218527.fig.006a
(a)
218527.fig.006b
(b)
218527.fig.006c
(c)
218527.fig.006d
(d)
Figure 6: Photomicrographs showing plagioclase phenocrystals in the dacites representing each weathering grade from I to IV ((a)–(d)) (crosed nicols, × 4 0 ; Plj phe.: plagioclase phenocrystal). Fresh dacite with an unweathered plagioclase phenocrystal showing cooling microfractures and opaque inclusions, and with unstained plagioclase microlites in abundance (a), slightly weathered dacite with a slightly sericitized plagioclase phenocrystal and lesser amount of plagioclase microlites (b), moderately weathered dacite with a plagioclase phenocrystal showing an increasing amount of sericite around the edges and center (c), and highly weathered dacite with a plagioclase phenocrystal extensively weathered to clay minerals (d).