Green Springs Pluton - Diorite and hornblendite. (VAZPAgs;0)

State	Virginia
Name	Green Springs Pluton - Diorite and hornblendite.
Geologic age	Proterozoic Y-Pennsylvanian
Original map label	PzZgs
Comments	Western Piedmont, Southwest and Central. From expanded explanation (ref. VA002): Diorite and hornblendite. Diorite, light- to dark-gray, fine- to coarse-grained. Hornblendite and amphibolite occur as dikes associated with diorite; these are coarse-grained, with blocky hornblende and plagioclase; epidote-rich alteration zones are common. Mineralogy: hornblende + plagioclase (intermediate composition); accessory minerals include apatite, titanite, zircon, garnet, pyrite, and magnetite. Augite, diopside, quartz, and potassium feldspar are locally present. Hornblende is largely replaced by chlorite or biotite; plagioclase contains abundant epidote inclusions. Late biotite porphyroblasts are common; these are commonly hydrated to form vermiculite. Rossman (1991) interprets the Green Springs to be a flattopped intrusive body with its upper surface approximately coincident with the present land surface. He notes that the pluton contains metasedimentary xenoliths that resemble the enclosing metagraywacke, and has a thermal aureole that is manifested by garnet and biotite porphryoblasts in the surrounding country rocks. Conley and Johnson (1975) concluded that the pluton was rootless at depth on the basis of a gravity study. Vermiculite is being extracted commercially from a deposit near the northeast margin of the pluton.
Primary rock type	diorite
Secondary rock type	hornblendite
Other rock types
Lithologic constituents	Major Igneous > Plutonic > Ultramafic > Hornblendite Igneous > Plutonic > Dioritic > Diorite
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	Louisa