Luzon Volcanic Arc

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The name Luzon Volcanic Arc was first proposed by Defant et al. [1] to describe a series of Miocene to recent volcanoes due to eastward subduction along the Manila Trench for approximately 1,200 km from the Coastal Range in Taiwan south to southern Mindoro in the Philippines. They presented representative geochemistry of a number of volcanoes along the arc and were able to show five distinct geochemical domains within the arc (Mindoro, Bataan, Northern Luzon, Babuyan, and Taiwan). The geochemistry of the segments verified that the volcanoes are all subduction related (e.g., strong Nb anomalies and calc-alkaline characteristics). Isotopes and trace elements allowed them to show unique geochemical characteristics in the north. They proposed that the geochemical variations northward (Babuyan segment) were due to the subduction of sediments derived from the erosion of continental crust (China and Taiwan).

Subsequently, Defant et al. [2] documented a distinct increase in Sr isotopic ratios with latitude northward. They concluded that this supported their original conjecture that the variations were due to an increasing "crustal" component in subducted sediments as the continental blocks in the north were approached (China and Taiwan). They pointed out that sediment thicknesses increased toward the north along the trench.

Defant et al. [3] also did a detailed paper on the geochemistry and tectonic setting of the southern Luzon arc and concluded that the geochemistry suggested that continental crust (probably from sediments) played an important role in the Macolod corridor [4] and the Mindoro segments. They pointed out that crustal collision had occurred in the south between the North Palawan-Mindoro crustal block and suggested that sediment contamination was derived from this region. The work substantiated preliminary early isotope and trace element studies on the central Luzon arc [5] [6]

Further work was done on the northern Luzon arc by McDermott et al. [7] who found systematic variations in an assortment of isotopes with latitude not only in the lavas analyzed over the 500 km section of the arc but also in sediments along the trench. They concluded that the only way to explain the latitudinal variations was through the addition of an increasing input of terrigenous sediments toward the continental regions in the north (China and Taiwan)


References[edit]

  1. ^ Defant, M. J., Jacques, D., Maury, R. C., de Boer, J., and Joron, J.-L., 1989, Geochemistry and tectonic setting of the Luzon arc, Philippines, Geol. Doc. Am. Bull, v. 101, p. 663-667.
  2. ^ Defant, M. J., Maury, R. C., Joron, J.-L., Feigenson, M.D., Leterrier, J., Bellon, H., Jacques, D., and Richard, M., 1990, The geochemistry and tectonic setting of the norther section of the Luzon arc (Philippines and Taiwan): Tectonophys., v. 183, p. 187-205.
  3. ^ Defant, M. J., Maury, R. C., Ripley, E. M., Feigenson, M. D., and Jacques, D., 1991, An example of island arc petrogenesis: Geochemistry and petrology of the southern Luzon arc Philippines: 1991, J. of Petrol., v. 32, p. 455-500.
  4. ^ Defant, M. J., de Boer, J., Oles, D., 1988, The western Luzon volcanic arc the Philippines: Two arcs divided by rifting: Tectonophys., v. 145, p. 305-317.
  5. ^ Knittle, U. and Defant, M. J., 1988, Sr isotope and trace element variations in Oligocene to recent igneous rocks from the Philippine island arc: Evidence for recent enrichment in the sub-Philippine mantle: EPSL, v. 87, p. 87-90.
  6. ^ Knittle, U., Defant, M. J., and Rakzek, I., 1988, Recent enrichment in the source region in arc magmas from Luzon Island, Philippines: Sr and Nd Isotopic evidence: Geol. v. 16, p. 73-76.
  7. ^ McDermott, F., Defant, M.J., Hawkesworth, C.J., Maury, R. C., Joron, J.-L., 1993, Isotope and trace element evidence for three component mixing in the genesis of north Luzon arc lavas (Philippines): Contrib. Mineral. Petrol. v. 113, p. 9-23.