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https://doi.org/10.5194/se-2017-138
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
31 Jan 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Solid Earth (SE).
Boninite and boninite-series volcanics in northern Zambales ophiolite: Doubly-vergent subduction initiation along Philippine Sea Plate margins
Americus Perez1, Susumu Umino1, Graciano P. Yumul Jr.2, and Osamu Ishizuka3,4 1Division of Natural System, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan
2Apex Mining Company Inc., Ortigas Center, Pasig City, 1605, Philippines
3Research Institute of Earthquake and Volcano Geology, Geological Survey of Japan, AIST, Tsukuba Central 7, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8567, Japan
4Research and Development Center for Ocean Drilling Science, JAMSTEC, 2-15 Natsushima, Yokosuka, Kanagawa 237-0061, Japan
Abstract. A key component of subduction initiation rock suites is boninite, a high-magnesium andesite that is uniquely predominant in Western Pacific forearc terranes and in select Tethyan ophiolites such as Oman and Troodos. We report the discovery of low-calcium, high-silica boninite in the middle Eocene Zambales ophiolite (Luzon island, Philippines). Olivine-orthopyroxene microphyric high-silica boninite, olivine-clinopyroxene-phyric low-silica boninite and boninitic basalt occur as lapilli fall deposits and pillow lava flows in the upper volcanic unit of the juvenile arc section (Barlo locality, Acoje Block) of Zambales ophiolite. This upper volcanic unit in turn overlies a lower volcanic unit consisting of basaltic andesite, andesite to dacitic lavas and explosive eruptives (subaqueous pahoehoe and lobate sheet flows, agglutinate, and spatter deposits) forming a low-silica boninite series. The overall volcanic stratigraphy of the extrusive sequence at Barlo resembles Holes U1439 and U1442 drilled by IODP Expedition 352 in the Izu-Ogasawara (Bonin) trench slope. The presence of proto-arc basalts in Coto Block (45 Ma), boninite and boninite series volcanics in Barlo, Acoje Block (44 Ma) and simultaneous and post-boninite moderate-Fe arc tholeiites in Sual and Subic, Acoje Block (44–43 Ma) indicate that the observed subduction initiation stratigraphy in the Izu-Ogasawara-Mariana forearc is present in Zambales ophiolite as well. Paleolatitudes derived from tilt-corrected sites in the Acoje Block place the juvenile arc of northern Zambales ophiolite in the western margin of the Philippine Sea Plate. In this scenario, the origin of Philippine Sea Plate boninites (IBM and Zambales) would be in a doubly-vergent subduction initiation setting.

Citation: Perez, A., Umino, S., Yumul Jr., G. P., and Ishizuka, O.: Boninite and boninite-series volcanics in northern Zambales ophiolite: Doubly-vergent subduction initiation along Philippine Sea Plate margins, Solid Earth Discuss., https://doi.org/10.5194/se-2017-138, in review, 2018.
Americus Perez et al.
Americus Perez et al.
Americus Perez et al.

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Short summary
The occurrence of boninite in northern Zambales ophiolite is reported. Boninite is a relatively rare high-magnesium andesite that is intimately associated with early arc volcanism and the initiation of subduction zones. Taken as a whole, the geological and geochemical characteristics of Zambales and Izu-Ogasawara-Mariana forearc volcanic sequences enables a refined geodynamic reconstruction of subduction initiation.
The occurrence of boninite in northern Zambales ophiolite is reported. Boninite is a relatively...
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