Norseman Goldfield

Western Australia, WA, Australia

Main commodities: Au
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The Norseman Goldfield comprises a number of gold deposits spread over a north-south interval of 65 km at the southern end of the Kalgoorlie Terrane, the westernmost element of the Eastern Goldfields Superterrane of the Archaean Yilgarn Craton in Western Australia.   These deposits are centred on the town of Norseman, some 165 km south of Kalgoorlie. Mines within the goldfield included the North Royal, Princess Royal and Harlequin ~6 to 8 km north of the town of Norseman, Regent, Phoenix, Ajax, Bullen, OK, Mararoa and Crown within 3 km north, east and south of the town, Cumberland, Iron King, Lady Miller and Penneshaw are ~3 to 10 km to the SE, and Scotia is ~30 km to the south.

The principal deposits were exploited by the Central Norseman Gold Corporation. Gold was first discovered in the district in 1892 at Dundas, 22 km south of Norseman. This was followed in 1894 by a gold discovery at Dundas Hills at the site of the future town of Norseman. The discovery claim was initially named the Dundas Reward, and renamed The Norseman. In 1935, Western Mining Corporation invested in the mine's infrastructure and expanded output under the management of its subsidiary, Central Norseman Gold Corporation Ltd which operated the mine until 2007. In 2002 Croesus Mining had taken control of Western Mining's share of the operation, but went into liquidation after it failed to produce sufficient gold to meet hedging commitments. The mine was then acquired by what was to become Norseman Gold who continued operations until its closure in 2014. It was Australia’s longest continuously running gold mining operation having been worked for 65 years in which time it produced ~170 t of gold. Underground resources remained in 2014.

The greenstone belt comprises a west dipping and facing sequence of units comprising from the east:
Penneshaw Formation - 100 m of basalt and felsic volcanics;
Noganyer Iron Formation - 1600 m of Iron Formation with intercalated sediments and ultramafic rocks;
Woolyeenyer Formation - 8000 m of pillow basalts, gabbro with interbedded slates and cherts near the base.
  This formation includes the Mararoa Basalt Sequence, the principal host to mineralisation, which comprises:
  - Agnes Venture Slate - 10 m of graphitic slate;
  - Mararoa Pillow Lavas - 1350 m of pillow basalt intruded by multiple gabbro dykes;
  - Gee Gee Slate - 2 m of chert and graphitic slate;
  - Bluebird Flows - 100 m of plagioclase megacrystic pillow basalt and gabbro
  - Empress Slate - 5 m of graphitic shale.
  The Mararoa Basalt Sequence is underlain by the 400 m thick Kingswood Basalt composed of ultramafic flows and pillow basalts; and is overlain by the 150 m thick Royal Amphibolite amygdaloidal basalt; the 100 m thick Crown Sills pillow basalt, graphitic slate and gabbro unit; and the 6000 m thick Desirable Pillow Lavas which have minor interflow sediment bands.
Mount Kirk Formation - a 6000 m thick mixed assemblage of felsic volcanics and volcanosediments with chert, iron formations and ultramafic sills.

The greenstone sequence is enveloped by batholithic granites to both the east and west, dated at 2650 to 2570 Ma.

An interval of approximately 1450 m of mainly pillow basalts and intruded gabbros with much lesser chert and graphitic shale in the lower section of the Woolyeenyer Formation has been identified as the prospective stratigraphic package that hosts gold mineralisation and is known as the Mararoa Basalt Sequence.   This sequence is folded into a steep west dipping homocline and is cut by a series of prominent NNW trending faults.

The orebodies exploited to 1990 were all quartz vein hosted in two habits, namely:
i). sub-vertical quartz veins trending east-west over lengths of <500 m, such as the Cumberland vein; and
ii). east dipping laminated reefs such as the Mararoa, Crown and Norseman striking north to NNW over strike lengths of kilometres.
Significant mineralisation in both is restricted to where they fall within the Mararoa Basalt Sequence.

These reefs are typically 0.5 to 2 m thick, occupying discrete dilational shears and contain a series of shoots, eg the Mararoa Reef has 5 separate en echelon shoots which are typically 900 to 1000 m long and extend 250 to 300 m down dip, but have frequent barren patches.   Alteration minerals are protolith controlled and include biotite, tremolite, actinolite, chlorite and carbonate (mainly calcite) with minor sulphides.   The main indications of good gold grade are sphalerite and galena.   Gold is asscoaited with banding within the reefs.

The principal reefs of the goldfield and their production to 1988 were: Royal (at the North Royal mine) - 2.816 Mt @ 19.3 g/t Au for 54.386 t Au,  Mararoa - 3.407 Mt @ 10.5 g/t Au for 35.648 t Au,  Crown - 2.923 Mt @ 11.2 g/t Au for 32.883 t Au,  Norseman - 0.222 Mt @ 16.4 g/t Au for 3.647 t Au,  Cumberland - 0.069 Mt @ 29.4 g/t Au for 2.025 t Au.

Total production from the goldfield to 1987 was - 9.7 Mt @ 13.6 g/t Au for 132 t pf gold.
In 1988 recoverable Proved + Probable Ore Reserves were:
    Underground - 1.26 Mt @ 7.6 g/t Au,
    Open pit - 0.55 Mt @ 5.4 g/t Au.

Remaining Mineral Resources within the goldfield include (Mininglink website, 2014, viewed 2019):
  Measured Resource - 5.6 Mt @ 1.9 g/t Au;
  Indicated Resource - 6.7 Mt @ 5.1 g/t Au;
  Inferred Resource - 10 Mt @ 6.2 g/t Au;
This represents a total of 106.5 t of contained gold. Pantoro Limited, which holds a 50% interest in the Central Norseman Gold Project state a current JORC compliant Mineral Resource of 136 t of gold in the Norseman Goldfield.

For detail consult the reference(s) listed below.

The most recent source geological information used to prepare this summary 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.

  References & Additional Information
   Selected References:
Archer N R, Turner B J  1998 - Norseman gold deposits: in Berkman D A, Mackenzie D H (Ed.s), 1998 Geology of Australian & Papua New Guinean Mineral Deposits The AusIMM, Melbourne   Mono 22 pp 265-271
Thomas A, Johnson K, MacGeehan P J  1990 - Norseman Gold deposits: in Hughes F E (Ed.), 1990 Geology of the Mineral Deposits of Australia & Papua New Guinea The AusIMM, Melbourne   Mono 14, v1 pp 493-504

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 takes no responsibility what-so-ever for inaccurate or out of date data, information or interpretations.

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