Sample 80MW0012 is a biotite orthogneiss with a
mineral assemblage of plagioclase (50%), K-feldspar (18%), quartz (15%),
biotite (12%), sericite (3%), sphene (1%), and trace oxides, chlorite,
and epidote. Plagioclase occurs in very altered porphyroclasts, wrapped
by biotite domains. Microperthitic K-feldspar grains are significantly
smaller than plagioclase porphyroclasts. Quartz commonly occurs in ~3mm
long aggregates aligned with the biotite domains, defining a minor
foliation. |