The T-Bill occurrence is located approximately 5 kilometres west of Park Creek and 14.5 kilometres north-northwest of Spruce Hill. Dease Lake is 135 kilometres to the northwest.
Regionally, the area lies at the eastern edge of the Intermontane Belt near the Kutcho fault and marks the boundary with rocks of the Omineca Belt. The oldest rocks in the area are a sequence of lower greenschist–grade metamorphosed sedimentary and volcanic rocks correlated based on lithological similarities to rocks of the Asitka Group found elsewhere (Geological Survey of Canada Open File 483). Fossil evidence from later regional mapping dates at least part of the sequence as Mississippian (Geological Survey of Canada Paper 80-1B, pages 207-211). A tentative Devonian to Permian age is assigned to these rocks. Five stratigraphic units have been recognized and are, from oldest to youngest: feldspathic chlorite schist; phyllite, sericite and calcareous sericite schist; massive rhyolite, chert and sericite schist; carbonate; and upper feldspathic chlorite schist. The rocks are complexly folded and have undergone at least two phases of deformation. They are predominantly calc-alkaline with minor alkaline members. Two Early Jurassic plutonic bodies intrude the formation: One is quartz monzonite in composition and the other is diorite. The sequence is similar in many respects to rocks of the Kutcho Formation in the southeastern corner of the Cry Lake map area.
Locally, a 1200-by 2300-metre area of metavolcanic rocks (andesite, rhyolite and dacite tuff and tuffite) altered to carbonate-muscovite-quartz schist hosts gold-bearing quartz-arsenopyrite veins. Alteration is confined to the core of a northeast-trending structural dome and is controlled by foliation and steep cross-cutting structures. Individual veins cut across foliation and are up to 2.5 metres wide but generally less than 30 centimetres wide, although vein swarms are common.
Lithologies underlying the occurrence have been subdivided into nine units based on primary mineralogy and metamorphic grade evident in drill core. The units are graphite schist, marble, chlorite feldspar schist, chlorite schist, chlorite schist with numerous quartz segregations, spotted chlorite schist, calcareous chlorite schist, quartz-muscovite-carbonate schist and basic dikes. All these rocks are highly deformed and show a strong schistose foliation that obliterates most of the primary volcanic and sedimentary textures.
Five types of alteration have been identified at the occurrence. Oxidation is intense in fault zones and adjacent open fractures. Chlorite alteration is pervasive in dacitic and andesitic protoliths. Sericite alteration is intense in rhyolitic protoliths, occuring as almost entire replacement or as sericitized bands preferentially altering certain compositional layering. Quartz veins and bands often exhibit sericite alteration in country rocks along their margins. Multiple episodes of pervasive carbonate alteration are present in all units. At least three stages of crystalline quartz-carbonate veinlets are present, two of which are typically mineralized with arsenopyrite and pyrite. Silicification is locally present as quartz flooding in tuffaceous protoliths. The alteration in the Bill group has been dated to 136 ± 5 million years (Early Cretaceous) using K-Ar methods on muscovite from 110 metres deep in drill hole 84-1; however, an Ar-Ar date from sericite in drill hole WG03-10 at a depth of approximately 189 metres yielded 194.6 ± 3.5 million years and is believed to be a more accurate age of the alteration (Assessment Report 35255).
A study of mineralized drillcore with greater than 1 gram per tonne gold revealed several consistent parameters of mineralization: Gold mineralization always occurs within quartz and arsenopyrite±carbonate veins and usually occurs at both the lower and upper contact of a quartz muscovite schist, often extending into the underlying and overlying greenstones. Quartz-arsenopyrite±carbonate veins gave a consistent strike of 090 to 110 degrees with a dip varying from 70 degrees south to 70 degrees north. Visible gold was found in most samples with greater than 10 grams per tonne gold; the gold lying along the outer part of the quartz vein just inside the outer arsenopyrite selvage . This unit has all the appearances of the quartz-sericite-pyrite zone within a porphyry copper deposit. The alteration assemblage represents a mesothermal package related to gold mineralization (Assessment Report 12559). Minor chalcopyrite, sphalerite, specular hematite, and hematite were observed in drillcore. The mineralization is open at depth.
In 1981, rock samples were reported to have yielded up to 15.80 grams per tonne gold, whereas a grab sample from the west end of the no. 5 trench yielded 0.32 gram per tonne gold and a 1.0 metre sample from the east end of the no. 6 trench yielded 0.10 gram per tonne gold (Assessment Report 10245).
In 1982, chip sampling from a new series of trenches yielded 0.33 gram per tonne gold over 12.0 metres, including 0.72 gram per tonne gold over 2.0 metres in trench no. 1; 0.52 gram per tonne gold over 6.0 metres, including 1.4 grams per tonne gold over 2.0 metres in trench no. 6, and 1.4 grams per tonne gold over 2.0 metres in trench no. 8 (Assessment Report 11075).
In 1983, diamond drilling intersected zones of quartz-arsenopyrite mineralization with intervals assaying 0.58 gram per tonne gold over 116.0 metres, including 4.25 and 12.51 grams per tonne gold over two 2.0-metre sections, in hole B83-1 ; 1.17 grams per tonne gold over 148.7 metres, including 34.97, 11.9 and 5.14 grams per tonne gold over three 2.0-metre sections, in hole B83-2; 0.32 gram per tonne gold over 187.2 metres in hole B83-3 and 0.73 gram per tonne gold over 164.0 metres, including 13.89 and 12.00 grams per tonne gold over two 2.0-metre sections and 10.98 grams per tonne gold over 4.0 metres in hole B83-6 (Assessment Report 11493 and 26661).
In 1984, diamond drilling yielded intercepts of 0.62 gram per tonne gold over 166.4 metres, including 16.5 and 15.6 grams per tonne gold over two 2.0-metre sections, in hole B84-2; 0.56 gram per tonne gold over 84.5 metres in hole 84-3; 10.6 grams per tonne gold over 1.5 metres in hole B84-4; 0.61 gram per tonne gold over 87.0 metres, including 24.7 grams per tonne gold over 1.5 metres, in hole B84-5; 1.02 grams per tonne gold over 63.4 metres, including 21.1, 15.5 and 26.5 grams per tonne gold over 1.3, 1.5 and 1.8 metres, respectively, in hole B84-7 and 1.07 grams per tonne gold over 75.3 metres, including 24.8 grams per tonne gold over 2.0 metres, in hole B84-8 (Assessment Report 12559 and 26661).
In 2001, float samples yielded up to 6.85 grams per tonne gold (Assessment Report 26661).
In 2003, drillhole 03-10 cut three intervals from 0.6 to 1.4 metres wide grading 12 to 20 grams per tonne gold within a 195-metre zone of sporadic, metre-wide intervals containing more than 0.5 gram per tonne gold (Stikine gold, News Release Sept 19, 2003). The other holes intersected fewer and weaker gold-bearing intervals and were reported to be located north and northeast of the previously drilled area.
In 2007, two grab samples (90016 and 90034) yielded 3.07 and 1.75 grams per tonne gold, respectively, and a float sample (90193) assayed 5.96 grams per tonne gold (Assessment Report 29605).
In 2014, a rock sample of pyritic, quartz-veined muscovite schist yielded 9.31 grams per tonne gold (Assessment Report 35255).
Work History
The earliest record of work in the area dates to 1976, when Cominco Ltd. undertook stream sediment sampling as part of a base-metals exploration program. A number of the samples collected were subsequently analyzed for gold and silver, which lead to the staking of the Bill property in early 1980, when a further program of soil sampling and geological mapping was completed, revealing a widespread gold-arsenic soil geochemical anomaly. The following year, Cominco Ltd. carried out a program of rock and soil sampling, geological mapping and six trenches on the area of the previously identified soil anomaly, defining an open-ended 1400- by 1800-metre gold-arsenic soil geochemical anomaly.
In 1982, Du Pont optioned the Bill property from Cominco and verified Cominco’s soil geochemical anomaly by detailing the core of it with soil samples spaced at 20 by 50 metres. Eleven trenches were blasted and rock sampled in an attempt to expose fresh bedrock. Magnetic, VLF-EM and induced polarization surveys were carried out over the same east-west grid lines. These showed north-northwest–trending linear magnetic lows and VLF conductors; a chargeability high from the IP survey was unrelated to soil geochemical anomalies and ascribed to graphitic schist.
In 1983, Du Pont extended the magnetics/VLF survey and drilled six holes, totalling 1174.7 metres, on the T-Bill soil anomaly, four of them directed to the east across the north-trending VLF conductors. With this program, Du Pont’s option was vested and they formed a 50:50 joint venture on the Bill property with Cominco. In 1984, Du Pont and Cominco completed a program of rock and soil sampling, nine diamond holes, totalling 1848.4 metres, and a ground electromagnetic survey on the T-Bill occurrence.
In 2001, Rimfire Minerals Corporation acquired the Bill property and carried out a program of prospecting; rock, silt and soil sampling; core resampling and geological mapping on the area as the BT 1-3 claims. The T-Bill soil anomaly was extended by 200 metres north-south and 500 metres east-west.
In 2002, Stikine Gold Corporation optioned the Williams property from Rimfire and carried out a 3-D induced polarization survey over the T-Bill prospect identifying broad zones of higher chargeability coinciding with graphitic phyllites and a resistivity high with two areas of high chargeability immediately north of the area previously drilled.
In 2003, Stikine Gold completed 11 diamond drill holes, totalling 2855 metres. Ten of the holes tested a gold soil anomaly and coincident low resistivity zone outlined by an IP survey. The anomaly measures 800 by 450 metres in size. The final hole explored a separate soil anomaly to the north. In 2006, Arcus Development Group Inc optioned the Williams property from Rimfire.
In 2007, Equity Engineering Ltd was contracted by Rimfire to carry out a program of geological mapping, prospecting and rock, soil and silt sampling on the Williams property. Work on the T-Bill focussed on the style of the veining and followed up on earlier soil geochemistry of the area. Quartz veins in trenches from previous programs were exposed and attitudes of the veins were measured to assist in interpretation of the geometry of the veins to assist in future exploration programs. The T-Bill area vein mineralization was determined to be dominantly west-northwest–trending with a weaker vein set trending to the north-northeast.
In 2014, Kiska Metals Corp. completed a program of prospecting, geological mapping and rock and soil sampling on the area.
