Advanced geophysical studies of accretion of oceanic lithosphere in Mid-Ocean Ridges characterized by contrasting tectono-magmatic settings


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dc.contributor.author Xu, Min
dc.coverage.spatial 9°30'-10°00’N
dc.coverage.spatial 23°20’-23°38’N
dc.coverage.spatial East Pacific Rise
dc.date.accessioned 2012-06-08T18:27:05Z
dc.date.available 2012-06-08T18:27:05Z
dc.date.issued 2012-02
dc.identifier.uri http://hdl.handle.net/1912/5218
dc.description Submitted 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 2012 en_US
dc.description.abstract The structure of the oceanic lithosphere results from magmatic and extensional processes taking place at mid-ocean ridges (MORs). The temporal and spatial scales of the variability of these two processes control the degree of heterogeneity of the oceanic lithosphere, represented by two end-member models: the classical Penrose Model exemplified by layered magmatic crust formed along fast-spreading MORs, e.g., East Pacific Rise (EPR); and the recently defined Chapman Model describing heterogeneous mafic and ultramafic lithosphere formed in settings of oceanic detachment faulting common along slow-spreading MORs, e.g., Mid-Atlantic Ridge (MAR). This thesis is using advanced marine geophysical methods (including finite-difference wave propagation modeling, 3D multi-channel seismic reflection imaging, waveform inversion, streamer tomography, and near-bottom magnetics) to study lithospheric accretion processes in MORs characterized by contrasting tectono-magmatic settings: the magmatically dominated EPR axis between 9°30'-10°00’N, and the Kane Oceanic Core Complex (KOCC), a section of MAR lithosphere (23°20’-23°38’N) formed by detachment faulting. At the EPR study area, I found that the axial magma chamber (AMC) melt sill is segmented into four prominent 2-4-km-long sections spaced every ~5- 10 km along the ridge axis characterized by high melt content (>95%). In contrast, within the intervening sections, the AMC sill has a lower melt content (41-46%). The total magma volume extracted from the AMC sill was estimated of ~46 × 106 m3, with ~24 × 106 m3 left unerupted in the upper crust as dikes after 2005-06 eruption. At the KOCC, I used streamer tomography to constrain the shallow seismic velocity structure. Lithological interpretation of the seismic tomographic models provides insights into the temporal and spatial evolution of the melt supply at the spreading axis as the KOCC formed and evolved. Investigation of a magnetic polarity reversal boundary in crosssection at the northern boundary of KOCC suggests that the boundary (representing both a frozen isotherm and an isochron) dips away from the ridge axis along the Kane transform fault scarp, with a west-dipping angle of ~45° in the shallow (<1 km) crust and <20° in the deeper crust. en_US
dc.description.sponsorship This thesis was funded by National Science Foundation grants OCE-9987004, OCE- 0621660 and OCE-0327885, WHOI Academic Program Office and WHOI Deep Ocean Exploration Institute. en_US
dc.format.mimetype application/pdf
dc.language.iso en_US en_US
dc.publisher Massachusetts Institute of Technology and Woods Hole Oceanographic Institution en_US
dc.relation.ispartofseries WHOI Theses en_US
dc.subject Geophysics en_US
dc.subject Mid-ocean ridges en_US
dc.title Advanced geophysical studies of accretion of oceanic lithosphere in Mid-Ocean Ridges characterized by contrasting tectono-magmatic settings en_US
dc.type Thesis en_US
dc.identifier.doi 10.1575/1912/5218

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