Helium Isotope Variations and mantle plume-spreading ridge interactions along the Galápagos Spreading Center

摘要: Along the Galapagos Spreading Center (GSC), 3He/4He varies from 8.5–5.9 RA. High ratios, resembling those in western and southern islands, are absent. This lack of high contrasts markedly with other localities plume–ridge interaction, such as Iceland, Easter, Amsterdam/St. Paul. The most striking feature is a gradient, decreasing westward 8.4–7.0 RA between 89 93°W, where GSC shallowest shows “axial high” morphology. intra-segment variability within this region indicates that magma crosses mantle/crust boundary at multiple points beneath individual ridge segments, lateral mixing crust upper mantle limited. Some may also reflect transfer discrete heterogeneity northern sector plateau. One possible explanation for absence along helium relatively ineffective downstream tracer material core plume, due to its preferential extraction archipelago compared incompatible, lithophile tracers. A second heterogeneous plume sheared by motion Nazca Plate relative migrating GSC. In case, having (from Fernandina Isabela) would be dispersed mostly away ridge, while edge low plus enriched Sr Pb isotope signatures periphery archipelago) smeared into sub-ridge mantle.