|Quadrangle map, 1:250,000-scale||TC|
|Quadrangle map, 1:63,360-scale||A-4|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||The Saddle Zone prospect is about 0.3 mile northeast of VABM 3345 'Tetlin' and about 7.9 miles northwest of the center of Tetlin Lake. The prospect is centered about 0.2 mile east-northeast of the center of section 11, T. 16 N., R. 13 E., of the Copper River Meridian. The location is accurate to within 500 feet.|
The Peak Zone is a ‘gold skarn’ prospect at the Tetlin Project that lies within the Yukon-Tanana Terrane. The host rock is a deformed marble lens (Illig, 2014). An inferred related intrusive is quartz monzonite. The main prograde metamorphism mineral is pyroxene while the main retrograde metamorphism minerals are amphibole and chlorite (Freeman, 2014a). The mineralization is characterized by gold hosted in skarn-altered carbonates, pyrrhotite dominant, with chalcopyrite, arsenopyrite, and lesser pyrite with anomalous silver, bismuth, cobalt, and sporadic anomalous molybdenum and tin. The mineralization is within an amphibole and chlorite alteration envelope (Freeman, 2014a). There is also green to black hornblende-chlorite and calcite alteration. Malachite and native copper are present in fractures below weathered sulfide mineralization. Quartz monzonite porphyry contains barren quartz magnetite veins (Van Treeck, 2013). Metal is zoned around the prospect as copper + gold proximal to mineralized center, and arsenic + lead + zinc distal to mineralized center. The indicated tonnage is 6 million tonnes with a gold grade of 3.46 grams per tonne, 11.87 grams of silver per tonne, and 25 percent copper (Freeman, 2014a).
The geophysical signature of the Peak zone is high relative magnetic susceptibility and a high relative conductivity/low relative resistivity associated with mineralization. Airborne magnetic and resistivity surveys have outlined the Peak Zone mineralization in the upper 150 meters of crust. Areas with a similar geophysical signature located near the Peak Zone are along inferred stratigraphic horizons and share geochemical signatures (Van Treeck, 2013).
This prospect is part of the Tetlin Project; it is hosted in Precambrian to Paleozoic greenschist to amphibolite-grade metamorphic rocks of the Yukon-Tanana Terrane intruded by Cretaceous to Tertiary felsic and intermediate plutonic bodies (Foster, 1970). District and regional scale northeast and northwest trending faults are present on the project and are often associated with gold and copper mineralization in this terrane (Freeman, 2014b). The project area is interpreted to be located in overlapping mineral belts of the Tintina gold belt with the Carmacks Porphyry Belt (Freeman, 2014a).Metallurgical test results were reported in 2014 by Contango ORE, Inc.. These results from three samples indicate that all samples achieved consistently high metallurgical recovery across the primary grind sizes that ranged from 49 to 115 microns. The proportion of contained gold recovered by gravity methods ranged from 8 percent to 30 percent with the lowest gravity recovery in a high copper bearing sample with progressively higher percentages of gold in the gravity concentrate as gold grade increased in the other samples. Primary sulfides identified in the analysis were pyrrhotite and chalcopyrite with lesser amounts of arsenopyrite, silver-bearing minerals, sphalerite and native gold. Primary silicate minerals include quartz, calcite, chlorite, potassium feldspar, amphibole and pyroxene. Abundant visible gold was observed in two of the three samples (Contango ORE, Inc., 2014b).
|Geologic map unit||(, )|
|Mineral deposit model||Skarn? (Cox and Singer, 1986; model 18b).|
|Mineral deposit model number||18b?|
|Age of mineralization||70 million years old, Cretaceous, according to U/Pb radioisotope dating techniques (Illig, 2014).|
|Alteration of deposit||Chlorite and amphibole alteration is associated with gold and silver mineralization (Illig, 2014).|
|Workings or exploration||
There has been no recorded past placer or lode mining or exploration drilling conducted on any prospect on the Tetlin Project until Contango Ore, Inc. completed its first reconnaissance exploration program in 2009 (Contango Ore Inc., 2012).
In 2008, Contango ORE, Inc. began acquiring and analyzing remote sensing data in the area of Peak Zone to begin exploration work targeting in the area. In 2009, the first reconnaissance program was conducted, followed by soil sampling and trenching (Freeman, 2014a). The first indication of mineralization was a linear gold-copper soil anomaly with a small induced polarization (IP) resistivity low (Illig, 2014). In 2010, the field program entailed prospecting, stream sediment sampling, and pan concentrate sampling, and focused basal soil sampling and IP surveys. In 2011, the basal soil sampling was continued, in addition to an airborne magnetic and resistivity survey and 11 holes (2,456 meters) of core drilling. The 2012 field program continued the basal soil sampling, along with a 50 hole (10,974 meters) core drilling program. The 2012 exploration work is what led to the discovery of Peak (Freeman, 2014b). Multiple drill intercepts with gold in excess of 10 parts per million (ppm) over 10 feet were reported. Gold is accompanied by variable silver of up to 500 ppm and copper of up to 1 percent over 100 feet The highest gold grade is associated with highly magnetic sulfide-bearing host rocks and also conductive sulfide-bearing host rocks. In 2013, Contango conducted an airborne magnetic and resistivity survey, and continued a basal soil sampling, stream sediment and pan concentrate sampling program, in addition to a 69 hole (14,625 meters) oriented core drilling program (Van Treeck, 2013).In 2014, Contango reported the following resource estimate with a cut-off grade of 0.5 gram per tonne: 1) indicated resources of 5,970,000 tonnes grading 3.46 grams of gold per tonne, 11.00 grams of silver per tonne and 0.25 percent copper, and 2) inferred resources 3,850,000 tonnes grading 2.07 grams of gold per tonne, 14.28 grams of silver per tonne and 0.23 percent copper (Contango ORE, Inc., 2014a). They also reported results from metallurgical testing that indicated that all samples achieved consistently high metallurgical recovery across the primary grind sizes that ranged from 49 to 115 microns (Contango ORE Inc., 2014b).
|Indication of production||None|
Indicated resources for the Peak Zone are reported, with a cutoff of 0.5 gram of gold per tonne equivalent and cut-off of 5,970,000 tonnes, to be 3.46 grams of gold per tonne, 11.00 grams of silver per tonne, 0.25 percent copper, 4.08 grams of gold per tonne equivalent, with total grams being 24,357,600 and total ounces of 783,115 (Contango Ore, Inc., 2014a).
Inferred resources for the Peak Zone are reported, with a cutoff of 0.5 gram of gold per tonne equivalent and cut-off of 3,850,000 tonnes, to be 2.07 grams of gold per tonne, 14.28 grams of silver per tonne, 0.23 percent copper, 2.69 grams of gold per tonne equivalent, with total grams being 10,356,500 and total ounces of 332,969 (Contango ORE, Inc., 2014a).Resource from 78 of 130 holes, 16,010 meters of core. Seven gold values were capped at 75.0 grams per tonne, 13 silver values at 252.0 grams per tonne and 7 copper values at 5.40 percent. Resource blocks are 10 by 10 by 5 meters, ore specific gravity is 3.15, waste specific gravity is 2.81. Grades for gold, silver, copper were interpolated using ordinary kriging. For gold equivalent calculation: gold = US$1318 per ounce, copper = $3.25 per pound, silver = $21.55 per ounce (Freeman, 2014a).
Additional commentsIn 2008, Contango ORE, Inc. signed a lease with Tetlin Village to control mineral rights on about 675,000 acres of fee simple land leased from the Tetlin Village(Freeman, 2014b).
|Reporters||V.C. Zinno (Alaska Earth Sciences, Inc.)|
|Last report date||3/15/2016|