Flint Hill Gneiss (VAYfh;0)

State	Virginia
Name	Flint Hill Gneiss
Geologic age	Proterozoic Y
Original map label	Yfh
Comments	Blue Ridge Basement Complex, Middle Proterozoic (Early or Pre-Grenville-Age) Gneisses. From expanded explanation (ref. VA002): Flint Hill Gneiss (Lukert and others, 1977). Segregation-layered quartzofeldspathic biotite gneiss contains quartz, plagioclase, microcline, green biotite, ilmenite, and titanite; accessories include epidote, apatite, and zircon. Segregation layering is defined by quartz-feldspar- and biotite-rich domains on the order of a few millimeters thick; migmatitic leucosomes of quartz and alkali feldspar cut segregation layering in places; veins of blue quartz are com mon. This unit is considered correlative with layered biotite granulite and gneiss (Ygb); the Flint Hill has been dated at 1081 Ma (U-Pb zircon; Lukert and others, 1977).
Primary rock type	gneiss
Secondary rock type
Other rock types
Lithologic constituents	Major Metamorphic > Gneiss > Biotite-gneiss
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	Fauquier - Greene - Madison - Rappahannock