Three principal granite provinces are defined across SE Asia, as follows. (1) The Western Thailand–Myanmar/Burma province consists of hornblende–biotite I-type granodiorite–granites and felsic biotite–K-feldspar (± garnet ± tourmaline) granites associated with abundant tin mineralization in greisen-type veins. New ion microprobe U–Pb dating results from Phuket Island show zircon core ages of 212 ± 2 and 214 ± 2 Ma and a thermal overprint with rims of 81.2 ± 1.2 and 85–75 Ma. (2) The North Thailand–West Malaya Main Range province has mainly S-type biotite granites and abundant tin mineralization resulting from crustal thickening following collision of the Sibumasu plate with Indochina during the Mid-Triassic. Biotite granites around Kuala Lumpur contain extremely U-rich zircons (up to 38000 ppm) that yield ages of 215 ± 7 and 210 ± 7 Ma. (3) The East Malaya province consists of dominantly Permian–Triassic I-type hornblende–biotite granites but with subordinate S-type plutons and A-type syenite–gabbros. Biotite–K-feldspar granites from Tioman Island off the east coast of Malaysia also yield a zircon age of 80 ± 1 Ma, showing Cretaceous magmatism in common with province 1. Geological and U–Pb geochronological data suggest that two east-dipping (in present-day coordinates) subduction zones are required during the Triassic, one along the Bentong–Raub Palaeo-Tethyan suture, and the other west of the Phuket–Burma province 1 belt. Supplementary material: A full description of U–Pb analytical methods used and data tables are available at www.geolsoc.org.uk/SUP18523 .

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The Malaysian granitoids of the Southeast Asian tin belt have been traditionally divided into a Permian to Late Triassic "I-type"dominated arc-related Eastern province (Indochina terrane) and a Late Triassic "S-type"-dominated collision-related MainRange province (Sibumasu terrane), separated by the Bentong-Raub Paleo-Tethyan suture that closed in the Late Triassic. The present study, however, shows that this model is oversimplifi ed and that the direct application of Chappell and White's (1974) I-and S-type classifi cation cannot account for many of the characteristics shared by Malaysian granitoids. Despite being commonly hornblende bearing, as is typical for I-type granites, the roof zones of the Eastern province granites are hornblende free. In addi tion, the Main Range province granitoids contain insignifi cant primary muscovite, and are dominated by biotite granites, mineralogically similar to many of the plutons of the Eastern province. In general, the Malaysian granitoids from both provinces are more enriched in high fi eld strength elements than typical Cordilleran I-and S-type granitoids. The mineralogy and geochemistry of the Eastern province granitoids, and their relationship with contemporaneous volcanics, confi rm their I-type nature. The bulk liquid lines of descent of both granitic provinces largely overlap with one another. Sr-Nd isotopic data further demonstrate that the Malaysian granitoids, especially those of the Main Range, were hybridized melts derived from two "end-member" source regions, one of which is isotopically similar to the Kontum orthoamphibolites and the other akin to the Kontum paragneisses of the Indochina block. However, there are differences in the source rocks for the two provinces, and it is suggested in this paper that these are related to differing proportions of igneous and sedimentary protoliths. The incorporation of sedimentary-sourced melts in the Eastern province is insignifi cant, which allowed the granites in this belt to maintain their I-type nature. The presence of minor primary tin mineralization in the Eastern province compared to the much more signifi cant tin endowment in the Main Range is considered to refl ect the incorporation of a smaller proportion of sedimentary protolith in the melt products of the former.

Evidence of Early Palaeozoic volcanism inPeninsular Malaysia is largely represented by felsic Gerik-Dinding meta-volcanic rocks; however, reliable absolute ages for the meta-volcanic rocks are still lacking. This restricts correlation of these meta-volcanic rocks with other Early Palaeozoic East Gondwana Proto-Tethys margin tectonic elements identified in the evolution of Southeast Asia. Here, we report petrographic data and zircon U-Pb age of the Gerik-Dinding metavolcanic rocks. Zircons from three Gerik-Dinding meta-volcanic rock samples yield Early to Middle Ordovician weighted mean 206 Pb/ 238 U ages between 480 and 460 Ma. The formation age of the meta-volcanic rocks coincides with the post-collision stage from the final amalgamation of Asian micro-continental fragments with the East Gondwana Proto-Tethys margin. Tectonic processes such as lithospheric delamination during the post-collision period could have induced the hot asthenosphere to underplate the continental crust and trigger crustal anatexis. With these findings, the Early Palaeozoic tectonic history of Peninsular Malaysia needs careful review.

The granitic rocks of the peninsula have traditionally been divided into two provinces, i.e., Western and Eastern provinces, corresponding to S-and I-type granite respectively. The Western Province granite is characterised by megacrystic and coarse-grained biotite, tin-mineralised, continental collision granite, whereas, the Eastern Province granite is bimodal I-type dominated by granodiorite and associated gabbroic of arc type granite. This paper reports the occurrence of an A-type granite from peninsular Malaysia. The rocks occur in the Besar, Tengah, and Hujung islands located in the southeastern part of the peninsula. The granite is highly felsic with SiO 2 ranging from 75.70% to 77.90% (differentiation index = 94.2-97.04). It is weakly peraluminous (average ACNK=1.02), has normative hypersthene (0.09-2.19%) and high alkali content (8.32-8.60%). The granites have many A-type characteristics, among them are shallow level of emplacement, high Ga, Fe T /MgO and low P, Sr, Ti, CaO and Nb. Calculated zircon saturation temperatures for the Besar magma ranging from 793 • to 806 • C is consistent with high temperature partial melting of a felsic infracrustal source which is taken as one of the mechanisms to produce A-type magma. The occurrence of the A-type granite can be related to the extensional back arc basin in the Indo-China terrane during the earliest Permian.