Bulletin of the Geological Society of Malaysia, Volume 17, Dec.1984, pp. 265 – 281
Jabatan Geologi, Universiti Malaya, Kuala Lumpur
Abstract: The clastic rocks of the islands of Rebak Besar and Rebak Kecil in west Langkawi are found to have undergone low grade regional metamorphism followed by contact metamorphism and metasomatism from a granitic source believed to occur under the Rebak rocks at no great depth and possibly underlying the adjacent seafloor. The regional metamorphism gave rise to the formation of slates, phyllitic slates and phyllites with low angle cleavages or schistosities and quartzites with strained quartz grains. The contact metamorphism was responsible for new growths of randomly orientated muscovite which also occurs as rosettes. Widespread tourmalinization and pyritization are evidence of metasomatism.
It is suggested that the Rebak rocks resemble some lithologies of the Upper Detrital Band and that the sea between the Rebak islands and the Machinchang hills is probably floored by extensions of the Raya granite. This may explain the absence of the Setul limestone in west Langkawi which may not be due to the presence of an unconformable contact between the Upper Devonian Rebak rocks and the Cambrian Machinchang Formation.