Bulletin of the Geological Society of Malaysia, Volume 26, April 1990, pp. 147 – 179
1Bundesanstalt fur Geowissenschaften und Rohstoffe, P.O. Box 510153, D-3000 Hannover 51, Fed. Rep. of Germany
2Geological Survey of Malaysia, P.O Box 1015, Ipoh Malaysia
Abstract: The Kuantan-Dungun area (6000 km2) 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 common 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 Bujang Melaka 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.
The behaviour of tin during magmatic evolution is related to the role of oxygen fugacity for the partitioning of metal between melt and crystallizing solid. Tin occurs in both the divalent and the tetravalent state. Low oxygen fugacity favours the partitioning of tin into the melt relative to the crystallizing solid. Low oxygen fugacity shifts the equilibrium to the left side of the reaction:
Sn2+ + 2O2- = SnO2 + 2θ
Ca(Ti, Sn) SiO5
Tin exhibits incompatible behaviour (with respect to the solid crystallizing from the granite magma) in a low oxygen fugacity environment and tends to decoupled behavior (independent of magmatic evolution) under an intermediate oxygen fugacity.
Tungsten occurs mainly in one valence state only (WVI) in the liquid phase as well as in the solid phase. The reaction is less dependent on oxygen fugacity than the corresponding reaction for tin:
WO2-4+ Fe2+ = FeWO4
The distribution coefficient of tungsten is relatively insensitive to oxygen fugacity, and tungsten enrichment in residual liquids may be produced under a wide range of oxygen fugacities.
The mixed ilmenite-series/magnetite-series characteristics (intermediate oxygen fugacity) of the Eastern Province, in general, and the Kuantan-Dungun area, in particular, constitute a less favourable environment for tin mineralization than the exclusively ilmenite-series Main Range batholith (low oxygen fugacity). This is reflected by the differences in total mine production of tin in Malaysia: 94% has come from the Main Range and 6% from the Eastern Province although the two areas are approximately the same size.
Mixed ilmenite-series/magnetite-series granitoids and pure ilmenite-series granitoids are equally favourable for wolframite mineralization because of its relative independence on oxygen fugacity. This is in agreement with the mine production of wolframite which is approximately equal in the Main Range and the Eastern Province.