LZ

Prospect, Inactive

Commodities and mineralogy

Main commodities Cu; Pb; Zn
Other commodities Ag; Au
Ore minerals arsenopyrite; chalcopyrite; galena; marcasite; pyrite; pyrrhotite; sphalerite; tennantite
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 63.1819
Longitude -144.1594
Nearby scientific data Find additional scientific data near this location
Location and accuracy The LZ prospect is on a ridge between Rumble Creek to the northwest and the Tok River to the southeast at an elevation of about 6,400 feet, near the center of section 7, T. 16 N., R. 7 E., Copper River Meridian. The location is accurate.

Geologic setting

Geologic description

The rocks in the vicinity of the LZ prospect are mainly interbedded and interfolded metasedimentary rocks (black phyllite, micaceous quartzite, calc-schist, marble) and minor metavolcanic rocks that consist of thinly banded white quartz-sericite schist and green quartz-chlorite-sericite schist. The rocks are part of the the lower Lagoon unit. The pervasive schistosity in the area generally strikes northwest and dips southwest at 30 to 50 degrees. Two small rhyolite porphyry dikes intrude the metasedimentary rocks (R.A. Blakestad and others, unpublished Resource Associates of Alaska Inc. report, 1976).
The LZ prospect has several layers of massive sulfides 0.5 to 4 feet thick in a stratigraphic section of 60 feet (J.K. Muntzert and others, unpublished Resource Associates of Alaska Inc. report, 1977; E. Hunter, written communication, 1998; Dashevsky and others, 2003). A typical sulfide specimen contains 1.2 percent copper, 5.62 percent lead, 11.1 percent zinc, 3.28 ounces of silver per ton, and traces of gold. The mineralized zones occur in or are intimately associated with quartz-sericite schist or quartz-sericite-chlorite schist (R.A. Blakestad and others, unpublished Resource Associates of Alaska Inc. report, 1976).
During the 1977 field season, massive sulfide mineralization was traced almost continuously over a strike length of 2,500 feet along a steep mountain slope. The mineralization is lost at the north end of this steep slope where it projects onto a broad dip slope with poor exposure; it is lost at the south end where it projects into a debris-filled cirque (J.K. Muntzert and others, unpublished Resource Associates of Alaska Inc. report, 1977). In the late 1990s American Copper and Nickel Company geologists confirmed at least three high-grade bands of massive sulfide 0.5 to 4 feet thick that shed blocks of mineralized rock to the talus field. Representative samples of these bands contain 1.0 percent copper, 7.0 percent lead, 10.0 percent zinc, 206 parts per million (ppm) silver, and 1.2 ppm gold (E. Hunter, written communication, 1998; Dashevsky and others, 2003).
Geologic map unit (-144.161643555132, 63.1815204628458)
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).

Production and reserves

Workings or exploration
Surface sampling, mapping, and limited drilling has been carried out on the LZ prospect. Culp (1982) prepared a masters thesis at the University of Alaska on the geology and mineralization of the PP-LZ trend. A single 130-foot core hole was drilled on the LZ prospect in 1977 but suffered severe core loss and did not hit the down-dip projection of the mineralized layer or unit (S.S. Dashevsky, written communication, 2003).
During the 1977 field season, massive sulfide mineralization was traced in outcrop almost continuously over a strike length of 2,500 feet along a steep mountain exposure. The mineralization is lost at the north end of this steep slope where it projects out onto a broad dip slope with poor exposure; it is lost at the south end where it projects into a debris-filled cirque.
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

References

Lange, I. M., Nokleberg, W.J., Newkirk, S. R., Aleinikoff, J.N., Church, S.E., and Krouse, R.H., 1993, Devonian volcanogenic massive sulfide deposits and occurrences, southern Yukon-Tanana terrane, eastern Alaska Range, Alaska: Economic Geology, v. 88, p. 344-376.
Reporters W.T. Ellis (Alaska Earth Sciences), A.S. Wyatt and S.S. Dashevsky (Northern Associates, Inc. ), and W.J. Nokleberg (USGS)
Last report date 3/20/2003