Hidden Dike

Prospect, Inactive

Commodities and mineralogy

Main commodities Sn
Other commodities Pb; Ag
Ore minerals cassiterite; galena
Gangue minerals pyrrhotite; quartz; tourmaline

Geographic location

Quadrangle map, 1:250,000-scale TE
Quadrangle map, 1:63,360-scale B-5
Latitude 65.49
Longitude -167.172
Nearby scientific data Find additional scientific data near this location
Location and accuracy 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).

Geologic setting

Geologic description

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 tourmalinated quartz porphyry contained 1.4 and 3.2 percent tin, 2.9 and 4.45 percent 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.
Geologic map unit (-167.174721695415, 65.489225061135)
Mineral deposit model Altered quartz porphyry dike in tactite. Deposit analog is not clear; possibly tin vein (model 15b?), or at depth: tin skarn, replacement, or greisen (models 14b?, 14c?, and 15c?) after Cox and Singer (1986).
Mineral deposit model number 14b?, 14c?, 15b?, 15c?
Age of mineralization 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 of deposit 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.

Production and reserves

Workings or exploration Only limited surface observations and sampling have been completed here.
Indication of production None
Reserve estimates Not defined


MRDS Number 10308417


Hudson, T.L., 1983, Interim report on the Lost River district, Seward Peninsula, Alaska: Anchorage, Alaska, Anaconda Minerals Company internal report (Report held by Cook Inlet Region, Inc., Anchorage, Alaska).
Hudson, T.L., and Arth, J. G., 1983, Tin granites of Seward Peninsula, Alaska: Geological Society of America Bulletin, v. 94, p. 768-790.
McDermott, M.M., 1983, Investigation of the magnetic contact aureoles of the Khotol and Black Mountain granites, Alaska: Anchorage, Alaska, Anaconda Minerals Company internal report (Report held by Cook Inlet Region, Inc., Anchorage, Alaska).
Reporters Travis L. Hudson (Applied Geology)
Last report date 5/10/1998