Sample 03MW2620 is a porphyritic foliated granite
composed of plagioclase (36%), K-feldspar (30%), quartz (25%), chlorite
(5%), epidote (1%), oxides (1%), sericite (1%), and trace hornblende,
muscovite, garnet, and biotite. This rock is characterized by coarse
porphyries of K-feldspar (17 mm) and plagioclase (14 mm) in a matrix of
quartz and micas. Perthitic K-feldspar grains show plagioclase
inclusions. Feldspar alteration to sericite and epidote is common.
Quartz grains are mostly equigranular, and some show serrated grain
boundaries. Irregular hornblende grains are rimmed by oxides and
epidote, suggesting replacement. Biotite is nearly all replaced by
finer-grained chlorite. |