Ruby Creek

Prospect, Active

Commodities and mineralogy

Main commodities Graphite
Ore minerals graphite; pyrrhotite
Gangue minerals amphibole; biotite; garnet; muscovite; plagioclase; quartz; sillimanite; sphene; zircon

Geographic location

Quadrangle map, 1:250,000-scale TE
Quadrangle map, 1:63,360-scale A-2
Latitude 65.037
Longitude -165.552
Nearby scientific data Find additional scientific data near this location
Location and accuracy Ruby Creek is a small east headwater tributary to Glacier Canyon Creek that flows northward across the Kigluaik Mountain front 0.4 mile northeast of Glacier Canyon Creek. It is located 0.5 mile east-southeast from the center of section 21, T. 5 S., R. 34. W., of the Kateel River Meridian. This creek is not identified by name on USGS topographic maps; its name comes from a location map made by Coats (1944). Ruby Creek is now encompassed as part of Graphite Creek Property (TE105, 2014). This location is 11.8 miles due east of White River and 2.4 miles northeast of the Christophosen mine (TE103) at elevations of 550 to 650 feet. It is at the abrupt break in slope on the north side of the mountain front, just upslope of the surface trace of the active Kigluaik normal fault. The graphite-bearing rocks are in the footwall of this fault. This location was not shown by Cobb and Sainsbury (1972), but Cobb (1975) summarized relevant references under the name 'Ruby Cr.' Location is accurate within 500 feet.

Geologic setting

Geologic description

Ruby Creek is now encompassed as part of the Graphite Creek record (TE105, 2014).
Flake graphite occurs as disseminations and high-grade tabular lenses within amphibolite facies metasedimentary rocks (Coats, 1944). The metamorphic rocks are primarily biotite-quartz schist with some sillimanite and garnet (Sainsbury, 1972). Small granitic plugs, dikes, and sills locally intrude the metamorphic rocks. The graphite-bearing schists are sharply bound to the north by the recently active Kigluaik fault, the principal fault along which late Cenozoic uplift of the Kigluaik Mountains has taken place (Hudson and Plafker, 1978). The graphite-bearing schists strike approximately parallel to the mountain front and dip north between 25 and 65 degrees. They form a zone along the mountain front that is 200 to 400 feet thick and possibly 20,000 feet long (Hudson, 1981; also see Christophosen Creek (TE103) locality to the west and Graphite Creek (TE105) locality to the east). To the south, the graphite-bearing schists are in conformable contact with other amphibolite facies metasedimentary rocks. The latter appear to be feldspathic and contain much less graphite. The graphite-bearing schists make up two general sequences; (1) a heterogeneous sequence of garnet-sillimanite-biotite-quartz schist with disseminated graphite and graphite-rich lenses, and (2) a more evenly layered biotite-quartz schist with disseminated graphite. The latter contains disseminated pyrrhotite and commonly weathers orange.
To the west of Ruby Creek, a 50-foot trench along strike exposes lenses up to 1 foot wide that are estimated to contain 70 percent graphite by volume. This zone of high-grade lenses has been traced along strike for 500 feet and is exposed over a vertical extent of 175 feet. The width of the graphite-rich zone was not recorded. A sample from this exposure contained 60 percent graphite of which 65 percent was coarser than 30 mesh to the inch (Coats, 1944). Other graphite-rich zones are present along Ruby Creek including a faulted section 4 feet wide with 1 to 6 inch wide graphite stringers and a 12 foot wide section with several 4 to 12 inch thick graphite-rich lenses. Individual lenses are not more than 20 feet long and seem to be about 12 times their width in length. The lenses overlap one another and come and go through the graphite-rich section (Coats, 1944). A sample of schist (plagioclase-biotite-quartz schist) with disseminated graphite from this locality was thought to have 5 to 10 percent graphite in thin section but laboratory analysis indicated a graphite content of 3 percent (Wolgemuth, 1982).
During 2011 and 2012, Graphite One conducted exploration work at the Graphite Creek Property. The majority of the exploration work was completed during the summer 2012 including: a time-domain helicopter-borne electromagnetic survey; geological mapping; surface grab, channel and bulk pit sampling; and an 18 drillhole program to test the graphitic units at depth (Duplessis and others, 2013). In 2013, a 10 drillhole program expanded the area of mineralization both easterly and westerly, more than doubling the length of the graphite zone, which was about 2.2 kilometers in 2012, and became 4.8 kilometers in 2013 (Eccles and Nicholls, 2014).
Geologic map unit (-165.55464373021, 65.036239952875)
Mineral deposit model Disseminated flake graphite (Orris and Bliss, 1992; model 37f).
Mineral deposit model number 37f
Age of mineralization The metamorphism that has developed coarse graphite in these rocks is Late Jurassic to Early Cretaceous in age.
Alteration of deposit Some shearing and deformation of graphite-rich lenses has accompanied faulting and oxidation of disseminated pyrrhotite has led to orange-staining of graphite-bearing rocks but other types of alteration are not identified.

Production and reserves

Workings or exploration
A 50 foot-long surface trench and a 20 foot-long drift were noted by Coats (1944) and other small surface workings (pits) are probably present. Exploration activity in the general area took place in 1994 (Swainbank and others, 1995) as well as in 2011 to 2013 (Duplessis and others, 2013; Graphite One Resources, 2014).
During 2011 and 2012, Graphite One conducted exploration work at the Graphite Creek Property. The majority of the exploration work was completed during the summer 2012 including: a time-domain helicopter-borne electromagnetic survey; geological mapping; surface grab, channel and bulk pit sampling; and an 18 drillhole program to test the graphitic units at depth (Duplessis and others, 2013). In 2013, a 10 drillhole program expanded the area of mineralization both easterly and westerly, more than doubling the length of the graphite zone, which was about 2.2 kilometers in 2012, and became 4.8 kilometers in 2013 (Eccles and Nicholls, 2014).
Indication of production Yes; small
Reserve estimates
The few miles along strike between the area of the Christophosen Creek (TE103)deposit and the Graphite Creek (TE105) deposit to the east has been estimated to contain 65,000 tons averaging about 60 percent graphite (Coats, 1944). This zone has also been estimated to contain, overall, more than 10 million tons of 10 percent or more graphite (Weiss, 1973).
The first mineral resource estimate for Graphite Creek (TE105), which also includes Christophosen Creek (TE103) and Ruby Creek, was prepared by Claude Duplessis, Eng., senior consultant for SGS Canada Inc. (SGS), and an independent Qualified Person under National Instrument (NI) 43-101, using the Canadian Institute of Mining, Metallurgy and Petroleum (CIM) Standards on Mineral Resources and Reserves, Definitions and Guidelines (Duplessis and others, 2013), which was updated the following year to include 2013 drill program results (Eccles and Nicholls, 2014).
They report an inferred resource of 186.86 million tonnes of schist containing 5.5 percent graphite with a recommended cut-off grade of 3 percent graphitic carbon (by LECO CR-412 Carbon Analyzer ) and an inferred resource of in-situ graphite of 10.34 million tonnes. For the list of other cut-off grades, refer to Eccles and Nicholls, 2014.
Production notes Some of the graphite shipments reported for the Alaska Graphite Company may have come from this locality. These shipments include 35 tons (1907) and 100 tons (1916 or 1917) of hand-sorted, high-grade material (Mertie, 1918; Harrington, 1919; Coats, 1944).

Additional comments

In January 2012, Graphite One Resources entered an option agreement to earn 100 percent interest in claims encompassing known graphite showings over a three year period through exploration work totaling approximately $1.525 million, which Graphite One has completed with its 2012 summer exploration program. The total Graphite Creek Property land package comprises 129 claims totaling 16,801 acres (6,799 hectares), essentially controlling all prospective lands of known graphite mineralization in the region (Duplessis and others, 2013). The historically-named Ruby Creek prospect is part of the overall Graphite Creek Project (Eccles and Nicholls, 2014).

References

MRDS Number A015735
Reporters Travis L. Hudson (Applied Geology); V.C. Zinno (Alaska Earth Sciences, Inc.); F.H. Wilson (USGS)
Last report date 2/25/2016