Bear Island Granodiorite

Bear Island Granodiorite (Cloos and Cooke, 1953; Drake and Lee, 1989). Leucocratic, fine-grained, muscovite biotite granodiorite and related quartz-albite-microcline pegmatite. Unit comprises small- to moderate-sized sheets and crosscutting bodies. Muscovite from pegmatite dated at 469±20 Ma, interpreted as time of cooling below 5000 C (Rb-Sr; Muth and others, 1979).
State Virginia
Name Bear Island Granodiorite
Geologic age Ordovician
Lithologic constituents
Igneous > Plutonic > Granitic > Granodioriteincludes pegmatites
Comments Western Piedmont (Northern)

Virginia Division of Mineral Resources, 1993, Geologic Map of Virginia: Virginia Division of Mineral Resources, scale 1:500,000.

Virginia Division of Mineral Resources, 2003, Digital Representation of the 1993 Geologic Map of Virginia, Publication 174, CD ROM (ISO-9660) contains image file, expanded explanation in pdf, and ESRI shapefiles, scale 1:500,000.

NGMDB product
Counties Fairfax