The three major tin granitoid belts are, from west to east: a) Western: From Phuket to Tenasserim. The tin deposits are associated with highlevel Cretaceous adamellite, granite and pegmatite. The mineralization extends over a wide vertical extent. b) Main Range: From Bangka to South Thailand. The tin deposits are associated with deep-seated large-microcline granite and adamellite of late Carboniferous and late Triassic age. The mineralization is confined to the roof zones of the batholith. c)

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... stern: From Billiton to Pahang-Trengganu. The tin-tungsten deposits are associated with adamellite to granite of Permian to mid Triassic high-level plutons. Mineralization extends over a wide vertical extent and there is an important Fe-Sn association. Only the Eastern Belt can be classified as Circum-Pacific type. It represents an epizonal volcano-plutonic arc characterized by plutonic rocks ranging from gabbro, through tonalite, granodiotite, adamellite to granite. Rhyolitic ignimbritic volcanic rocks are important. The Western Belt has some of the Eastern Belt characteristics, but lacks the range of plutonic rocks, and volcanic rocks are absent. However, the Tertiary opening of the Andaman Sea requires that the Burmese-Indonesian volcanic arc formerly was adjacent to the adamellite-granite belt. The Main Range Belt is interpreted as resulting from crustal anatexis of the leading edge of the western craton as it attempted to subduct beneath the Eastern volcano-plutonic arc following the late Triassic closure of the central marginal basin.