Unnamed (on western edge of McBride Glacier)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Au; Cu
Other commodities Ag; Mo; Zn
Ore minerals arsenopyrite; chalcopyrite; pyrite; pyrrhotite

Geographic location

Quadrangle map, 1:250,000-scale SK
Quadrangle map, 1:63,360-scale A-3
Latitude 59.09
Longitude -136.07
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is in the Glacier Bay National Park and Preserve on the western edge of the McBride Glacier at an elevation of approximately 2000 feet. (Note: the text in Brew and others (1978) notes this occurrence at an elevation of 2500 feet, but they plotted it where the 2,000-foot contour line intersects the western edge of the McBride Glacier) It is near the center of section 13, T. 32 S., R. 55 E. of the Copper River Meridian. The approximate location is shown as number 7 in Cobb (1972 [MF 424]) and is more accurately located as number 77 on Plate III of Brew and others (1978).

Geologic setting

Geologic description

The following description is summarized from Brew and others (1978).
Arsenopyrite, chalcopyrite, pyrite, pyrrhotite, and traces of gold occur in ankeritic zones near an irregular, interfingered contact that marks a facies change between marble and phyllite. About 10 separate zones are present, each less than 10 feet wide and less than 100 feet long. The zones are copper and iron stained and are conformable to the bedding of the metasediments. One zone forms the hanging wall of 5-foot-wide andesite dike that contains chalcopyrite and pyrite. A 2-foot channel sample across an iron-stained zone in marble contained 0.003 ounce of gold per ton, 13,000 ppm copper, 200 ppm zinc, 15 ppm silver, 7,000 ppm arsenic, 5 ppm molybdenum, and more than 5,000 ppm manganese. Four other samples contained lesser amounts of metals. MacKevett (1971) reported a grab sample of sulfide-bearing rock that contained 0.088 ounce of gold per ton. The metasediments that host the deposit are Permian and Permian(?) in age which establishes a maximum age for the mineralization. Granitic intrusives in the general area are Cretaceous to Tertiary in age (Brew and others, 1978).
Geologic map unit (-136.071885913828, 59.0896106659324)
Mineral deposit model This is only an occurrence with little available information . Based on the descriptions by Brew and others (1978) it appears to be a skarn or replacement occurrence (Cox and Singer, 1986; models 18b? or 19a?).
Mineral deposit model number 18b?, 19a?
Age of mineralization Unknown. The Permian and Permian(?) age of the metasedimentary host rocks establishes a maximum age, but the mineralization may be related to nearby Cretaceous or Tertiary granitic intrusives (Brew and others, 1978).

Production and reserves

Workings or exploration Only sampling of outcrops.
Indication of production None

Additional comments

The occurrence is within Glacier Bay National Park and Preserve where mining and prospecting are restricted.

References

MRDS Number A013122

References

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