The granitic rocks
present in this report are from the Ban Pang and Ban Mai Takhian area,
Amphoe Li, Changwat Lumphun that are considered to be part of eastern Li
granite. They comprise variably textured silicified granitic rocks and
monzogranites. The silicified granitic rocks show hiatal, megacrystic and
fine-graned equigranular textures. The groundmass of the inequigranular
varietics is texturally similar to the fine-grained equigranular rocks.
Abundant anhedral quartz, crystals, either as isolated grains or as clusters
devoid of conscrtal appearance, are the dominant features of the silicified
granitic rocks. The monzogranites have medium-grained scriate and equigranular
textures. Their quartz crystals are typically almost anhedral, and form
clusters with consertal relationship. Both the granitic types have principal
constituents, i.e. quartz, alkali feldspar (orthoclase and microcline)
and plagioclase, typical of monzogranites but for one sample which is compositionally
syenogranite. Biotite occurs as a subordinate constituent to the principal
minerals. Minor and trace constituents are zircon/monazite, apatite and
opaque mineral, and may include andalusite, cordierite, orthopyroxene,
muscovite and tourmaline. The accessory mineral assemblage reveals that
the studied granitic rocks are peraluminous granite (S-type), and that
the granitic magna might have emplaced and solidified at pressures less
than 0.6 kb (ca. 2 km). Almost all the silicified granitic rocks might
have been derived from monzogranites by a silicification process.