Abstract

U-Pb zircon dating of granitoid plutons from the West Coast Province of Peninsular Malaysia yields precise and unambiguous ages of 198–220 Ma (late Triassic). These ages are considerably older than previously reported K-Ar mica ages which have been largely reset, but agree with or are younger than Rb-Sr whole rock apparent ages. The U-Pb zircon ages are considered to represent the best estimate of the intrusive ages of the plutons. Some of the problems associated with the interpretations of the pre-Triassic Rb-Sr whole rock apparent ages are discussed here and alternative ways to explain these ages in the light of recent work are considered. Reversely discordant patterns displayed by zircon populations from a number of plutons yield consistent upper intersection ages of ~1500–1700 Ma that approximately date source-derived, inherited zircon components. The Precambrian ages of these inherited zircon components suggest that the West Coast Province S-type granitoids are derived from sedimentary sources recycled, at least in part, from mid-Proterozoic crystalline basement sources.

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