Unnamed (west of Rendu Inlet)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Fe
Ore minerals magnetite; pyrite
Gangue minerals calcite; quartz

Geographic location

Quadrangle map, 1:250,000-scale MF
Quadrangle map, 1:63,360-scale D-2
Latitude 58.913
Longitude -136.65
Nearby scientific data Find additional scientific data near this location
Location and accuracy The occurrence is at an elevation of about 2000 feet on the top of the ridge between Rendu Inlet and Glacier Bay about 0.7 miles northwest of VABM Rendu. The location is accurate within a few hundred feet. The location is number 39 of MacKevett and others (1971), number 32 of Cobb (1972), and number 44 of Kimball and others (1978).

Geologic setting

Geologic description

Poddy magnetite-rich skarn deposits occur in limestone-marble units of Devonian-Silurian age at or near medium-coarse-grained intrusions of hornblende quartz diorite of Cretaceous age (Rossman, 1963 B 1121-K; Brew and others, 1978). Calc-silicate rich phases of the skarn consist of tactite composed of grossularite-rich garnet and epidote accompanied by quartz, chlorite, and calcite. Magnetite and pyrite locally form poddy masses. The area is poorly exposed and other deposits, inferred from magnetic anomalies, could be buried by overburden. Based on three samples reported by MacKevett and others, 1971 (locality 39, table 9) the iron content of the skarn ranges from about 5 percent to more than 10 percent. No precious metals were detected and copper and other valuable metals are present at near background levels. Titanium values are low, so magnetite is inferred to be an essentially pure phase.
Geologic map unit (-136.651866197202, 58.9126067741536)
Mineral deposit model Pyrite-magnetite (Fe) skarn (Cox and Singer, 1986; model 18d).
Mineral deposit model number 18d
Age of mineralization Cretaceous.

Production and reserves

Workings or exploration There are no workings. MacKevett and others (1971) collected samples and ran magnetic traverses in the occurrence area. Magnetic anomalies of as much as 5500 gammas are attributed to concealed masses of magnetite skarn.
Indication of production None

Additional comments

Deposits appear to be small, but the mixed marble-quartz diorite area is favorable for other deposits.
The area is in Glacier Bay National Park and Preserve.

References