LP

Prospect, Active

Commodities and mineralogy

Main commodities Pb; Zn
Other commodities Ag; Au; Cu
Ore minerals arsenopyrite; chalcopyrite; galena; gold; magnetite; pyrite; pyrrhotite; sphalerite
Gangue minerals chlorite; quartz; sericite

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale A-1
Latitude 63.2485
Longitude -144.0864
Nearby scientific data Find additional scientific data near this location
Location and accuracy The LP prospect is approximately 4 miles south-southeast of the confluence of Robertson River and Rumble Creek. It is at an elevation of about 6,400 feet on the southwest side of the remnant glacier located in the SW1/4 section 16, T. 17 N., R. 7 E., Copper River Meridian. The LP massive sulfide is situated approximately halfway between the PP2 (MH345) and DW (MH338) prospects. The location is accurate.

Geologic setting

Geologic description

The LP massive sulfide zone was discovered by geophysical exploration in 1977 and verified by drilling and mapping of outcrops of the massive sulfide at the base of the LP cliffs in 1978. Subsequent geological and geophysical work and drilling has established a zone that extends at least 1,200 feet along strike, extends at least 450 feet down-dip, averages about 11 feet thick, and has a maximum thickness of 18 feet. A total of 5,657 feet in 15 holes has been core drilled at this prospect (American Copper and Nickel Company, unpublished data, 1998). This drilling has defined an inferred resource of 0.7 million tons averaging 0.4 percent copper, 2.1 percent lead, 4.9 percent zinc, 66 parts per million (ppm) silver, and 2.2 ppm gold (Dashevsky and others, 2003).
The LP prospect is in a narrow exposure of felsic metavolcanic rocks of the upper Lagoon unit, and it is surrounded and overlain by unmineralized metavolcanic rock of the Tiger unit. The Lagoon unit is a succession of dark gray, rusty, phyllitic metamorphosed mudstones interbedded with light-gray to white to pale-green siliceous quartz-sericite(-chlorite) schist. Locally the rocks contain coarse-grained blue quartz eyes and rare fragmental volcanic textures preserved as chloritized lithic fragments. The upper part is dominated by white to pale-green, massive to laminated quartz-eye-bearing quartz-sericite(-chlorite-pyrite) schist; finely laminated schist with minor metamorphosed black mudstone; and thin intercalations of quartzite and fine-grained metamorphosed grit. The protoliths of the volcanic rocks of the upper Lagoon unit are mainly rhyodacite and dacite, but they also include rare rhyolite and minor andesite and basalt (Dashevsky and others, 2003).
Geologic map unit (-144.088650503328, 63.248124418086)
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 Development of sericite, quartz, pyrite, and carbonate in the hanging wall; extensive chlorite and magnesium enrichment and sodium depletion in the footwall.

Production and reserves

Workings or exploration The LP massive sulfide zone was discovered by geophysical exploration in 1977 and verified by drilling and mapping of outcrops of the massive sulfide at the base of the LP cliffs in 1978. Subsequent geological and geophysical work and drilling has established a zone that extends at least 1,200 feet along strike, extends at least 450 feet down-dip, averages about 11 feet , and has a maximum thickness of 18 feet. A total of 5,657 feet in 15 holes has been core drilled at the prospect (American Copper and Nickel Company, unpublished data, 1998).
Indication of production None
Reserve estimates Drilling has defined an inferred resource of 0.7 million tons averaging 0.4 percent copper, 2.1 percent lead, 4.9 percent zinc, 66 parts per million (ppm) silver and 2.2 ppm gold. The resource calculation includes only those contiguous bodies with a true thickness greater than 8 feet and a gross metal value of greater than $80.00 per ton at 1998 prices (Dashevsky and others, 2003).

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) and A.W. Wyatt and S.S. Dashevsky (Northern Associates Inc.)
Last report date 3/20/2003