Article Geochemistry 3 Volume 4, Number 9 Geophysics 27 September 2003 8511, doi:10.1029/2003GC000531 GeosystemsG G ISSN: 1525-2027 AN ELECTRONIC JOURNAL OF THE EARTH SCIENCES Published by AGU and the Geochemical Society Genovesa Submarine Ridge: A manifestation of plume-ridge interaction in the northern Gala´pagos Islands Karen S. Harpp Department of Geology, Colgate University, Hamilton, New York 13346, USA (
[email protected]) Daniel J. Fornari Geology and Geophysics Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA Dennis J. Geist Department of Geological Sciences, University of Idaho, Moscow, Idaho 83844, USA Mark D. Kurz Marine Chemistry and Geochemistry Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA [1] Despite its circular coastline and calderas, Genovesa Island, located between the central Galapagos Platform and the Galapagos Spreading Center, is crosscut by both eruptive and noneruptive fissures trending NE-SW. The 075° bearing of the fissures parallels that of Genovesa Ridge, a 55 km long volcanic rift zone that is the most prominent submarine rift in the Galapagos and constitutes the majority of the volume of the Genovesa magmatic complex. Genovesa Ridge was the focus of detailed multibeam and side-scan sonar surveys during the Revelle/Drift04 cruise in 2001. The ridge consists of three left stepping en echelon segments; the abundances of lava flows, volcanic terraces, and eruptive cones are all consistent with constructive volcanic processes. The nonlinear arrangement of eruptive vents and the ridge’s en echelon structure indicate that it did not form over a single dike. Major and trace element compositions of Genovesa Ridge glasses are modeled by fractional crystallization along the same liquid line of descent as the island lavas, but some of the glasses exhibit higher Mg # than material sampled from the island.