Abstract

This paper presents the geology of the granites and their associated Sn-Ta mineralization of the Phuket, Phangnga and Takua Pa tin-field, southern Thailand. The tin-field was producing more than half of all tin mined in Thailand. During 1961 to 1990, more than 400,000 long tons of tin concentrates were produced from this district. Much of the tin is recovered from alluvium (on-shore and off-shore) by dredging and gravel pump methods. A significant amount of tin is also mined from primary deposits, ilmenite, monazite, columbite-tantalite, zircon and wolframite are the chief by-product minerals of the tin mining operation.

Tin deposits are associated closely with the granites that were recognized as the Western Tin Province of the Southeast Asian tin belt. The granites have been classified into ten units on the basis of their lithology and mineralogy. Except for the Khao Prathiu granite that has I-type affinity, the other granites have S-type affinities. All granites were emplaced during the Cretaceous, i.e. 78-98 Myr ago.

There are three types of tin deposits exposed in the region. The first is the pegmatites which contain minor amounts of cassiterite and associated Li-Ta-Nb minerals. The pegmatites are closely related to highly fractionated S-types granites. The second is the argillic dissemination. It is specially associated with highly fractionated S-type granite, i.e. leucocratic granite and the Nok Hook granite. Mineralogically, these granites are characterized by muscovite and tourmaline-muscovite. Endogeneous quartz-cassiterite-wolframite vein swarms are the third significant deposit.

 

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