The oldest rocks in the area are Permian limestones of the Asitka Group, which generally occur in thrust contact with Upper Triassic Stuhini (Takla) Group volcanics, and as roof pendants within the Early Jurassic Black Lake Suite. Stuhini Group rocks are dominantly alkaline to subalkaline, submarine mafic volcanics. Unconformably overlying the Stuhini Group are Lower Jurassic Hazelton Group rocks representing a probable island arc sequence of volcanics and associated sediments. The Lower Jurassic Toodoggone Formation represents a distinctive quartz-bearing facies of the Hazelton Group, and comprise dominantly calcalkaline, intermediate to felsic subaerial volcanics. The youngest rocks in the area are Upper Cretaceous-Eocene (?) Sustut Group sediments, which unconformably overlie the Toodoggone volcanics. Granodiorite and quartz monzonite of the Black Lake Suite intrude the Toodoggone and Stuhini rocks. The regional structure is dominated by major dextral strike-slip faults.
The Shasta property is underlain by two distinct lithologies of the Toodoggone volcanics. They are the pyroclastic series (Attycelley Member) and the epivolcaniclastic series (Saunders Member). The pyroclastic series unconformably overlies pyroxene feldspar phyric basalt flows and breccias of the Stuhini Group. In the central part of the property, the pyroclastics consist of dacitic feldspar quartz crystal tuffs, chloritic and heterolithic lapilli tuffs, and an underlying feldspar-quartz-biotite porphyry flow. These units all contain characteristic orange-weathering plagioclase feldspars. The epivolcaniclastic series consists of green to maroon feldspar phyric tuffs, heterolithic agglomerates, lahars and ash tuffs. These strata overlie the pyroclastic series, but are typically seen in fault contact with them.
The deposit occurs in a rotated fault block dominated by north to northwest striking normal and/or dextral faults. These are cut by minor east to northeast-striking crossfaults. Strata underlying the area generally dip gently north to northwest, coinciding with the regional attitude, except in a central fault-bounded panel of pyroclastic series rocks which dips steeply southwest. The north striking Shasta fault bounds one side of this rotated fault block, separating epivolcaniclastic from pyroclastic series rocks. This fault also forms the hangingwall of the Creek zone stockwork.
Mineralization and alteration are essentially restricted to the pyroclastic series and underlying Stuhini Group rocks. The overall lack of alteration and mineralization in the epivolcaniclastics suggest that these rocks were deposited, or displaced by faulting, after the mineralizing event. The absence of alteration at the hangingwall contact with the Creek zone supports this interpretation. However, the recent discovery of small isolated veins and alteration zones in these rocks, some distance into the hangingwall, suggests that the epivolcaniclastic rocks may, after all, have been deposited prior to mineralization.
The Shasta deposit is an epithermal multiphase quartz-carbonate stockwork/breccia vein deposit containing significant silver and gold mineralization. The deposit is spatially related to a dacitic dome of lower Middle Jurassic age. Significant mineralized zones are hosted by pyroclastic series rocks that were deposited on the flank of a coeval dacite dome. The Shasta deposit consists of multiple overlapping quartz-calcite stockwork/breccia systems that display generally similar characteristics. They occur as narrow (less than 1 metre) curviplanar breccias that pinch and swell within wider (greater than 10 metre) sections of variable alteration and veining intensity over strike lengths of up to 500 metres. Quartz and calcite gangue occur individually in single-stage veins, as multistage banded veins and breccias, and also intimately mixed in a single stage. Both gangue minerals display open-space filling textures in banded veins and rare drusy vugs. Calcite is dominantly late, commonly occurring in the centre of earlier quartz veins and as the matrix in quartz vein and silicified wallrock breccias.
Native gold and silver, electrum and acanthite mineralization occurs erratically within quartz and calcite stockworks and breccias. Grades of mineralization appear to be independent of the intensity of alteration or brecciation. However, some of the highest silver values occurs in late-stage calcite breccia. Gold to silver ratios vary unsystematically from 1:10 to 1:100, with a deposit average of about 1:45.
Native gold and silver, electrum and acanthite mineralization is associated with finely disseminated grey sulphides and coarser grained pyrite. The main sulphide phases are pyrite, sphalerite, galena and minor chalcopyrite, in decreasing order of abundance. Two distinct types of pyrite are recognized: disseminated euhedral crystals occurring in altered wallrock; and disseminated subhedral to irregular, fractured grains, with inclusions of galena, occurring in quartz and calcite gangue. The latter type is commonly associated with other base metal sulphides.
The fine grained grey sulphide is dominantly sphalerite, which occurs as irregular worm-like grains interstitial to quartz and calcite, and also as larger grains in contact with pyrite and/or galena. Some pyrite grains appear to be corroded and replaced by sphalerite. Most sphalerite contains abundant fine inclusions of exsolved chalcopyrite.
Galena occurs as subrounded inclusions in pyrite, or fills fractures in pyrite and forms discrete irregular grains, interstitial to other sulphides, quartz and calcite. Chalcopyrite occurs as exsolved inclusions in sphalerite, or interstitially between other sulphides and as free grains.
Scanning electron microscope analyses identified native gold and silver, electrum and acanthite. The gold and silver minerals occur as inclusions in base metal sulphides, as rims around sulphide grains, and minute free grains. Acanthite coexists with native gold, but not with electrum or native silver. Appreciable silver is also contained in galena.
Wallrock alteration is divided into four types: potassic, chloritic, phyllic and propylitic. Only potassic and chloritic alteration are directly associated with mineralization.
Propylitic alteration occurs on a regional scale and is characterized by an assemblage of chlorite + pyrite +/- carbonate, mainly replacing mafic phenocrysts and lapilli fragments in pyroclastic series rocks.
Potassic alteration is associated with early quartz veins, and characterized by pervasive silicification and potassium metasomatism, resulting in distinctive orange-pink bleaching of stockwork zones, up to tens of metres wide. This alteration may also occur as narrow envelopes, less than 1 centimetre across, around quartz veins. Generally, increasing intensity of potassium metasomatism has resulted in the progressive replacement of plagioclase phenocrysts, chloritic lapilli fragments and groundmass, in that order, by potassium feldspar and quartz. Minor sericite and clay minerals occurs locally in the most intensely altered zones, but this may be a later feature.
Chloritic alteration is dominantly, although not exclusively, associated with late-stage calcite veins and is represented by the assemblage chlorite +/- epidote +/- hematite. It occurs disseminated within veins and replacing wallrock fragments. Hematite and epidote also occur independently, in early to late fractures. This alteration has a more restricted distribution than potassic alteration.
Phyllic alteration is relatively uncommon, irregular and restricted. It is the latest event, overprinting both potassic and chloritic alteration, and usually destroying primary textures. It consists of pervasive sericite and finely disseminated pyrite, and does not appear to be spatially related to any particular features of the rock.
The Creek and JM zones host most of the known reserves and outcrop over strike lengths of 350 and 500 metres, respectively. The Creek zone strikes 180 degrees and dips moderately west. The JM zone strikes 150 degrees and dips steeply northeast. These zones appear to merge to the north. The Shasta fault forms the hangingwall of the Creek zone at surface, but appears to diverge from the zone as the fault attitude flattens with depth. The Creek and JM zones are hosted by two similar units of feldspar quartz crystal lapilli tuff (one with heterolithic fragments, the other with dominantly chloritic fragments) which do not appear to exert lithological control on mineralization or alteration. The Creek zone is characterized by a well-defined stockwork system with strong silicification and coeval potassic alteration. Phyllic alteration occurs locally. Late calcite veining with associated chloritic alteration is abundant lower in the zone. Calcite veinlets continue through the footwall of the Creek zone and may persist for several tens of metres into relatively unaltered rock. Silver and gold mineralization occur in both quartz and calcite veins, usually intimately associated with blebs of fine-grained pyrite. In calcite veins, pyrite is commonly associated with chloritic alteration of wallrock fragments. At higher levels in the zone, sulphide and silver-gold mineralization in quartz veins is commonly fine grained, and calcite veins are typically barren. At lower elevations, however, mineralization in calcite veins is usually coarse grained and quartz veins are sparsely mineralized.
Quartz and calcite breccias occur irregularly throughout the stockwork zone. Typically, wide (greater than 10 centimetre) single-stage veins of either gangue mineral are barren or poorly mineralized, whereas narrower veins, multistage veins, and particularly mixed quartz-calcite stage veins tend to carry abundant mineralization. Sulphide and silver-gold mineralization tends to precipitate at the margins of veins and at contacts between different stages of gangue.
The JM zone is generally similar to the Creek zone, but lacks the well-defined structural control of the hangingwall fault of the Creek zone. Potassic alteration and quartz stockworks appear more pervasive and somewhat stronger, while calcite veins and chloritic alteration are more restricted. Hematite and epidote alteration is locally abundant in the wallrock. Early, narrow (less than 2 centimetre) quartz veins are commonly grey to green and fine grained. Late calcite breccias are usually wider (10-30 centimetres), and contain a coarse white calcite matrix that is usually barren. Gold and silver mineralization occurs in both quartz and calcite veins, but more commonly in narrow (less than 1 centimetre) veinlets toward the footwall of the zone. Two isolated occurrences of silver-gold mineralization in intensely silicified and potassic altered wallrock were noted in drill core, suggesting that early stages of quartz may be mineralized.
There are five stages of quartz and calcite vein filling in the Creek and JM zones: Quartz I, II and III, and Calcite I and II. Quartz I comprises silicification and associated potassic alteration, and is widespread but only rarely mineralized. Quartz II consists of fine grained, grey to clear quartz in narrow veins that are frequently well mineralized. Quartz III is fine grained, dark grey to green, commonly forms wide breccias, and is generally barren. Calcite I is white to green, associated with chloritic alteration, is commonly well mineralized and frequently occurs with Quartz II as a single intimately mixed stage or as breccia matrix. Calcite II is white or cream coloured, very coarse grained and generally forms barren late-stage veins. The bulk of silver-gold and sulphide mineralization is contained in Quartz II and Calcite I stages (Fieldwork 1989).
The O zone, situated 500 metres southeast of the JM zone, strikes 130 degrees, dips steeply northeast and is hosted by feldspar quartz crystal lapilli tuffs and overlying polymictic agglomerate. Alteration and mineralization in the O zone is markedly different from that of the Creek and JM zones. Early alteration is characterized by strong pervasive epidote, chlorite and hematite that is overprinted by moderate potassic alteration and weak silicification. Intense stockworks and breccias form well-defined zones with sharp boundaries, but are poorly mineralized. Veins are quartz dominant, and although calcite is present, it is not intimately mixed with quartz as in the Creek and JM zones. Late fractures with narrow (less than 1 centimetre) potassium feldspar and quartz envelopes are commonly filled by calcite with abundant epidote and pyrite. Analytical results from diamond drilling in 1987 yielded assays of 25.36 grams per tonne gold across 0.97 metre (Northern Miner - November 16, 1987).
The outlying East zone, 750 metres northeast of the JM zone, outcrops in the feldspar-biotite-quartz porphyry unit. The zone strikes approximately northwest. Pyrite is abundant in quartz veins and is locally semimassive. Chalcopyrite is common and occurs with galena along hairline fractures in moderately potassically altered wallrock. Silver-gold mineralization occurs in both quartz and calcite veins, but is concentrated in pyrite-rich quartz veins. Late potassic alteration is superimposed on strongly epidote altered wallrock. A distinctive alteration type confined to the East zone is the conversion of plagioclase to dark green, translucent sericite (?) accompanied by pervasive phyllic alteration.
The Rainier zone, 300 metres south of the Creek zone, is hosted by feldspar quartz crystal lapilli tuff and strikes roughly north with a subvertical dip. The zone has been subjected to extensive faulting and its morphology is unclear. Analytical results from diamond drilling in 1987 yielded assays of 8.77 grams per tonne gold and 90.84 grams per tonne silver across 2.4 metres (Vancouver Stockwatch - November 24, 1987).
The Jock zone, outcropping immediately northeast of the JM zone, is also poorly defined due to complex faulting. Mineralization and alteration styles of the Rainier and Jock zones are similar to the Creek and JM zones respectively. Analytical results from diamond drilling in 1987 at the Jock zone yielded assays of 1.67 grams per tonne gold and 114.49 grams per tonne silver across 8.1 metres (Northern Miner - November 16, 1987).
Eleven mineralized zones are recognized on the property. Recent exploration has shown that the Rainier, Cayley, Baker, Upper Rainier, JM and Creek zones are all segments of a continuous vein system.
An open pit and underground operation at the Shasta property has processed 40,819 tonnes of ore since mill start-up in October 1989 (George Cross News Letter No. 140 (July 20), 1990). The ore is mined from the JM zone which has been developed over a strike length of 228 metres with widths up to 12 metres. Approximately 137 metres of the strike length carries ore grade mineralization (George Cross News Letter No. 208 (October 26), 1990). The ore is trucked about 11 kilometres to the Baker mine mill (094E 026) for processing. The mill was purchased by Sable Resources Ltd. and has been extensively rehabilitated and expanded.
A 1989 drill program established in situ geological reserves of 1,259,961 tonnes at 5.07 grams per tonne gold equivalent based on 2 grams per tonne gold equivalent cut-off grade for three main zones (George Cross News Letter No. 140 (July 20), 1990).
A new ore shoot opened underground on the JM zone has indicated reserves of 57,147 tonnes grading 8.57 grams per tonne gold and 514.2 grams per tonne silver from the 1250-metre elevation to surface, a distance of 48 metres. The zone is open below the 1250-metre elevation (George Cross News Letter No. 228 (November 26), 1990).
Mining from 1989 to August 1991 produced 122,533 tonnes of ore yielding 32,932 kilograms of silver and 601 kilograms of gold. Some of the 1991 ore (about 10,000 tonnes) was from the Multinational B zone of the Baker Mine (094E 026).
In 1998, Sable Resources drilled 9 holes and outlined about 8000 tonnes grading 12 grams per tonne gold equivalent in an extension to the JM zone (Information Circular 1999-1, page 10). They planned to mine up to 10,000 tonnes by open-pit methods, however mining and milling was deferred until 1999.
Sable mined 8580 tonnes of gold-silver ore in 2000. Head grades averaged 10.29 grams per tonne gold equivalent (Information Circular 2001-1, p. 5). Trenching and induced polarization programs were completed on the Vein A and B zones.
The Shas 1-176 claims were staked in July 1972 for Shasta Mines & Oil Ltd. Exploration work in 1973-74 included geological mapping, a magnetometer survey over 31.5 line-miles and a geochemical soil survey of about 2,100 samples. The company name was changed in February 1975 to International Shasta Resources Ltd. By that date the property had been reduced to 6 claims, Shas 31, 33, 35-38. Two adjacent claims, the Sha 1 (6 units) and Sha 2 (2 units) were acquired in July 1975. Work in 1975 and 1977 included further geological and geochemical surveys, trenching and sampling.
Asarco Exploration Company of Canada, Limited held an option for a brief period in 1978 and carried out geological mapping and trenching.
Newmont Exploration of Canada Limited in 1983 acquired from International Shasta an option to earn a 70% interest in the property. Work in addition to geophysical and geochemical surveys and trenching included 674 metres of diamond drilling in 9 holes on the Main zone and the newly discovered Creek zone in 1983 and 2,003 metres of drilling on the Creek zone in 1984.
Newmont vended its interest in the property to Arctic Red Resources Corp in silver and argentite have been reported. Chalcopyrite and bornite occur 1985 but they forfeited it in 1986.
In 1987, Esso Minerals Canada Ltd. optioned the property in 1987 and carried out two seasons of extensive exploration with the main result of this work being the discovery of the JM and O Zones. In 1987, Esso Minerals Canada conducted geological mapping, soil geochemical and geophysical surveys, 2400 metres of trenching and diamond drilling of 2382 metres. In 1989, Esso Minerals diamond drilled 3657 metres.
Homestake Mineral Development Company acquired Esso's interest and in 1989 diamond drilled 64 holes for 5985 metres. Open pit mining of high grade ore was started in the Creek and JM zones. In 1990, Homestake conducted underground mining on the JM zone which was developed over a length of 229 metres with widths up to 12 metres. The ore was processed at Sable Resources Ltd. mill.
In addition to the exploration program operated by Homestake, International Shasta and Sable Resources Ltd. mined and processed ore from the Creek, JM and D zones. The initial 1989 open-pit operation shifted to an underground operation in 1990.
In 1994, Sable acquired 100% ownership of the Shasta mineral claims and mining lease. Two small drill programs were carried out by Sable in 1994 and 1995 with no furtherer ore grade zones delineated. Sable Resources Ltd. drilling on the Shasta property returned disappointing results on the main target, the JM zone, but the final three holes on the Creek zone returned encouraging gold-silver assays.
In 2000, Sable Resources Ltd. mined and processed 8581 tonnes of gold-silver ore from the Shasta mine. At the Baker mine itself, five closely spaced lines of Induced Polarization survey, completed on each of the past-producing A and B veins, identified possible extensions of the two mineralized structures. The survey also identified two new structures, northwest of and parallel to the B vein. An eight-hole, 360-metre diamond drilling program on the Ridge zone targeted the Beck vein. However, there were no high grade intersections.
In 2001, Sable Resources Ltd. mined and milled approximately 1300 tonnes of mineralized material from two zones at its Baker gold-silver mine located about 40 kilometres north of the Kemess mine in the Toodoggone camp. The ore was mined from surface on the A vein and from an open cut on the B. Several lines of IP were run over projected extensions of the A and B vein systems and identified several resistivity anomalies. Six diamond drill holes tested the most promising resistivity anomaly, the TD zone, and intersected a massive quartz-calcite-pyrite vein up to 12 metres wide. While assay results were disappointing, only a portion of the vein was evaluated and drilling will continue in vein.
In 2002, Further north, owner/operator Sable Resources Ltd. explored its Chappelle property, which surrounds the Baker (094E 026) mine, for both high-grade gold and bulk tonnage gold+/-copper mineralization. Nine drill holes and two trenches evaluated a 300 metre by 1000 metre gold soil geochemical anomaly in the Black Gossan area, where oxidized pyritic andesite of the Triassic Takla Group forms a prominent gossan. Five holes targeted I.P. resistivity lows east and west of the B zone, a high-grade gold vein that has been mined on a seasonal basis. Results from the work have not been disclosed.
In 2003, approximately 1400 tonnes of Shasta vein material was mined and processed by Sable at its nearby Baker mill. A small diamond program in 2003 located some potentially ore grade material in the Creek Zone.
In 2004, exploration was carried out by Sable Resources on five areas of the Chappelle and Shasta claims. A total of 2622.39 metres of NQ Diamond Drilling was completed in 35 holes. Also a small IP survey was completed. The zones drilled included the Creek, JM, Black Gossan, North Quartz and Upper Ridge zones. In the lower Creek Zone a resource was identified that was amenable to open pit mining. In the upper Creek Zone a potential minable resource was identified although more drilling was needed. In the JM Zone the main trend was not extended but a second potential zone was located. In the Black Gossan Zone it was demonstrated that this is indeed a copper-gold system that requires deeper drilling and an I.P. survey. In the North Quartz Zone it been demonstrated that this zone does not carry gold and silver. In the Upper Ridge Zone, where high-grade float has been located, the I.P. survey did locate some targets.
In 2005, Sable Resources Ltd mined approximately 5000 tonnes of ore from an open cut at its Shasta epithermal gold-silver mine. Sable drilled 11 holes on its Shasta epithermal vein deposit (MINFILE 094E 050), prior to its limited mining campaign, in order to confirm additional ore grade material for future mining. Sable Resources also drilled two holes into the Black Gossan zone, a bulk tonnage copper-gold target on its Chappelle property (MINFILE 094E 026) that encompasses the Baker mine. The zone is characterized by a large area of oxidized pyritic Takla Group andesite that coincides with a copper-gold geochemical anomaly. It may be indicative of a buried porphyry system. Reported metal production was 15.2 kilograms (488 ounces) of gold and 320.8 kilograms (10 314 ounces) of silver (Exploration and Mining in BC 2005, pages 44, 47).
In 2006, Sable Resources Ltd completed a 20-hole diamond drilling program on its Shasta epithermal gold-silver deposit east of Black Lake. The company plans to commence development early in 2007 and will utilize its nearby 100 tonne per day mill and tailings facilities on the Baker mine site. Sable also drilled a deep core hole to test its Black Gossan porphyry copper-gold prospect, on the Chappelle claims (MINFILE 094E 026), and drilled seven core holes to investigate epithermal gold-silver mineralization on the Ridge zone near the Baker mine site.
In 2007, Sable Resources Ltd continued re-development of its Shasta underground gold, tapping a series of structurally controlled quartz-carbonate breccia veins. About 500 tonnes of ore were stockpiled and the goal is to resume shipments in 2008. Current underground development is in the Creek zone with 500 metres of underground development planned, while surface drilling targeted the East, Jock and O zones.
In 2008, milling of silver-gold ore from Sable Resources' underground Shasta mine began as a seasonal operation. 450 metres of underground development was reported.
In 2010 Sable Resources Ltd reported that it was in the process of mining the Shasta deposit and was shipping the run-of-mine ore to the nearby Baker mill located approximately 9 kilometres to the west. Upgrade work continued throughout the year toward maintaining a mining/milling rate of 180 tonnes per day. Production was reported for two months only, totalling 1450 gold equivalent ounces (Exploration and Mining in BC 2010, page 4).
A 2010 drill program off-lease program was conducted by Sable Resources Ltd. The property was owned by Sable and Multinational Mining. The off-lease drilling was done in conjunction with a program of diamond drilling on the Shasta mining lease. A total of 324 metres of NQ diamond drilling was completed in 2 holes for the off-lease program. One drillhole was drilled to extend the strike-length of the Shasta Fault to the north, across Jock creek and the interpreted J1 fault structure that appears to offset the Shasta Fault. The other drillhole tested for the down-dip extension of a high grade surface showing located near the south-east corner of Mining Lease #243454.
In 2011, Sable Resources Ltd's Shasta mine continued to be an intermittent gold and silver producer.
In 2012, Sable Resources Ltd continued seasonal operations at the Shasta underground mine. Production was between 10 000 and 20 000 tonnes of milled ore, enough to maintain the operation. The company estimates reserves of 5000 tonnes, with the inclusive resource at 25 000 tonnes, enough to support two more years of mining; an additional 130 000 tonnes of historical resource is held nearby at the Baker and Mets properties (Exploration and Mining in BC 2012, page 5).
In 2013, Sable Resources Ltd placed their seasonal underground Shasta Mine on care and maintenance.