Unnamed (west of Rendu Glacier)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Ag; Au; Cu; W
Other commodities Zn
Ore minerals chalcopyrite; goethite; pyrite; pyrrhotite; sphalerite
Gangue minerals augite

Geographic location

Quadrangle map, 1:250,000-scale SK
Quadrangle map, 1:63,360-scale A-5
Latitude 59.03
Longitude -136.8
Nearby scientific data Find additional scientific data near this location
Location and accuracy
This occurrence is in Glacier Bay National Park and Preserve at an elevation of about 5,000 feet near the top of the steep west face of a ridge west of Rendu Glacier. It is in the SE1/4, section 6, T. 33 S., R. 52 E. of the Copper River Meridian. It corresponds to sample sites 65048 to 65050 on Figure C-44 in Brew and others (1978). Location 3 of Cobb (1972; MF-424), which refers to the 'Rendu Glacier' deposit, is probably the same occurrence but is shown about 0.5 miles farther to the west and is considered to be a less accurate location. Still (1991 [BOM, v. 2, sec A) refers to this as the 'Massive Chalcopyrite Deposit.'
The deposit is extremely inaccessible. It can only be reached from a helicopter landing site on the ridge by a 200 foot rappel down a vertical to overhanging cliff that continues down for another 3,000 feet.

Geologic setting

Geologic description

The following description is summarized from Brew and others (1978).
A massive-sulfide zone is located between a 5-foot-wide epidote-bearing diorite zone grading into white diorite to the south and a 10-foot-wide section of calc-silicate rock grading into marble to the north. The calc-silicate rock is predominately garnet, epidote, and diopside with thin sulfide and scheelite veins. The massive-sulfide zone consists of chalcopyrite, augite, goethite, pyrrhotite, scheelite, and sphalerite; the augite and scheelite is replaced by chalcopyrite and pyrrhotite. The mineralization probably formed as a result of metasomatic replacement of marble in a high temperature contact zone. The sulfide zone is 12 feet wide by 80 feet long. The average grade of two samples across the zone is 0.52% tungsten, 5% copper, 7 ounces of silver per ton, and 0.15 ounce of gold per ton. Four of seven grab samples from the 10-foot-wide calc-silicate zone contained from 159 to 11,000 ppm tungsten. Similar mineralization is present elsewhere in the vicinity of this occurrence, but access is limited because of the steep terrain. The mineralization is probably Cretaceous or younger in age, based on the age of the diorite that hosts this occurrence.
Geologic map unit (-136.801883775204, 59.0296032197476)
Mineral deposit model Skarn, contact metasomatic (Cox and Singer, 1986; model 18a or 19a).
Mineral deposit model number 18a or 19a
Age of mineralization Probably Cretaceous based on the age of the diorite that hosts this occurrence (Brew and others, 1978).
Alteration of deposit Skarn, tactite.

Production and reserves

Indication of production None

Additional comments

The deposit is within Glacier Bay National Park and Preserve where exploration and development is restricted.

References

MRDS Number A013117

References

Reporters T.C. Crafford (T. Crafford & Associates, Anchorage)
Last report date 2/4/2001