Cascade

Occurrence, Active

Commodities and mineralogy

Main commodities Cu; Zn
Other commodities Ag; Pb
Ore minerals chalcopyrite; galena; pyrite; sphalerite
Gangue minerals calcite; chlorite; dolomite; graphite; quartz; sericite

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale A-1
Latitude 63.1625
Longitude -144.117
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Cascade occurrence is one-half mile west of the upper Tok River at an elevation of about 4,700 feet. It is approximately 8,000 feet southeast of the LZ East prospect (MH328). The occurrence about one-half mile southeast of the center of section 17, T. 16 N., R. 7 E., Copper River Meridian. The location is accurate.

Geologic setting

Geologic description

The Cascade occurrence is one part of a series of massive sulfide occurrences (MH327-MH328, MH350-MH353) that are intermittently exposed for 7 miles along strike in a thrust-repeated section of the lower Lagoon unit (Dashevsky and others, 2003). Outcrop with semimassive sulfides forms a backdrop for a small waterfall, and massive sulfide lenses are exposed on a cliff face above the waterfall. The occurrence is in a pelitic metasedimentary sequence that consists of metasiltstone, quartzite, carbonaceous phyllite, and siliceous marble or calcareous schist.
At least two layers with sulfide lenses have been identified, each associated with a thin limestone unit. The sulfide lenses are as much as 1 foot thick but average less than 6 inches. Samples of the massive sulfides average 0.5 percent copper, 0.4 percent lead, 1.8 percent zinc, 20 parts per million silver, and 15 parts per billion gold. A sample taken beneath the waterfall had an alkaline depletion index of 0.98, it is among the strongest alteration in the Delta district (E. Hunter, unpublished data, 1998).
Geologic map unit (-144.119242422618, 63.1621204936063)
Mineral deposit model Kuroko massive sulfide (Cox and Singer, 1986; model 28a).
Mineral deposit model number 28a
Age of mineralization The lower Lagoon unit, which is part of the metamorphic sequence that includes the rocks at this deposit, has been dated as Devonian on the basis of one SHRIMP U-Pb zircon age of 372 +/- 6 Ma at the nearby LZ East prospect (MH328) (Dashevsky and others, 2003).
Alteration of deposit A sample taken beneath the waterfall had an alkaline depletion index of 0.98, it is among the strongest alteration in the Delta district (E. Hunter, unpublished data, 1998).

Production and reserves

Workings or exploration Limited surface sampling and an electromagnetic geophysical survey have been carried out in the vicinity (S.S. Dashevsky, written communication, 2003).
Indication of production None

Additional comments

The unpublished data that is cited can be seen by contacting Grayd Resources Inc. in Vancouver, B.C., Canada (www.grayd.com), or Northern Associates Inc. in Fairbanks, Alaska.

References