The influence of ridge geometry at the ultraslow-spreading Southwest Indian Ridge (9º-25ºE) : basalt composition sensitivity to variations in source and process
Standish, Jared J.
MetadataShow full item record
Southwest Indian Ridge
KeywordCrust; Geochemistry; Knorr (Ship : 1970-) Cruise KN162; Melville (Ship) Cruise VAN-7; Agulhas (Ship) Cruise AG22
Between 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.
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 2006
Suggested CitationThesis: Standish, Jared J., "The influence of ridge geometry at the ultraslow-spreading Southwest Indian Ridge (9º-25ºE) : basalt composition sensitivity to variations in source and process", 2006-02, DOI:10.1575/1912/1508, https://hdl.handle.net/1912/1508
Showing items related by title, author, creator and subject.
Spatial variability of bottom turbulence over a linear sand ridge mooring deployment and AUTOSUB AUV survey cruise report R/V RRS Challenger, cruise number 146 Broken Bank, North Sea, U.K., 17 – 28 August 1999 cruise report Voulgaris, George; Trowbridge, John H.; Terray, Eugene A. (Woods Hole Oceanographic Institution, 2001-08)Two successful AUTOSUB deployments were carried out during August 1999 as part of the AUTOSUB Thematic Program project titled “Spatial Variability of Bottom Turbulence over a Linear Sand Ridge,” funded by the Natural ...
The Subduction experiment : cruise report RRS Charles Darwin cruise number 73 subduction 3 mooring deployment and recovery cruise, 30 September-26 October 1992 Trask, Richard P.; Jenkins, William J.; Sherman, Jeffrey; McPhee, Neil M.; Ostrom, William M.; Payne, Richard E. (Woods Hole Oceanographic Institution, 1993-03)Subduction is the mechanism by which water masses formed in the mixed layer and near the surface of the ocean find their way into the upper thermocline. The subduction process and its underlying mechanisms were studied ...
The Marine light - mixed layer experiment cruise and data report, R/V Endeavor : cruise EN-224, mooring deployment, 27 April-1 May 1991, cruise EN-227, mooring recovery, 5-23 September 1991 Plueddemann, Albert J.; Weller, Robert A.; Dickey, Thomas D.; Marra, John F.; Tupper, George H.; Way, Bryan S.; Ostrom, William M.; Bouchard, Paul R.; Oien, Andrea L.; Galbraith, Nancy R. (Woods Hole Oceanographic Institution, 1993-05)The Marine Light - Mixed Layer experiment took place in the sub-Arctic North Atlantic ocean, approximately 275 miles south of Reykjavik, Iceland. The field program included a central surface mooring to document the temporal ...