Source lithology of the Galápagos plume

• Main Author: Vidito, Christopher Allen, 1976-
• Other Authors: Vidito, Christopher Allen, 1976- (author), Herzberg, Claude T (chair), Feigenson, Mark D (internal member), Carr, Michael J (internal member), Rutgers University, Graduate School - New Brunswick
• Format: Thesis
• Language: English
• Published: 2012
• Subjects: Geological Sciences; Galapagos Rift; Darwin Island; Galapagos; Redonda; Roca
• Online Access: http://hdl.rutgers.edu/1782.1/rucore10001600001.ETD.000067010

We have measured the contents of Ni, Ca, and Mn in olivine phenocrysts from volcanoes in the Galápagos archipelago to infer the mantle source lithologies. Results show that peridotite is the dominant source lithology for Fernandina, Floreana, Genovesa, Marchena, Pinta, 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). Only a minor pyroxenite component contributes to Fernandina and Floreana. Peridotite is also the dominant source lithology for Volcan Wolf, Alcedo, and Cerro Azul, and that these have isotopic compositions that can be defined by mixing of the 4 endmembers. Peridotite is therefore the dominant source lithology of the Galápagos plume. However, pyroxenite melting is significant in two spatially separated domains which are also isotopically distinct: Roca Redonda, Volcan Ecuador, Sierra Negra in the enriched western part of the archipelago and Volcan Darwin, Santiago, Santa Cruz, and Santa Fe in the depleted east. An implication is that the western and eastern pyroxenite domains likely represent two separate bodies of recycled crust within the Galápagos mantle plume. Isotopically enriched and depleted domains of the archipelago melted from both peridotite and pyroxenite, and there is no relationship between source lithology and its isotopic characteristics. The identification of peridotite source melting in volcanoes with isotopic characteristics that have been attributed to recycled crust points to the importance of mixing in OIB genesis, in agreement with studies on the Canary Islands. M.S. Includes bibliographical references by Christopher Allen Vidito