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Northern Galápagos Province: Hotspot-induced, near-ridge volcanism at Genovesa Island

¹ Department of Geology, Colgate University, Hamilton, New York 13346, USA
² Geology Department, Macalester College, St. Paul, Minnesota 55105, USA
³ Department of Geology, Colgate University, Hamilton, New York 13346, USA

Genovesa Island is a small volcano located between the Galápagos hotspot and the Galápagos spreading center. Several observations suggest that Genovesa may not have originated as a direct product of the Galápagos plume, but instead by anomalous activation of the upper mantle by the plume. Genovesa's lavas exhibit remarkably homogeneous, depleted compositions with no detectable plume contribution; the volcano's trace element contents indicate a deeper origin than either pristine spreading center lavas or most lavas from the Galápagos Archipelago. Genovesa is virtually indistinguishable from the Lamont Seamounts (near the East Pacific Rise) in composition, volume, height, and distance from the ridge; and Genovesa formed close to its current near-ridge location, more recently than previously assumed (age younger than 350 ka). Numerous similar volcanoes populate the northern perimeter of the Galápagos Archipelago. We propose that the northern volcanic province is the result of the serendipitous combination of excess temperatures, weak lithosphere, and regional stresses from interaction between the plume and the ridge, yielding volcanism where none would be observed otherwise. The Galápagos system may define an eruptive process at hotspots, distinct from the Hawaiian model, in which plume-related volcanism can be regionally diffuse, coeval, and compositionally variable. Such a mechanism has profound implications for our understanding of plume-ridge interactions, as well as for island ages and adaptive radiation in the Galápagos.

Key Words: Galápagos • Galápagos spreading center • geochemistry • hotspots • mid-ocean ridge • seamounts

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