Jualin (Coeur-Alaska)

Mines, Active

Commodities and mineralogy

Main commodities Ag; Au; Te
Other commodities Cu; Fe; Mo; Pb; Zn
Ore minerals chalcopyrite; friedrichite-aikinite; galena; gold; hessite; molybdenite; pavonite; petzite; pyrite; rucklidgeite; sphalerite; sylvanite
Gangue minerals calcite; dolomite; quartz

Geographic location

Quadrangle map, 1:250,000-scale JU
Quadrangle map, 1:63,360-scale D-4
Latitude 58.8389
Longitude -135.0446
Nearby scientific data Find additional scientific data near this location
Location and accuracy This site represents the consolidation by Coeur-Alaska of more than 10 mines and prospects, 25 patented claims, and 483 unpatented claims along a northwest-trending belt about 2 miles long that extends from the head of Berners Bay along Johnson Creek. By 2008, Coeur-Alaska had done considerable new underground exploration along this belt, discovered new veins, and connected many of the old workings. The work is far advanced and Coeur-Alaska plans to mine the deposit as a single entity. This site is referred to as the Jualin deposit/property, which is part of Coeur-Alaska's 'Kensington Project' which also includes the Kensington deposit/property (JU261) to the northwest, which is described separately. The coordinates are near the center of the Coeur-Jualin deposit. The Coeur-Jualin deposit now covers the old Jualin mine (JU 044) and several other mines and prospects (JU040, JU041, and JU045 to JU052); however, these are still described individually in ARDF for their pre-Coeur-Alaska geologic and historical data. This site is located 0.5 mile east-northeast from the center of section 15, T. 35 S., R. 62 E., of the Copper River Meridian. The location is accurate, though degree of accuracy not reported.

Geologic setting

Geologic description

The modern history of the Jualin deposit started in 1978 and eventually included a large block of 10 old mines and prospects, 25 patented claims, and 483 unpatented claims. From 1983 to 1993, the area was explored by a succession of companies including Bear Creek Mining Company, International Curator Resources, Granges, and Placer-Dome USA. In 1993, Coeur entered into a joint venture on the property with Curator and in 1994, Coeur acquired a 100 percent interest in the Jualin. Beginning in about 1980, exploration also began at the Kensington deposit (JU261) deposit to the northwest; this involved a succession of different companies on what became another large block of old mines, prospect, and new claims. In 1995, Coeur gained control of the Kensington deposit too Coeur subsequently carried out major drilling and underground work on both properties and as of 2008 the two main components of the Kensington Project are the Jualin deposit and the contiguous Kensington deposit (JU261).
In 2006, Coeur prepared an intensive NI 43-101 report (Birak, 2006) on the Kensington Project that is largely the basis of this description. As of 2006, the Jualin deposit had been defined by 72,000 feet of drilling; it and the contiguous Kensington deposit (JU261) had been explored by 27,000 feet of underground workings. As of 2006, the resources of the Kensington Project, that is, both the Jualin deposit described here and the contiguous Kensington deposit (JU261 ) are: 1) 617,000 tons of indicated resources with a grade of 0.436 ounce of gold per ton (at a cut off grade of 0.12 ounce of gold per ton); 2) 2,499,000 tons of inferred resources with a grade of 0.234 ounce of gold per ton (at a cut-off grade of 0.12 ounce of gold per ton); and 3) 4,206,000 tons of probable reserves with a grade of 0.250 ounce of gold per ton (at a cut-off grade of 0.16 ounce of gold per ton), all estimated at a gold price of $375 per ounce. The mine plant for the project is largely completed but the start of production is in abeyance pending resolution of permitting and legal issues. As of April, 2008, the current status of the project could be seen at the Coeur-Alaska web site (http://www.kensingtongold.com/).
The Jualin deposit is largely in the Cretaceous Jualin Diorite, a northwest-trending stock about 5 miles long and 3 miles wide that is bordered on the east by Triassic metavolcanic rocks of the Wrangellia Terrane and to the west by pelitic sedimentary rocks of the Cretaceous Treadwell Formation, part of the Gravina Belt. The structure of the area is dominated by two regional-scale, northwest-trending faults: the Gastineau shear zone which is southwest of the Kensington mineralization and the Kensington shear zone that trends through the mineralization. The Kensington shear zone has several strands and movement along them controlled the development of the veins in the Kensington Project. Four periods of deformation are recognized in the Kensington shear zone that span the period from 110 Ma (D1) to 53 Ma (D4). The gold veins are coeval with the D3 deformation, which developed a system of right-lateral, reverse, wrench faults.
As described by Birak (2006), the Jualin deposit consists of two deposits: Jualin Veins 1-4 and the Empire Zone. He recognizes several stages of mineralization, two of which are economically significant. The most important are large high-grade quartz-carbonate veins that often contain several ounces of gold per ton. High-grade portions of these veins were previously mined to a depth of about 300 feet; they typically contained 0.5 to 0.6 ounce of gold per ton. The Number 4 vein was discovered in 1990 by drilling and contains more than 1.0 ounce of gold per ton. The Jualin 1-4 veins strike northwest, parallel the regional structure, and dip steeply northeast. They vary from 2 to 20 feet wide and have been traced down dip more than 1,000 feet. The veins are known over an area about 500 feet wide and extend at least 1,000 feet along strike. The second style of mineralization consists of zones of low-angle, quartz-filled extension fractures between the principal shear-hosted veins. These zones vary from 20 to 50 feet thick and generally extend less than 100 feet along strike or dip; they typically average less than 0.06 ounce of gold per ton. The Empire is the largest and richest of these zones; it is about 50 feet wide, 1,000 feet long and averages about 0.10 ounce of gold per ton.
The Jualin mineralization consists of quartz-dolomite veins and veinlets with pyrite, chalcopyrite, galena, sphalerite, molybdenite, hessite, petzite, sylvanite, and native gold. Even small amounts of sulfides indicates gold in excess of 0.50 ounce of gold per ton. Several old deposits now included in the Coeur-Jualin deposit, the Valentine (JU046) and Flemming (JU049), have characteristics of massive sulfide deposits (Casey, 2000) in that they contain markedly more chalcopyrite and sphalerite than other deposits in the belt. The Valentine also has a unusual suite of bismuth sulfosalts including pavonite ((Ag,Cu)(Bi,Pb)3S5), bismuthinite (Bi2S3), a member of the friedrichite (Pb5Cu5Bi7S18) - aikinite (PbCuBiS3), solid-solution series, and rucklidgeite? ((Bi,Pb)3Te4).
Geologic map unit (-135.046412278864, 58.8385725344867)
Mineral deposit model Te-Au pyrite-carbonate-quartz-carbonate-pyrite veins (Cox and Singer, 1986; model 22b).
Mineral deposit model number 22b
Age of mineralization About 55Ma. Precedes the 53 Ma deformational event and younger than the Cretaceous Jualin Diorite. Hydrothermal muscovite from the nearby Kensington mine has been dated at 53.4 Ma to 56.5 Ma (Miller and others, 1994).
Alteration of deposit Albitization and silicification adjacent to the veins (Birak, 2006).

Production and reserves

Workings or exploration
The modern history of the Jualin deposit started in 1978 and eventually included a large block of 10 old mines and prospects, 25 patented claims, and 483 unpatented claims. From 1983 to 1993, the area was explored by a succession of companies including Bear Creek Mining Company, International Curator Resources, Granges, and Placer-Dome USA. In 1993, Coeur entered into a joint venture on the property with Curator and in 1994, Coeur acquired a 100 percent interest in the Jualin. Beginning in about 1980, exploration also began at the Kensington deposit (JU261) deposit to the northwest; this involved a succession of different companies on what became another large block of old mines, prospect, and new claims. In 1995, Coeur gained control of the Kensington deposit too Coeur subsequently carried out major drilling and underground work on both properties and as of 2008 the two main components of the Kensington Project are the Jualin deposit and the contiguous Kensington deposit (JU261).
In 2006, Coeur prepared an intensive NI 43-101 report (Birak, 2006) on the Kensington Project that is largely the basis of this description. As of 2006, the Jualin deposit had been defined by 72,000 feet of drilling; it and the contiguous Kensington deposit (JU261) had been explored by 27,000 feet of underground workings. The mine plant for the project is largely completed but the start of production is in abeyance pending resolution of permitting and legal issues.
Through the end of 2012, 104,618 ft. of core drilling in 142 holes has been reported at the Jualin and Empire Zones. This drilling has shown that near where Jualin Veins 1, 2 and 3 begin to fade away into weakly mineralized fractures, a new set of strong, well mineralized veins begins (Barry, 2013).
Extensive surface drilling was completed at Jualin in 2014 in order to define the northern extent of mineralization along strike of the Vein number 4 zone and increase the drill density spacing to define an inferred resource. There were 47 drill holes completed totalling 58,363 feet (Beebe and others, 2015).
Indication of production Yes
Reserve estimates
Birak (2006) reported the resources of the Kensington project, including both the Jualin deposit described here and the contiguous Kensington deposit (JU261), were: 1) 617,000 tons of indicated resources with a grade of 0.436 ounce of gold per ton (at a cut off grade of 0.12 ounce of gold per ton); 2) 2,499,000 tons of inferred resources with a grade of 0.234 ounce of gold per ton (at a cut-off grade of 0.12 ounce of gold per ton); and 3) 4,206,000 tons of probable reserves with a grade of 0.250 ounce of gold per ton (at a cut-off grade of 0.16 ounce of gold per ton), all estimated at a gold price of $375 per ounce.
A resource estimate for just the Jualin deposit was made by Beebe and others in 2015. The inferred resource using a cut-off value of 0.123 ounces per ton gold is 289,000 tons grading 0.62 ounces per ton gold containing 179,000 ounces of gold.
Production notes Although development is well advanced, there has been no production from the Jualin deposit as defined by Coeur-Alaska since the 1990s. About 65,000 ounces of gold was produced in the Berners Bay district prior to WWII. That production is documented individually in the ARDF records for the old mines in the vicinity of the Jualin deposit. (See the location field for their ARDF numbers).

Additional comments

The Kensington mine area consists of two contiguous properties controlled by Coeur Alaska: the Kensington Group and Jualin Group. These two Groups constitute the Kensington Consolidated Property Package (Property Package) (Barry, 2013).
The Kensington Group includes the Raven (formerly Horrible, JU027), Kensington (JU261), Eureka (JU031), Johnson (JU030), and Elmira (JU032) mineral deposits (Barry, 2013).
The Jualin Group includes the Jualin and the Empire mineral deposits. Both Groups are held through a combination of federal patented and unpatented lode mining and mill site claims and state of Alaska claims, all of which are either owned or held by lease agreements. The combined land holdings total over 14,000 acres, approximately 1,150 of which are covered by Federal patented lode claims (Barry, 2013).

References

References

Huber, J.A., and Barnett, J.C., 1989, 1988 Progress Report, Gold Fork Project: Unpublished report for International Curator Resources, Ltd., Denver, Colo., 35 p.
Kucinski, R., Porterfield, J., and Croff, C., 1985, Kensington Project summary report - 1985: Unpublished report for Placid Oil Co., 27 p.
Reporters D.J. Grybeck (Port Ludlow, WA); V.C. Zinno (Alaska Earth Sciences, Inc.); N.V. King (Alaska Earth Sciences, Inc.)
Last report date 3/15/2016