|
|||||
|
|
The oceanic substratum of Northern Luzon: Evidence from xenoliths within Monglo adakite (the Philippines) |
|
| Authors: | Betchaida D Payot Sebastien Jego Rene C Maury Mireille Polve Michel Gregoire Georges Ceuleneer Rodolfo A Tamayo Jr Graciano P Yumul Jr Herve Bellon and Joseph Cotten |
| Institution: | Tectonics and Geodynamics Academic Group, National Institute of Geological Sciences, University of the Philippines, Diliman, 1101 Quezon City, The Philippines,;Institut des Sciences de la Terre d'Orléans (ISTO), 1A, rue de la Férollerie, 45071 Orléans, France,;UMR 6538 Domaines Océaniques, Universitéde Bretagne Occidentale, 6, avenue Le Gorgeu, C.S. 93837, 29238 Brest Cedex 3, France,;UMR 5563 LMTG, Observatoire Midi-Pyrénées, 14 rue Edouard Belin, 31400 Toulouse, France,;UMR 5562 DTP, Observatoire Midi-Pyrénées, 14 rue Edouard Belin, 31400 Toulouse, France and;Philippine Council for Industry and Energy Research and Development-DOST, General Santos Avenue, Bicutan, 1631 Taguig, The Philippines |
| Abstract: | Abstract A 8.65 Ma adakitic intrusive sheet exposed near Monglo village in the Baguio District of Northern Luzon contains a suite of ultramafic and mafic xenoliths including in order of abundance: spinel dunites showing typical mantle-related textures, mineral and bulk rock compositions, and serpentinites derived from them; amphibole-rich gabbros displaying incompatible element patterns similar to those of flat or moderately enriched back-arc basin basalt magmas; and amphibolites derived from metabasalts and/or metagabbros of identical affinity. A single quartz diorite xenolith carrying a similar subduction-related geochemical signature has also been sampled. One amphibolite xenolith provided a whole-rock K–Ar age of 115.6 Ma (Barremian). We attribute the origin of this suite to the sampling by ascending adakitic magmas of a Lower Cretaceous ophiolitic complex located at a depth within the 30–35 km thick Luzon crust. It could represent an equivalent of the Isabela-Aurora and Pugo-Lepanto ophiolitic massifs exposed in Northern Luzon. |
| Keywords: | adakite dunite gabbro Luzon crust ophiolite the Philippines xenolith |