The tectonic framework of Indonesia is complicated by interaction of the Eurasian continental, the Indian oceanic and the Australian continental as well as the Pacific• Philippine oceanic plates. During Late Palaeozoic-Early Cainozoic time, the region of western Indonesia (Kalimantan, Sumatra, Sulawesi, west and central Java) had been part of "the Eurasian landmass. In Cainozoic time, this region formed the con• tinental terrain bounding Eurasia on the southeast.
The region of western Indonesia may be grouped into four overlapped tectonic
zones: (1) the Late Palaeozoic-Mesozoic tectonic zone, connecting Sumatra, Riauw• Bangka-Billiton islands, Anambas Natuna islands, west and central Kalimantan; (2) the Late Mesozoic-Early Tertiary tectonic zone, connecting southwestern Sumatra, west and central Java, southeast Kalimantan as well as Sulawesi (including Sumba continental fragment); (3) the Cainozoic tectonic zo°'-.of volcanic Sunda arc, con• necting Sumatra, Java and the Lesser Sunda islands, and the volcanic belt of western and northern Sulawesi; ( 4) the tectonic zone of nonvolcanic Sunda arc comprising the Cainozoic subduction complex at west of Sumatra.
The tectonically separated unit of the tin-area (Sumatra, Riauw-Bangka-Billiton
islands, and perhaps also Anambas islands) is presumably dominated by Late Palaeozoic-Mesozoic deformation and magmatism, underlain by pre-Late Palaeozoic (Precambrian ?) continental crust. Mineralization of tin is generally related to the intrusions of granite during diastrophic episodes of major geologic events, with the main periods of folding and igneous activity taken place in Late Palaeozoic, Mesozoic and Early Cainozoic time. The Late Palaeozoic granites are highly felsic, and are characterized by the absence of hornblende. Their country rock consists of isoclinally folded dynamothermal greenschist facies metasediments; there is no hornfels thermal aureole. These granitic magmas evolved within the crust -as a wet magma and resulted from anatexis of sialic rock in part of the pre-Late Palaeozoic rocks. The tin bearing Mesozoic-Early Tertiary granites intruded the country rocks and contain muscovite, biotite, tourmaline, garnet, alkali feldspar, sodic plagioclase, and traces of ilmenite. These tin granites do not show any foliation or any stressed features.
The principal metallic mineral areas of Sumatra, as well as west and central Kalimantan, and their association with Triassic-Jurassic, Jurassic-Cretaceous, and Cretaceous-Early Tertiary igneous and metamorphic activities, are characterized by precious, base, rare, and ferro-alloy metallic mineral deposits. Since Late Tertiary
* Presented at the international symposiumon Metallogenyof Asia and the panel discussion on. Metallogenic Map of South and East Asia, held at Tsukuba and Tokyo in January

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