The Fosdick migmatite dome is composed of migmatitic paragneiss and orthogneiss, likely derived from the Swanson Formation and the Devonian Ford Granodiorite, respectively, and various granites. The granites are silicic (71-75 wt% SiO2) and slightly peraluminous (1.0-1.2 A.S.I.), and may be grouped into K-rich and K-poor types. For the K-rich type, preliminary Nd isotope data permit partial melting of Ford Granodiorite as the source, which is supported by comparison between the whole-rock chemistry of the granites and glass compositions in melting experiments with an appropriate protolith. For the K-poor type, the particular source is not clearly defined at present, and these granites might be derived from either the Swanson Formation or the Ford Granodiorite by disequilibrium melting.