The Canlaon and its neighbouring volcanoes in the Negros Belt/Philippines

Abstract

Mt Canlaon is an active, potentially dangerous strato-volcano in the Negros volcanic arc on the island of Negros (Philippines). Its volcanic activity during the last 125 years was nearly exclusively restricted to phreatic eruptions and permanent fumarolic emissions. On account of the lack of petrological and chemical data, 52 samples of Negros volcanics have been analysed with regard to their major and trace element composition. The bulk of the rocks are typical calc-alkaline andesites and basaltic andesites, which belong to the high K-calc-alkaline series with tendencies to shoshonites. A similar but less K-rich distribution is shown by the eruption products of the other volcanoes of Negros, partially plotting into the fields of normal calc-alkaline series. Compared with other Cenozoic Philippine volcanics, i.e. from the Bicol and Central Luzon Belts and from Hibok-Hibok volcano, the Negros suite differs significantly by its higher levels of K 2O. The Negros volcanics correspond to typically continental or microcontinental associations like those developed in the central Andes or on the North Island of New Zealand. We suppose that the fluids of the subducted Sulu Sea crust (east of Palawan) may control the isotopic and trace element variations in the southwestern Philippine island arc, including the generation and evolution of the Negros magmas.