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Pilgrims Rest, Sabie |
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Mpumalanga, South Africa |
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Au
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
Available as Full Text for direct download or on request. |
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The Sabie - Pilgrims Rest gold field is located 300 km ENE of Johannesburg in Mpumalanga Province, South Africa. A series of hard rock mines were distributed over a NNE elongated area of ~140 x 30 km along the Great Escarpment of Southern Africa (#Location: Beta - 24° 55' 4"S, 30° 44' 22"E).
This field is the third largest gold district in South Africa, having produced 168 tonnes of gold since alluvial gold was found in 1873, to 1971 when mining ceased.
The stratigraphic succession in the goldfield is that of the normal Transvaal Supergroup, except that the Penge Iron Formation and much of the Duitschland Subgroup and are absent, and the Chuniespoort Group is separated from the overlying Pretoria Group by the Bevett's Unconformity. The stratigraphic succession, upwards from the Archaean basement granite, includes remnants Godwan and Wolkberg Group clastic sediments that unconformably overlie basement. The Transvaal Supergroup is separated from the Wolkberg Group by an angular unconformity. The Black Reef Quartzite Formation at the base of the Transvaal Supergroup, is overlain by the Chuniespoort Group, made up almost entirely by the thick carbonate rocks of the ~2.55 Ga Malmani Dolomite Subgroup, in the absence of the overlying Penge Iron Formation and all but the uppermost Duitschland Subgroup. The quartzites, shales and minor basalts of the ~2.25 Ga Pretoria Group overlie the Duitschland Subgroup dolomites, quartzites and shale. Numerous dykes and sills, principally of Bushveld age, with some post-dating the Complex, have intruded into the Transvaal Supergroup.
The goldfield covers an area of some 600 km2 and is hosted by sedimentary rocks of the Palaeoproterozoic Transvaal Supergroup, near the eastern margin of the Bushveld Complex which is believed to have acted as a heat engine. The bulk of the gold bearing lodes of the field are hosted by the dolomites and lesser shales of the Malmani sub-group which overlies the Black Reef feldspathic quartzites of the lower Transvaal sequence. A large number of mafic dykes and sills have been intruded into the host sequence. Pre-Bushveld dykes and sills have been observed being cut by the gold bearing lodes, while syn-Bushveld intrusives cut the gold mineralised veins. Mineralisation may have been close to the 2054 Ma granitic phase of the Bushveld Complex.
Mineralisation occurs as quartz-carbonate-sulphide-gold veins which are either vertical, concordant with shallowly dipping (<5 to 10°) bedding or associated with dykes and sills. The horizontal veins are the most significant and are composed of multiple sheets of quartz (the bulk of the veins) and carbonate (dolomite, ferro-dolomite, calcite), usually with thin slivers of carbonaceous shale and dolomite hosts and average 5 to 40 cm in thickness. These lodes are principally controlled by flat, bedding parallel shears located mainly on shale partings within the Malmani Dolomites. Thickenings to massive quartz stockworks and breccia zones up to 3 m wide are locally abundant and economically important. Historic gold grades ranged from trace to 60 g/t Au, varying along strike, but averaging 9 g/t Au in the shoots worked throughout the district. Vein emplacement is controlled by low angle, southeastward verging bedding parallel shear thrusts. Ore minerals include gold, pyrite, arsenopyrite, fahlore (tetrahedrite-tennantite), chalcopyrite, bismuth sulphosalts and bismuth, and were emplaced in three phases.
The bulk of mineralised zones that have been historically recovered from the concordant, bedding parallel reefs were from the Glynn's and Theta Reefs. The Glynn's Reef is 1 to 2 km south of the township of Sabie, and is hosted within the Oaktree Formation, the lowest significant carbonate bed above the base of the Malmani Subgroup. This reef has also been mined extensively at the Elandsdrift, Glynn's Lydenburg and Vaalhoek Mines. The Theta Reef is ~2 km SW of the township of Pilrim's Rest (38 km NNW of Sabie), near the current Beta mine, and is hosted by the younger Eccles formation, the uppermost carbonate in the Malmani Subgroup, and was historically the principal source of gold mineralisation mined in the Pilgrim's Rest area.
Discordant reefs are characterised by a variety of gold mineralisation styles, and are found throughout the Sabie-Pilgrim's Rest Goldfield, commonly referred to as cross reefs, blows, veins and leaders. They can be found sporadically throughout the stratigraphy as a varying assemblage of gold-quartz-sulphide mineralisation generally striking NE, with a very variable composition, depth and width. A number of major north to NE trending lineaments
are evident throughout the Sabie-Pilgrim's Rest Goldfield, reflecting a series of near-vertical faults and dykes, most notably those forming the Fraser Morgan
graben. The period of northerly faulting is thought to post date a period of east-west normal faulting. One such cross-reef is the Rietfontein Reef, a sub-vertical hydrothermal quartz vein which strikes NNE and fills a 1 to 3 m wide fracture in basement granite. The gold-bearing material, which is erratically developed and refractory, is noted for its high silver content. Gold is associated with pyrite, arsenopyrite and chalcopyrite.It has been prospected to depths of 400 m by historical drilling.
Mining was resurrected in 2011 by Stonewall Resourced Limited. JORC compliant resources prior to mining were estimated at 31 October, 2011 at a series of deposits, as follows (Competent Persons Report to Stonewall Resources by Minxcon Pty Ltd, 2013):
• Measured resource
Underground mine - 0.17 Mt @ 4.77 g/t Au (from 1 mine, Frankfort)
Open pit mine - 0.151 Mt @ 1.59 g/t Au (from 1 mine, Hermansburg)
Tailings - 2.294 Mt @ 0.77 g/t Au (from 5 historic mines, Glynn's Lydenburg, Blyde 1 to 4)
TOTAL - 2.165 Mt @ 1.08 g/t Au.
• Indicated resource
Underground mine - 2.755 Mt @ 5.78 g/t Au (from 5 mines, Frankfort, DH/Clewer, Beta, Rietfontein, Olifantsgeraamte)
Open pit mine - 3.173 Mt @ 0.88 g/t Au (from 3 mines, Hermansburg, DG1, DG5)
Tailings - 0.012 Mt @ 0.58 g/t Au (from 1 historic mine, Blyde 5)
TOTAL - 5.940 Mt @ 3.20 g/t Au.
• Inferred resource
Underground mine - 14.535 Mt @ 3.91 g/t Au (from 13 mines, of which Vaalhoek, Ponieskrantz, Rietfontein, Glynn's and
Malieveld each contribute >0.5 Mt)
Open pit mine - 0.801 Mt @ 0.80 g/t Au (from 3 mines, Hermansburg, DG1, DG5)
Tailings - 2.451 Mt @ 3.07 g/t Au (from 2 mines, Blyde 3a, TGME Plant )
Plant floats - 0.041 Mt @ 0.54 g/t Au
TOTAL - 17.949 Mt @ 3.36 g/t Au.
TOTAL RESOURCE - 26.504 Mt @ 3.28 g/t Au, containing 87 t of gold.
This summary is drawn in part from "Muller, C., van Heerden, D., Odendaa, N.J., Engelmann, U. and Clemente, D., 2012 - An Independent Competent Persons' Report on the TGME Gold Project, Mpumalanga Province, South Africa; prepared by Minxcon Pty Ltd for Stonewall Mining Limited, 168p."
The most recent source geological information used to prepare this decription was dated: 2012.
Record last updated: 11/6/2016
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.
Pilgrims Rest - Beta
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Boer R H, Meyer F M, Robb L J, Graney J R, Vennemann T W, Kesler S E 1995 - Mesothermal-type mineralization in the Sabie-Pilgrims Rest Gold field, South Africa: in Econ. Geol. v90 pp 860-876
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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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