Layered Porphyrobliastic Pyroxene Granulite

Leucocratic to mesocratic, segregation-layered quartzofeld-spathic granulite contains prominent potassium feldspar porphyroblasts; major mineralogy, quartz, plagioclase, K- feldspar, orthopyroxene or clinopyroxene, and magnetite-ilmenite; hornblende, reddish-brown biotite, and garnet are widespread minor constituents. Accessory minerals include apatite and zircon. Segregation layering is defined by millimeter- to centimeter scale quartz-feldspar- and pyoxene-rich domains; migmatitic leucosomes of alkali feldspar and blue quartz are common. This rock-type is considered to be pre-Grenville-age country rock, although no radiometric data is available.
State Virginia
Name Layered Porphyrobliastic Pyroxene Granulite
Geologic age Proterozoic Y
Lithologic constituents
Major
Metamorphic > Granulite
Comments Blue Ridge Basement Complex, Middle Proterozoic (Early or Pre-Grenville-Age) Gneisses
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.

NGMDB product
Counties Amherst - Bedford - Botetourt - Floyd - Montgomery - Roanoke - Rockbridge - Roanoke