Bear Island Granodiorite (VAObi;0)

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	Major Igneous > Plutonic > Granitic > Granodioriteincludes pegmatites
Comments	Western Piedmont (Northern)
References	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	NGMDB product page for 34878
Counties	Fairfax

Bear Island Granodiorite

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.