Repository logo
 

Mantle plume capture, anchoring, and outflow during Galápagos plume-ridge interaction


Change log

Authors

Gibson, SA 
Geist, DJ 
Richards, MA 

Abstract

jats:titleAbstract</jats:title>jats:pCompositions of basalts erupted between the main zone of Galápagos plume upwelling and adjacent Galápagos Spreading Center (GSC) provide important constraints on dynamic processes involved in transfer of deep‐mantle‐sourced material to mid‐ocean ridges. We examine recent basalts from central and northeast Galápagos including some that have less radiogenic Sr, Nd, and Pb isotopic compositions than plume‐influenced basalts (E‐MORB) from the nearby ridge. We show that the location of E‐MORB, greatest crustal thickness, and elevated topography on the GSC correlates with a confined zone of low‐velocity, high‐temperature mantle connecting the plume stem and ridge at depths of ∼100 km. At this site on the ridge, plume‐driven upwelling involving deep melting of partially dehydrated, recycled ancient oceanic crust, plus plate‐limited shallow melting of anhydrous peridotite, generate E‐MORB and larger amounts of melt than elsewhere on the GSC. The first‐order control on plume stem to ridge flow is rheological rather than gravitational, and strongly influenced by flow regimes initiated when the plume was on axis (>5 Ma). During subsequent northeast ridge migration material upwelling in the plume stem appears to have remained “anchored” to a contact point on the GSC. This deep, confined NE plume stem‐to‐ridge flow occurs via a network of melt channels, embedded within the normal spreading and advection of plume material beneath the Nazca plate, and coincides with locations of historic volcanism. Our observations require a more dynamically complex model than proposed by most studies, which rely on radial solid‐state outflow of heterogeneous plume material to the ridge.</jats:p>

Description

Keywords

plume-ridge interaction, Galapagos volcanism, mantle flow, mantle plume, spreading center

Journal Title

Geochemistry, Geophysics, Geosystems

Conference Name

Journal ISSN

1525-2027
1525-2027

Volume Title

16

Publisher

American Geophysical Union (AGU)
Sponsorship
Natural Environment Research Council (NE/H01053X/1)
We thank Galápagos National Park authorities and CDRS for permitting fieldwork in Galápagos. D. Villagomez and D. Toomey generously shared their extensive seismic data set for Galápagos, and D. McKenzie kindly provided help with temperature calculations. End-member compositions of Galápagos mantle reservoirs in Figure 4 were estimated from principal component analysis; data related to these calculations are available in the supporting information. We are grateful to Kaj Hoernle and two anonymous reviewers for their constructive comments on an earlier version of this manuscript. The research was funded by the University of Cambridge, Geological Society of London, NERC (RG57434), and NSF (EAR 0838461, EAR 0944229, and EAR-11452711).