Discussion on the granites of the southeast Asian tin belt

Abstract

T. T. Khoo writes: I refer to the informative paper by Cobbing et al. 1986 on the granites of the southeast Asian tin belt and particularly on the Peninsular Malaysian granites. However, I note that some aspects of Peninsular Malaysian geology are more complex than suggested in the paper. The authors mentioned that the granites of the Main Range province are of Triassic age quoting various sources including Bignell & Snelling (1977). It is further mentioned that the ages of the envelope range from Ordovician to Devonian and therefore the granites are about 150 Ma younger than the host rocks. The age range of the host rocks stated by the authors is erroneous and in fact should be Cambrian to Upper Triassic which could narrow the age difference between the granites and envelope considerably. Further aspects of the geology of some areas within the Main Range province as delineated by Cobbing et al. 1986 are as follows: 1. The granites of Langkawi, which are unfortunately not shown in figs 1 and 2, the sedimentary formations of Machinchang (Cambrian), Setul (mainly Ordovician–Silurian), Singa (Carboniferous) and Chuping (Permian). The stratigraphy and palaeontology of the Langkawi islands are well studied and Jones (1981) gives most of the details. Contact metamorphism of the sediments by the granites in Langkawi has been found to be extensive (Khoo 1984). 2. The Jerai granite in Kedah Peak area intrudes sediments similar to the Cambrian Machinchang Formation called the Jerai quartzite (Bradford 1972) and a reasonably wide