Charnockite (VAYc;0)

State	Virginia
Name	Charnockite
Geologic age	Proterozoic Y
Original map label	Yc
Comments	Blue Ridge Basement Complex, Middle Proterozoic (Grenville-Age) Plutonic Rocks. From expanded explanation (ref. VA002): Charnockite. Includes dusky-green, mesocratic, coarse- to very-coarse-grained, equigranular to porphyritic, massive to vaguely foliated pyroxene-bearing granite to granodiorite; contains clinopyroxene and orthopyroxene, intermediate-composition plagioclase, potassium feldspar, and blue quartz. Reddish-brown biotite, hornblende, and poikilitic garnet are present locally; accessory minerals include apatite, magnetite-ilmenite, rutile, and zircon. Geophysical signature: charnockite pods in the southeastern Blue Ridge produce a moderate positive magnetic anomaly relative to adjacent biotite gneisses, resulting in spotty magnetic highs. This unit includes a host of plutons that are grouped on the basis of lithology, but are not necessarily consanguineous. These include Pedlar charnockite, dated at 1075 Ma (U-Pb zircon, Sinha and Bartholomew, 1984) and Roses Mill charnockite (Herz and Force, 1987), dated at 1027 +/- 101 Ma (Sm-Nd, Pettingill and others, 1984).
Primary rock type	granitic gneiss
Secondary rock type
Other rock types
Lithologic constituents	Major Igneous > Plutonic > Charnockite
Map references	Digital Representation of the 1993 Geologic Map of Virginia", 2003, CD ROM (ISO-9660) contains image file, expanded explanation in pdf, and ESRI shapefiles, viewing software not included. This is a digital version of "Geologic Map of Virginia" published in 1993. Available from: https://www.dmme.virginia.gov/commerce/ [https://www.dmme.virginia.gov/commerce/]
Unit references	Virginia Division of Mineral Resources, 1993, Geologic Map of Virginia: Virginia Division of Mineral Resources, scale 1:500,000 Digital Representation of the 1993 Geologic Map of Virginia - expanded explanation: 2003, Commonwealth of Virginia, Department of Mines, Minerals, and Energy, Divsion of Mineral Resources, Publication 147, 85 pp Digital Representation of the 1993 Geologic Map of Virginia", 2003, CD ROM (ISO-9660) contains image file, expanded explanation in pdf, and ESRI shapefiles, viewing software not included. This is a digital version of "Geologic Map of Virginia" published in 1993. Available from: https://www.dmme.virginia.gov/commerce/ [https://www.dmme.virginia.gov/commerce/]
Geographic coverage	Albemarle - Amherst - Augusta - Bedford - Botetourt - Fauquier - Floyd - Franklin - Greene - Loudoun - Madison - Montgomery - Nelson - Page - Rappahannock - Roanoke - Rockbridge - Rockingham - Warren - Bedford - Roanoke