The origin of the silicic domes in the Macolod Corridor, Philippines
Abstract
The petrogenesis of silicic magmas in areas that do not contain continental crust is often unclear. This study examines the composition of domes associated with Mount Makiling stratovolcano, Philippines, to understand the generation of silicic magmas, in an island arc setting. Makiling volcano and associated domes are located in the Macolod Corridor. The corridor is a tectonic depression between the West Luzon Arc (produced by east dipping South China Sea plate) and the East Luzon Arc (produced by the west dipping Philippine Sea plate) with numerous volcanic features. The volcanism in this part of the Macolod Corridor has occurred sporadically over at least the past million years. Sampling of Makiling volcano indicates a continuous range in composition from basaltic andesite to dacite. The range in composition in the domes is wider, from basalt to rhyolite. The chemical variation in samples from individual domes is small, and may be an indication of monogenetic nature of the magmatic activity. Howerver, most of the domes have similar compositions, with SiO2 modes of 70% and with little variation of other chemical parameters that may indicate derivation from a larger silicic magma system. At least one dome has bimodal composition, one set of samples ranges in composition form basalts-basaltic andesite and the other set of samples consists of dacites. There is a dubious association among the magmas from the Macolod corridor with subduction zone magmatism, the rocks from Makiling volcano and most of those sampled from the domes are calc-alkaline with large Nb and Ti depletion on spider diagrams. Conversely, one dome has tholeiitic characteristics with higher FeO/MgO ratios for a given SiO2 content. The major and minor elements data in the samples from Makiling volcano plot on trends that show little scatter. All the samples follow on a single trend for Mg, Fe, and Ca. Though, for other elements (Ti, Al, Sr, Na, K, Rb, and Zr) the samples from the northeastern part of the volcano consistently fall off the trend delineated by the samples for other sections of the volcano. The geochemically diverse data set will be used to model the origin of the dacitic and rhyolitic volcanic products in an area void of continental crust.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2002
- Bibcode:
- 2002AGUFM.V12A1412F
- Keywords:
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- 3600 MINERALOGY AND PETROLOGY (replaces;
- 3640 Igneous petrology;
- 3655 Major element composition;
- 3670 Minor and trace element composition;
- 9320 Asia