Sex: Male
Education:
- Doctor of Philosophy in Science, Kanazawa University Japan, 2018
- Bachelor of Science in Geology, University of the Philippines 2011
Field of Specialization:
Igneous Petrology and Geochemistry
Chemical Geodynamics
Ocean Floor Geoscience
Tectonic evolution of the Western Pacific Region
Early volcanic arc evolution and maturation
Ancient and modern marginal basins of the Western Pacific
Researches:
Article title: Origin and age of magmatism in the northern Philippine Sea basins
Authors: Osamu Ishizuka,Kenichiro Tani,Rex N. Taylor,Susumu Umino,Izumi Sakamoto,Yuka Yokoyama,Gen Shimoda,Yumiko Harigane,Yasuhiko Ohara,Chris E. Conway,Americus Perez,Shun Sekimoto
Publication title: Geochemistry, Geophysics, Geosystems 2021
Abstract:
A Robust tectonic reconstruction of the Philippine Sea Plate around ∼52 Ma is a prerequisite in understanding the process of subduction initiation and establishment of the Izu-Bonin-Mariana arc. This study investigates origins and timing of basin formation in the still poorly understood oldest part of the northern Philippine Sea plate. We have established that andesitic magmatism in the form of the Northern Philippine Sea volcanics is widely distributed across this area. It is founded on both a Mesozoic arc terrane (Daito Ridge Group) and an intervening basin (Kita-Daito Basin). Their narrow Eocene age range (45-41 Ma) and lack of systematic spatial variation in geochemistry implies that this magmatism was not associated with on-going subduction, but related to the rifting/spreading event forming the Kita-Daito Basin. The arc-like geochemistry of the volcanics seems to indicate melting of lithospheric mantle which had been previously metasomatized by Mesozoic subduction of a plate with Pacific-MORB isotopic characteristics. Late Eocene basaltic magmatism also found in the Kita-Daito Basin does not have arc-like characteristics, and could have formed from low-degree melts of asthenospheric mantle associated with the final stage of Kita-Daito Basin spreading. As onset of activity of the Northern Philippine Sea volcanics is essentially synchronous with the magmatism associated with the Oki-Daito mantle plume, it is possible that both magmatism and rifting of the Kita-Daito Basin were triggered by the arrival of the Oki-Daito mantle plume in this region. These results demonstrate that the Kita-Daito Basin postdates subduction initiation of the Pacific Plate along the Izu-Bonin-Mariana arc.
Full text link https://doi.org/10.1029/2021GC010242
Article title: Juxtaposition of Cenozoic and Mesozoic ophiolites in Palawan Island: New insights on the evolution of the Proto-South China Sea.
Authors: Jesley Mei A. Dycoco, Betchaida D. Payot, Gabriel Theophilus V. Valera, Florence Annette C.Labis, Julius A.Pasco, Americus D.C. Perez, KenichiroTani
Publication title: Tectonophysics 819: 229085, 2021
Abstract:
The proto-South China Sea (proto-SCS) is a fully consumed Mesozoic plate that once existed between the South China-Eurasian margin and Borneo. Remnants of this oceanic domain are believed to be emplaced as ophiolitic lithologies in Palawan and Zambales, Philippines and Borneo. Cretaceous and Eocene ophiolitic lithologies are exposed in the central and southern portions of Palawan island. The Eocene central Palawan Ophiolite (CPO) is composed of mantle peridotites, isotropic and layered gabbros, and massive and pillow lavas. In lieu of a sheeted dike complex, mafic dikes with distinct bake-and-chill margins cut the CPO, from the metamorphic sole to the crustal section. The Cretaceous southern Palawan Ophiolite (SPO) comprises of peridotite and pillow basalt exposures. Isotropic olivine gabbros are mainly preserved as floats. Troctolite and olivine gabbro dikes also cut the peridotites in the SPO.
The CPO crustal rocks and mafic dikes have dominantly back-arc basin basalt affinities. The SPO lithologies exhibit ocean island basalt-like signatures with a mafic dike showing island arc basalt-like compositions. A plagiogranite sample from Puerto Princesa indicates an Eocene age (40.01 ± 0.54 Ma) for the CPO. U-Pb dating of olivine gabbro and syenite floats yielded a minimum age of Early Cretaceous (100.73 ± 1.07 and 102.97 ± 1.07 Ma, respectively) for the SPO. This is the first reported radiometric age for the now completely subducted Mesozoic proto-SCS exposed in southern Palawan, which complements existing paleontological dates. Geochemical and geochronological characteristics of the SPO and CPO are similar to those of the Darvel Bay and Telupid Ophiolites in Borneo, which are interpreted to originate from the proto-SCS. The CPO and SPO are thus construed to represent fragments of the proto-SCS emplaced in Palawan. Complex tectonic processes in the region during the Cretaceous to Eocene led to the inception of multiple subduction and rifting events involving the proto-SCS.
Full text available upon request to the author
Article title: Proceedings of the Oman Drilling Project
Authors: Kelemen, P.B., Matter, J.M., Teagle, D.A.H., Coggon, J.A.,and the Oman Drilling Project Science Team
Publication title: International Ocean Discovery Program Publications
Abstract:
No available
Full text link https://tinyurl.com/8dvpstbm
Article title: Boninite and boninite-series volcanics in northern Zambales ophiolite: Doubly-vergent subduction initiation along Philippine Sea Plate margins.
Authors: Americus Perez, Susumu Umino, Graciano P. Yumul Jr., and Osamu Ishizuka
Publication title: Solid Earth 9(3): 713-733, 2018
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, for the first time, 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 the Zambales ophiolite. This upper volcanic unit overlies a lower volcanic unit consisting of basaltic andesite, andesite to dacitic lavas and explosive eruptive material (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 depleted proto-arc basalts in the Coto Block (45 Ma) (Geary et al., 1989), boninite and boninite series volcanics in Barlo (Acoje Block (44 Ma)) and simultaneous and post-boninite moderate-Fe arc tholeiites in Sual and Subic areas of the Acoje Block (44–43 Ma) indicate that the observed subduction initiation stratigraphy in the Izu–Ogasawara–Mariana forearc is also present in the Zambales ophiolite. 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.
Full text link available upon request to the author
Article title: Geochemical and geophysical characteristics of the Balud Ophiolitic Complex (BOC), Masbate Island, Philippines: implications for its generation, evolution and emplacement.
Authors: Pearlyn C. Manalo, Carla B. Dimalanta, Decibel V. Faustino-Eslava, Betchaida D. Payot, Noelynna T. Ramos, Karlo L. Queaño, Americus D. C. Perez, and Graciano P. Yumul Jr.
Publication title: Terrestrial, Atmospheric, Oceanic Sciences 26 (6), 687-700, 2015
Abstract:
This paper presents the first field, geochemical and geophysical information on the recently recognized Early Cretaceous Balud Ophiolitic Complex (BOC) in the island of Masbate in the Central Philippines. Mapping of the western limb of the island revealed that only the upper crustal section of the BOC is exposed in this area. Geochemically, the pillow basalts are characterized by transitional mid-oceanic ridge basalt-island arc tholeiitic compositions. Gravity surveys yielded low Bouguer anomaly values that are consistent with the highly dismembered nature of the BOC. Short wavelength, high amplitude magnetic anomalies registered across the study area are attributed to shallow magnetic sources. This is taken to support the model that the ophiolitic complex occurs as thin crustal slivers that are not deeply-rooted in the mantle. Comparing BOC with other ophiolites in the Central Philippines, such as those in the islands of Sibuyan, Leyte and Bohol, suggests the possibility of a common or contiguous source for similarly-aged and geochemically composed crust-mantle sequences in the region.
Full text link https://tinyurl.com/2ka9chs2
Article title: Enriched and depleted characters of the Amnay Ophiolite upper crustal
section and the regionally heterogeneous nature of the South China Sea mantle.
Authors: Americus d.C.Perez, Decibel V. Faustino-Eslava, Graciano P. Yumul Jr., Carla B. Dimalanta, Rodolfo A. Tamayo Jr., Tsanyao Frank, Yange Mei-Fu Zhou
Publication title: Journal of Asian Earth Sciences 65, 107-117, 2013
Abstract:
The volcanic section of the Middle Oligocene Amnay Ophiolite in Mindoro, Philippines has previously been shown to be of normalmid-oceanic ridge basalt (NMORB) composition. Here we report for the first time an enriched mantle component that is additionally recorded in this crustal section. New whole rock major and trace element data are presented for nine mafic volcanic rocks from a section of the ophiolite that has not been previously examined. These moderately evolved tholeiitic basalts were found to have resulted from the bulk mixing of ∼10% ocean island basalt components with depleted mantle. Drawing together various geochemical characteristics reported for different rock suites taken as representatives of the South China Sea crust, including the enriched MORB (EMORB) and NMORB of the East Taiwan Ophiolite, the NMORB from previous studies of the Amnay Ophiolite and the younger ocean floor eruptives of the Scarborough Seamount–Reed Bank region, a veined mantle model is proposed for the South China Sea mantle. The NMORB magmatic products are suggested to have been derived from the more depleted portions of the mantle whereas the ocean island basalt (OIB) and EMORB-type materials from the mixing of depleted and veined/enriched mantle regions.
Full text available upon request to the author
Article title: Geology of northwestern Mindoro and its adjoining islands: Implications for terrane accretion in west central Philippines.
Authors: A. P. B. Canto, J. T. Padrones, R.A.B. Concepcion, A. D. C. Perez, R. A. Tamayo Jr., C. B. Dimalanta, D. V. Faustino-Eslava, K. L. Queaño, G. P. Yumul., Jr
Publication title: Journal of Asian Earth Sciences 61, 78-87, 2012
Abstract:
In over four decades, terrane studies of Mindoro Island have evolved from one terrane- to three terrane-models. Recent mapping of northwestern Mindoro and the islands of Lubang and Ambil roughly agrees with a 1990 suggestion that the island is composed of two terranes: the Central Range and the San Jose Platform. However, in contrast to this older model, our study, which takes into consideration the petrochemical and paleontological characteristics of the units, subdivides Northwest Mindoro into the Amnay Ophiolite and the Halcon Metamorphic terranes. Southwest-verging thrust faults parallel to the currently active Manila Trench demarcate the younger Amnay Ophiolite from the latter. Components of the older Mangyan Ophiolitic Complex, formerly thought to represent a terrane distinct from the metamorphic body, are now suggested to occur as disrupted bodies enclosed within the schists of the Halcon Metamorphics. The timing of incorporation of these megaclast materials and the regional metamorphism that occurred is constrained by the deposition of the sedimentary sequences of the Late Eocene Lasala Formation. Petrochemical studies of these younger sedimentary units reveal their continent-derived character. Therefore, accretion of the Cretaceous Mangyan Ophiolitic Complex marks the collision between the Cretaceous oceanic lithosphere and mainland Asia that is considered to be the protolith of the Halcon Metamorphics. A subsequent collision occurred which led to the amalgamation of the Amnay Ophiolite suite to the metamorphosed terrane.
Full text available upon request to the author
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