Field relation, petrochemistry and classification of the volcanic rocks from the eastern part of Tioman Island, Pahang

The volcanic rocks from eastern part of the Tioman Island can be divided into volcanic lava and pyroclastic types. Geochemically volcanic lavas can be classified as andesite, dacite and rhyolite. The proportion of quartz, K-feldspar and plagioclase of the three rock types are: rhyolite (Quartz: 60-65%, K-feldspar: 10-15%, Plagioclase: 10- 15%), dacite (Quartz: 40-50%, K-feldspar: 25-30%, Plagioclase: 15-25%) and andesite (Quartz + K-feldspar: 15-25%, Plagioclase: 55-65%). Both rhyolite and dacite may have a common origin. On the other hand, the andesite samples show a slight concave upward REE pattern which may be the result of minerals such as garnet, clinopyroxene and amphibole having remained residual in their source. The presence of garnet constraints the mafic source to be within the lower crust (deeper than 25 km) or upper mantle