Abstract
Chemistry of the Permo-Triassic and Cretaceous-Tertiary granitoids in the Malay Peninsula region was reviewed putting an emphasis on the Y and HREE contents. The major Permo-Triassic granitoids are mainly felsic I-type ilmenite series. Some magnetite-bearing granitoids, like those of the East Belt of Malaysia may belong to an intermediate series. The Cretaceous-Tertiary granitoids look similar but become I-type magnetite series toward the Tertiary igneous rocks along the Central Valley Belt of Myanmar where adakitic granitoids occur in a small area. HREE, whose contents are very much correlated with Y content, are concentrated in two modes of occurrence: one with coarse-grained biotite granites observed, e.g, in the Samui Island of the southern Thailand and Dingdings pluton of western Malaysia, while the other is Sn-W mineralized fine-grained leucogranitic stocks at Hermingyi, Lower Myanmar, and several places including Yod Nam mine of the Central Belt.
