Gold-silver mineralization at the London-Virginia Mine, Buckingham County, Virginia

The London-Virginia Mine in Buckingham County is one of several abandoned gold mines that are scattered throughout the polydeformed metavolcanic and metasedimentary rocks of the Virginia Piedmont. Production began at the London-Virginia in 1853 and continued intermittantly through 1939. Gold mineralization (averaging 1.2 ppm but with localized concentrations of up to 14.1 ppm) occurs within a ferruginous quartzite lens and a muscovitic schist contained in the Cambrian Chopawamsic Formation. The deposit consists of a series of conformable stratigraphic units which include, from bottom to top: 1) a garnetiferous chlorite schist 2) a magnetite schist 3) a quartz-muscovite schist 4) a ferruginous quartzite and 5) a chlorite-biotite schist. These lithologies represent periods of submarine volcanism (units 1 and 5) and volcaniclastic sedimentation (unit 3) with intervening episodes of hydrothermal exhalative activity (units 2 and 4). The mineralogic assemblages characteristic of the exhalative units suggest that the premetamorphic sediments were rich in hydrothermal silica, goethite, amounts of barite, gold. The deposit limonite, and pyrite with minor calcite, base metal sulfides and is believed to have formed as a result of exhalative processes analogous to those currently active in the Atlantis II Deep of the Red Sea. Silica-rich, hypersaline brines discharging through fractures in the sea floor ponded in a local basin. The episodic influx of volcaniclastic debris and extensive deposition of hydrothermal silica diluted the concentration of sulfides and gold to produce a low-grade, siliceous mineralized zone. The local exhalative event was terminated when the basin was capped by a volcanic flow.