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File Created: 24-Jul-85 by BC Geological Survey (BCGS)
Last Edit:  17-Aug-15 by Sarah Meredith-Jones(SMJ)

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NMI 093K3 Mo1
Name ENDAKO, ENDAKO MINE, STELLA, BOOT, JAY, MO, TAN, COMO, FRANDER, MISPAT Mining Division Omineca
BCGS Map 093K005
Status Producer NTS Map 093K03E
Latitude 54º 02' 10" N UTM 10 (NAD 83)
Longitude 125º 06' 36" W Northing 5989599
Easting 361820
Commodities Molybdenum, Copper, Zinc, Tungsten, Bismuth Deposit Types L05 : Porphyry Mo (Low F- type)
Tectonic Belt Intermontane Terrane Stikine
Capsule Geology

The Endako deposit is located on a hillcrest approximately 160 kilometres west of Prince George in central British Columbia. The mine area encompasses several showings (093K 007, 10, 13, 14) and includes the 1.7 kilometre Endako pit, the mined out Denak East pit and the partially developed Denak West pit (093K 008).

In 1989, Placer Dome completed 14 diamond-drill holes in the mine area in an attempt to extend known ore reserves and to gather geotechnical information. Placer Dome completed 22 diamond-drill holes on the Endako deposit in 1992. Production began in 1965 and by 1993 a total of 231 million tonnes had been mined yielding more than 157.5 million tonnes of molybdenum.

The Endako orebody is centrally situated within the Late Jurassic Francois Lake batholith. At least ten phases based on distinct textural and compositional changes have been recognized in the composite batholith. The orebody consists of an elongate stockwork of quartz-molybdenite veins developed within the Endako quartz monzonite phase and three types of felsic pre-ore dikes. The Endako quartz monzonite is bounded on the south by Francois granite and on the north by Casey alaskite and Glenannan granite. Post-ore basalt and andesite dikes crosscut the quartz monzonite, pre-ore dikes and mineralized stockwork.

In general terms, the orebody is a series of major east-striking veins oriented en echelon to form a zone elongated in a northwesterly direction. Length and width dimensions of the zone are approximately 3360 by 370 metres, of which the western 1830 metres is offset to the north by the West Basalt fault with a 1150 metre relative right-hand movement. Divided by this fault into two distinct domains, the east half dips moderately south and plunges west, while the west half dips east. Molybdenite, pyrite and magnetite are the most abundant primary metallic minerals. Minor chalcopyrite and traces of sphalerite, bornite, specularite and scheelite are also present. Single occurrences of beryl and bismuthinite have been reported. Molybdenite occurs in two types of veins. Large veins (up to 1.2 metres wide) contain laminae and fine disseminations of molybdenite. Fine fracture-fillings and veinlets of quartz-molybdenite occur as stockworks adjacent to the major veins. Alteration types include pervasive kaolinization, envelopes with potassium feldspar and envelopes with sericite.

A pyrite zone bounds the orebody to the south across a major fault. In this zone, mineralization consists of quartz, pyrite, minor magnetite and rare molybdenite. The mineralization occurs as fracture-filling in a poorly developed stockwork. The orebody is localized at or near the intersection of regional northwest and east structures.

Three distinct hydrothermal alteration phases are seen in the Endako ore zone. Introduced K-feldspar is noted as envelopes adjacent to veins and fractures. A second type of envelope seen is a fine-grained band of quartz-sericite and finely disseminated pyrite. Both of these envelopes can vary in width from 0.3 to 5 centimetres. Also pervasive kaolinization of the Endako quartz monzonite is present.

The claims were originally staked in 1927 when two local men staked four mineral claims to cover an area of quartz-molybdenite float. Two short shafts were sunk in 1934, one on the 0.6 metre “Stellar” vein. During the period of 1934 to 1961, the property was examined by many geologists and several mining companies, but physical work was confined primarily to trenching and some sampling.

In May of 1962, trenching and a diamond drilling programs were commenced by Endako Mines Limited. Canex Aerial Exploration Ltd. entered the exploration of the property in October of the same year, and completed 190 diamond-drill holes for a total of 24,000 metres and 810 metres of underground work for bulk sampling. The decision to develop the property for production was announced in March of 1964. Construction of the 9,000 tonne-per-day mine plant and development of the open pit began in June 1964, and the mine was officially opened on June 8, 1965.

In 1965, pit development by Endako Mines Ltd. consisted of the removal of 1.01 million cubic metres of overburden to permit the extension of mining from the west pit into the east pit. At the beginning of the year, a 9,000 tonne-per-day concentrator commenced operation; later improvements to the concentrator increased this rate to 13,500 tonnes per day. A total of 3,569,000 tonnes of ore at an average grade of 0.174 per cent Mo were milled for the year of 1965. Mill recovery was reported at 81.3 per cent with a total of 4.67 million kilograms of molybdenum being produced. Mineable reserves as of April 30, 1966 were 79,079,000 tonnes at 0.132 per cent Mo or 142,839,000 tonnes at 0.102 per cent Mo (Property File Cyprus Anvil Endako Mines Ltd., 1966).

The Denak East open pit is mined out and is currently being backfilled with waste (ca. 1994). The ore contains progressively less stockwork and dips shallower as one traverses from the Endako pit in the southeast to the Denak West pit in the northwest.

Production from the Denak pit (093K 008), which is now part of the Endako mine, is included. Mine life is estimated at 10 years (ca. 1996) at present levels of production.

Proven and probable ore reserves estimated by the company were 117,600,000 tonnes grading 0.077 per cent molybdenum at January 1, 1995; in addition measured and indicated mineral resources were estimated at 147,850,000 tonnes grading 0.061 per cent molybdenum (Information Circular 1996-1, page 8).

Reserves as of January 1, 1996 are 104,843,000 tonnes grading 0.077 per cent molybdenum (Information Circular 1997-1, page 9).

In early 1997, Placer Dome Canada Limited sold the Endako molybdenum mine to Thompson Creek Mining Company of Denver, Colorado (75 per cent) and Nissho Iwai Corp. of Japan (25 per cent). During 1997, Endako expected to mine 20.8 million tonnes and mill 10.6 million tonnes grading 0.131 per cent molybdenum to produce approximately 6500 tonnes of molybdenum. A modest drilling program and geophysical survey were carried out in 1997.

At January 1, 1997, proven and probable reserves are estimated at 124,887,000 tonnes grading 0.066 per cent molybdenum. An additional 131,003,000 tonnes grading 0.065 per cent molybdenum were listed as measured and indicated (T. Schroeter, personal communication, 1997). Proven and probable reserves (including stockpiles) on January 1, 1998 were 121,757,000 tonnes at 0.065 per cent molybdenum. Mine cutoff grade is 0.04 per cent molybdenum (Exploration in BC 1997, page 12). As at January 1, 2000, reserves are estimated at 80,000,000 tonnes grading 0.074 per cent molybdenum (Information Circular 2001-1, page 6).

The following is by Anderson, R.G. et. al, from the Appendix to the Nechako Project Newsletter, Volume 3, Number 5, May 30, 1997: "A northwesterly-trending Jura-Cretaceous batholith in eastern Stikinia hosts the Endako porphyry molybdenite deposit. It has been variously considered part of the Jurassic Topley Intrusions, Endako Intrusions and Early Cretaceous Francois Lake Plutonic Suite. New mapping, geochronology, and chemical and isotopic analyses define at least 3 constituent suites: poorly mineralized Middle Jurassic (170-160 Ma) Stag Lake suite; well-mineralized Late Jurassic (160-150 Ma) Francois Lake suite (host to Endako-style, low-fluorine, porphyry Mo deposits); and unmineralized, satellitic mid- to Late Cretaceous Fraser Lake suite and Eocene (?) stocks.

Middle Jurassic Stag Lake intrusions define the eastern and northeastern batholith margins and include sequentially-intruded biotite-hornblende diorite and gabbro, and hornblende-biotite quartz monzodiorite and granodiorite; biotite quartz monzonite to monzogranite may represent related felsic phases. The rocks are commonly mesocratic and xenolith-, clinopyroxene- and titanite- bearing. Mineral and xenolith foliation is most common near contact zones between mafic and intermediate phases. The suite is compositionally heterogeneous but is generally of calc-alkaline, metaluminous, moderate-potash and volcanic arc affinities and closely resembles the coeval Three Sisters Plutonic Suite in northeastern Stikinia north of the Stikine River.

Late Jurassic Francois Lake biotite monzogranite plutons to the northwest are the most quartz-rich, leucocratic, and mineralized of all and are further subdivided based on grain size, biotite abundance, degree of alteration, intergranular textures, and intrusive relationships. The suite records a complex, protracted history that included: emplacement, solidification, locally intense veining, Mo and pyrite mineralization and alteration, and late dykes, fractures, and joints. The suite is coeval with Upper Jurassic volcanic rocks to the north and south. The structural control on the co-spatial but younger (<145 Ma) mineralizing system suggests a possible dextral, transtensional tectonic environment for emplacement. The rocks are distinctly high silica, calcalkaline, weakly peraluminous, moderately to high potash, and of volcanic arc affinity with a relatively primitive or juvenile radiogenic and stable isotopic character."

The combined proven and probable reserves for the Endako pit at October 1, 2003 is 38,200,000 tonnes grading 0.072 per cent molybdenum. The Denak pit has a combined proven and probable reserve of 22,700,000 tonnes grading 0.069 per cent molybdenum and the surface stockpile is 26,300,000 tonnes grading 0.04 per cent molybdenum (Alan Morrish, General Manager and Vice President, Thompson Creek Mining Ltd.).

In 2003, mining continued at Endako. The pit, which is elongated west-northwest, measures 650 metres by 230 metres and is 250 metres deep.

In 2004, narrow mining width in the pit coupled with wall instability that interrupted mining led to a 10% reduction in the tonnage milled. Pit expansion comprises a major push-back of the south wall and a less extensive set back of the north wall that will enable a return to the scheduled rate of molybdenum production. Ten exploratory holes were drilled southeast of the Endako pit to follow up on a mineralized intercept.

In 2005, the Endako mine, owned 60% by Thompson Creek Mining Ltd and 40% by Sojitz Moly Resources Inc, celebrated its 40th year of operation. Reserves are sufficient until 2013. Endako ore averaged 0.060% molybdenum during the year, a lower grade than in 2004. The company completed a major stripping program in the Endako pit, to access ore and stabilize the north and south walls. At year-end Endako began a 4500-metre exploration drill program.

In October of 2006 Blue Pearl Mining Ltd. acquired Thompson Creek Metals Company including its interests in Endako. In May 2007, Blue Pearl changed its name to Thompson Creek Metals Company Inc. Endako mine is now owned 75% by Thompson Creek and 25% by Sojitz Corporation. (Thompson Creek Annual Report 2007).

During 2007 the Endako pit was the focus of mining activity, but ore was also sourced for milling from the Denak West pit and stockpiles. Plans for 2008 are to shift the focus primarily to the Denak West and East pits and to mine the walls between all three pits to create one large pit (Thompson Creek Annual Report 2007).

Reported reserves and resources at December 31, 2007 were 292.8 million tonnes grading 0.050 per cent Mo combined Proven and Probable reserves; 138 million tonnes grading 0.050 per cent Mo Measured resources; 354.1 million tonnes grading 0.040 per cent Mo Indicated resources. Reported reserves include stockpiles and resources and were reported at a 0.02 per cent cut-off (Thompson Creek Annual Report 2007).

Reported reserves and resources as of January 2011 were 282.2 million tonnes grading 0.046 per cent Mo combined Proven and Probable reserves, 80.2 million tonnes grading 0.034 per cent Mo combined Measured and Indicated resources and 55.8 million tonnes grading 0.037 per cent Mo Inferred resources (Technical Report - Endako Molybdenum Mine - February 2011 www.thompsoncreekmetals.com).

Reserves and resources as of December 31, 2014 were reported as:
Thompson Creek Metals Company Annual Report 2014
___________________________________________
Category Amount (tonnes) Mo (%)
Proven +
Probable 33,400,000 0.049
Measured 47,600,000 0.047
Indicated 61,600,000 0.047
Measured +
Indicated 109,200,000 0.047
Inferred 2,200,000 0.039
Reserves calculated at 0.030% Mo cut-off
Resources calculated at 0.025% Mo cut-off
___________________________________________


Operations were temporarily suspended December 31, 2014 due to weakness in the molybdenum market (Northern Miner December 12, 2014).

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