Spreading rate, spreading obliquity, and melt supply at the ultraslow spreading Southwest Indian Ridge

摘要: We use bathymetry, gravimetry, and basalt composition to examine the relationship between spreading rate, obliquity, melt supply at ultraslow Southwest Indian Ridge (SWIR). find that regional scales (more than 200 km), reflects variations in mantle melting are primarily controlled by large-scale heterogeneities temperature and/or composition. Focusing on adjacent SWIR regions with contrasted we effect of obliquity production is significant (about 1.5 km less produced for a decrease 7 mm/a 4 effective rates, ESR) but not enough produce near-amagmatic most oblique ridge, unless associated an anomalously cold depleted source. Our observations lead us support models which upwelling beneath slow ridges somewhat focused accelerated, thereby reducing rate upper cooling supply. To explain why very nonetheless have large outcrops mantle-derived ultramafic rocks and, many cases, no evidence axial volcanism (Cannat et al., 2006; Dick 2003), develop model combines migration along axis more volcanically robust areas, trapping lithospheric mantle, transport dikes may only form where has gathered build sufficient overpressure. These would open perpendicularly direction least compressive stress favor formation orthogonal ridge sections. The resulting segmentation pattern, prominent volcanic centers long intervening avolcanic or nearly sections, specific regions. It also observed arctic Gakkel underlain mantle.