LPH

Prospect, Active

Commodities and mineralogy

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

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale A-1
Latitude 63.2426
Longitude -144.0728
Nearby scientific data Find additional scientific data near this location
Location and accuracy The LPH prospect is about 0.1 mile east of peak 7505 in the upper reaches of a glacial cirque. It is at an elevation of about 7,000 feet in the NE1/4 section 21, T. 17 N., R. 7 E., Copper River Meridian. The location is accurate.

Geologic setting

Geologic description

The LPH massive sulfide occurrence was discovered in 1977 in the upper reaches of a glacial cirque. Fine-grained, pyritic massive sulfides with distinctive quartz knots and silica gangue occur as float, rubble crop, and in glacial ice and debris for approximately 100 feet along strike before they are covered by a glacier at both ends. Vitreous blue chalcanthite (?) as a secondary oxidation product is present on pyrite-rich massive sulfides (S.S. Dashevsky, oral communication, 2003). The massive sulfide overlies a gabbro sill that is foliated in part; the massive sulfides are separated from the sill by a thin band of graphitic phyllite and sericite-quartz schist (J.K. Muntzert and others, unpublished Resource Associates of Alaska, Inc. report, 1977).
The LP prospect is in a narrow exposure of felsic metavolcanic rocks of the upper Lagoon unit of Devonian age; it is surrounded and overlain by unmineralized metavolcanic rocks 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 (-144.075050077011, 63.2422244502148)
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 Geological and geophysical surveys were conducted on the LPH prospect by Resource Associates of Alaska from 1976 to 1981, by Phelps Dodge in 1990, and by American Copper and Nickel Company from 1994 to 1997 (S.S. Dashevsky, oral communication, 2002). A total of 285 feet in two holes was drilled in 1978 at this prospect. Both holes were terminated early due to frozen or stuck rods.
Indication of production None
Reserve estimates The LPH prospect has an inferred resource of 1.1 million tons averaging 0.4 percent copper, 2.5 percent lead, 5.1 percent zinc, 73 parts per million (ppm) silver, and 1.4 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