The Tam developed prospect is situated in the Swannell Ranges (Omineca Mountains), approximately 22 kilometres north of Old Hogem and 61 kilometres north-northeast of Takla Landing. The original showing, now known as the Cirque, was discovered in a north-facing basin overlooking Haha Creek in the late 1940s.
The area is underlain by mesozonal plutonic rocks assigned to the Late Triassic to Early Cretaceous Hogem Intrusive Complex which have been emplaced into volcanic rocks of the Middle Triassic to Lower Jurassic Takla Group, east of the Pinchi fault zone. The plutonic rocks form an elongate batholith, extending from Chuchi Lake, north to the Mesilinka River. Garnett (1978) subdivided the southern Hogem batholith into three distinct phases: I) Late Triassic to Middle Jurassic Hogem granodiorite and Hogem basic suite, II) Middle Jurassic Duckling Creek and Chuchi Syenite complexes and III) Early Cretaceous granite. The structural setting of the batholith and the intruded Takla Group is one of vertical tectonics associated with graben development (Bulletin 70).
Three rock units predominate in the area of the occurrences. The first comprises mottled grey-pink-red, medium to coarse-grained equigranular to porphyritic, massive to foliated, strongly magnetic mesocratic syenite. The second unit consists of pink, brown and/or orange-coloured, medium to very coarse-grained, massive to weakly foliated, weakly magnetic leucocratic syenite. Both these units form part of the Duckling Creek Syenite Complex. Pendants(?) comprising an assemblage of foliated border facies or epizonal roof rocks including greenstone, greenschist, mica schist (paragneiss) and deformed volcaniclastics (Takla Group?) also occur within these intrusions. In addition to these rocks, Phase I monzodiorite/ syenodiorite and quartz monzonite tentatively grouped with Phase III granites have also been mapped in the area (Assessment Report 20914).
Several localized areas of copper mineralization, including the Boundary, Creek, Ridge and Midway prospects, have been observed to occur within pendant rocks (foliates) adjacent to a leucosyenite plug. Others, like the Cirque and Fault prospects, occur entirely within intrusive rocks.
The Boundary deposit is located at the intrusive contact between a northwest-trending, vertically-dipping septum of foliates and a leucosyenite plug with associated dikes. Remnants of altered mesocratic syenite intrude and are preserved within the foliates. Copper mineralization occurs both as fine-grained disseminations and as fracture fillings (quartz +/- pyrite, quartz +/- chalcopyrite, biotite +/- chalcopyrite, potassium feldspar +/- chalcopyrite, magnetite +/- chalcopyrite and chalcopyrite +/- pyrite veins, veinlets, stringers and discontinuous seams). Some mineralized fractures show reddish potassium feldspar +/- pyrite +/- sericite alteration envelopes. Quartz vein stockwork is poorly developed. Chalcopyrite to pyrite ratios are very high near the core of the deposit, but an outer pyrite halo is either weak or poorly preserved. No propylitic alteration assemblages were observed within or marginal to the deposit, but the strongest copper mineralization is clearly coincident with strong potassic (secondary potassium feldspar and biotite) alteration. Gold values are generally erratic and low in comparison to other porphyry copper-gold deposits (Assessment Report 20914, page 7).
The Creek showing, 500 metres south of the Boundary deposit, consists largely of disseminated fine-grained blebs of chalcopyrite within schistose to gneissic monzonite. The Ridge showing, a further 350 meters to the south, consists of malachite-stained, highly fractured schistose monzonite. The Cirque showing, 500 metres southwest of the Ridge, consists of disseminated chalcopyrite in magnetite-rich biotite syenite intruded by leucosyenite dikes. The Fault showing, a further 0.5 kilometre south of the Cirque showing, consists of disseminated chalcopyrite and bornite in iron-stained foliated monzonite exposed in a prominent northwesterly trending lineament. The Midway showing, 650 metres southeast of the Boundary deposit, consists of sparsely disseminated chalcopyrite in dark, fine, grey foliated monzonite. Malachite mineralization hosted by greenschist and local mesosyenite-hosted drusy quartz veins carrying disseminated bornite have also been outlined within and northwest of the Slide grid, north of Haha River.
Faults, where observed in drill core, are postmineral and accompanied by strong argillic alteration. It is speculated that a strong northwest-trending zone truncates the deposit to the southeast with possible right-lateral displacement to the northwest. Interpolation between surface lineaments and the location of faults observed in drill core suggests that the deposit is almost entirely enclosed within a down-faulted block or the keel-shaped protuberance of a roof pendant engulfed by the intrusions (Assessment Report 20914).
UMEX carried out a number of programs on the Hogem batholith between 1969 and 1975. Geochemical and geophysical surveys and fourteen diamond-drill holes, for a total of 2,127 metres, was completed on the Boundary zone. Work carried out to 1974 resulted in the definition of inferred (possible) reserves for the Boundary deposit of 7.2 million tonnes grading 0.55 per cent copper and 4.11 grams per tonne silver (Dyson, 1974 (as reported in Assessment Report 20914)).
In 2006, the Boundary (Tam) target was mapped and covered by IP and magnetic geophysical surveys by Teck Cominco. A strong IP chargeability high is associated with the known Boundary mineralization that persists to the northwest and southeast but at weaker levels. Interpretation of the Boundary mineralization from previous drilling suggests a southwest dip to the mineralization in this area. No drilling occurred at Boundary in 2006 but in light of the new discovery of copper-gold-silver mineralization at the Slide prospect to the this area will require drill testing.
Mineralization in the Boundary area was first discovered in the late 40’s by Kennco Explorations but not until the early 70’s was any extensive work conducted. From 1969 to 1975, Union Miniere Explorations and Mining Corporation Limited (UMEX) conducted programs of geological mapping, soil and rock sampling, IP and magnetic geophysical surveys, trenching and diamond drilling (25 holes, 3629m) on the Boundary, Midway, Cirque and Fault targets. This work resulted in the definition of inferred (possible) reserves (pre 43-101) for the Boundary deposit of 7.2 million tonnes grading 0.55 percent copper and 4.11 grams per tonne silver (Dyson, 1974, as reported in Assessment Report 20914). The best drill hole from the Boundary deposit is 0.68 per cent copper over 179.8 metres in hole 74-6 from 3.7-183.5 metres including 1.59 per cent copper over 39.6m from 3.7-43.3 metres. (1970s drill Logs provided in Assessment Report 20914.) Copper mineralization occurs both as fine-grained disseminations and as fracture fillings within fine grained foliated and massive potassium altered syenites.
While developing the Boundary prospect, UMEX also carried out exploration programs in the Slide area documenting mineralization in outcrop in 1973. From 1973 to 1975 UMEX conducted geological mapping, soil geochemical surveys, IP geophysical surveys and drilled three diamond drill holes totaling 326.2m. The best results from this work was 0.43% Cu over 10ft in hole T-17.
In 1990 and 1991, Major General Resources Ltd. and Varitech Resources Ltd. carried out programs of mapping, rock and soil sampling, IP and magnetic geophysical surveys over the Boundary, Midway and Slide showings but did not drill test any targets. A 10m random chip sample from the 1970’s Slide hand trench returned 1.27% Cu from malachite stained fine grained potassium altered gneissic monzonite or greenschist.
L.B. Warren staked claims over the Jan-Tam-Misty area several times since 1995; prospecting was intermittent to 2006 when Warren optioned the property to Teck Cominco Limited. In 2006, the work program included: 40.45 km of line cutting, IP and magnetic geophysical surveys on the Misty, Boundary and Slide (new MINFILE) grids, detailed mapping in the Misty (093N 001), Boundary and Slide areas, property wide geological mapping, an airborne radiometric and magnetic survey totaling 323 line km and the drilling of 10 NQ diamond drill holes totaling 3069.8m on the Misty and Slide targets.
Teck Cominco completed an extensive drilling program (about 5000 metres) concentrated on the Jan-Tam-Misty property in 2007. In 2008, the company completed about 1200 metres of drilling on its 2007 targets Boundary and Slide, and on one new target.