Metaperidotite, Metapyroxenite, and Hornblende Metagabbro

Metaperidotite, greenish-black, dark-yellowish brown weathering, medium-grained, massive; consists of serpentine, amphibole, dark chlorite, and magnetite; serpentine replaces subhedral olivine; non-pleochroic amphibole occurs as single crystals, presumably pseudomorphic after subhedral to anhedral pyroxene; some amphibole occurs as large poikilitic crystals. Hornblende metagabbro, greenish-black, medium grained, speckled-white-weathering, massive, with a weak foliation and well-preserved primary igneous fabric; subhedral plagioclase is replaced by clinozoisite and albite; anhedral pyroxene is replaced by fibrous tremolite; brown hornblende occurs as subhedral single crystals. Metapyroxenite, dark-greenish-gray to greenish-black, light-greenish-gray weathering, medium-grained, weakly-foliated actinolite-rich rock contains lesser chlorite; amphibole is pseudomorphic after pyroxene.
State Virginia
Name Metaperidotite, Metapyroxenite, and Hornblende Metagabbro
Geologic age Proterozoic Y
Lithologic constituents
Major
Metamorphic > Metaigneous > Metaintrusive > Metagabbro
Metamorphic > Metaigneous > Metaintrusive > Metaultramafic > Metapyroxenite
Metamorphic > Metaigneous > Metaintrusive > Metaultramafic > Metaperidotite
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.

NGMDB product
Counties Loudoun