Origin of the nelsonite dikes of Amherst County, Virginia

Abstract

Numerous bodies of nelsonite have been found in Amherst County, in the Piedmont Province of Virginia. As these bodies consist largely of ilmenite and apatite they are of more than usual economic and scientific interest. Most of them occur as dikes intruded parallel to the foliation of hydrothermally altered Lovingston quartz-mica gneiss, but some also occur in anorthosite. The dikes are believed to be genetically related to somewhat younger hypersthene granodiorite that has invaded the gneiss, and through differentiation also has yielded the anorthosite as well as numerous pegmatites. Intrusion of the granodiorite was followed by hydrothermal solutions that altered the top of the solidified intrusive, the overlying Lovingston gneiss, and the somewhat earlier intruded nelsonite.