GEOLOGY OF THE PENGKALAN HULU-BETONG TRANSECT ...

56
of crytallization. Instead of xenoliths, autolith also present randomly throughout the
granite in the forms of oval, rounded, elongate segregation and clots.
A B
Figure 40: A typical Bintang granite (Trgrbt) at Pong Hydroelectric Dam, Sungai Pong, Kelian
Intan area, Malaysia.
A- Porphyritic biotite granite
B- Porphyritic biotite granite with xenolith
3.3.3 Chantharat granite (Trgrch)
Distribution
The Chantharat granite (Trgrch) covers approximately 20% of the Transect area and is
only exposed on the Thai side. It can be observed on the road-cuts along the local road
from Ban Chantharat to Ban Ai Yoe Quin, and Ban Chantharat to Ban Chulaporn 10,
along the eastern flank of the Transect area. Dykes and veins are locally found along the
intrusive margins.
Petrography
The vast majority of the Chantharat granite (Trgrch) is characterized by its medium- to
coarse-grained, sparsely megacrystic to good megacrystic, unfoliated to weakly foliated,
biotite granite (Figure 41). The local alignment of the K-feldspar megacrysts is in the
NNE-SSW direction, subparallel to the strike of the major structural features of the
Transect area. K-feldspar can be seen as large megacrysts of light grey to chalky white
colour with elongate to tabular, euhedral to subhedral habits. Population concentration of
the K-feldspar megacrysts varies from sparsely megacrysts to locally concentrated
megacrysts. Weakly foliated K-feldspar megacrysts are locally observed.
Biotite groundmass is observed as euhedral book crystals and subhedral to anhedral
flakes crystals with single to clusters habits. Plagioclase presents in groundmass as chalky
white colour, euhedral to subhedral, tabular to equant crystals. K-feldspar groundmass
forms subhedral to euhedral crystals with tabular habit. Quartz can be observed as
anhedral to subhedral crystals, single and clusters with subrounded to subangular habits.
Cognate and accidental xenoliths also present in these rocks.