Blue Lead

Mines, Active

Alternative names

Blue Lead Extension
Rob

Commodities and mineralogy

Main commodities Ag; As; Au; Sb
Other commodities Cu; Pb; Te; W
Ore minerals arsenopyrite; covellite; digenite; gold; jamesonite; pyrite; stibnite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale BD
Quadrangle map, 1:63,360-scale B-1
Latitude 64.3603
Longitude -144.20323
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Blue Lead and Blue Lead Extension Mines are about 2 miles north of the north peak '5080' of Black Mountain. They are at an elevation of about 3,790 feet at the head of Johnson Creek, near the southeast corner of section 29, T. 6 S., R. 17 E., of the Fairbanks Meridian. The location is accurate.

Geologic setting

Geologic description

The Goodpaster region was first explored for placer gold in 1915. In the early 1930s, gold-bearing quartz veins were discovered in the upper Tibbs Creek area. By the winter of 1936, the first underground workings were begun. A 450-foot tunnel was driven following a small vein, termed the Blue Lead Extension. After disappointing results, the work was stopped. In the summer of 1936, five men drove a 300-foot tunnel at the outcrop of the Blue Lead vein (Reed, 1937). During the winter of 1937, a 300-foot tunnel was driven at the nearby Grizzly Bear Mine (BD018) and a 50-ton mill was constructed. In the summer of 1938, the mill was moved to the Blue Lead Mine and operated for a year and a half until the fall of 1939 (Joesting, 1938). The Blue Lead and Blue Lead Extension have approximately 775 feet of underground workings. There was limited exploration in the 1970s.
From 1995 to 1999, The Stone Boy Joint Venture (Sumitomo Metal Mining and WGM Inc.) spent more than $1.3 million exploring in the area; they did extensive surface mapping and sampling, surface and airborne geophysics, and 16,215 feet of diamond drilling in 26 holes. The location of the holes is vague but they drilled at least 3 holes at the Blue Lead prospect (Flanders, 2010). In 2002, Freegold Ventures optioned a large block of claims that covered the Blue Lead and several other nearby deposits that are described separately: the Grizzly Bear (BD003), Michigan Lode (BD025), Gray Lead (BD017), Wolverine (BD057), Upper Trench, Lower Trench (BD058) and O'Reely (BD059). Freegold has continued the exploration through early 2012 as the Rob project (Flanders, 2010; Freegold Ventures Ltd., 2012). The work has included extensive geologic mapping, surface sampling, and geochemical and geophysical surveys. Freegold commissioned a comprehensive NI 43-101 report that summarized their and previous work (Freeman, 2004). The report was updated in 2010 (Flanders, 2010).
The Blue Lead Mine produced 132 ounces of gold and 25 ounces of silver from approximately 150 tons of ore (Thomas, 1970).
As interpreted by Bailey (2001), Freeman (2004), and Flanders (2010) this and the several other similar deposits in the area are near the contact of a large Cretaceous biotite granodiorite pluton and a mixed unit of Paleozoic biotite gneiss, feldspar-biotite augen gneiss, and quartzite that form a large gneiss dome. Locally the granodiorite is cut by hornblende, andesite porphyry dikes. The rocks are locally intensely sheared and this and the nearby Gray Lead (BD017), Grizzly Bear (BD018) and Michigan Lode (BD025) Mines are aligned along the northeast-trending Gray Lead fault. This shearing is observed in the underground workings and also at the surface where it is marked by pronounced saddle-like depressions across the spurs separating the westward-flowing tributaries of Tibbs Creek.
The lode deposits in the area are gold-bearing quartz veins in shear zones in the metamorphic and igneous rocks. The quartz veins contain gold +/- base metal +/- silver and a variable combination of sulfides, including arsenopyrite, covellite, digenite, jamesonite, pyrite, and stibnite. Typically, the gold content decreases as sulfides increase. The veins are commonly 2 to 3 feet in width but some are as wide as 8 feet (Thomas, 1970). When gold is present, it is usually extremely fine grained. However, veins at the nearby Grizzly Bear Mine (BD018) contain relatively coarse gold, which is easily visible in hand specimen. The Blue Lead Mine is centered on a 2.5-foot-wide quartz vein with jamesonite and minor pyrite (Menzie and Foster, 1979). In the underground workings, the vein is nearly flat lying or dips gently to the north (Reed, 1937). Glover (1950) reports a range in gold fineness of 724.4 to 773.7 for the Blue Lead Mine. Freeman (2004) and Flanders (2010) classified the Blue Lead as a 'intrusion-hosted, probably intrusion-related gold vein with variable silver, tungsten, and bismuth'.
Freeman (2004) indicated the nine holes have been drilled on the Blue Lead, Blue Lead Extension, and Grizzly Bear (BD018) deposits, presumably during the joint-venture exploration from 1995 to 1999. The highest gold value was a 1.0-foot interval that contained 0.92 ounce of gold per ton, 28.2 parts per million (ppm) silver, and 4,650 ppm arsenic.
Geologic map unit (-144.205554654628, 64.3599350270823)
Mineral deposit model Silver-gold-quartz veins and stockwork, +/- arsenic, copper, lead, antimony, tellurium, and tungsten (Cox and Singer, 1986; model 22c).
Mineral deposit model number 22c
Age of mineralization Probably genetically related to a nearby Cretaceous granodiorite intrusive.
Alteration of deposit Not described in detail but alteration is associated with the veins.

Production and reserves

Workings or exploration
The Goodpaster region was first explored for placer gold in 1915. In the early 1930s, gold-bearing quartz veins were discovered in the upper Tibbs Creek area. By the winter of 1936, the first underground workings were begun. A 450-foot tunnel was driven following a small vein, termed the Blue Lead Extension. After disappointing results, the work was stopped. In the summer of 1936, five men drove a 300-foot tunnel at the outcrop of the Blue Lead vein (Reed, 1937). During the winter of 1937, a 300-foot tunnel was driven at the nearby Grizzly Bear Mine (BD018) and a 50-ton mill was constructed. In the summer of 1938, the mill was moved to the Blue Lead Mine and operated for a year and a half until the fall of 1939 (Joesting, 1938). The Blue Lead and Blue Lead Extension have approximately 775 feet of underground workings. There was limited exploration in the 1970s.
From 1995 to 1999, The Stone Boy Joint Venture (Sumitomo Metal Mining and WGM) spent more than $1.3 million exploring in the area; they did extensive surface mapping and sampling, surface and airborne geophysics, and 16,215 feet of diamond drilling. In 2002, Freegold Ventures optioned a large block of claims that covered the Blue Lead and several other nearby deposits that are described separately: the Grizzly Bear (BD003), Michigan Lode (BD025), Gray Lead (BD017), Wolverine (BD057), Upper Trench, Lower Trench (BD058) and O'Reely (BD059); and explored them as the Rob project. Through early 2012, Freegold has continued to explore them (Flanders, 2010; Freegold Ventures Inc., 2012).
Freeman (2004) states that 9 holes have been drilled on the Blue Lead, Blue Lead Extension, and Grizzly Bear (BD018) deposits, apparently during the 1995-1999 joint venture.
Indication of production Yes; small
Production notes The Blue Lead Mine produced 132 ounces of gold and 25 ounces of silver from approximately 150 tons of ore (Thomas, 1970).

References