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1 National Taiwan University, Taipei, Taiwan

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40 Ar/ 39 Ar and Fission Track constraints on Miocene Tectonics in the Buruanga Peninsula, Panay Island, Central Philippines. Monika Walia 1 , T. F. Yang 1 , T. K. Liu 1 , C. H. Lo 1 , L. S. Teng 1 , W. M. Yuan 2 , Ling Chung 1 , G. P. Yumul 3 , C. B. Dimalanta 4. - PowerPoint PPT Presentation
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40 Ar/ 39 Ar and Fission Track constraints on Miocene Tectonics in the Buruanga Peninsula, Panay Island, Central Philippines Monika Walia 1 , T. F. Yang 1 , T. K. Liu 1 , C. H. Lo 1 , L. S. Teng 1 , W. M. Yuan 2 , Ling Chung 1 , G. P. Yumul 3 , C. B. Dimalanta 4 1 National Taiwan University, Taipei, Taiwan 2 China University of Geosciences, Beijing, 100083, China 3Department of Science and Technology, Bicutan, Taguig, Metro Manila 4 National Institute of Geological Sciences, University of Philippines, Diliman, Philippines
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  • 40Ar/39Ar and Fission Track constraints on Miocene Tectonics in the Buruanga Peninsula, Panay Island, Central PhilippinesMonika Walia1, T. F. Yang1, T. K. Liu1, C. H. Lo1, L. S. Teng1, W. M. Yuan2, Ling Chung1, G. P. Yumul3, C. B. Dimalanta4 1National Taiwan University, Taipei, Taiwan2China University of Geosciences, Beijing, 100083, China3Department of Science and Technology, Bicutan, Taguig, Metro Manila4National Institute of Geological Sciences, University of Philippines, Diliman, Philippines

  • ~7 cm/yr

    ~9 cm/yr

    The Philippines is sandwiched between two oppositely dipping subduction zones The Philippine island arc is built on oceanic crust which was modified by several episodes of magmatism

  • Age of collisionThe Palawan Microcontinental block, which was rifted from Mainland Asia started to collide with the Philippine Mobile Belt during Early to Middle Miocene {Yumul et al., 2003 and reference therein} Paleomagnetic reconstructions show that the Palawan microcontinental Block-Philippine Mobile Belt collision occurred in the Late Miocene, somewhat later than is commonly envisaged {Queano et al., 2007}

  • [from Dimalanta, 2006]

  • The rock units are limestone, chert, siliceous mudstone and quartz-rich sandstone

    In the east of the peninsula, pyroclastic flow deposits and clastic rocks (polymictic conglomerates, arkosic and lithic sandstones and shale)

    Serpentinized peridotites (harzburgite and dunite) in the northeastern part of the study area

  • Field ObservationsQuartz-rich sandstone, siliceous mudstone, shale

  • Field Observations

    mudstone-wackestoneMassive to beddedBeds dipping NW

  • Field Observations

    Plio-Pleistocene (Cruz & Lingat, 1996)Limestone

  • Field ObservationsUltramafic rocks

    Dunites and harzburgitesHighly serpentinizedHighly fractured

    opxserpentine1 mm

  • Late Middle MioceneUnits:1. Quartz-poor sandstone, mudstone, shale2. Conglomerates with harzburgite and gabbro clastsField Observations

  • PN 1: Quartz Diorite

  • PN 1: Quartz Diorite

    Early Miocene20.8+1 Ma19.5+1 Ma (Bellon & Rangin, 1991)

  • PN 5: Intrusive Rock

  • PN 7B: Sandstone

  • PN 7B: Diorite

  • Hornblende Ar

  • FISSION TRACK DATA

    No.SampleMineral datedNsNs iNiU(ppm)( 2)Central age (Ma 1)P (2) %1.PN 1Zircon512.5226252.182274436.811.82.5

  • RESULTS16.1 Ma10.1 Ma13.6 Ma50.9 Ma

  • RESULTS9.3 Ma7.1 Ma16.9 Ma

  • 40Ar/39Ar RESULTS

  • Ar-Ar HornblendeFT ApatiteFT ZirconAr-Ar BiotiteAr-Ar Hornblende

  • Ar-Ar HornblendeFT ZirconAr-Ar HornblendeFT Zircon

  • Ar-Ar hornblende ages suggest the time of intrusion of the diorite bodies in the area ~84 Ma in the eastern part and ~30 Ma in the western partTectonic activity is recorded by the zircon FT and Ar-Ar system over a temperature range of ~250 C to ~500 C around 17-20 Ma This may be inferred as the time of collision of the microcontinent with the mobile belt We interpret the last stage of cooling recorded by the fission track system as representing the timing of later successive events/soft collisions ranging from 9-13 Ma In the western coast of the island, apatite ages show partial resetting and zircon ages are unaffected by the tectonic event being away from the suture zoneCONCLUSIONS

  • Thank you for the attention ~~

    *Philippine Island ArcPhilippine Mobile BeltPhilippine Sea PlateEurasian PlateNorth Palawan Block based on Ramos, 2005


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