Prospect, Active

Commodities and mineralogy

Main commodities Ag; As; Au; Bi
Other commodities Cu
Ore minerals arsenopyrite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale BD
Quadrangle map, 1:63,360-scale B-2
Latitude 64.387
Longitude -144.5412
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Beverly prospect is on top of a ridge in the headwaters of California Creek, about 0.5 mile southwest of hill 3620. The prospect is at about the center of an area with several drill holes on a large block of claims outlined by Baknes (2008). It is about 0.6 mile south-southeast of the center of section 15, T. 6 S., R 16 E., of the Fairbanks Meridian. The location is accurate.

Geologic setting

Geologic description

The rocks in the area are part of the Yukon-Tanana Terrane of the northern Cordillera; they consist largely of late Paleozoic to Devonian medium- to high-grade metamorphic rocks that have been intruded by Cretaceous and Tertiary granitic stocks and batholiths (Baknes, 2008; Wilson and others, 1998). The metamorphic rocks are structurally complex with an older, middle to early Paleozoic and/or late Proterozoic unit that consists of gneiss, schist, quartzite, and amphibolite and a younger, Mississippian and/or Devonian unit that consists largely of augen gneiss that locally forms domal structures. The metamorphic rocks are intruded by 55 Ma to 107 Ma, granitic plutons. The structure of the area is complex and difficult to determine because of poor exposure but several major thrust fault have been identified as well as a series of northeast-trending, northwest-dipping high-angle faults.
The dominant mineralization in the area and the target of most of the exploration are deposits related to Cretaceous intrusions, several classic examples being the Fort Knox Mine (FB115) near Fairbanks and the nearby Pogo Mine (BD033). These deposits are characterized by an association with moderately reduced, I- and S- type granitic intrusions and a lithophile, gold-bismuth-tungsten-arsenic-tellurium-molybdenum(-tin-copper-lead-antimony) suite of elements. The deposits vary from low-sulfide, sheeted or stockwork deposits in the intrusions to replacement deposits, veins, and stockworks in the country rock. The mineralization at the nearby Pogo deposit is the model used in exploring this and other prospect in the area. The mineralization at Pogo consists of thick gently-dipping quartz veins that grade laterally into pegmatite dikes related to 107 Ma syenite and monzonite intrusions. The quartz veins contain about 3 percent sulfides, mainly arsenopyrite, pyrite, pyrrhotite, loellingite, chalcopyrite, bismuthinite, native bismuth and native gold. The veins are associated with biotite alteration overprinted by sericite-dolomite-chlorite-quartz alteration, that extends into the country rock for several meters.
Soon after the recognition of nearby Pogo as a major and economically attractive deposit in 1998, Rimfire Minerals Corporation in conjunction with several joint-venture partners began work in the area and identified this deposit. In 2008, they entered into a joint venture with Rubicon Minerals Corporation and commissioned a thorough technical report on their properties in the Goodpaster District (Baknes, 2008), which is the source of most of the information on this prospect.
Most of the Beverly prospect is in augen gneiss intruded by granitic dikes. The area has been studied only in reconnaissance and the only mineralization consists of quartz boulders in float; a sample contained 2,370 parts per billion (ppb) gold, 0.2 part per million (ppm) silver, 39 ppm bismuth, and 90 ppm copper. Rubicon Minerals Corp. drilled 6 holes in the Beverly area that totaled 1,505.6 meters. Two of the holes cut 4 significant intersections of mineralization 0.76 to 10.30 meters long; they contained 0.96 to 2.24 grams of gold per ton, 0.92 to 10.3 grams of silver per ton, and 436 to greater than 1 percent arsenic.
Geologic map unit (-144.543536157891, 64.3866280344188)
Mineral deposit model Quartz veins and stockwork zones related to nearby Cretaceous intrusions.
Age of mineralization Probably about 107 Ma based on similarities to the nearby Pogo Mine.
Alteration of deposit Not specified.

Production and reserves

Workings or exploration Surface sampling and geochemical and geophysical surveys beginning in 1999 and continuing through 2007. Rubicon Minerals Corp. drilled 6 holes in the Beverly zone that totaled 1,505.6 meters.
Indication of production None