Webbs Silver Project
|Exploration Licence||Ownership||Area (Km2)|
- Highest grade undeveloped silver project in Australia, with a JORC compliant resource of over 12Moz of silver.
- Positive metallurgical results indicate >90% silver recovery to doré bars.
- Great potential to grow the resource to support open pit and underground operations.
- Current drilling program in place which is expected to continue to grow the existing high grade resource.
The Webb’s Project is located in the New England region of northern NSW approximately 255km southwest of Brisbane. The nearest regional centre is Glen Innes about 45km to the south of Webbs.
Geology, Mineralisation and Target models
The Webb’s deposit lies within the New England Orogen which extends from north- eastern NSW and into the eastern of Queensland. The New England Orogen is a significant mineral province in Eastern Australia and hosts a variety of mineral deposits.
The dominant geological feature in the Webbs region is the early Triassic aged Mole Granite. The Mole Granite is part of the New England Batholith and intrudes Permo-Carboniferous sedimentary and silicic volcanic rocks. The Mole Granite is related to extensive mineralisation in the region with over 2,000 separate mineral occurrences within and outboard of the granite. Mineralisation in the project area consists of polymetallic single or multiple vein–lode zones which are structurally controlled and commonly fractured to locally brecciated. Metal associations include combinations of Ag-Cu-Pb-Zn-As-Sn-W-Sb-Bi and Au.
Silver–base metal mineralisation at Webb’s is developed in a narrow 2km long north trending zone which is marked by scattered old workings. Mineralisation is hosted in steeply dipping zones of quartz-sericite-carbonate-chlorite altered meta-siltstone up to 15m wide. Ore sulphides, tetrahedrite, sphalerite, galena and chalcopyrite occur as fracture fill veins and local dissemination with accessory arsenopyrite. Minor cassiterite and stannite also occur.
Silver mineralisation at Webb’s was discovered in 1884. From 1884 to1901 approximately 55,000t were mined at an average grade of at least 23oz/t. Numerous shafts, some up to 50m deep, and smaller prospecting pits occur along the 2km long trend. The Main shaft is 210m deep.
In 1946-47 Zinc Corporation conducted mapping, sampling, costeaning and metallurgy. A private venture re-developed Webbs Main from 1962-1965 and there was minor production from underground, old dumps and tailings material. In 1962-63 the NSW Department of Mines provided drilling aid for 8 diamond core holes drilled from surface and underground positions. Underground sampling and surveying were also undertaken. In 1969 Planet Management and Phoenix Mines NL conducted exploration programmes including geological mapping, induced polarisation (IP), follow-up diamond core and percussion drilling in 40 holes. Planet reported several narrow high grade drill intersections. The project lay idle until 2000 when Australian Geoscientists and Polymetals conducted metallurgical tests on dump material, and other sampling. In 2003 Mt Conqueror Minerals NL purchased the project and conducted sampling, mapping, limited drilling (2 holes) and estimated a resource from historical data.
Current and Planned Work
Work by Silver Mines
Silver Mines Limited acquired the project in 2006 and has since conducted aggressive drilling campaigns including both reverse circulation (RC) and diamond drilling. Extensive IP surveys, ground electromagnetic methods (EM), mapping and sampling have also been undertaken. This has led to the discovery of high grade silver resources potentially amenable to open cut mining followed by underground mining. Mineralisation remains open in several gaps along strike. Importantly mineralisation remains open at depth in many locations as most drilling to date has targeted the upper 120m or so of the deposit.
Silver Mines have also conducted a Scoping Study to investigate potential open pit viability. This was based on the assumption of producing silver rich concentrates for sale. More recently Silver Mines has conducted metallurgical testwork using the Albion Process TM. This has demonstrated the potential to recover over 90% of silver to doré bars.
The current resources at a 70ppm Ag cut-off are approximately 1.49Mt @ 245ppm Ag, 0.27% Cu, 0.71% Pb and 1.56% Zn. Importantly over 70% of the resource is contained in the Measured and Indicated categories as shown below.
|Resource Class Measured
||Tonnes (t) 194,000
||Ag (g/t) 364
||Cu % 0.29
||Ag (oz) 2,269,000
|Total M & I
There is excellent potential to grow the resource as high grade mineralisation remains open at depth in many locations.
Silver Mines have been evaluating the metallurgy of the Webbs deposit for some time. Recently SVL have been testing a flow sheet incorporating the Albion ProcessTM. This work has indicated silver recoveries of over 90% to doré bars is achievable. The flow sheet utilises conventional grinding and bulk flotation followed by ultra-fine grinding and atmospheric oxidation (the Albion ProcessTM). Silver is then recovered by standard cyanidation and doré production.
Once the test work is completed a Scoping study will be undertaken to investigate capital and operating costs associated with a 500,000 tonne per annum plant producing around 4Moz of silver doré per annum.
Silver Mines completed its most recent drilling program at Webbs in 2013. The program consisted of both reverse circulation (RC), including 5,000 meters of prepaid RC drilling, and diamond drilling. This program was designed to expand the existing resource base at depth where no drilling had previously taken place. Announcements in relation to this drilling program can be found under News and Announcements, Latest News.