Geochemistry of silicic magmas in the Macolod Corridor, SW Luzon, Philippines: evidence of distinct, mantle-derived, crustal sources for silicic magmas |
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| Authors: | Thomas A Vogel Timothy P Flood Lina C Patino Melissa S Wilmot Raymond Patrick R Maximo Carmencita B Arpa Carlo A Arcilla James A Stimac |
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| Institution: | (1) Department of Geological Sciences, Michigan State University, East Lansing, MI 48824-1115, USA;(2) Department of Geology, St. Norbert College, 100 Grant Street, De Pere, WI 54115-2099, USA;(3) Philippine Institute of Volcanology and Seismology, Quezon City, Philippines;(4) University of the Philippines—Diliman, National Institute of Geological Sciences, Quezon City, Philippines;(5) Unocal Philippines, Inc, 12th Floor, Citibank Tower, 1226 Makati City, Philippines |
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| Abstract: | Silicic volcanic deposits (>65 wt% SiO2), which occur as domes, lavas and pyroclastic deposits, are relatively abundant in the Macolod Corridor, SW Luzon, Philippines.
At Makiling stratovolcano, silicic domes occur along the margins of the volcano and are chemically similar to the silicic
lavas that comprise part of the volcano. Pyroclastic flows are associated with the Laguna de Bay Caldera and these are chemically
distinct from the domes and lavas at Makiling stratovolcano. As a whole, samples from the Laguna de Bay Caldera contain lower
concentrations of MgO and higher concentrations of Fe2O3(t) than the samples from domes and lavas. The Laguna de Bay samples are more enriched in incompatible trace elements. The silicic
rocks from the domes, Makiling Volcano and Laguna de Bay Caldera all contain high alkalis and high K2O/Na2O ratios. Melting experiments of primitive basalts and andesites demonstrate that it is difficult to produce high K2O/Na2O silicic magmas by fractional crystallization or partial melting of a low K2O/Na2O source. However, recent melting experiments (Sisson et al., Contrib Mineral Petrol 148:635–661, 2005) demonstrate that extreme
fractional crystallization or partial melting of K-rich basalts can produce these silicic magmas. Our model for the generation
of the silicic magmas in the Macolod Corridor requires partial melting of mantle-derived, evolved, moderate to K-rich, crystallized
calc-alkaline magmas that ponded and crystallized in the mid-crust. Major and trace element variations, along with oxygen
isotopes and ages of the deposits, are consistent with this model.
Electronic Supplementary Material Supplementary material is available for this article at |
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