Show simple item record

dc.contributor.authorGeorgen, Jennifer E.  Concept link
dc.coverage.spatialSouthwest Indian Ridge
dc.date.accessioned2010-06-25T12:40:11Z
dc.date.available2010-06-25T12:40:11Z
dc.date.issued2001-09
dc.identifier.urihttps://hdl.handle.net/1912/3692
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 September 2001en_US
dc.description.abstractThis thesis studies interactions between mid-ocean ridges and mantle plumes using geophysics, geochemistry, and geodynamical modeling. Chapter 1 investigates the effects of the Marion and Bouvet hotspots on the ultra-slow spreading, highly-segmented Southwest Indian Ridge (SWIR). Gravity data indicate that both Marion and Bouvet impart high-amplitude mantle Bouguer anomaly lows to the ridge axis, and suggest that long-offset transforms may diminish along-axis plume flow. Building upon this observation, Chapter 2 presents a series of 3D numerical models designed to quantify the sensitivity of along-axis plume-driven mantle flow to transform offset length, spreading rate, and mantle viscosity structure. The calculations illustrate that long-offset transforms in ultra-slow spreading environments may significantly curtail plume dispersion. Chapter 3 investigates helium isotope systematics along the western SWIR as well as near a global array of hotspots. The first part of this study reports uniformly low 3HetHe ratios of 6.3-7.3 RlRa along the SWIR from 9°-24°E, compared to values of 8±1 Ra for normal mid-ocean ridge basalt. The favored explanation for these low values is addition of (U+ Th) into the mantle source by crustal and/or lithospheric recycling. Although high HetHe values have been observed along the SWIR near Bouvet Island to the west, there is no evidence for elevated 3HetHe ratios along this section of the SWIR. The second part of Chapter 3 investigates the relationship between 3HetHe ratios and geophysical indicators of plume robustness for nine hotspots. A close correlation between a plume's flux and maximum 3HetHe ratio suggests a link between plume upwelling strength and origination in the deep, relatively undegassed mantle. Chapter 4 studies 3D mantle flow and temperature patterns beneath oceanic ridge-ridge-ridge triple junctions (TJs). In non-hotspot- affected TJs with geometry similar to the Rodrigues TJ, temperature and upwelling velocity along the slowest-spreading of the three ridges are predicted to increase within a few hundred kilometers of the TJ, to approach those of the fastest-spreading ridge. Along the slowest-spreading branch in hotspot-affected TJs such as the Azores, a strong component of along-axis flow directed away from the TJ is predicted to advect a hotspot thermal anomaly away from its deep-seated source.en_US
dc.description.sponsorshipFunding was provided by the National Science Foundation through grants OCE- 9811924 and OCE-9907630, and by a National Defense Science and Engineering Graduate Fellowship.en_US
dc.format.mimetypeapplication/pdf
dc.language.isoen_USen_US
dc.publisherMassachusetts Institute of Technology and Woods Hole Oceanographic Institutionen_US
dc.relation.ispartofseriesWHOI Thesesen_US
dc.subjectMantle plumesen_US
dc.subjectMid-ocean ridgesen_US
dc.subjectKnorr (Ship : 1970-) Cruise KN162en_US
dc.subjectPolarstern (Ship) Cruise PS86en_US
dc.subjectAgulhas (Ship) Cruise AG22en_US
dc.titleInteractions between mantle plumes and mid-ocean ridges : constraints from geophysics, geochemistry, and geodynamical modelingen_US
dc.typeThesisen_US
dc.identifier.doi10.1575/1912/3692


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record