Granite magmatism and tin-tungsten metallogenesis in the Kuantan-Dungun area, Malaysia

Abstract

The Kuantan-Dungun area (6000 km 2) is an important tin district which produced about 40 % of all tin mined in the Eastern Granite Province of Peninsular Malaysia. It is the most important wolframite-producing district in Malaysia. The largest underground tin mine of Malaysia (Sungei Lembing) is also located in this area. The granitoids that occupy about 30% of the area have a Permian age (240-275 Ma) except for a Triassic stock at Paka near Dungun (220 Ma). The composition of the granitoids ranges from gabbro to biotite granite (monzogranite). The largest part is occupied by biotite granite which exhibits characteristics of both S-type granite derived from a sedimentary source rock and I-type granite derived from an igneous protolith. Hornblende-biotite granite (to granodiorite) and gabbro (to quartz diorite) are subordinate. The basic to intermediate rocks have affinities to tholeiitic magma and are not genetically linked to the granites by fractional crystallization. But the gabbroic rocks and the granites may have had a co=on heat source. Only in hydrothermally altered portions, the Kuantan-Dungun granites show elevated Sn concentrations (up to 34 ppm Sn). The tin concentrations in unaltered rocks are low (averaging 3 ppm Sn). The Kuantan-Dungun granites have in common with other granites in the Eastern Province, tin concentrations that seem to be unrelated to the differentiation stage, i.e. tin is a decoupled element. Both the low tin concentrations and the decoupled behavior of tin are unusual features of granites associated with tin deposits. The metallogenesis of tin in the wolframite-cassiterite area of Kuantan-Dungun is different from that in cassiterite-dominated S-type granite systems with very subordinate wolframite in the Main Range, of which the BujangMelaka pluton in the Kinta Valley is a typical example. The Main Range batholith, in general, and the Bujang Melaka pluton, in particular, show a significant increase in tin concentration with increasing degree of magmatic differentiation, i.e. tin is much higher in late-stage differentiates than in less evolved rocks. But for the Kuantan-Dungun granites, the distribution coefficient of tin between melt and solid must have been near 1 during most of the crystallization history of the magma. Tin enrichment did not take place until the residual fluids separated from the crystallizing magma.