New airborne magnetic data and previous rock chip assays results have greatly enhanced the prospectivity of the
In addition very high grade silver as well as gold results from
For example, Impact's Commonwealth and Silica Hill deposits contain bonanza grades of silver in both massive sulphide lenses as well as in epithermal veins, an important factor to consider given the current resurgence in the silver price. Some key results from these deposits are also reviewed in this report as part of a reassessment of the entire Lachlan portfolio for its silver potential.
Previous Work by Impact
The
At the
None of these prospects has been drilled. The results of a detailed soil geochemistry survey at
At Greenobbys, Impact has identified high grade epithermal gold-silver mineralisation that is much younger than the porphyry copper-gold mineralisation and which has not been extensively explored for in the entire region.
Here, rock chips returned up to 9.5g/t gold (six samples with more than 1 g/t gold) and 215 g/t silver (7 ounces of silver with four samples containing more than 1 ounce per tonne) from veins of Kfeldspar and quartz. In addition the veins contain a remarkable array of pathfinder metals in particular bismuth (up to 745 ppm), molybdenum (up to 519 ppm) and tellurium (up to 40 ppm), together with appreciable amounts of the pathfinder metals selenium-thallium-antimony-arsenic-lead-barium and tungsten (ASX Release 23rd June 2020).
All of these features are interpreted to indicate the veins are related to fluids released from a potassium rich granite and which may represent a 'telescoped' epithermal system covering at least several hundred square metres. The veins are open along trend and at depth as there is no recorded drilling in the area.
Telescoping refers to the significant overlap between proximal and distal metal and mineral assemblages and suggests the possible rapid collapse of the parent hydrothermal system. This is encouraging for the discovery of bonanza gold -silver veins. The
New Airborne Magnetic Data
Impact recently completed a detailed airborne magnetic and radiometric survey over the western parts of the Commonwealth project area at 50 metre line spacing. This has allowed new insights into the geology and structure of the area and a detailed interpretation of the data is in progress.
At
A rock chip sample taken by
At Greenobbys the new magnetic data shows that the vein system occurs at the margin of a magnetic granite called the Wuuluman Granite (Carboniferous age). There are indications of the NW trending structures in the data. Of note is a north west trending magnetic low that is up to 500 metres thick and lies about 1 kilometre south of the vein system at Greenobbys. This is a clear zone of destruction of magnetite by hydrothermal fluids which has never been explored and is a priority area for follow up field checking.
Together,
At Boda South the new magnetic data confirms that the southern end of the
HIGH GRADE SILVER AT THE COMMONWEALTH AND SILICA HILL DEPOSITS
The Commonwealth and associated Silica Hill deposits occur in the centre of Impact's Commonwealth project and comprise a high sulphidation volcanogenic massive sulphide deposit and an epithermal gold-silver deposit respectively. Both deposits are characterised by exceptional silver grades.
Impact has defined Inferred Resources at these two deposits that contain 88,000 ounces of gold and 3.3 million ounces of silver from surface to a depth of 250 metres, well within the range of open pit mining (ASX Release 22nd August 2018).
Commonwealth (Main Shaft to Commonwealth South) comprises an Inferred Resource of 912,000 tonnes at 2.4 g/t gold, 44 g/t silver, 1.2% zinc and 0.5% lead including 142,000 tonnes at 4.5 g/t gold, 161 g/t silver, 4.6% zinc and 1.7% lead in the high grade massive sulphide lens at Main Shaft.
Silica Hill, which was discovered by Impact comprises an Inferred Resource of 710,000 tonnes at 0.8 g/t gold and 88 g/t silver.
The resources are open along trend and at depth and extensive further resource definition and extensional drilling is required to follow up key intercepts at Main Shaft and Silica Hill as outlined below.
At Main Shaft the massive sulphide lens is still open at depth and along trend to the north and south east. For example, the resource is open to the north down plunge from drill hole CMIPT084 and at depth below drill hole CMIPT021.
Hole CMIPT084 returned: 5.7 metres at 3.8 g/t gold, 347 g/t silver, 10.8% zinc and 3.7% lead from 52.1 metres down hole; including 0.7 metres at 15.6 g/t gold, 245 g/t silver, 8.6% zinc and 1.9% lead and 0.5 metres at 4.9 g/t gold, 917 g/t silver, 10.2% zinc and 4.6% lead from 56.9 metres.
Hole CMIPT021 returned: 8.1 metres at 6 g/t gold, 193 g/t silver, 5.9% zinc, 2.3% lead and 0.16% copper from 71 metres including 2.9 metres at 9.3 g/t gold, 201 g/t silver, 11.6% zinc, 4.7% lead and 0.2% copper.
At Silica Hill, a virgin discovery by Impact located 60 metres to 250 metres north east of Main Shaft mineralisation comprises high grade veins and disseminations of sulphide with gold and extensive visible silver minerals (antimony and arsenic sulphosalts: proustite-pyrargyrite). These minerals are exceptionally rare in
There are also zinc and lead credits to the mineralisation at Silica Hill with the sulphides present being similar to those at Commonwealth-Main Shaft. They are interpreted as being part of the same overall mineralised system.
The disseminated mineralisation between the veins has helped form thick zones of near-surface modest grade mineralisation with the potential for bulk open pit mining. For example discovery hole CMIPT011 returned bonanza-grade silver within a sulphide vein in a thick zone of silver-gold mineralisation as follows: 48.6 metres at 137 g/t silver (4.4 ounces) and 0.5 g/t gold from 122 metres down hole, including, 23 metres at 224 g/t silver (7.2 ounces) and 1.0 g/t gold from 147.7 metres, which includes 0.9 metres at 3,146 g/t silver (101 ounces) and 2.4 g/t gold from 148.1 metres
Three diamond drill holes have also established that there is a low grade silver halo of up to 10 g/t silver around the Silica Hill mineralisation that is at least 500 m by 500 m in dimension. For example Hole CMIPT072 returned 146 metres at 0.04 g/t gold and 5 g/t silver. In addition CMIPT078 drilled at the eastern end of the northern mineralised zone returned the thickest intercept of gold and silver to date in this zone and indicates improving grades to the east and returned: 117 metres at 0.3 g/t gold and 11 g/t silver.
This attests to the scale of the mineralised system at Silica Hill which is still open in all directions and further deeper drilling is required.
Impact's work at Commonwealth-Silica Hill has demonstrated compelling similarities to the world class
Over its 14 year mine life
In the past two years TSX:V listed company
The similarities between Commonwealth, also interpreted as a high sulphidation VMS, and
Furthermore, Commonwealth and
NEXT STEPS
The new magnetic data and previous exploration results by Impact and others strongly support the potential for the
In addition, a detailed interpretation of the new airborne magnetic and radiometric survey is also in progress together with a review of previous exploration data. All of this new data will be interpreted and synthesised to help define follow up work programmes which will include drilling later in 2020.
Contact:
Tel: (61 8) 6454 6666
Email: info@impactminerals.com.au
(C) 2020 Electronic News Publishing, source