Hidden Dike Prospect, Lost River Valley, Port Clarence Mining District, Nome Census Area, Alaska, USAi

Regional Level Types
Hidden Dike Prospect	Prospect
Lost River Valley	Basin
Port Clarence Mining District	Mining District
Nome Census Area	Census Area
Alaska	State
USA	Country

Location: The Hidden dike prospect is located on the northwest flank of the ridge between Crystal Creek and the upper part of Cassiterite Creek. Both creeks are east tributaries to Lost River in the York Mountains. The prospect is at about 750 foot elevation and only 0.5 mile upstream from the confluence of Crystal Creek and Lost River. This locality was not identified separately by Cobb and Sainsbury (1972) or Cobb (1975) but the surface trace of the Hidden dike was mapped by Sainsbury (1969, plate 1).
Geology: The Hidden dike is a felsic quartz porphyry that is bordered by layered tactite developed in Ordovician limestone. The contact with tactite is irregular, brecciated, and locally strongly altered. Tourmaline, galena, and pyrrhotite are present in the more strongly altered rocks. Two samples of tourmalized quartz porphyry contained 1.4 and 3.2% tin, 2.9 and 4.45% lead, and 1.1 and 2.9 opt silver. The layered tactite was only weakly anomalous in tin (to 110 ppm) and other elements (Hudson, 1983). This prospect, the Dalcoath dike prospect 0.75 mile to the east (TE052), the extensive tactite development at lower elevations of the ridge where the Hidden and Dalcoath dikes are located, and an apparently related magnetic anomaly (McDermott, 1983) suggests the possibility of a tin mineralizing system at depth in this general area (Hudson, 1983). The surface dikes are not believed to be directly responsible for the nearby tactite development.
Workings: Only limited surface observations and sampling have been completed here.
Age: The age of the mineralization is assumed to be related to the development of tin systems in the Lost River area and therefore Late Cretaceous, the age of the tin-mineralizing granites there (Hudson and Arth, 1983).
Alteration: Calc-silicate tactite is well developed in carbonate rocks bordering the Hidden dike. The dike itself is variably replaced by tourmaline but large parts are unaltered. The border of the dike appears to have localized irregular solution breccias.
Reserves: Not defined

Commodities (Major) - Sn; (Minor) - Pb, Ag
Development Status: None
Deposit Model: Altered quartz porphyry dike in tactite. Deposit analog is not clear; possibly

Other Databases

Link to USGS - Alaska:	TE053

Other Regions, Features and Areas containing this locality

References