Plagiogranite Tonalite

Plagiogranite tonalite (Pavlides, 1990). Includes leucocratic to mesocratic plagioclase- and quartz-rich metamorphosed intrusive rocks containing little or no potassium feldspar. Plagioclase is variably altered to epidote, white mica, and chlorite. Quartz, generally blue, forms granoblastic aggregates that locally have cores of coarse-grained quartz with wavy extinction. Garnet is present locally. Hornblende, generally a minor constituent, is particularly abundant in the southwest portion of the pluton. Many of the plagiogranitic rocks have undergone cataclasis and are protomylonitic to mylonitic.
State Virginia
Name Plagiogranite Tonalite
Geologic age Cambrian-Ordovician
Lithologic constituents
Igneous > Plutonic > Granitic > Tonalite
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 Culpeper - Fauquier - Spotsylvania - Stafford