Gunung Jerai Analysis

Summary of the geology of Gunung Jerai
Gunung Jerai is a mountainous region located in central Kedah, between the borders of Kuala Muda and Yan district. The highest point of Gunung Jerai is recorded to be 1217 meters and Gunung Jerai covers a total area of 86.4 square kilometers (Lee et al., 2004). According to Bradford (1972), the existence of Gunung Jerai can be related to the Jerai Formation and the Patani Formation.
The Jerai Formation, named after Gunung Jerai itself, is of Cambrian age with thickness of 1425 meters. Jones (1970) has divided the Jerai Formation into two members which are the lower member and the upper member. The lower member is near 900 meters thick and it consists of quartz-mica, schist and phyllite. Also present is
The Patani Formation is of Silurian age and the boundaries of this formation actually overlie the Jerai Formation. The thickness of Patani Formation is 1524 meters. Bradford (1972) has divided the Patani Formation into three facies which are argillaceous, arenaceous and calcareous. The lithology of Patani Formation consists of argillaceous sequence of shale and mudstone, commonly ferruginous and subject to lateritization and in places phyllitic or pyritiferous. A less extensive arenaceous facies of sandstones or orthoquartzite can also be found with the presence of limestone on Bidan Island. The Patani Formation is believed to have a deep gulf or geosynclinal basin depositional
This is equivalent to the age of the Main Range granite which is about 198 to 220 Ma. Therefore, it can be said that the Jerai granite intrusion is an extension of the magmatism that moved westward from the trench in the subduction zone, which forms the Main Range (Ghani et al., 2013). On the other hand, the pegmatite granite intrusion is regarded to be as another episode of intrusion which takes place after the biotite-muscovite granite and tourmaline granite intrusion as it has an age of 204.6 ± 4.3