HR: 0830h
AN: V31C-0951    [PDF]
TI: Explosive and Effusive Silicic Magmatism in the Macolod Corridor, Luzon Islands, Philippines
AU: * Wilmot, M S
EM: Wilmotme@msu.edu
AF: Michigan State University,, Department of Geological Sciences, East Lansing, MI 48824-1115
AU: Flood, T P
EM: flootp@mail.snc.edu
AF: St. Norbert College, Department of Geology, 100 Grant Street, De Pere, WI 54115-2099
AU: Patino, L C
EM: patinoL@msu.edu
AF: Michigan State University,, Department of Geological Sciences, East Lansing, MI 48824-1115
AU: Vogel, T A
EM: vogel@msu.edu
AF: Michigan State University,, Department of Geological Sciences, East Lansing, MI 48824-1115
AU: Arpa, C B
EM: arpamari@msu.edu
AF: Michigan State University,, Department of Geological Sciences, East Lansing, MI 48824-1115
AU: Arpa, C B
EM: arpamari@msu.edu
AF: Philippine Institute of Volcanology and Seismology, Quezon City, Quezon City, 111 Philippines
AU: Arcilla, C
EM: carloarcilla@hotmail.com
AF: University of the Philippines, Diliman, National Institute of Geological Sciences, Quezon City, 111 Philippines
AU: Maximo, R P
EM: maximo@phivolcs.dost.gov.ph
AF: Philippine Institute of Volcanology and Seismology, Quezon City, Quezon City, 111 Philippines
AB: Silicic magmatism occurs in the Macolod Corridor, Luzon Island, Philippines. Luzon Island is an oceanic arc related to the subduction of the South China Sea plate eastward under the Philippine. Several silicic domes and voluminous pyroclastic deposits occur in the Macolod Corridor, which is a pull-apart rift zone that cuts across Central Luzon. The Laguna de Bay caldera occurs on the northern margin of the Corridor and has been the source of several pyroclastic flows that contain abundant silicic pumice fragments. Dating the different types of volcanic deposits reveals similar ages for the domes and some of the ash-flows sheets. Ar/Ar dates of three of the domes, Trapiche, Mt. Bulalo and Mt. Bijang has yielded ages of 43$\pm$17 ka, 15$\pm$7 ka, and 66$\pm$14 ka, respectively. $^{14}$C dates of the pyroclastic samples from Laguna de Bay area used in this study are 42-47 ka (unpublished PHIVOLCS report, 1999). The silica concentrations for the high-silica portion for the domes and ignimbrites are also similar, averaging 66 wt.% SiO$_{2}$ (normalized anhydrous) for Laguna de Bay, and 68 wt.% for the domes. The chemical compositions of both the domes and Laguna de Bay samples put them outside the field of adakites. Thus, it is unlikely that the silicic magmas represent subducting slab melts. Despite the similar ages, SiO$_{2}$ concentrations, and proximity of the domes and caldera, they are chemically distinct with respect to both major and trace element concentrations. The Laguna de Bay samples have higher REE, Th concentrations and lower CaO and Na$_{2}$O concentrations than the dome samples. Negative Eu anomalies are present in the Laguna de Bay samples and not in the dome samples. These data are consistent with plagioclase fractionating from the dome magmas producing the Laguna de Bay magmas.
DE: 1020 Composition of the crust
DE: 3640 Igneous petrology
DE: 3655 Major element composition
DE: 3670 Minor and trace element composition
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting