Georgetown Intrusive Suite (VACAgi;0)

State	Virginia
Name	Georgetown Intrusive Suite
Geologic age	Cambrian
Original map label	[gi
Comments	Western Piedmont, Northern. From expanded explanation (ref. VA002): Georgetown Intrusive Suite (Flemming and others, in press). Tonalite, quartz gabbro, quartz diorite, metapyroxenite, and hornblendite. Tonalite, medium- to coarse-grained, massive to strongly-foliated, biotite-, biotite-hornblende-, and garnet-biotite-hornblende-bearing; color index 20 to 40; contains abundant mafic inclusions. Quartz gabbro and quartz diorite, mostly medium- to coarse-grained quartz-augite-hornblende metagabbro, lesser quartz diorite, and much lesser quartz norite; commonly contains thin cumulus layers of metapyroxenite and augite-hornblende fels. Forms small to medium-sized layered sills and localized border zones of tonalite plutons. Metapyroxenite and hornblendite, dark-green to black, massive to well-foliated, medium- to coarse-grained; includes serpentinite, soapstone, and talc schist. Forms small pods and xenolith swarms within or along the borders of larger tonalite and quartz gabbro plutons.
Primary rock type	tonalite
Secondary rock type	gabbro
Other rock types	greenstone; hornblendite
Lithologic constituents	Major Metamorphic > Metaigneous > Metaintrusive > Metagabbroquartz metagabbro Igneous > Plutonic > Granitic > Tonalite Minor Igneous > Plutonic > Dioritic > Dioritequartz diorite Incidental Igneous > Plutonic > Ultramafic > Hornblenditehornblendite Metamorphic > Metaigneous > Metaintrusive > Metaultramafic > Metapyroxenite
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	Fairfax