1998 Eruption at Volcán Cerro Azul, Galápagos Islands: I. Syn-Eruptive Petrogenesis |
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| Authors: | Rachel Teasdale Dennis Geist Mark Kurz Karen Harpp |
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| Institution: | (1) Department of Geosciences, California State University, Chico, Chico, CA 95929, USA;(2) Department of Geological Sciences, University of Idaho, Moscow, ID 83844-3022, USA;(3) Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA;(4) Department of Geology, Colgate University, Hamilton, NY 13346, USA |
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| Abstract: | The 1998 eruption of Volcán Cerro Azul in the Galápagos Islands produced two intra-caldera vents and a flank vent that erupted more than 1.0×108 m3 of lava. Lava compositions changed notably during the 5-week eruption, and contemporaneous eruptions in the caldera and on the flank produced different compositions. Lavas erupted from the flank vent range from 6.3 to 14.1% MgO, nearly the entire range of MgO contents previously reported from the volcano. On-site monitoring of eruptive activity is linked with petrogenetic processes such that geochemical variations are evaluated in a temporal context. Lavas from the 1998 eruption record two petrogenetic stages characterized by progressively more mafic lavas as the eruption proceeded. Crystal compositions, whole rock major and trace element compositions, and isotope ratios indicate that early lavas are the product of mixing between 1998 magma and remnant magma of the 1979 eruption. Intra-caldera lavas and later lavas have no 1979 signature, but were produced by the 1998 magma incorporating olivine and clinopyroxene xenocrysts. Thus, early magma petrogenesis is characterized by mixing with the 1979 magma, followed by the magma progressively entraining wehrlite cumulate mush.Editorial Responsibility: M.R. Carroll |
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| Keywords: | Galá pagos Cerro Azul Syneruptive Petrogenesis Active Volcanism Basalt |
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