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Gympie

Queensland, Qld, Australia

Main commodities: Au
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The Gympie gold field is located within the town of Gympie, 177 km north of Brisbaine in south-east Queensland, Australia.

The gold field is some 7 km long by 3 km wide and since 1867 when alluvial gold was first discovered has produced 105 tonnes of gold, predominantly from lode deposits.   Most of the mines had closed by 1930, although a modern operation was commenced during the 1990's.

The hardrock production has come entirely from quartz lodes which are hosted by the Permian Gympie Group, composed of (from the base):  1). 350 m of agglomerate, amygdaloidal basalt and basaltic andesite,  2). 700 to 1000 m of volcanic conglomerate, andesitic and basaltic lava, tuff, agglomerate, feldspathic arenite and carbonaceous shale, known as the Rammutt Formation  3). up to 140 m of bioclastic calcarenite with carbonaceous mudstone, mudstone and siltstone, and  4). at least 600 m of shale interbedded with fine lithic arenite.

All of the quartz lodes are structurally controlled and hosted by the Rammutt Formation.   The gold field occupies the strongly faulted core of a partly dismembered domal structure.   The volcanics and the Rammutt Formation were deposited near a volcanic centre possibly controlled by one of the long lived fault structures of the gold field.

There are two distinct styles of quartz vein, namely:  1). The north striking and steeply west dipping Gympie vein quartz lodes which produced high grade shoots developed preferentially where the lodes cut carbonaceous units of the upper Rammutt Formation and  2). Inglewood lodes which are composed of vein quartz, usually containing brecciated volcanics of the Rammutt Formation and microdiorite (from dykes) within the NW trending, near vertical Inglewood Fault and contain free fine gold (with minor amounts of copper and arsenic).   Two of the largest mines, the Scottish Gympie and No. 2 South Great Eastern mined Inglewood lodes.

Alteration associated with either vein style is only weak, comprising patchy chlorite, hematite, and epidote and has not been conclusively connected with the gold mineralisation.

In addition to the 105 t of gold mined from 1867 to 1930, in 1990 there was potential for an additional 31 t of Au over a strike length of 1300 m between the depths of 600 and 1000 m with lodes averaging 2 m in thickness and carrying 12 to 16 g/t Au, based in part on historic production and grades.

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:
Kitch R B, Murphy R W  1990 - Gympie Gold field: in Hughes F E (Ed.), 1990 Geology of the Mineral Deposits of Australia & Papua New Guinea The AusIMM, Melbourne   Mono 14, v2 pp 1515-1518


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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