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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).
State |
Virginia |
Name |
Charnockite |
Geologic age |
Proterozoic Y |
Lithologic constituents |
Major
Igneous > Plutonic > Charnockite
|
Comments |
Blue Ridge Basement Complex, Middle Proterozoic (Grenville-Age) Plutonic Rocks |
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.
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NGMDB product |
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Counties |
Albemarle - Amherst - Augusta - Bedford - Botetourt - Fauquier - Floyd - Franklin - Greene - Loudoun - Madison - Montgomery - Nelson - Page - Rappahannock - Roanoke - Rockbridge - Rockingham - Warren - Bedford - Roanoke
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