Occoquan Granite

Occoquan granite (Lonsdale, 1927; Drake and Froelich, 1986). Light-gray, medium- to coarse-grained, muscovite-biotite monzogranite and lesser granodiorite and tonalite. In many places the rock has a strong quartz-rod lineation, and locally, two foliations. The Occoquan has been dated at about 560 Ma (U-Pb zircon; Seiders and others, 1975), 494±14 Ma (Rb-Sr whole-rock; Mose and Nagel, 1982), and 479±9 Ma (U-Pb single-crystal zircon; J.N. Aleinikoff, written communication, 1993).
State Virginia
Name Occoquan Granite
Geologic age Cambrian-Ordovician
Lithologic constituents
Igneous > Plutonic > Granitic > Granite
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 - Prince William - Alexandria