An AMF-PGC International Study Tour
Developed & Managed by Porter GeoConsultancy
Archaean Gold '97
Archaean Gold & Related Ore Deposits of North America & Africa
4 - 29 July 1997 - In Two Separate Modules
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Dome Mine Complex, Timmins-Porcupine, Ontario.
Image: Dome Mine Complex, Timmins-Porcupine, Ontario.   
DEPOSIT DESCRIPTIONS

The deposits on the itinerary were as follows:

Module 1 - North America - Sat 5 to Fri 18 July 1997
Module 2 - Africa - Mon 21 to Tues 29 July 1997

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MODULE 1 - NORTH AMERICA

Lupin

Lupin is hosted by an Archaean Banded Iron Formation within the Slave Archaean Province in northern Canada. Gold is associated with quartz veins and concentrations of pyrrhotite or pyrite and arsenides in iron formation. The quartz veins contain 0.03 to 1.00 ppm Au, while a zoned sequence of hydrothermal alteration in the iron formation envelopes the quartz veins. Immediately adjacent to the veins, there is a calc-silicate assemblage of hedenbergite+ quartz± epidote± scheelite± grossular, also with 0.03 to 1.00 ppm Au. The next zone is iron-sulphide rich, with pyrrhotite-pyrite + hornblende+ quartz± hedenbergite± epidote± actinolite. This zone carries 5 to 30 ppm Au. Further from the veins the iron formation is un-mineralised (=0.03 ppm Au), lacks sulphide and comprises grunerite+ quartz± magnetite. In the transition zone, hornblende replaces grunerite, and iron sulphides replace amphibole and magnetite. The alteration sequence is developed on a scale of millimetres to metres and in areas of dense veining there is no un-mineralised iron formation between adjacent veins. Production between start-up in 1982 and 1887 was 28.25 t at an average grade of 11.12 g/t Au. In that year proven and probable reserves were 3.4 Mt @ 11.4 g/t Au for 38.65 t Au. Production in 1995 was 5.6 t Au.

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Miramar Con

Miramar Con is a shear hosted lode deposit within the 50 km long Yellowknife greenstone belt of the Archaean Slave Province in northern Canada. In contrast to the Superior Province, overall the Slave has much higher proportion of sediments to volcanics. The Con mine has production + reserves of around 175 t Au. Gold occurs in a series of shoots of quartz-ankerite veining accompanied by chlorite-carbonate-sericite-sulphide alteration. The average grade mined has been 17 g/t Au. Production in 1994 was 3.7 t Au. The mine is owned by Miramar Mining Corporation.

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Giant Yellowknife

The Giant Mine is also in the Yellowknife Greenstone Belt. It has a number of significant differences to Miramar Con as well as similarities. The gold mineralisation occurs within a major ductile-brittle shear zone where it cuts a tholeiitic basalt unit with intercalated sediments. It occurs as irregular pods and lenses of quartz-carbonate-sulphide vein material enveloped by sericite-chlorite-carbonate schist. Giant is owned and operated by Royal Oak Mines Inc. Production from 1948 to 1987 totalled 12.9 Mt @ 16.5 g/t Au, for approximately 213 t Au. Production in 1994 was 0.43 Mt @ 8 g/t Au which yielded 3.15 t Au. Reserves at the end of 1994 were 2.395 Mt @ 9.8 g/t Au.

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Campbell - Red Lake

The Campbell mine in the Uchi Greenstone belt of the Superior Province, is some 600 km NW of the Hemlo Greenstone Belt and 1000 km to the NW of the Abitibi Belt. After the two main Hemlo mines, Campbell is currently the largest gold producer in Canada, with an annual output of 10 t. The mine is operated by Placer Dome. The orebody is present as quartz-carbonate fissure veins and siliceous replacement zones. Historic production in the Red Lake area has exceeded 300 t Au. Current reserve grades are around 19 g/t Au.

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Hemlo

Golden Giant and David Bell are two of the three main mines at Hemlo which together account for a reserve of around 600 t Au. The orebodies are within the Schreiber-Hemlo Greenstone Belt, some 600 km SE of Red Lake and 400 km west of the Abitibi Belt, within the Superior Province. These orebodies are within and adjacent to the major structural discontinuity, the Heron Bay-Hemlo Fault Zone. The Hemlo mineralisation is located at the highly sheared contact between sediments and felsic volcanics (as quartz-eye muscovite schist) in a dextral shear. Gold occurs as microscopic native metal within silicified schist after both felsic volcanics and sediments, and is associated with strong disseminated pyrite and barite, accompanied by molybdenite. Although veins and veinlets are present and mineralised they are not the main hosts of ore. The greenstone belt in the Hemlo area is metamorphosed to amphibolite facies in contrast to the generally greenschist Abitibi Belt to the east. Golden Giant is owned by Battle Mountain, while David Bell and Williams are held by Teck Corp and Homestake. In 1994 the three mines produced 34 t Au. Williams and Golden Giant each produce around 14 t Au per annum. Grades range from 6.5 g/t at Williams, to 10.85 g/t at Golden Giant, to 14 g/t at David Bell.

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Manitouwadge

Manitouwadge is hosted by felsic volcanics of the Schreiber-Hemlo Greenstone belt. It has now closed, but produced more than 50 Mt of ore @ 1.9% Cu, 3.7% Zn, 52 g/t Ag, 0.15% Pb, 0.2 g/t Au. It is structurally connected to the Hemlo line, and although not primarily a gold mine, bears some overall relationship to Hemlo. The Manitouwadge orebodies are elongated, pencil shaped and strongly modified by structure.

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Kidd Creek

The Kidd Creek Mine is within the Timmins district, on the northern fringe of the Porcupine mining camp, some 30 km from the Dome mine, but within the same structural zone. As such, like Geco at Hemlo it appears to be part of the same gross mineralised system. Reserves + production total more than 120 Mt @ 7% Zn, 1.3% Cu, 0.4% Pb, 165 g/t Ag. It occurs within a suite of felsic volcanics of the Abitibi Greenstone Belt, overlain by greenstones. The ore is composed of stringer and massive banded and brecciated pyrite, sphalerite and galena associated with carbonaceous rocks. The main alteration is sericitisation, silicification and chloritisation. The mine is operated by Falconbridge Ltd.

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Dome

The Dome mine is within the western Abitibi Greenstone Belt of the Superior Province and comprises steeply dipping quartz veins within zones of early pervasive carbonate alteration and later local fuchsite-pyrite. The deposit is around 1 km to the north of the Destor-Porcupine Fault, one of the major dislocations of the belt known as "Breaks". The lodes are thought to lie in a splay of this fracture zone, and occur near the contact between greenstones and sediments, but also near lensoid quartz-feldspar porphyry bodies. Historical production + reserve at the Dome mine total around 335 t Au. The mine is owned by Placer Dome and produces around 5.5 t of Au per annum. Current reserve grades are 3 g/t Au.

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Bouquet #2 and Laronde

The Bousquet #2 and Laronde mines lie within the southern central Abitibi Greenstone Belt in the Superior Province. They exploit disseminated and sheared massive sulphide pyritic gold and base metal mineralisation in sheared mafic and felsic volcanics and adjacent sediments. The Bousquet #2 mineralisation is contained within a 500 m wide belt of intense, anastomosing ductile shear zones and pervasive alteration. It lies just to the north of the major Cadillac Break shear zone, and just to the south of the Destor-Porcupine Break. The larger veins are mainly sulphides, with lesser quartz and carbonate. The sulphides are principally pyrite, with associated chalcopyrite, galena and pyrrhotite. Production from Laronde is 4.5 t Au per annum, Bousquet 1 & 2 mines, which are around 1.5 km apart, together output approximately 7.2 t Au, while the adjacent Doyon mine (which is part of the same mining complex, and with Bousquet #1 exploits vein style mineralisation, but will not be visited) contributes a further 7.5 t Au. Current production grades are around 7.5 g/t Au at Bousquet and Laronde, and 6.5 g/t Au at Doyon. At Laronde reserves in 1995 were 10.4 Mt @ 2 g/t Au, 100 g/t Ag, 0.14% Cu, 10.6% Zn. The Bousquet #2 and Laronde mines work different parts of the same ore zone. The Bousquet/Doyon mine complex is owned by Barrick Gold Corporation, while Laronde is controlled by Agnico Eagle. In the nearby Doyon mine gold is present in structurally controlled lodes which differ from the sulphide lodes as Bousquet and Laronde. These and the other gold deposits of the Quebec Abitibi are found within and adjacent to major structural "breaks", such as the Cadillac Break shear zone, and the Destor-Porcupine Break. In addition however, around 22% of the gold from the Abitibi Belt in Quebec has come from massive sulphide base metal deposits within felsic volcanics. The largest of these was Horne, at Noranda, now exhausted, which yielded 58 Mt @ 2.18% Cu, 4.8 g/t Au for 275 t Au.

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MODULE 2 - AFRICA

Witwatersrand Basin Gold

The Witwatersrand mines in the Johannesburg, Klerksdorp and Welkom districts in particular have contributed over 50% of all of the gold produced in the world to date. This production has come from over 150 mines which have extracted over 4.5 billion tonnes of ore to yield more than 42 000 t Au at an average grade of 9.3 g/t Au. The host rocks were deposited between 3100 and 2700 Ma, much the same as the auriferous greenstone belts on the adjoining Zimbabwe Craton to the north, the Slave and Superior Provinces in Canada and the Yilgarn Block in Western Australia. The form of the gold mineralisation is however, different, but may well be part of the same global evolutionary processes. The clastics of the Witwatersrand Supergroup are overlain by the 7800 m thick Ventersdorp basaltic to andesitic lavas, and are underlain by the Dominion Group mafic volcanics. East Driefontein is in the West Rand District near Johannesburg and is operated by Gold Fields of South Africa. Lorraine is another Witwatersrand mine, 300 km WSW of those of the West Rand at Johannesburg. Target is immediately to the north of Lorraine, and is said to potentially be the biggest new Witwatersrand mine of the next decade. It has stacked reefs, which have yielded intersections of up to 121 m @ 5.2 g/t Au. Avgold, the owner, plans to introduce fully mechanised mining and reduce costs to $US 200/oz.

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Eastern Transvaal Consolidated Mines (Barberton)

These mines are developed within pre 3100 Ma greenstones of Barberton Mountain Land in the pre-Witwatersrand basement of the eastern Kaapvaal Craton. Production to 1985 totalled 250 t Au from over 350 mines, although 70% came from just 4 operations. These are the New Consort (55 t Au), Sheba Group (69 t Au from 25 fracture hosted orebodies), Fairview (37 t Au) and Agnes (19 t Au). All others yielded less than 6 t. The present East Transvaal Consolidated operation produces around 3.5 t Au per annum at an average grade of 15 g/t Au, with reserves in 1994 of 15 t Au. It is unusual for significant production to emanate from pre-3100 Ma greenstone belts.

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Renco

Renco is a medium sized mine within the northern marginal zone of Limpopo Mobile Belt where it cuts the south-eastern margin of the Zimbabwe Craton. Reef zones bearing gold, together with bismuth, copper and iron sulphides are found in granulite facies rocks that are highly contorted. The reefs are transgressed by the foliation and isoclinal folding of the Archaean Limpopo Mobile Belt. The reefs are associated with a very fine grained brown to white, laminated quartz-magnetite granulite. The average reef width is 126 cm, with a grade of 9.4 g/t Au, 37 ppm Bi and 0.16 Cu. Production in 1994 was 2.1 t Au. The mine is owned and operated by Rio Tinto Zimbabwe.

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For more information contact:   T M (Mike) Porter, of Porter GeoConsultancy   (mike.porter@portergeo.com.au)

This tour was designed, developed, organised, managed and escorted by
T M (Mike) Porter of Porter GeoConsultancy Pty Ltd.

Porter GeoConsultancy Pty Ltd
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LINDEN PARK, 5065
South Australia
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