Abstract

Twenty-one new chemical analyses of granitic rocks of the northwest Adirondacks are presented; three of the predominant hornblende microperthite granite and equivalent gneiss, nine of alaskite to confirm that the quartz content of the alaskite is less than 42 per cent, eight of microcline-rich granitic gneisses to further elucidation of the problem of their origin, and one of sodium granitic gneiss. The compositions of the granitic rocks as a whole are plotted and their interrelationships discussed. Three additional analyses of biotite-quartz-plagioclase gneiss are also included; this gneiss is the major raw material which has formed the host rock for migmatites and for granitization to yield much porphyroblastic granite gneiss and microcline-rich granitic gneiss.

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