GEOLOGY OF THE PENGKALAN HULU-BETONG TRANSECT ...

British American Tin Mines Company Limited until World War II. After the War, this
mine was controlled by the Thai Tin and Rubber Company under the Royal Thai
Government until 1949. Total production of tin since the beginning of operation was
500,000 tonnes. During that period, efficiency of ore dressing was quite low, i.e. only
18% – 36% of tin could be separated. However in 1940 minerals separation was
improved by chemical process, called “Cavaet Method”. A total 400,000 tonnes of
tailings with >1% of tin contents were left around the mine.
Cassiterite in this mine normally occurred in quartz stringers-veins stockworks, in
quartzite and shale of the Kanchanaburi Formation. In the mineralized veins, 1% – 2% of
cassiterite is commonly associated with garnet and Fe minerals. The mineral assemblage
in the contact zone is composed of galena, pyrite, chalcopyrite, arsenopyrite, and
magnetite.
iv. Than To Deposit
Figure 48: Open-cut at Pin Yoh mine, Bannang Sta District, Thailand.
This deposit is situated at Ban Than To, Than To District, 6 o 02′ 42″ N, 101 o 12′ 42″ E
on the topographic map Sheet 5221 III of scale 1:50,000. This deposit is in the contact
zone of granite and sedimentary rocks. The former mining area has now been completely
flooded by water below the Bang Lang Dam.
v. Ai Yoe Weng Deposit
This deposit is located in Betong District at Lat. 5 o 55′ 00″ N – 5 o 55′ 20″ N and Long.
101 o 07′ 30″ E – 101 o 10′ 30″ E, on topographic map Sheet 5220 IV (Amphoe Betong). It
is within the contact zone of granite and sedimentary rocks of the Kanchanaburi
Formation which includes hornfel, quartzite, phyllitic quartzite, slate and phyllite.
Generally, pyrite disseminates throughout these rocks, especially, in the fractures. Quartz
veins cut the rocks in the E-W direction. Mineral assemblage of the veins is composed of
pyrite, arsenopyrite and cassiterite. Cassiterite was also commonly found in the Ai Yoe
Weng stream and Ai Yoe Kem stream. This deposit consists of two mines; Prachuab and
Ai Yoe Weng mines.
Prachuab mine is situated at Km 98 on the way from Yala to Betong town (28 km north
of Betong). The overburden is generally composed of gravels of biotite granite,
tourmaline-biotite granite, and quartz. The bedrock is phyllitic quartzite. Gravel pump
mining had been carried out to exploit the tin placer deposit.
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