Virtual Museum ID: 19-BCGS-GB2
Magnesite is a magnesium carbonate mineral. It forms when magnesium rich rocks are altered by metamorphism or chemical weathering. A few ways magnesite forms are through the precipitation as a secondary mineral in veins, formation in the regolith above weathering ultramafic rocks, and the alteration of limestone, marble or other carbonate rick rocks by regional, contact or hydrothermal metamorphism. It is used to produce magnesium oxide which is important in the steel industry as a refractory and a raw material for the chemical industry.
The information listed below relates to the current holding location or collection that the sample is from, and whether the item is viewable at that location or is part of a private collection. Coordinates are given as guides, and we remind you that collecting specimens from these locations is not allowed. Caution is advised visiting such sites and Below BC assumes no responsibility for any injuries or trespassing charges that may occur as a result of the viewer entering these sites.
Original Collection:British Columbia Geological Survey (BCGS)
Virtual Museum ID:19-BCGS-GB2
Date Added to VM:2019-05-07
Sample Origin:Tatsamenie Lake area
Specific Site:Golden Bear deposit
Datum:08 (NAD 83)
Primary Mineral Formula:MgCO3
Advanced Geological Information
The following section provides geological data relating to the specimen or the site it was collected from, when available. Information has been obtained from various sources including private and government datasets but may not be up to date. Any geological time periods or ages listed often relate to the primary geology of the area, and may not be the actual date of an event such as mineral formation.
Minfile ID:104K 079
In the Tatsamenie Lake area, intensely folded and regionally metamorphosed Permian, Triassic and older strata are separated from less folded and less metamorphosed Mesozoic sedimentary and volcanic rocks by a pre-Upper Triassic unconformity. Foliated hornblende diorite of Juro-Triassic age intrude the pre-Upper Triassic rocks. These are commonly altered to chlorite, hematite and epidote. The Mesozoic strata are overlain unconformably by flat-lying Upper Tertiary and Pleistocene plateau basalts of the Level Mountain Group.
The Permian strata consists of a 760 metre succession of limestone and dolomitic limestone, with local chert, shale and sandstone. The pre-Upper Triassic rocks consist of fine-grained crystal tuff to lapilli tuff with intercalated phyllite and greenstone, and minor chert, jasper, greywacke and limestone. These are Stikine assemblage.
A major north to northwest trending fault, known as the Ophir Break Zone, extends through the area for over 10 kilometres and is defined by areas of intense fracturing with abundant slickensiding, areas of carbonaceous and siliceous black siltstone and gouge, and linear quartz-iron carbonate-pyrite-fuchsite(?) (listwanites) and quartz-dolomite alteration zones. X-ray work by Schroeter on fuchsite-looking material did not confirm the existence of fuchsite (Personal Communication, Schroeter, T. 1988). The listwanites occur in the tuffs. The Ophir Break Zone is bounded on the west by the West Wall fault and on the east by the Ultramafic fault.
Mineralization consists of pyrite, trace arsenopyrite and scorodite, native gold, pyrrhotite, chalcopyrite in amygdules in lapilli and altered fuchsite-bearing(?) tuff, stibnite, tetrahedrite and hessite. Pyrite occurs as late-stage veinlets and as earlier breccia matrix filling, fragments within breccias, wispy rims on silicified limestone fragments in breccia, and local laminations in fine bleached tuff. Locally, gypsum is associated with mineralization.
One deposit, the Bear Main, and two showings, the Fleece Bowl (104K 087) and the Totem Silica (104K 088) zones, occur along the major north trending structure. The deposits are about 1.5 kilometres apart and exploration and development is progressing from the south to north deposit.
The Bear Main zone is a pod composed of silicified dolomitized limestone and brecciated and altered tuffs. The zone has been traced by drilling along a length of 1 kilometre, across a width of 10 metres and to a depth of at least 200 metres. The dolomite locally displays a quartz stockwork with resistant veinlets of quartz.
Heterolithic and monolithic breccias occur between the silicified dolomite and altered tuff. The hanging wall Bear fault cuts the tuffaceous rocks and is marked by a zone of black gouge. A thick section of ash, lapilli and crystal tuffs and mafic flows occur above the hanging wall. The lapilli tuff contains a chalcopyrite marker zone. A one metre wide dyke of black basalt (Tertiary) intrudes the mineralized zone.
Alteration minerals in the zone include quartz, dolomite and pyrite within the limestones and dolomite, kaolinite, sericite, illite, chlorite and pyrite in the metavolcanics. Age dating of sericite from the alteration zone, which gave an apparent age of 204 Ma plus or minus 7 Ma, suggests the main period of mineralization occurred in Early Jurassic (Fieldwork 1986).
Reserves calculated in 1987 for the Bear Main zone were as follows:
Mineable, diluted open pit and underground ore reserves were as follows:
Reference: North American Metals Corp. Annual Report (1987)
The mineralization is primarily epigenetic, although supergene enrichment occurs locally. The deposits are characteristic of a low to medium temperature, low salinity, mesothermal system. Likely, mineralized solutions ascended the fault zone to an area of extensive tectonic brecciation and alteration. Intrusive activity, alteration and mineralization along the major regional fault is postulated to have occurred over a 50 million year period, from 156 to 206 million years (Jurassic age) (Schroeter, 1987).
Chevron became interested in the Tulsequah area as a result of a company study that examined potential gold exploration areas in British Columbia. Regional geological reconnaissance work by L.A. Dick in 1980 gave support for a broader exploration program, and in early 1981 the SAM 1 and SAM 2 claims were staked.
In the summer of 1981, geochemical reconnaissance was carried out south of Tatsamenie Lake. One soil sample taken just northeast of Muddy Lake yielded a 700 ppb Au value. This resulted in the staking of the BEAR, TOTEM and POLE claims. Later that summer, a soil samples were collected, one of which yielded returned a 9200 ppb gold directly below the Bear Main Zone. Grab samples taken that summer on the Bear Main Zone yielded assay values as high as 24.0 g Au/t (Assessment Report 15751).
A program of trenching, prospecting and mapping was completed by Chevron in 1982. This program outlined the Bear Main Zone and led to the discovery of surface mineralization at Fleece Bowl on the TOTEM claim. In 1983 diamond drill equipment was brought into the property by D6 and D8 tractors along the winter trail from Telegraph Creek, Drilling on the Bear Main Zone commenced in April of that year and a total of 27 holes were completed on the BEAR claim. In addition, five holes were drilled on the TOTEM claim and a number of interesting intersections were obtained in Fleece Bowl. Trenching and drill road building with heavy tracked equipment were initiated in 1983 and base camp was established.
The Bear-Totem project expanded in 1984. Four diamond drills completed a total of 58 holes and portions of the BEAR and TOTEM claims were mapped. The main switchback road was also constructed in the summer of 1984.
The program was scaled down in 1985 and 14 holes were drilled on the BEAR claim. A total of 17 holes were drilled on the TOTEM claim north of Fleece Bowl; however, no new mineralization was discovered. Surface trenching and mapping programs were also completed.
In 1986, operator North American Metals completed an exploration program whose purpose was to upgrade Chevron's drill-indicated reserve base on the Bear Deposit. These drill indicated reserves total 661,000 tonnes at average grade of 15.4 g Au/t (Assessment Report 15751). The North American Metals work program consisted of 914 metres of underground excavation and 1860 metres of surface and underground diamond drilling. It defined a significant tonnage of gold mineralization that could be extracted by both open pit and underground mining methods. A mine feasibility study was in progress in 1986.
North American Metals Corp. and Chevron Canada Resources Ltd. continued with underground development work on the Golden Bear deposit discovered in 1981. The companies submitted their Stage I report in 1987 and, in October, received approval-in-principle for the combination open-pit and underground mine from the Environment and Land Use Committee (ELUC) of the provincial cabinet. Current reserves for the Bear zone are 625,400 tonnes grading 18.63 grams per tonne gold (Exploration in BC 1987). An access road is being built to enable the mine to go into production at 350 tonnes per day
Development work continued on the Golden Bear west of Dease lake in 1988. The property is now owned by the Golden Bear Operating Company, a subsidiary of Homestake Mineral Development Company and Chevron Canada Resources Ltd. A gravel road was constructed to provide access to the minesite. On-site construction included building a permanent camp, upgrading both the airstrip and roads on the property and starting foundations for the plant. Current plans are for the mine to be in production in late 1989 at a milling rate of 350 tonnes per day.
The Golden Bear deposit of Golden Bear Operating Company and Homestake Mining (B.C.) Ltd., located 11.0 west of Dease Lake, is British Columbia’s newest gold mine with reserves in 1989 of 1.63 million tonnes grading grams per tonne gold. Mineralization at Golden Bear occurs in silicified and breccia zones along a major fault which juxtaposes Permian limestone and Upper Triassic andesites. Open-pit mining started in the summer of 1989 with some underground mining in the fall and enough ore was stockpiled to run the plant through the winter. Utilizing the latest technology, the plant uses dry grinding, fluidized-bed roasting and carbon-in-pulp leaching to recover the gold. At the end of the year the 360 tonne per day facility was in the.start-up phase.
The Golden Bear mine milled 1620 tonnes of ore in 1989, but did not ship bullion until February 1990; the production statistics were recorded in 1990. Production for the Golden Bear is reported for the years 1990 to 1994, inclusive. From a total of 612,866 tonnes mined, 1,653,379 grams of silver and 6,763,036 grams of gold were produced.
The mine was purchased by Wheaton River Minerals on July 2, 1993 when the mine was in a shutdown mode with just 6 months reserves left to be mined and processed. Following the purchase, mine exploration and development extended the reserves of the Bear Main zone to just over 90,710 tonnes grading 16 to 22 grams per tonne gold. Mining in the Bear zone ceased in 1994.
In 1993, the Grizzly zone was discovered with a drillhole which analysed 14.4 grams per tonne gold over 15.4 metres of core length (7 to 8.2 metres true width). A decline was driven during the fall of 1994 and the spring of 1995 on the Grizzly zone, approximately 400 metres below the mined out Bear Main zone. The Grizzly zone is on the footwall side of a 70 metre wide, fault-bounded limestone lens. It consists of a series of anastomosing faults internal to the carbonate lens.
Underground drilling was completed August 8, 1995 and the decline allowed to flood. Drill core clearly shows that best gold grades are correlated with heavily disseminated fine pyrite in a well-healed (silicified) fault breccia.
The near-surface Kodiak A zone, 3 kilometres north of the mill, contains an estimated reserve of 824,000 tonnes grading 3.3 grams per tonne gold; the Kodiak B zone contains probable geological reserves of 278,112 tonnes grading 8.6 grams per tonne gold (Information Circular 1997-1, page 20). The Kodiak C zone was reported to contain 275,758 tonnes grading 7.8 grams per tonne gold (George Cross New Letter No.114 (June 15), 1994). In 1996, a 61-hole reverse circulation drilling program further tested the East Low Grade Stockpile zone. This zone contains a previously calculated resource estimated at 2,470,000 tonnes grading 1.3 grams per tonne gold (Information Circular 1997-1, page 20).
In the fall of 1994, a new zone (Ursa) of both higher grade refractory and lower grade, potentially leachable oxide ore, was discovered north of the Kodiak A zone. Gold mineralization at Ursa occurs within 100 metres of surface on the west wall of the steeply dipping Ursa fault, in a thinly bedded graphitic limestone. Below 100 metres, the fault breccia is healed by calcite which did not allow entry of gold-bearing fluid. Massive dolomite/chert in the footwall of the fault is barren because it did not brecciate during faulting to provide open space. Gold is associated with hematite and limonite in the Ursa fault zone and is highly leachable. North American Metals geologists intrepret the hematite to be primary (hypogene) and an important exploration guide because brecciation and hematite are the only visual guides to gold mineralization.
The Golden Bear mine closed in September 1994 due to exhaustion of refractory ore reserves in the Bear Main zone. Two benches were mined on the Kodiak A zone in late 1994 before work was curtailed due to bad weather. The ore is stockpiled pending formulation of an Ursa mine plan and completion of the heap leach pad (P. Wojdak, personal communication, 1995).
In 1995, with Explore B.C. Program support, North American Metals Corporation completed an extensive program of underground and surface diamond drilling on the Grizzly and Ursa zones. A total of 5606.7 metres in 33 underground holes was drilled on the Grizzly zone, which identified two significant new ore shoots. Preliminary calculations indicate the Grizzly zone to contain 152,945 tonnes grading 23.39 grams per tonne gold at a 12 grams per tonne gold cutoff. The Ursa zone received 4560.2 metres of surface diamond drilling in 30 holes which confirmed the existence, size and extent of this recently discovered zone (Explore B.C. Program 95/96 - M118,M119).
An expanded feasability study, completed in late 1996, involving mining and milling of material from the Kodiak A and Ursa zones, estimated the recovery of 6656 kilograms of gold from 1,528,000 tonnes grading 5.1 grams per tonne gold over a six year period. Mineable heap leachable reserves in the Ursa zone are estimated at 511,000 tonnes grading 7.0 grams per tonne gold (Information Circular 1997-1, page 20).
Construction of the Kodiak heap leach pad was commissioned by Wheaton River Minerals Limited and North American Minerals Corporation in late July 1997 and ore was loaded onto the pad. Leaching began on August 6th and the first gold bars were poured on August 13th. The official opening of the heap leach mine was on September 17, 1997.
During 1997, mining and heap leaching were completed on the Kodiak A deposit (reserves estimated at 759,000 tonnes grading 3.3 grams per tonne gold), one of three deposits to be mined. A total of 360,000 tonnes of ore was crushed and put on the 528,000-tonne capacity Fleece Bowl pad for processing. The high leaching rate predicted in the feasibility study was quickly confirmed and, by the end of October, when the operation was shut down for the winter months, a total of 952 kilograms (30,600 ounces) of gold had been produced, exceeding the planned output for 1997 by 19 per cent. The average grade of the ore stacked on the leaching pad, at 3.47 grams per tonne, surpassed feasibility projections by about 16 per cent. Recovery rates exceeded 90 per cent. Another 168,000 tonnes of Kodiak A ore will be placed on this pad next June.
The Ursa deposit has proven and probable reserves of 519,400 tonnes grading 6.9 grams per tonne. Pre-stripping of the deposit continued into mid-October 1997 and the liner for the second, (1,000,000-tonne capacity Totem Creek) leach pad was installed during the third quarter and it is ready for stacking when mining and processing resumes next spring. A second processing plant will be built adjacent to this pad. Next year, the first full year of production, mining at Kodiak A and Ursa is expected to boost production to 1229 kilograms (39,500 ounces) of gold.
With the exception of the Grizzly, all the zones at Golden Bear are oxidized and exhibit many characteristics of Carlin-type, sediment-hosted micron gold deposits. Mineralization is hosted by hydrothermally brecciated and silicified dolomites. While only three deposits are included in the mine plan, others are known; the most advanced of these is the Kodiak C, which contains about 276,000 tonnes of material grading 7.8 grams per tonne gold. Kodiak B contains 183,900 tonnes grading 8.7 grams per tonne gold. The Grizzly zone contains an estimated 152,945 tonnes of refractory ore grading 20.5 grams per tonne gold. Reserves and resources are reported in Wheaton River Minerals Ltd., 1998 Annual Report.
Based on the geochemical and geophysical results North American Minerals drilled 5 HQ and NQ drillholes into the Limestone Creek Fault Zone in 1996. The first hole intersected a strongly altered volcanic, either a fault sliver or a dyke within the fault, that returned a value of 7.93 g/t gold over 4.57 metres (Assessment Report 25315). Two holes drilled 100 metres to the north and south, respectively, failed to return any significant gold values. In 1997, trenching and drilling exploration programs tested the C+C zone along Limestone Creek (LCF) in the western part of the property. Diamond drilling in 1997 below the mineralized intersection obtained during the 1996 program failed to return significant gold mineralization. The strongest mineralization detected to date in the Limestone Creek Fault Zone is hosted in a very strongly altered volcanic rock or dyke that lies within the fault zone. The mineralized material is an orangy red colour, is very soft, and completely oxidized. Significant gold mineralization was considered a possibility along strike to the northwest or southeast although a cessation of work in this area was recommended in 1997.
During 1997, drilling on the higher grade Grizzly deposit extended the structure by at least 75 metres to the north. Wheaton River is evaluating the potential for heap leaching the East low grade stockpile, which it estimates to contain 200,000 tonnes of 2.9 grams per tonne gold. A feasibility study is expected during 1998.
The Kodiak A is mined out in 1998; mining begins on the Ursa and Kodiak B in 1999. All of the 1998 production came from ore stacked on the Fleece Bowl pad. Additional heap leach production will be from the Totem Creek pad.
In November 1999, Wheaton River merged with Kit Resources Ltd. Production during 1999 equalled 2227 kilograms of gold. A total of 390,434 tonnes grading 5.63 grams per tonne gold was mined from the Ursa zone pit and stacked on the Totem Creek heap-leach pad. In addition, 155,551 tonnes grading 3.10 per cent gold, previously stockpiled from the Kodak A deposit, were also stacked on the Totem Creek pad. The Fleece Bowl leach pad contributed 57 kilograms to production. Recoveries of gold from the Totem Creek and Fleece Bowl leach facilities were 78.3 per cent and 92.4 per cent, respectively. During 1999, an eight-hole, 1200-metre drilling program tested three target areas: the northerly extension of the Ursa deposit along the projected trace of the Ursa fault, the South Zone, and the 1700-metre level below the Kodiak A zone, at the same level as the Kodiak B and Ursa deposits. Plans for the year 2000 include mining and leaching of the approximately 300,000 tonnes of ore remaining in the Ursa zone, and further leaching of about 35,000 tonnes of lower grade Kodiak A ore on the Totem Creek pad. Underground work will begin on the Kodiak B deposit, which is expected to yield about 183,900 tonnes of refractory ore grading 8.7 grams per tonne gold over the next two years.
Proven and probable reserves are 407,496 tonnes at 8.7 grams per tonne gold; inferred resources are 428,900 tonnes at 12.3 grams per tonne gold (Wheaton River Website, February 2000).
Combined Measured, Indicaed, and Inferred Resources for the Grizzly zone were reported in Wheaton River's 1998 Annual Report of 152,900 tonnes grading 20.5 grams per tonne Au (www.sedar.com - released May 20, 2000).
Just over 380,000 tonnes was mined in 2000, the final year in which mining occurred. Production in 2001 and 2002, estimated to total 1040 kilograms of gold, came from stockpiles and residual leaching. The mine closed in 2002.