The lodes were intersected in a 15-hole diamond drilling program which aimed to infill and confirm continuity, grade distribution and geological definition of each lode.
A 2017 open-pit mining scoping study at Withnell outlined the potential to extend the previously mined 45-metre open pit to a new depth of around 120 metres.
A further two lodes have been identified in the area and provide further resource potential, but these have not yet been tested.
Highlighted results from the first lode include: 4.85 metres at 8.46 g/t from 158.15 metres, including 0.35 metres at 70.4 g/t from 159.2 metres; 5.6 metres at 5.24 g/t from 166.3 metres, including 0.95 metres at 21.3 g/t from 170.2 metres; and 1.4 metres at 20.05 g/t from 228.7 metres.
The second lode delivered assays of 3.8 metres at 6.85 g/t from 151.7 metres and 7.97 metres at 7.48 g/t from 137.03 metres, including 2.5 metres at 14.52 g/t from 138.5 metres.
The results indicate a large gold system with multiple high-grade stacked lodes, open at depth and along strike, beneath the 377,300-ounce Withnell resource.
De Grey technical director Andy Beckwith said: “Our focus going forward will be to continue step-out drilling to define the limits of the high-grade lodes both down-dip and along strike.
“The potential to materially increase resources and improve economics to include high-grade underground mining is compelling.”
The results have successfully confirmed:
Lode definition, geology and continuity along-strike and dip;
High-grade nature of mineralisation;
Stacked nature of lodes and potential for additional splays off the main lodes;
High strike rate of intersecting both lodes 1 and 2, along-strike and down-dip;
Previous drill intersections, both low and high-grade, which provides confidence in the deeper wide-spaced drill results; and
Potential for higher grade shoots within the broad mineralised system.
Withnell plan showing proposed open pit cutback and the 4 known underground lodes
The economic impact of a high-grade underground mine being added to the proposed open pit mining strategy is substantial in terms of potential to increase revenues, mine life and annualised production rates.
De Grey’s Pilbara project has strong potential to define additional resources along its plus-200-kilometre strike length of mineralised shear zones.
Only 10% of the shear zones have undergone detailed shallow reverse circulation (RC) and diamond drilling to a nominal depth of 100-150 metres, which has already defined mineral resources containing over 1.2 million ounces of gold.
Follow-up diamond drilling is expected to test Withnell’s depth extensions and define the limits of the gold mineralisation associated with the discovered lodes.
Subsequent infill drilling, subject to positive results, will aim to better define higher-grade shoots within the broader mineralisation.
De Grey will hold a general meeting this Friday at 11am local time at Perth’s QV1 Conference Centre at 250 St Georges Terrace.