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Zimbabwe Craton Gold Overview - Wanderer Group, Shamva, Cam and Motor, Globe and Phoenix, Lonely, Rezende, Renco, Dalny, Freda Rebecca, Golden Quarry, Venice, Indarama, Jena, Glencairn, Blue Rock, Shamrock, Inez, Arcturus, Babs, Muriel, Gaika |
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Zimbabwe |
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Au
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Super Porphyry Cu and Au
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More than 6000 Archaean gold occurrences are associated with major deep seated lineaments where they cut elongate, strongly deformed greenstone belts within the 800 km long by 500 km wide Zimbabwe Craton. The craton is composed of early Archaean (>3.2 Ga averaging around 3.5 Ga) Sebakwean Group gneisses and greenstones and the more extensive late Archaean (3.0 to 2.6 Ga) greenstone sequences of the Bulawayan, Belingwean and Shamvian Supergroups and associated intrusive granitoids, all of which have been compexly deformed. These greenstone belts are distributed more or less along the north-western margin of the craton and to a lesser degree along its south-eastern margin with a cumulative strike length of more than 1000 km. They are in general intruded by syn to late tectonic granitoids.
The total historical gold production from Zimbabwe to 2004 has been around 2700 tonnes, with an annual output of some 20 tonnes. To 1990, some 290 mines had produced a total of more than 0.3 tonnes each, while only 7 have yielded more than 30 tonnes of recovered gold throughout their life. These include the Wanderer Group near Selukwe - 36.5 t associated with iron formation in the older Archaean Sebakwean Group greenstones; the Shamva Mine - 51.5 t from 5.2 g/t Au stringer and disseminated mineralisaiton in Shamvian felsic volcaniclastics; the Cam and Motor Mines near Gatooma - 146 t of gold from 12.4 g/t Au ore in veins hosted by mafic lavas and greywackes to 2003 - remaining reserves in 2018 of 3.019 Mt @ 5.79 g/t Au; the Globe and Phoenix Mines near Kwekwe - 120 t of gold from 27.5 g/t Au ore, mainly in veins cutting ultramafic magnesite schists and lesser granite; the Lonely Mine near Bubi - 34.7 t of gold from 17.5 g/t Au veins in mafic lavas and serpentinite; the Rezende Mine near Umtali/Mutare - 37.8 t of gold from 10.4 g/t Au veins in mafic lavas and quartz diorite; and the Dalny Mine near Chakari - 43 t of gold from 7.8 g/t Au veins in andesites to 2003 - Remaining reserve in 2018 of 0.512 Mt @ 4.78 g/t Au.
The next largest were the Muriel - 21 t Au in 13.9 g/t Au veins; the Arcturus - 24 t of 10.2 g/t Au veins; and the Gaika - 22 t of 8.6 g/t Au ore. The remaining mines had all yielded less than 15 tonnes of gold.
The majority of production has been from the younger Archaean greenstones belts which are more extensive than those of the more restricted Sebakwean greenstones. The majority of the gold has been derived from shear hosted and quartz vein accumulations (historically 38% and 31% respectively) both of which have averaged around 8.3 g/t Au. Low grade (averaging 3.5 to 5 g/t Au) stockwork and disseminated mineralisation hosted by intrusives has been historically unimportant, but is becoming more significant, while BIF hosted ores have amounted for around 4% of the country's output at an average grade of 4.9 g/t Au.
Current/recent significant producers and resources include the rich Freda Rebecca Mine - annual production 1988 to 2000 averaged 1.5 t of recovered gold from ore with a grade of 1.5 g/t Au; the Dalny, Golden Quarry and Venice Mines; the Bubi and Isabella Mines; the Jena with 1.7 Mt @ 7.8 g/t Au (2003) and Indarama with 13.5 Mt @ 3.3 g/t Au (2003); the Eureka mine with reserves + resources of around 45 tonnes of gold; the Connemara heap leach operation with 3.2 Mt @ 1.95 g/t Au (2003); the Renco Mine; the Babs, Beehive, Glencairn, Blue Rock and Shamrock mines the Inez Mine with less than 20 tonnes of gold at 10 g/t (2003); and the group of Arcturus, How, Anzac, Mazowe, Muriel, Redwing, Shamva and Tiger Reef mines which in 2002 accounted fro 20% of Zimbabwe's production. All are now relatively small mines.
The most recent source geological information used to prepare this decription was dated: 2003.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
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Selected References:
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Blenkinsop T G, Oberthur T, Mapeto O 2000 - Gold mineralization in the Mazowe area, Harare-Bindura-Shamva greenstone belt, Zimbabwe: I. Tectonic controls on mineralization: in Mineralium Deposita v35 pp 126-137
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Foster R P, Mann A G, Stowe C W, Wilson J F 1986 - Archaean gold mineralization in Zimbabwe (Full paper): in Anhaeusser C R, Maske S, (Eds.), 1986 Mineral Deposits of South Africa Geol. Soc. South Africa, Johannesburg v1 pp 43-112
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Klemm, D.D., Krautner, H.G., 2000 - Hydrothermal alteration and associated mineralization in the Freda-Rebecca gold deposit - Bindura District, Zimbabwe: in Mineralium Deposita v.35, pp. 90-108.
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Oberthur T, Blenkinsop T G, Hein U F, Hoppner M, Hohndorf A, Weiser T W 2000 - Gold mineralization in the Mazowe area, Harare-Bindura-Shamva greenstone belt, Zimbabwe: II. Genetic relationships deduced from mineralogical, fluid inclusion and stable isotope studies, and the Sm-Nd isotopic composition of scheelites: in Mineralium Deposita v35 pp 138-156
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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