Garrisonville Mafic Complex

Garrisonville Mafic Complex (Pavlides, 1990). Fine- to coarse-grained, massive to foliated amphibolite and hornblendite with lesser metapyroxenite, metawebsterite, and metanorite. Amphiboles in amphibolite are dominantly hornblende, which is poikilitic in places; actinolite and cummingtonite are present locally. Intermediate-composition plagioclase commonly shows alteration to clinozoisite or epidote. Quartz and chlorite are present in variable amounts in some amphibolites; magnetite and ilmenite are common accessory minerals. Hornblendite consists of coarse-grained hornblende in a groundmass of finer-grained hornblende, plagioclase, and quartz. At the western edge of the complex, talc-amphibole schist occurs near the contact with the country rock; metamorphic alteration is less intense in the western portion than in the east.
State Virginia
Name Garrisonville Mafic Complex
Geologic age Proterozoic Z-Cambrian
Lithologic constituents
Major
Metamorphic > Amphibolite
Minor
Igneous > Plutonic > Ultramafic > Hornblendite
Incidental
Metamorphic > Metaigneous > Metaintrusive > Metaultramafic
Metamorphic > Metaigneous > Metaintrusive > Metaultramafic > Metapyroxenite
Comments Western Piedmont (Northern)
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 Stafford