The groundmass is recrystallized and hydrothermally altered to a variable degree, probably reflecting the autometasomatic effects of deuteric
fluids, as well as the slightly later contact metamorphic and metasomatic effects of intrusion of the Lake George granodiorite and antimony vein mineralization in the area.
and hydrothermal activity were important in the formation of the bentonite.
This sample is medium grained, holocrystalline, very fresh (i.e., complete absence of any deuteric
alteration such as chlorite, white mica, carbonate, etc.), and most importantly is barren of megacrysts and xenoliths (Fig.
Albite lamellae and veins (An<5) in many perthitic grains may have formed by alteration within the parent intrusion (deuteric
) or during deep burial.
Despite the presence of magmatic sulphide and local alteration minerals, many of the mafic rocks retain igneous textures and assemblages with minimal deuteric overprint.
Mafic rocks in the southern portion of the pluton generally retain much of their original igneous character whereas deuteric alteration is most pervasive in the northern portion of the pluton.