Title

A Preliminary Survey of the Northeast Seamounts, Galápagos Platform

Document Type

Article

Publication Date

10-6-2014

Abstract

A simple plume model cannot fully explain the origin of the Galápagos Islands because magmatism continues east of the current position of the hotspot and young volcanoes occur north of the main platform between the hotspot and the Galápagos Spreading Center (GSC). The evolution of this pattern over time can be elucidated by a set of 3-6Ma seamounts that lie off the northeast margin of the Galápagos platform. The three largest seamounts appear to be drowned islands that host twelve different lava types. Three of these have slightly enriched trace element compositions, while the rest are primitive basalts with highly depleted incompatible element compositions-more depleted than western GSC MORB and different from any on the islands. These ultra-depleted lavas could have been produced by partial melting of a previously depleted component of the Galápagos mantle plume as it interacted with the thinner lithosphere at the northeastern boundary of the platform. Regional paleoreconstructions over the past 6 My show that the smallest seamount formed over the present position of the hotspot, consistent with its enriched lava compositions. The three larger seamounts formed east of the hotspot-evidence that significant magmatism east of the hotspot has been continuous-but a major difference from the present islands is that these volcanoes did not form on the shallow platform. Magmatism north of the hotspot did not begin until the encroachment of the 90°50'W Galápagos transform fault and an apparent 60-70km shift northward of the hotspot.

Publication Name

The Galapagos: A Natural Laboratory for the Earth Sciences

First Page

335

Last Page

362

DOI

10.1002/9781118852538.ch16

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