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Geochemistry of Lavas from Taal Volcano, Southwestern Luzon, Philippines: Evidence for Multiple Magma Supply Systems and Mantle Source Heterogeneity |
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| Authors: | MIKLIUS ASTA; FLOWER MARTIN F J; HUIJSMANS JOEP P P; MUKASA SAMUEL B; CASTILLO PATERNO |
| Institution: | 1Department of Geological Sciences, University of Illinois P.O. Box 4348, Chicago, Illinois 60680 2Energieonderzoek Centrum Nederland Westerduinweg 3, Postbus 1, 1755 ZG Petten, Netherlands 3Department of Geological Sciences, University of Michigan Ann Arbor, Michigan 48109 4Division of Marine Geology and Geophysics, Rosenstiel School of Marine and Atmospheric Sciences, University of Miami Florida 33149 * Present address: U.S.G.S. Hawaiian Volcano Observatory, P.O. Box 51, Hawai: National Park, Hawaii 96718 |
| Abstract: | Taal Volcano is a highly active center in the southwest Luzonvolcanic field. Recent eruptions are confined to Volcano Island,a plexus of cinder cones and tuff rings surrounding a centralcrater, occupying (and post-dating) a massive volcano-tectonicdepression resulting from multiple phases of collapse. Taallava series can be distinguished from each other by differencesin major and trace element trends and trace element ratios,indicating multiple magmatic systems associated with discretecenters in time and space. On Volcano Island, contemporaneous lava series range from typicallycalc-alkaline to iron-enriched. Major and trace element variationin these series can be modelled by fractionation of similarassemblages, with early fractionation of titano-magnetite inless iron-enriched series. However, phase compositional andpetrographic evidence of mineral-liquid disequilibrium suggeststhat magma mixing played an important role in the evolutionof these series. We interpret this to mean that mixing occurredalong a line of descent defined by fractional crystallization,with mixing occurring over larger compositional intervals inthe less iron-enriched series, consistent with numerical modelling. Between-series incompatible element ratio differences are notexplicable through differential partial melting of a homogeneoussource (also confirmed by variation in Pb isotopic ratios),suggesting a supply system from discrete melt zones in heterogeneousmantle. |
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