88 Group

Prospect, Active

Commodities and mineralogy

Main commodities Au
Other commodities As; Cu; Sn
Ore minerals arsenopyrite; cassiterite; chalcopyrite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale CI
Quadrangle map, 1:63,360-scale B-2
Latitude 65.4375
Longitude -144.7532
Nearby scientific data Find additional scientific data near this location
Location and accuracy The 88 Group prospect is about 5 miles southwest of Circle Hot Springs, near the divide between the head of Half Dollar Creek and Ketchem Creek. In 2008, the 88 Group is part of an approximately 5,000-acre property that was being explored by Millrock Resources Inc. as a single endeavor. The outline of the claim block and the site of recent exploration is uncertain but the coordinates near the northwest corner of section 18, T. 7 N., R. 14 E., are within the block, if not near the center of it .

Geologic setting

Geologic description

The 88 Group prospect is in a dark, mafic peripheral phase of a Cretaceous, coarse-grained porphyritic granitic pluton. Both lode and placer gold is found at these claims (Vetter, 1995). Wiltse and others (1995) mapped the bedrock in the area and described the pluton as a chloritized porphyritic (hornblende-)biotite monzogranite to syenogranite. They also mapped a mafic dike in the area as black to dark gray, aphanitic to slightly porphyritic rock with major plagioclase, augite, hornblende and magnetite.
Gold mineralization occurs in heavily Fe-oxide stained, quartz-rich greisen zones up to six feet across, within fractures, and in stockwork veins. A significant aspect of the prospect is the large amount of grus that covers the area to a depth of 10 to 20 feet and pans considerable gold. Other heavy minerals found in the panned concentrates include abundant sphalerite, and small amounts of arsenopyrite, chalcopyrite, cassiterite(?), and monazite(?).
Gold occurs in samples of mineralized exposures along about 2,000 feet of ditch along the Portage Creek road. The mineralization is within heavily Fe-oxide stained, quartz-filled greisen zones that average about 3 inches wide. Phyllic and argillic alteration is present along vein margins and is also controlled by fractures. Strong zinc anomalies, up to 0.5 percent, and moderate arsenic values were noted. Tin was not detected in the rock samples but two panned-concentrate samples contained anomalous tin values. The dominant trend in mineralization is N50W with near vertical dips (Bakke, 1991).
As described by Millrock Resources Inc. (2008), the 88-Group mineralization consists of gold-bearing quartz veins and stockworks that occur in three structurally controlled zones 3 to 25 meters wide. Placer Dome USA and AMAX Exploration previously sampled the property and drilled three holes. The drilling intersected numerous zones with anomalous gold values up to 745 parts per billion gold. One of the zones in altered granite that was sampled at the surface contained 8.92 grams of gold per tonne across a width of 25 meters. Several other prospects are on the property. The mineralization at the Silver Chalice prospect consists of quartz-sulfide veinlets in altered sedimentary rocks; grab samples contained up to 32.0 grams of gold per tonne. The Portage prospect is similar. The Silver Chalice and Portage prospects may be recent names for two sites previously included in ARDF, a nearby unnamed occurrence (DI065) and the Top Dollar occurrence (DI058). These occurrences are probably all within the property that was being explored by Millrock in 2008.
Geologic map unit (-144.755641742244, 65.4371374024591)
Mineral deposit model Auriferous greisen zones and gold-quartz veins in granitic rocks.
Age of mineralization Probably related to the Cretaceous granitic intrusion that hosts at least some of the mineralization.
Alteration of deposit Mineralization occurs within heavily Fe-stained, quartz-filled greisen zones that average about 3 inches wide. Phyllic and argillic alteration is present along vein margins and also along fractures (Bakke, 1991).

Production and reserves

Workings or exploration Surface sampling beginning in the 1991 or before; three holes drilled. Being explored by Millrock Resources in 2008.
Indication of production None

References

References

Bakke, Arne, 1991, Fairbanks gold, in Vetter, 1995, Joker and 88 group, property summary: Fairbanks, Alaska, Vetter and Associates, 24 p.
Millrock Resources Inc., 2008. Ketchem: http://www.millrockresources.com/index.php/projects/ketchem/ (as of May 25, 2008).
Vetter, R., 1995, Joker and 88 group property summary: Fairbanks, Alaska, Vetter and Associates, 24 p.
Reporters C.J. Freeman, J.R. Guidetti Schaefer, A.S. Clements (Avalon Development Corporation); D.J. Grybeck (Port Ludlow, WA)
Last report date 6/5/2008