Glacier Creek

Prospect, Active

Alternative names

Main Zone
RW Zone
South Wall Zone
Palmer

Commodities and mineralogy

Main commodities Ag; Au; Ba; Cu; Pb; Zn
Ore minerals barite; arsenopyrite; chalcopyrite; galena; gold; magnetite; pyrite; pyrrhotite; sphalerite; tennantite; tetrahedrite
Gangue minerals calcite; quartz

Geographic location

Quadrangle map, 1:250,000-scale SK
Quadrangle map, 1:63,360-scale B-4
Latitude 59.3966
Longitude -136.3919
Nearby scientific data Find additional scientific data near this location
Location and accuracy The various parts of the Glacier Creek prospect as defined in 2011 are often referred to separately as the Main Zone, RW Zone, and South Wall Zone, but recent work has united them geologically in an overall estimate of their mineral resources. In plan view, this prospect extends east-west for about 900 meters; the center is about 500 meters east-southeast of Peak 1745 (meters), locally called Mount Morian, which is east of the head of the Little Jarvis Glacier. The center is about 0.6 mile southwest of the center of section 34, T. 28 S., R. 55 E., of the Copper River Meridian. A map of the prospect is figure 8 of Greig and Giroux (2010). This location is accurate within 50 feet.

Geologic setting

Geologic description

The rocks in the region are part of the Upper Triassic Hyd Group that hosts similar volcanic massive sulfide deposits the length of southeastern Alaska (Newberry and others, 1997). The rocks are predominantly massive and pillow basalts and fragmental basalt and andesite(?), intercalated with siltstone, tuff, and rare rhyolite flows and dikes. They have been subject to greenschist-facies metamorphism; folding and faulting locally repeats the stratigraphy in places, and the rocks are highly altered.
In 2006, Constantine Metal Resources acquired the property under a long-term lease and began actively exploring it. Their work has included detailed geologic mapping and sampling, ground geochemical and geophysical surveys, and through 2009, they had drilled 32 holes totaling more than 12,000 meters (Constantine Metal Resources Ltd., 2010).
There have been several published studies of the Glacier Creek prospect by government and academia (MacKevett and others, 1974; Still, 1984; Still and others, 1991; Newberry and others, 1997) and unpublished studies by industry. The consensus has long been that the prospect is a Late Triassic, stratiform volcanogenic massive-sulfide deposit. However, many of the earlier studies suffered from the complexity of the geology, the lack of systematic geologic control at depth, and the difficulty in producing an overall synthesis from the scattered outcrops of mineralization at the surface. While questions remain, the recent synthesis by Greig and Giroux (2010), based on the drilling and other work by Constantine Metal Resources Inc., presents the best description of the deposit to date.
As described by Greig and Giroux (2010) most of the mineralization at the Glacier Creek prospect is in two massive-sulfide horizons: 1) the (upper) RW Zone which is up to 15 meters thick, consists of baritic massive sulfides +/- chert, tuff, and argillite; and 2) the (lower) Main Zone with drill intercepts of up to 35 meters of baritic massive sulfides. The ore minerals in the massive-sulfide horizons are mainly coarse-grained barite, with sphalerite, pyrite, chalcopyrite, and galena, along with less abundant magnetite, pyrrhotite, arsenopyrite, tetrahedrite, and tennantite. Quartz is conspicuous, calcite less so. The two massive sulfide horizons are separated by 70 to 135 feet of rhyolite and basalt that are intensely altered to quartz, sericite, and pyrite (or QSP alteration as it is locally called), and are cut by scattered vein and stockwork mineralization. Basalt underlies the Main Zone and the rocks above the RW zone are more than 150 feet of massive and pillow basalts, a thick gabbro sill, and thin tuffaceous limestone beds.
The structure of the Glacier Creek prospect is a large overturned antiform that trends about east-west for at least 500 meters. The north limb is nearly horizontal but the south limb dips steeply north and is overturned. The hinge of the fault is displaced by a north-dipping thrust fault.
The mineralization in the RW and Main zones persist along both limbs of the antiform but its geometry and grade remain to be worked out. (Constantine refers to the mineralization on the flat north limb of the fold as the RW and Main Zones; the mineralization along the steep overturn south limb as the South Wall Zone.) As known in 2010, the mineralization has been traced along strike for 450 meters down to a depth of 525 meters and was open at both ends and down dip.
Constantine drilled 10 more holes in the summer of 2010 (Constantine Metal Resources Ltd., 2010). Some notable intercepts were 20.8 meters with 1.03 percent copper, 5.01 percent zinc, 0.14 gram of gold per tonne, and 11.3 grams of silver per tonne; and 10.15 meters with 0.70 percent copper, 6.51 percent zinc, 1.02 percent lead, 0.39 gram of gold per tonne, and 89.7 grams of silver per tonne. While noteworthy in themselves, the intercepts also give the general tenor of intercepts in the many holes drilled previously.
In 2014, Constantine drilled 5 holes to test a 400 meter by 400 meter target area modeled from borehole geophysical data. All 5 holes intersected significant mineralization, including drillhole CMR14-65, which yielded the widest intersection drilled to date – 89 meters grading 0.79 percent copper, 5.03 percent zinc, 21.1 grams of silver per tonne and 0.32 gram of gold per tonne. These results have extended the South Wall Zone a further 100 meters west and 50 meters lower in elevation (Constantine Metal Resources Ltd., 2014).
In 2016, Dowa funded a $3.7 million exploration program. Two holes were drilled at the CAP prospect (SK060) totaling 595 m; they intersected semi-massive pyrite, and intervals with anomalous silver and other pathfinder elements. Constantine also sampled rocks at the CAP (SK060), Nunatak (SK058), Gullies (SK070), MHC (SK068), Jag, Waterfall, Boundary (SK057), and Tsirku prospects and obtained many promising assays. Constantine completed environmental assessment work for the U.S. Bureau of Land Management and began construction of its Glacier Creek access road, which will connect the resource area to the Haines highway (Athey and Werdon, 2017).
Geologic map unit (-136.393764567533, 59.3962645850065)
Mineral deposit model Besshi- or Kuroko-type volcanogenic massive sulfide (Cox and Singer, 1986; models 24b or 28a)
Mineral deposit model number 24b or 28a
Age of mineralization Late Triassic by analogy with other similar deposits of that age along the length of southeastern Alaska and into Canada (Greig and Giroux, 2010).
Alteration of deposit Quartz-sericite-pyrite (phyllic) alteration and chloritic alteration developed within mafic metavolcanics (Greig and Giroux, 2010).

Production and reserves

Workings or exploration
The deposit was discovered in 1969 by Merrill Palmer and associates and has been explored by a succession of companies. These include Alyu Mining in 1976 and 1977; Anaconda Minerals in 1979 and 1980; Southeastern Minerals from 1980 to 1983; Bear Creek Mining from 1983 to 1985; Newmont Exploration from 1987 to 1989; Granges Exploration Ltd. in 1989; Cominco Alaska from 1990 to 1993; Kennecott Minerals from 1993 to 1997, Rubicon Minerals from 1998 to 2000; and Toquima Minerals Corp. in 2004 (Greig and Giroux, 2010). It was also mapped and sampled by the U.S. Geological Survey (MacKevett, 1971; MacKevett and others, 1974) and the U.S. Bureau of Mines (Still, 1984) and by the Alaska Division of Geological and Geophysical Surveys (Still and others, 1991). In 2006, Constantine Metal Resources acquired the property under a long-term lease and began actively exploring it. Their work has included detailed geologic mapping and sampling and ground geochemical and geophysical surveys. Through 2009, they had drilled 32 holes totaling more than 12,000 meters. Constantine drilled 10 more holes in the summer of 2010 (Constantine Metal Resources Ltd., 2010).
Constantine drilled 10 more holes in 2013, targeting open edges of the South Wall and RW zones of the 2010 resource estimate, with step-out distances ranging from 30 to 100 meters. Focus was on targets at elevations above the 1,100 meter level. These holes provided further confirmation of the geological model. Highlights of results are 1) South Wall Zone I step-out hole CMR13-49 intersected 24.7 meters (80.9 feet) near true width of 2.02 percent copper, 8.47 percent zinc, 31.7 grams of silver per tonne and 0.51 gram of gold per tonne, and 2) drill holes CMR13-50, which intersected precious metal-rich RW Zone oxide mineralization including 37.5 meters (123 feet) of 123.2 grams of silver per tonne and 0.62 gram of gold per tonne. The intersection includes a partially unoxidized subinterval of 13.7 meters (45 feet) grading 0.51 percent copper, 4.97 percent zinc, 1.61 percent lead, 134.3 grams of silver per tonne and 0.71 gram of gold per tonne (Constantine Metal Resources Ltd., 2013).
As of September 29, 2014, Constantine’s 2014 drill program had drilled 11 holes totaling approximately 6,913 meters, focused on increasing inferred mineral resources and expanding the footprint of the mineralized system. Five of the holes drilled were to test a 400 meter by 400 meter target area modeled from borehole geophysical data. All 5 holes intersected significant mineralization, including drillhole CMR14-65, which yielded the widest intersection drilled to date – 89 meters grading 0.79 percent copper, 5.03 percent zinc, 21.1 grams of silver per tonne and 0.32 gram of gold per tonne. These results have extended the South Wall Zone a further 100 meters west and 50 meters lower in elevation (Constantine Metal Resources Ltd., 2014).
In 2016, Dowa Metals and Mining Co., Ltd. completed its $22 million earn-in and has exercised its option to participate as a joint-venture partner on the Palmer project. Constantine Metal Resources Ltd. owns 51 percent participating interest and Dowa 49 percent, with Constantine as operator. In 2016, Dowa funded a $3.7 million exploration program. Two holes were drilled at the CAP prospect (SK060) totaling 595 m; they intersected semi-massive pyrite, and intervals with anomalous silver and other pathfinder elements. Constantine also sampled rocks at the CAP (SK060), Nunatak (SK058), Gullies (SK070), MHC (SK068), Jag, Waterfall, Boundary (SK057), and Tsirku prospects and obtained many promising assays. Constantine completed environmental assessment work for the U.S. Bureau of Land Management and began construction of its Glacier Creek access road, which will connect the resource area to the Haines highway (Athey and Werdon, 2017).
Indication of production None
Reserve estimates
Greig and Giroux (2010) estimated the resources of the Glacier Creek prospect. Using a Net Smelter Return (NSR) cutoff of 50 US dollars, the RW and South Wall zones have an inferred resource of 4.750 million tonnes with an average grade of 1.84 percent copper, 4.57 percent zinc, 0.28 gram of gold per tonne, and 29.1 grams of silver per tonne; at a NSR of 75 US dollars, there is an inferred resource of 4.120 millions tonnes with an average grade of 2.01 percent copper, 4.79 percent zinc, 0.16 percent lead, 0.30 gram of gold per tonne, and 30.5 grams of silver per tonne; and at a NSR of 100 US dollars, the inferred resource is 3 million tonnes with an average grade of 2.31 percent copper, 5.14 percent zinc, 0.17 percent lead, 0.33 gram of gold per tonne, and 33.3 grams of silver per tonne.
At the Palmer project, Constantine Metal Resources Ltd. has delineated an inferred resource of 8.1 million tonnes at 1.41 percent Cu, 5.25 percent Zn, 31.7 grams of silver per tonne, and 0.32 gram of gold per tonne (Gray and Cunningham-Dunlop, 2015).
Production notes None.

References

MRDS Number A010664; A013088

References

Constantine Metal Resources Ltd., 2010, Constantine continues to expand copper-zinc rich deposit at the Palmer VMS project, Alaska: http://www.constantinemetals.com/news/index.php?&content_id=107 (News release, Sept. 14, 2010).
Constantine Metal Resources Ltd., 2013, Constantine Intersects 24.7 meters of 2.0 percent Copper and 8.5 percent Zinc in Additional Step-out Drilling at the Palmer VMS Project: http://constantinemetals.com/news/2013/index.php?&content_id=201 (News Release, Oct. 8, 2013, as of Sept. 16, 2014).
Constantine Metal Resources Ltd., 2014, Constantine Intersects 89 meters of 5.0% Zinc, 0.8% Copper, 21 g/t Silver and 0.3 g/t Gold at the Palmer VMS Project, Alaska: http://constantinemetals.com/news/2014/index.php?&content_id=218 (News Release, Sept. 29, 2014, as of Dec. 24, 2014).
Greig, C.J., and Giroux, G.H., 2010, Palmer VMS project, southeast Alaska; Mineral resource estimation and exploration update: Technical l report for Constantine Metal Resources Ltd. 82 p. (posted on www.sedar.com, Mar. 8, 2010) http://www.sedar.com/GetFile.do?lang=EN&docClass=24&issuerNo=00023827&fileName=/csfsprod/data104/filings/01543498/00000001/C%3A%5CSEDAR%5CCEM_Filings%5CPalmer_43-101_Rept_CEM_2010.pdf (as of December 24, 2014).
Newberry, R.J., Crafford, T.C., Newkirk, S.R., Young, L.E., Nelson, S.W., and Duke, N.A., 1997, Volcanogenic massive sulfide deposits of Alaska, in Goldfarb, R.J. and Miller, L. D., eds., Mineral deposits of Alaska: Economic Geology Monograph 9, p. 120-150.
Reporters T.C. Crafford (T. Crafford & Associates, Anchorage); D.J. Grybeck (Contractor, USGS); V.C. Zinno (Alaska Earth Sciences, Inc.); M.B. Werdon (DGGS)
Last report date 8/26/2017