThe main body of work consisting of major element, trace element, and isotopic data acquisition and interpretation (Chapter 2 & 3) was funded by H. Dick’s grant from the National Science Foundation-OCE 9907630. National Science Foundation-OCE 0137325 supported the U-series work described in Chapter 4. The published work of Chapter 5 was funded by National Science Foundation-EAR 9804891, NSF-OCE 9416620, and NSF-OCE 0096634.en
dc.format.extent22777371 bytes
dc.format.mimetypeapplication/pdf
dc.language.isoen_USen
dc.publisherMassachusetts Institute of Technology and Woods Hole Oceanographic Institutionen
dc.relation.ispartofseriesWHOI Thesesen
dc.subjectCrusten_US
dc.subjectGeochemistryen_US
dc.subjectKnorr (Ship : 1970-) Cruise KN162en_US
dc.subjectMelville (Ship) Cruise VAN-7en_US
dc.subjectAgulhas (Ship) Cruise AG22en_US
dc.titleThe influence of ridge geometry at the ultraslow-spreading Southwest Indian Ridge (9º-25ºE) : basalt composition sensitivity to variations in source and processen
dc.typeThesisen
dc.identifier.doi10.1575/1912/1508


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