Non-stable rock fragments are composed of K-feldspar with abundant perthitic
lamellae and plagioclase.
From the lowest to the upper, these units are [12, 13] (i) B3 facies (-880 to -750 m), which contains euhedral pink-colored K-feldspars, zinnwaldites, and hosts commonly micaschists enclaves with quartz-ferberite veins; (ii) B2 facies (-750 to -450 m) consisting of a lepidolite-rich granular granite with idiomorphic quartz crystals and small amounts of K-feldspars; (iii) B1 facies (-450 to -100 m) corresponding to an albite-lepidolite-rich granite containing globular quartz crystals with typical "snowball" textures and rare anhedral perthitic
Tennis, "A web resource for the study of alkali feldspars and perthitic
textures using light microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy," Journal of Geoscience Education, vol.
potassium feldspar occurs as subhedral to euhedral twinned crystals up to 1.25 cm in diameter.
The feldspar is essentially perthitic
; albite occurs in small quantities.
Lee MR, Parsons I (1995) Microtextural controls on weathering of perthitic
Plagioclase ranges from (23.8% -45.6%) Microcline often intergrown graphically and are sometimes perthitic
with albite occurring as patchy perthite.
On the basis of the relative proportions (volume %) of the three essential minerals, that is, perthitic
alkali feldspar (50-55%), quartz (28-33%), and plagioclase (2-3%), these largely hypidiomorphic and inequigranular to subequigranular rocks fall within the compositional field of alkali feldspar granite (Figure 2).
The main minerals in the sample are quartz, perthitic
orthoclase, plagioclase with sericite, epidote and chlorite.
Pocket zones are characterized by quartz crystals, perthitic
microcline, platy albite, orthoclase, biotite, lithium-iron micas and kaolinite.
The feldspar fraction is dominantly altered orthoclase feldspar and perthitic
ortho-clase feldspar with traces of microcline and plagioclase.
Lee MR, Parsons I (1995) Microtextural controls of weathering of perthitic