Tibbit

Prospect, Inactive

Commodities and mineralogy

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

Geographic location

Quadrangle map, 1:250,000-scale CV
Quadrangle map, 1:63,360-scale D-7
Latitude 60.873
Longitude -146.564
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Tibbit prospect is at an elevation of about 1600 ft., approximately 0.75 mi. northeast of Copper Mountain. It is in S1/2 sec. 36, T. 11 S., R. 8 W., of the Copper River Meridian. The location is accurate to within 1000 ft. This prospect is shown as #11 in Cobb (1972: MF-392) and as C-81 in Jansons and others (1984).

Geologic setting

Geologic description

The country rocks at this prospect are mafic volcanic rocks and sedimentary rocks of the Tertiary Orca Group (Nelson and others, 1985). The deposit consists of chalcopyrite, pyrite, and pyrrhotite in one- to eight- foot wide shear zones (Cobb, 1979: MF-392).
Jansons and others (1984) report that two grab samples contained 0.59% and 2% Cu, and 1.8 ppm and 6.4 ppm Ag; two chip samples contained 430 ppm and 0.93% Cu, 240 ppm and 0.13% Zn, and 3.4 ppm and 12.7 ppm Ag. Cobb (1979: OFR 79-973) reported one assay value of 1.9 oz Au/ton.
Geologic map unit (-146.565996170585, 60.8724525139038)
Mineral deposit model Cyprus massive sulfide (Cox and Singer, 1986; model 24a)
Mineral deposit model number 24a
Age of mineralization Probably Tertiary based on the age of the host rocks.

Production and reserves

Workings or exploration The deposit was explored in the early 1900s by four adits and by open cuts (Cobb, 1979: MF-392). However, in the 1980s only one 20 ft. adit could be found (Jansons and others, 1984). Jansons and others (1984) report that two grab samples contained 0.59% and 2% Cu, and 1.8 ppm and 6.4 ppm Ag, and that two chip samples contained 430 ppm and 0.93% Cu, 240 ppm and 0.13% Zn, and 3.4 ppm and 12.7 ppm Ag. Cobb (1979: OFR 79-973) reported one assay value of 1.9 oz Au/ton.
Indication of production None
Reserve estimates Inferred reserves of 500 tons @ 0.72% Cu.

Additional comments

Nelson and others (1985) interpret the country rocks as accreted ocean crust. Crowe and others (1992; 1993) and Sainsbury (1993) discuss the genesis of the volcanogenic massive sulfide deposits in this area.
Chugach Alaska Corporation, Anchorage, Alaska has control of these lands.

References

MRDS Number 10307356

References

Sainsbury, C.L., 1993, Geology and geochemistry of volcanogenic massive sulfide deposits and related igneous rocks, Prince William Sound, south-central Alaska, A discussion: Economic Geology, v. 88, p. 1284-1285.
Reporters S.W. Nelson, Anchorage, AK
Last report date 6/10/2000