Gulf Of Maine

A number of specimens of granite dredged from the Gulf of Maine prove to be chemically peralkaline (Hermes et al., 1978) but only samples dredged from Cashes Ledge (Toulmin, 1957) and Three Dory Ridge (Hermes et al., 1978, p. 1763) contain sodic amphibole and pyroxene. The Cashes Ledge rock consists of equant microperthite subhedra, quartz, hornblende, sheaves of acicular riebeckite, aegirine, fayalite, astrophyllite, (?)aenigmatite, zircon and magnetite (Toulmin, 1957). However, rocks described from Cashes Ledge by Hermes et al. (1978, p. 1763), although chemically peralkaline, are not described as containing peralkaline amphibole or pyroxene. Samples from three collecting sites at Three Dory Ridge consist predominantly of perthitic K-feldspar, 38-41% quartz and accessory sphene, opaques, zircon and apatite; samples from two sites contain 3% of sodic amphibole.