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Lady Bountiful, Lady Bountiful Extended |
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Western Australia, WA, Australia |
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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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The Lady Bountiful and Lady Bountiful Extended gold deposits are 14 km WSW of Broad Arrow and some 36 km north-west of Kalgoorlie in the Kalgoorlie Terrane, the western most element of the Eastern Goldfields Superterrane of the Archaean Yilgarn Craton, Western Australia.
Gold was initially mined in the area from 1896 to 1909 as a small scale underground operation. Large scale open pits were developed from 1985 to 1988, and then an underground decline from 1988 until around 1992. These now abandoned deposits are part of the northern section of the Mount Pleasant cluster of deposits.
The regional stratigraphy comprises a succession of tholeiitic and high Mg basalts and sediments intruded by differentiated ultramafic and mafic sills. The deposits lie on the SW limb of a gently SE plunging anticline, within these greenstones, near the contact with the Liberty Granite which intrudes the core of the anticline.
The majority of the open pit workings at Lady Bountiful are witin the Liberty Granite, a massive, coarse grained, equigranular biotite-hornblende adamellite, east of its contact with the well differentiated Mount Pleasant Sill (coarse dolerite-granophyric dolerite-pegamtitic/fine/coarse dolerite-pegmatitic dolerite and medium grained pyroxene gabbro). This sill passes below a sequence of pillowed and massive basalts and foliated shales to the west.
Within the Mount Pleasant Sill, the Lady Bountiful Main Lode is an east-west trending, 75-85° N dipping quartz veined, 2 to 3 m wide shear that displaces the granite-sill contact. Within the Liberty Granite it becomes three en echelon mineralised shears.
The ore of the main open pit is present as a stockwork zone over a 500x100 m zone to the north and south-east of the Lady Bountiful Main Lode and comprises three main vein directions, steep north dipping NE and east-west trendig and flat dipping.
Mineralisation is present as both primary and secondary ore. In the Mount Pleasant Sill, the gold of the Main Lode is associated with pyrite in quartz veins. Within the Liberty Granite it occurs as quartz-carbonate veins with coarse pyrite and other sulphides in pervasively (sericite, K feldspar and albite) altered adamellite. The primary mineralisation at Lady Bountiful Extended, immediately to the east of Lady Bountiful and entirely within the Liberty Granite is a similar adamellite hosted style. The primary lodes have been upgraded by supergene processes at the current water table, below an interval of weathering and strong leaching.
Secondary mineralisation is exploited at Lady Bountiful and Lady Bountiful Extended, both as channel deposits containing clasts of mineralised quartz and as residual gold at a depth of around 30 m at the granite sand to saprolite interface. This latter style is believed to be derived from widespread mineralised quartz veins within the adamellite and was precipitated at a palaeo-water table.
Proven reserves at Lady Bountiful in 1987 were:
Open pit - 0.97 Mt @ 2.6 g/t Au.
Underground - 0.37 Mt @ 9 g/t Au.
At Lady Bountiful Extended there were:
in situ reserves - 0.98 Mt @ 4.2 g/t Au
For detail consult the reference(s) listed below.
The most recent source geological information used to prepare this decription was dated: 1990.
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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Bartsch R D 1990 - Lady Bountiful Gold deposit: in Hughes F E (Ed.), 1990 Geology of the Mineral Deposits of Australia & Papua New Guinea The AusIMM, Melbourne Mono 14, v1 pp 401-404
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Devlin S P, Crimeen J D 1990 - Lady Bountiful Extended Gold deposit: in Hughes F E (Ed.), 1990 Geology of the Mineral Deposits of Australia & Papua New Guinea The AusIMM, Melbourne Mono 14, v1 pp 405-410
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Mason D R 2004 - Thermodynamic modelling of lode-gold deposits in Archaean granitoids: Woodcutters and Lady Bountiful mines, Kalgoorlie region, Western Australia: in Australian J. of Earth Sciences v51 pp 431-438
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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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