Article Volume 14, Number 10 15 October 2013 doi: 10.1002/ggge.20270 ISSN: 1525-2027 Lithological structure of the Galapagos Plume Christopher Vidito and Claude Herzberg Department of Earth and Planetary Sciences, Rutgers University, 610 Taylor Road, Piscataway, New Jersey, 08854-8066, USA (
[email protected]) Esteban Gazel Department of Geosciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA Dennis Geist Department of Geological Science, University of Idaho, Moscow, Idaho, USA Karen Harpp Geology Department, Colgate University, Hamilton, New York, USA [1] We have measured Ni, Ca, and Mn in olivine phenocrysts from volcanoes in the Galapagos Archipelago to infer the mantle source lithologies. Results show that peridotite is the dominant source lithology for Fernandina, Floreana, Genovesa, Wolf Island, and Darwin Island. These volcanoes largely characterize the PLUME, WD, FLO, and DUM Nd, Sr, and Pb isotopic endmembers of Harpp and White (2001). Volcan Wolf, Alcedo, Marchena, and Cerro Azul, also produced from the melting of peridotite sources, have isotopic compositions that can be defined by mixing of the four isotopic endmembers. Our analysis suggests that peridotite was present in the sources of the volcanoes covered in this study and therefore is the dominant source lithology of the Galapagos plume. Pyroxenite melting is generally focused in two isotopically distinct domains: Roca Redonda, Volcan Ecuador, and Sierra Negra in the enriched western part of the archipelago and Santiago, Santa Cruz, and Santa Fe in the depleted east. One implication of this finding is that the Western and Eastern Pyroxenite Domains represent two separate bodies of recycled crust within the Galapagos mantle plume.