McLeod

Prospect, Undetermined

Commodities and mineralogy

Main commodities Mo
Other commodities Ag; Cu; Mn; Pb; Sn; U; W
Ore minerals ferrimolybdite; molybdenite
Gangue minerals magnetite; pyrite; pyrrhotite; quartz; tourmaline; zircon

Geographic location

Quadrangle map, 1:250,000-scale UL
Quadrangle map, 1:63,360-scale B-1
Latitude 63.2711
Longitude -159.2846
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is located on the southwestern flank of the Kaiyuh Mountains, approximately 11.5 miles southeast of Blackburn, an abandoned settlement on the Yukon River. The discovery trenches, now caved, are at an elevation of 1025 feet on a north-trending ridge locally known as Camp Ridge. Camp Ridge is approximately 1400 feet southeast of hill 1170. The site is on the northeastern side of the ridge in the NE1/4 NW1/4 sec. 5, T. 26 S., R. 3 W., Kateel River Meridian. The location is accurate within 300 feet. This is an unnumbered locality in Cobb (1972 [MF 427]). The prospect is on Doyon, Ltd. selected lands. References describing recent exploration are available for review at the offices of Doyon, Ltd. in Fairbanks, Alaska.

Geologic setting

Geologic description

This deposit consists of platy aggregates and grains of molybdenite in sparse, northeast-trending, milky-white quartz veinlets and veins up to 8 inches thick (Mertie, 1937). The veins cut hornfels, clastic sedimentary rocks, minor intermediate to mafic volcanic rocks, and biotite-quartz-feldspar porphyritic dikes, near the southwestern margin of a Cretaceous or Tertiary quartz-feldspar-porphyritic granite stock. The stock is exposed in a 3/4-square-mile area, but the extent of the hornfels suggests that the pluton is considerably larger at depth (Bressler and others, 1979). The dikes postdate the stock and generally strike northeast. The general strike of the strata is northwesterly with gentle dips to the northeast and southwest. There is very little outcrop, but vein float trending about N60E can be traced in frost-riven rubble for several hundred feet on the ridge and downslope (West, 1954).
The deposit also contains pyrite, pyrrhotite, molybdenite altered to ferrimolybdite, magnetite, zircon, and tourmaline (West, 1954). Selected samples of molybdenite- and ferrimolybdite-bearing quartz vein material assay 0.23 to 1.49% Mo. A sample submitted in 1942 by McLeod (probably from this prospect) contained approximately 4% molybdenite (Joesting, 1943). Early indications of elevated uranium content were not substantiated by sampling by the U.S. Geological Survey (West, 1954, p. 9-10). No sample contained more than 0.0003% eU.
The mineralized veins are mainly in highly fractured, silicified pyritic hornfels adjacent to biotite-quartz -porphyritic dikes. Mineralized veinlets in the dikes are rare. A multi-element and molybdenum soil anomaly that marks the deposit measures 3500 by 2700 feet (Bressler and others, 1979). The anomaly partly coincides with mapped alteration and with exposures of molybdenite-bearing quartz veinlets; the anomaly is open to the southwest (Bressler and others, 1979).
Also see UL004 and 005.
Geologic map unit (-159.287013904377, 63.2703971070503)
Mineral deposit model Porphyry Mo (Cox and Singer, 1986; model 16a and 21b)
Mineral deposit model number 16a, 21b
Age of mineralization The molybdenite-bearing veins presumably are related to the cooling phase of the Upper Cretaceous or Tertiary porphyritic granite stock.
Alteration of deposit The intrusive rocks are locally silicified and sericitized (Mertie, 1937). The adjacent country rocks are marked by extensive hornfelsing, secondary pyrite, and chloritic alteration.

Production and reserves

Workings or exploration Several prospect pits and trenches were dug and caved prior to 1945 (West, 1954). There has been no underground exploration at this site. Surface exploration and mapping was conducted by Bear Creek Mining Company in 1976 (Fields, 1976), and by WGM, Inc., on behalf of Doyon, Ltd., in 1979 and 1980 (Bressler and others, 1979; Lessman, 1979). Airborne and radiometric surveys were completed in 1980 (Boniwell, 1981).
Indication of production None

Additional comments

This property is on Doyon, Ltd. selected lands. For more information contact Doyon, Ltd., in Fairbanks, Alaska.

References

MRDS Number A013467

References

Andrews, Tom, Enns, S., and Ruzicka, J., 1978, McLeod project area report, Doyon project 1978: Doyon Report 78-32, 11 p. (Report held by Doyon, Limited, Fairbanks, Alaska).
Boniwell, J.B., 1981, Airborne geophysics over the McLeod prospect, Kaiyuh Mountains, Nulato, Alaska: Doyon Report 81-05, 9 p. (Report held by Doyon, Limited, Fairbanks, Alaska).
Boniwell, J.B., 1981, An addendum to the report on airborne geophysics over the McLeod prospect, Kaiyuh Mountains, Nulato, Alaska: Doyon Report 81-08, 16 sheets. (Report held by Doyon, Limited, Fairbanks, Alaska.)
Bressler, J., Cleveland, G., Ruzicka, J., 1979, 1979 annual progress report McLeod project area: Doyon Report 79-33, 48 p. (Report held by Doyon, Limited, Fairbanks, Alaska).
Bright, M.J., 1982, Evaluation of WGM data from Doyon, Limited's McLeod molybdenum prospect: Doyon Report 82-52, 8 p. (Report held by Doyon, Linited, Fairbanks, Alaska).
Fields, E.D., 1976, Regional mineral survey of the Kaltag withdrawal area (Doyon, Limited) and examination of the McLeod molybdenum prospect, Kaltag, Alaska: Doyon Report 76-21, 9 p. (Report held by Doyon, Limited, Fairbanks, Alaska).
Lessman, J., 1979, Doyon project 1979 annual progress report: Doyon Report 79-31, 5 p. (Report held by Doyon, Limited, Fairbanks, Alaska).
Reporters S.S. Dashevsky
Last report date 8/7/2001