LPP

Occurrence, Inactive

Commodities and mineralogy

Main commodities Cu; Pb; Zn
Other commodities Ag
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 A-1
Latitude 63.1277
Longitude -144.013
Nearby scientific data Find additional scientific data near this location
Location and accuracy The LPP occurrence is located about 2 miles north of Dry Tok Creek at an elevation of about 4,300 feet. It is about one-half mile northwest of the center of section 36, T. 16 N., R. 7 E., Copper River Meridian. It is accurately located about 8,000 feet southeast along strike from the PP prospect (MH352), but it corresponds to just one point along the mineralized layer or unit.

Geologic setting

Geologic description

The LPP occurrence is at the southeastern end of a series of massive sulfide occurrences (MH327-MH328, MH350-MH353) that are intermittently exposed along a strike length of 7 miles in a thrust-repeated section of the lower Lagoon unit (Dashevsky and others, 2003).
The rocks in the vicinity of the occurrence are metamorphosed felsic siliceous, sericitic to chloritic schists of volcaniclastic origin. The metavolcanic rocks are interlayered with metasedimentary rocks consisting of quartzite, carbonaceous phyllite, black calcareous schist, and marble. Small, nonresistant, weathered diabase dikes intrude the metamorphic rocks in the area (R.A. Blakestad and others, unpublished Resource Associates of Alaska Inc. report, 1976).
The LPP occurrence is one of several deposits along a Devonian stratigraphic unit. Abundant iron-stained float of sponge-textured siliceous material occurs along this series of deposits; this gossan-like material is the product of oxidation of pyrite in a siliceous matrix (S.S. Dashevsky, written communication, 2003). At several locations, disseminated pyritic sulfide bands 0.5 to 3.0 feet thick have appreciable sphalerite and chalcopyrite contents. Samples contain as much as 0.5 percent copper, to 0.5 percent lead, 0.5 to 2.5 percent zinc, and 10 to 30 parts per million silver (Rodney A. Blakestad and others, unpublished Resource Associates of Alaska Inc. report, 1976). No high-grade mineralization has been located at the LPP occurrence, but it is one of several that together define a favorable massive sulfide unit (E. Hunter, unpublished data, 1998).
Geologic map unit (-144.015239524202, 63.1273214869919)
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).
Alteration of deposit Weak dolomite alteration (Lange and others, 1993).

Production and reserves

Workings or exploration Only surface sampling and mapping has been done near the LPP occurrence.
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) and A.W. Wyatt and S.S. Dashevsky (Northern Associates Inc.)
Last report date 3/20/2003