Potomac Terrane

Region East, Northeast; Southeast
Mineral systems
Deposit types
Other minerals

Information leading to the delineation of this focus area

Basis for focus area Extent of the Potomac Terrane in Maryland, which is bounded on the west by the Pleasant Grove fault, and covered by Cretaceous and Tertiary Coastal Plain deposits on the east.
Identified resources Historical production of gold.
Production Unknown.
Status Past mining.
Estimated resources Unknown.
Geologic maps Southworth and others (2008), scale 1:100,000; Lyttle and others (2017), scale 1:100,000; Cloos and Cooke (1953), scale 1:62,500; Crowley and others (1976), scale 1:62,500; Edwards (1993), scale 1:62,500; Higgins and Conant (1990), scale 1:62,500; Jonas (1928), scale 1:62,500; Southwick and Owens (1968), scale 1:62,500; Froelich (1975), scale 1:62,500; Kuff (1981), scale 1:24,000.
Geophysical data Inadequate aeromagnetic and aeroradiometric coverage.
Favorable rocks and structures Rock units of the Potomac Terrane.
Deposits Montgomery County gold mines; Maryland mine (MRDS dep_id: 10068001), Bethesda mine (MRDS dep_id: 10068003), Harrison mine (MRDS dep_id: 10068004), Irma mine (MRDS dep_id: 10068006); many more in MRDS.
Evidence from mineral occurrences MRDS; Maryland Geological Survey.
Geochemical evidence Favorable mineralogy and rock type.
Geophysical evidence Unknown.
Evidence from other sources Unknown.
Comments Many old mine sites now in urbanized areas.
Cover thickness and description Variable cover and saprolite, some urban areas.
Authors Rebecca Kavage Adams, William Junkin, David K. Brezinski, Stephen G. Shank.
New data needs Geophysical data, geologic mapping, and geochemical analyses.
Geologic mapping and modeling needs Geologic mapping of 7.5-minute quadrangles (1:24,000 scale), but incomplete.
Geophysical survey and modeling needs A high-resolution airborne magnetic and radiometric survey with approximately 200 m line spacing.
Digital elevation data needs Lidar mostly complete except for Baltimore County (Maryland) where it is planned and funded.