GEOLOGY OF THE PENGKALAN HULU-BETONG TRANSECT ...

arsenopyrite and grossularite are common. The product obtained from this mine is
composed of tin 25% and lead 37%, and the final product was usually refined as mixture
of tin and lead.
After the mining activities stopped, the surrounding area was found to have been
polluted by toxic materials derived from the tailings, such as lead and arsenic. Due to this
impact, the Department of Mineral Resources Thailand was engaged by the government
for rehabilitation work to mitigate the impact of toxic materials to the environment since
1999, by using the secure landfill method and reforestation (Figures 46 & 47).
A
Figure 46: Tham Thalu mine, Thailand
A- Abandoned open-cut of the mines.
B- B- Rehabilitated area by reforestation.
Mai mine is located to the west of Tham Thalu mine. Normally, cassiterite and sulphide
minerals occur in the contact zone between granite and shale. Cassiterite was transported
and accumulated as a placer deposit 50 m to the east of a Permian limestone cliff.
Bulan mine is situated at Ban Buluan, 1.5 km to the northwest of Tham Thalu mine. It is
in the contact zone between granite and limestone. Normally, cassiterite occurs in skarn
and sulphide mineral veins.
Bayor mine situated in the north of Mai mine and 1 km to the west of Bulan mine. It is
also in the contact zone, and quartz veins. Cassiterite commonly occurs in quartz veins
and placer deposits.
Na Sua mine is located in the valley of Ban Balae, 1 km to the northwest of Bulan mine.
The mine, started operation in 1970, was initially mined for copper (bornite, chalcanthite
and chalcopyrite). Unfortunately, the intended copper ore were disqualified due to high
percentage of cassiterite (>4%) in copper. Consequently, only tin was produced.
The earlier open-cut of Na Sua mine is situated in the contact zone of porphyritic
biotite granite and dark grey limestone. Due to metasomatism, the limestone were
metamorphosed to marble and skarn, and yielded sulphide minerals, such as chalcopyrite,
bornite, chalcanthite, sphalerite, galena and cerussite. In addition, pyrite, arsenopyrite,
hematite, scheelite and cassiterite also occurred (Sutthakorn, 1970). The later open-cut of
the mine, sulphide minerals such as pyrrhotite, galena, sphalerite, occur 40 m in width,
cut into the fault in skarn.
Generally, cassiterite is associated with pyrrhotite. To the north, pyrite veins are
observed cutting the quartzite with NW-SE strike direction and dipping 75 0 NW. Based
B
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