O'Reely

Prospect, Active

Alternative names

Oreely
Rob

Commodities and mineralogy

Main commodities Ag; As; Au; Sb
Other commodities Cu; Pb; Te; W
Ore minerals arsenopyrite; 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 64.3404
Longitude -144.2148
Nearby scientific data Find additional scientific data near this location
Location and accuracy The O'Reely prospect is near the head of Tibbs Creek, about 0.5 mile north of the north peak (5080) of Black Mountain. It is about 0.3 mile north-northeast of the center of section 5, T. 6 S., R. 18 E., of the Fairbanks Meridian. The location is accurate.

Geologic setting

Geologic description

Although several mines and prospects have been known since the 1930s within a mile or so of this prospect, the O'Reely vein was first described by Freeman in 2004. From 1995 to 1999, The Stone Boy Joint Venture (Sumitomo Metal 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. They did not drill the O'Reely prospect.
In 2002, Freegold Ventures optioned a large block of claims that covered the O'Reely vein and the several other nearby deposits that are described separately: the Grizzly Bear (BD003), Michigan Lode (BD025), Wolverine (BD057), and Upper Trench/ Lower Trench (BD058). 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 in 2004 that summarized their and previous work (Freeman, 2004). The O'Reely vein was first mentioned in it. The 2004 report was updated in 2010 by Flanders (2010).
As interpreted by Bailey (2001) and Freeman (2004), this and the several other similar prospects in the area are near the contact of a large Cretaceous biotite granodiorite pluton that intrudes a large dome of Paleozoic biotite gneiss, feldspar-biotite augen gneiss, and quartzite. The granodiorite is cut by hornblende andesite-porphyry dikes. The rocks are locally intensely sheared and the nearby Michigan Lode (BD025), Blue Lead (BD003), and Grizzly Bear (BD018) deposits are aligned along the northeast-trending Gray Lead fault. The O'Reely vein is in the granodiorite near the contact with Paleozoic gneiss near a similar fault.
The O'Reely vein is probably similar to the other mines and prospects in the immediate area in that it is a gold -quartz vein along a shear zone. The quartz veins typically contain gold +/- base metal +/- silver and a variable combination of sulfides, including arsenopyrite, jamesonite, pyrite, and stibnite. The veins are commonly 2 to 3 feet in wide but some are as wide as 8 feet (Thomas, 1970). The O'Reely vein strikes northeast and can be traced for about 1,500 feet. Freeman (2004) describes the O'Reely vein as a 'polyphase hydrothermal breccia'. Two samples contained 8.04 and 8.38 grams of gold per ton, 16.10 and 53.70 parts per million (ppm) silver, 1,065 and 1,985 ppm arsenic, 15.35 and 39.70 ppm bismuth, 1,800 and 4,210 ppm lead, and 761,1,000 ppm antimony, and anomalous bismuth and tellurium (Freeman 2004). Other surface samples of veins and altered granite collected in subsequent years varied greatly in their relative and specific metal content but they have essentially the same association of metals.
In 2007, Freegold drilled 9 holes on the O'Reely vein (Freegold Ventures Ltd., 2007). All of the holes cut the vein in mineralized intercepts from 5 to 20 feet wide. Of the 128 intervals that were assayed, 31 contained over 0.2 gram of gold per tonne; the highest was 2.1 grams of gold per tonne across 3 feet. The drilling indicated that the vein is continuous for at least 750 feet horizontally and does not have any structural offsets.
Geologic map unit (-144.217124942405, 64.3400351970016)
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 pluton.
Alteration of deposit Not described in detail but alteration is associated with the veins.

Production and reserves

Workings or exploration Although several mines and prospects have been known since the 1930s within a mile or so of this prospect, the O'Reely vein was first described by Freeman in 2004. From 1995 to 1999, The Stone Boy Joint Venture (Sumitomo Metal 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. They did not drill the O'Reely prospect. In 2002, Freegold Ventures optioned a large block of claims that covered the O'Reely vein and the several other nearby deposits that are described separately: the Grizzly Bear (BD003), Michigan Lode (BD025), Wolverine (BD057), and Upper Trench/ Lower Trench (BD058). They continued to explore them as a unit as the Rob project through early 2012 (Flanders, 2010; Freegold Ventures Ltd., 2012). The work has included extensive geologic mapping, surface sampling, and geochemical and geophysical surveys. In 2007, Freegold drilled 9 holes on the O'Reely vein (Freegold Ventures Ltd., 2007).
Indication of production None

References