Unnamed (southeast of peak 7057)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Cu; Pb; Zn
Other commodities Ag; Au
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 B-1
Latitude 63.3066
Longitude -144.3415
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is on the north side of the Robertson River 6.6 miles due west of the confluence of Rumble Creek and the Robertson River at an elevation of about 3,700 feet. The prospect is 1.4 miles southeast of peak 7057 and in the SW1/4 section 30, T. 18 N., R. 6 E., Copper River Meridian. The location is accurate.

Geologic setting

Geologic description

This occurrence is a zone of highly altered felsic metavolcanic rocks in the upper Lagoon unit; it is in a layer or unit similar to the large DW-LP sulfide system (MH334, MH338-341, MH346). Disseminated pyrite is common within the altered volcanic rocks, and zones of semimassive sulfides as much as one foot thick were found. The semimassive sulfides averaged 0.08 percent copper, 0.5 percent lead, 1.0 percent zinc, 15 parts per million silver, and 250 parts per billion gold (E. Hunter, unpublished data, 1998). The protoliths of the Lagoon unit are rhyodacite and dacite, but the unit contains rare rhyolite and minor andesite and basalt. (Dashevsky and others, 2003).
Geologic map unit (-144.343749347636, 63.3062227870031)
Mineral deposit model Kuroko massive sulfide (Cox and Singer, 1986; model 28a).
Mineral deposit model number 28a
Age of mineralization The Drum unit, which is part of the metamorphic sequence that includes the rocks at this deposit, has been dated at the Devonian-Mississippian boundary on the basis of one SHRIMP U-Pb zircon age of 359 +/- 6 Ma at the nearby DD South prospect (MH325).
Alteration of deposit Massive sulfides occur within an intense altered horizon marked by chlorite; there is peripheral sericite-quartz-pyrite -/+ chalcopyrite alteration.

Production and reserves

Workings or exploration American Copper and Nickel Company explored this area; they found that disseminated pyrite is common in the altered volcanic rocks and there are local zones of semimassive sulfides as much as one foot thick. This area was evaluated by soil sampling and UTEM geophysical surveys following up the strong alteration and favorable stratigraphy. The soil sampling confirmed the presence of an anomalous base metal unit or layer, but the UTEM survey failed to identify a significant electromagnetic conductor (E. Hunter, unpublished data, 1998).
Indication of production None

Additional comments

Unpublished data cited is available for viewing by contacting Grayd Resources Inc. in Vancouver, B. C., Canada (www.grayd.com), or Northern Associates Inc. in Fairbanks, Alaska.