“The majority of the prospective basement rocks within Ardea’s large, strategic tenement package in the Eastern Goldfields of Western Australia are concealed by surface cover and lake clays. However, detailed project assessment has demonstrated that fertile major gold-controlling structures pass through Ardea’s tenements. To intersect significant gold mineralisation in the initial RC drill program at the Aphrodite North area demonstrates proof of concept and is a credit to the Exploration Team. This result is especially exciting as it is only one of many targets defined within Ardea’s extensive BTZ gold target inventory.”
— Ardea’s Managing Director, Andrew Penkethman
The Bardoc Tectonic Zone (BTZ) is a major, gold-fertile, crustal-scale structure that transects the Kalgoorlie Terrane of the Eastern Goldfields. The regional shear/fault system strikes from Paddington in the south to northwest of Ghost Rocks in the north and extends over an approximate 125km strike length, of which some 65km occurs within Ardea tenure. Ardea’s Goongarrie Hub is unique among the world’s lateritic nickel-cobalt deposits in that it has developed on ultramafic rocks that are within and are a part of a major, crustal-scale gold-mineralised structure being the BTZ.
The BTZ typically dips moderately to the west, hosting the Paddington, Goongarrie, Comet Vale, Yunndaga, Menzies, Lady Irene and Lady Isobel historic gold mining centres. To the south, the BTZ is contiguous with the Boulder-Lefroy Fault, the host to the Kalgoorlie Golden Mile, New Celebration and St Ives gold mining centres and is considered to be part of a single gold-fertile crustal structural system stretching from St Ives in the south to Ghost Rocks in the north.
Ardea gold exploration throughout the Goongarrie Hub is using a systematic multi-disciplinary camp-scale approach to assess the obscured greenstone sequence. For reference, the modelled Goongarrie gold camp is around the strike-length of the St Ives gold camp and more than twice the strike-length of the world-ranking Kundana gold camp.
Aphrodite North Gold Line and Lily Albany Gold Discovery
The Aphrodite North area is located approximately 80km north of the City of Kalgoorlie-Boulder and 6km north along strike of the 1.7Moz Aphrodite gold deposit (BDC, ASX release 25 June 2020). The area is entirely covered by transported material and thus exhibits no surface anomalism. The target structure extends in a northnorthwest orientation throughout Ardea’s granted Mining Lease, M29/426.
Lily Albany is the first gold discovery in the Aphrodite North area by any company and was confirmed by Ardea during the December Quarter 2020. It is located 3km east of Ardea’s 25km long line of nickel-cobalt laterite deposits that define Goongarrie. Lily Albany is a proof-of-concept discovery that resoundingly illustrates the gold fertility of the BTZ within Ardea’s tenure.
During May to June 2021, assay results were received from the 15 resource definition RC drill holes completed for 2,122m and two diamond drill holes completed for 365m during the March Quarter 2021 (ASX release 22 June 2021). Highlights from this drilling include:
- From diamond drilling at the buried Lily Albany discovery (ALAD0002):
- 6.8m at 1.48g/t Au from 51m including 3.8m at 2.28g/t Au from 51m was intercepted in strongly oxidised material
- 9m at 1.53g/t from 170m including 3m at 3.79g/t Au from 170m was intercepted in fresh rock
- Shallow RC drilling at Lily Albany has extended the footprint of oxidised gold mineralisation beneath transported cover:
- AANR0029: 4m at 3.22g/t Au from 40m including 2m at 5.81g/t Au from 42m and 2m at 3.22g/t Au from 66m
- AANR0032: 10m at 1.78g/t Au from 108m including 6m at 2.78g/t Au from 112m These results continue to build the Lily Albany story
The RC program aimed to extend gold mineralisation in the oxidised zone, whilst the diamond drilling aimed to define controls on the primary gold mineralisation.
These results further confirm continuity of the extensive saprolitic gold mineralisation with gold mineralisation open in every direction.
2020 Drilling Highlights
RC drilling at Aphrodite North within the Bardoc Tectonic Zone (BTZ) intercepted significant gold mineralisation in newly-defined mineralised lodes.
- AANR0001: 6m at 3.60g/t Au from 44m from the West 2 Lode
including 2m at 9.99g/t Au from 44m
and 8m at 4.94g/t Au from 172m to 180m EOH in Main Lode
including 4m at 9.42g/t Au from 172m
- AANR0002: 10m at 1.52g/t Au from 76m from the East 2 Lode
and 2m at 0.63g/t Au from 226m to 228m EOH from Main Lode
- AANR0004: 12m at 0.73g/t Au from 160m (lode to be determined)
including 2m at 2.39g/t Au from 162m
- AANR0006: 4m at 1.01g/t Au from 140m (lode to be determined)
Holes AANR0001 and AANR0002 were stopped whilst drilling in mineralised Main Lode due to drilling difficulties associated with wet surface clays.
The second round of RC drilling completed at Lily Albany confirmed shallow to deep mineralisation, indicating vertical extent of an orogenic gold system over all depths drilled, with results including:
- AANR0008: 10m at 3.55g/t Au from 40m
including 2m at 15.50g/t Au from 44m
- AANR0009: 18m at 1.07g/t Au from 216m
including 2m at 2.45g/t Au from 218m
- AANR0010: 10m at 1.30g/t Au from 136m
including 2m at 3.06g/t Au from 136m
- AANR0014: 6m at 1.68g/t Au from 246m
Results supplement earlier reported results from the first round of RC drilling:
- AANR0001: 6m at 3.60g/t Au from 44m
including 2m at 9.99g/t Au from 44m
- and 8m at 4.94g/t Au from 172m to 180m EOH
including 4m at 9.42g/t Au from 172m
The Lily Albany gold discovery is open in all directions. The most recent drilling confirms continuity on adjacent, 80m-spaced sections, but the original widely spaced (320m line spacing) drilling from earlier in 2020 shows strong gold anomalism over the entire ~2.6km strike length of the target structures. Numerous structural and geophysical gold targets within this area are yet to be drilled, even those contiguous with Lily Albany, so investigation of the potential of the area has only just begun.
Zeus Gold Discovery
Zeus is located approximately 70km northwest of Kalgoorlie-Boulder.
During March-June 2021 assay results were received and interpreted from the 19 holes drilled for 1,150m. Highlights include (ASX release 22 June 2021):
- ABFR0321: 8m at 2.57g/t Au from 2m
including 4m at 4.35g/t Au from 4m
and 2m at 1.83g/t Au from 24m
- ABFR0317: 2m at 1.56g/t Au from 48m
- ABFR0318: 2m at 1.22g/t Au from 124m
Importantly, the result from ABFR0321, which is from only 2m depth, below shallow surface cover, represents Ardea’s second best intercept at Zeus.
Notable previous intercepts from the first program (ASX release, 13 August 2020) include:
- ABFR0303: 10m at 12.97g/t Au from 42m
including 4m at 28.25g/t Au from 44m
- ABFR0304: 6m at 2.07g/t Au from 68m
including 2m at 2.41g/t Au from 68m
and 2m at 2.52g/t Au from 72m
Importantly, these high-grade intercepts all cluster within 40m of one another. In addition to the near-surface intercept, deeper intervals at ABFR0317 and 0318 may represent the down-plunge extent of the mineralised zone.
Grafters and Lady Charlotte Gold Prospects
The Grafter gold prospect is an underexplored area, covering 3.7 x 1.5 km in the south-eastern Goongarrie Hub, located approximately 65km north northwest of the City of Kalgoorlie Boulder. Around 80% of the area is covered by transported and laterite cover and has been interpreted from a combination of field work and desk top studies as a deformed mafic hanging wall sequence highly prone to gold mineralisation. As the area was previously held by prospectors, there has been no modern systematic exploration. The Ardea exploration team have identified similar structural relationships to BTZ-BLF “structure kinks” as documented at the Paddington, Kalgoorlie and New Celebration gold camps.
During the March 2021 quarter, 16 RC holes were drilled for 1,344m to test a variety of potential infrastructure, geochemical, structural and geophysical targets. Several stand-out gold intercepts were returned from the most recent drilling at Lady Charlotte and include (ASX release 26 May 2021):
- ABFR0354: 4m at 1.12g/t Au from 50m
- ABFR0360: 12m at 5.20g/t Au from 42m
including 8m at 7.49g/t Au from 42m
- ABFR0361: 8m at 4.06g/t Au from 54m
including 4m at 6.86g/t Au from 56m
Mineralisation around these new intercepts is hosted by a Layered Mafic Complex with multiple shear zones apparent in RC drill chips. Mineralisation is open in every direction except the east. Ardea’s in-house, high resolution structural models show intersections of several structures and orientations at Lady Charlotte, but it is not yet clear which of these specific structures provides the main gold mineralisation controls. Tightly spaced follow-up RC drilling has been planned to delimit the extent of gold mineralisation and the controls on its distribution and will be considered as part of future site infrastructure drilling programs.
Like the Brighton-Grafters trend, several distinct sites were selected for RC drilling and returned anomalism that is currently being interrogated.
Further work at Goongarrie West should utilise widely spaced lines of aircore drilling to define gold anomalism and ground water distributions.
The host mafic Missouri Basalt contains significant gold deposits 20km west at the Siberia gold mining centre, and 10km north along strike at the Comet Vale gold mining centre.
High water flows were intersected in several holes at Goongarrie West which are being analysed pursuant to the current water extraction licence applications with the State authority. Additionally, the Goongarrie West area has been identified as a potential site for a rail spur line servicing the proposed plant site.
BD-X3 and BD-X4
The BD-X3 and BD-X4 targets are located south and along strike of the historic Goongarrie Gold Mining Centre immediately east of the KNP Goongarrie Hub proposed plant site in an area where the natural topography had been selected as a process water storage site and/or retention pond for water shed from the plant site.
The areas were targeted for gold assessment for several reasons, including:
- Their proximity east of the Pamela Jean and Patricia Anne nickel-cobalt-scandium laterite deposits which requires that the status of the ground be defined for infrastructure or mining purposes.
- The areas are located between 3km and 6km south directly along strike from the main Goongarrie Mining Centre, and less than 1km south of the southernmost workings at Duffer and Junction.
- The area is mostly covered by a mantle of transported material that has discouraged historic exploration.
- Analogous structures to those controlling gold mineralisation at Goongarrie are clearly defined in Ardea geophysical interpretations throughout the BD-X targets.
A first-pass aircore drill program was designed to test the weathered profile (to blade refusal), with Ardea’s standard 4m composites collected. Initial results received during March-June 2021 (ASX release 22 June 2021) are very promising and include:
- AGSA0080: 4m at 1.99g/t Au from 36m
- AGSA0086: 4m at 4.21g/t Au from 8m
Ardea has identified a particular set of structures in geophysical interpretations that are preferentially mineralised within mafic rocks (the above quoted intercepts) and show significant anomalism where the structures cross ultramafic rocks. These particular structures will be the targets for follow-up RC drill exploration efforts south along strike from Goongarrie.
Windanya Gold Prospect
Windanya is a historical gold mining centre that was operational in the 1900s. It is hosted within the BTZ, 20km south of the GNCP Scotia Dam nickel-cobalt deposit. Historic gold workings are evident on the tenement and extend as a corridor to other workings to the north and south of the Ardea tenement. The trend of the mineralised zone appears to be approximately 330˚.
Gold mineralisation appears to be focused on a marker unit designated by the Geological Survey of WA as the Big Dick Basalt and the overlying Mt Pleasant Gabbro. The location of the mineralisation, in the hangingwall of the Siberia Komatiite, is analogous to the New Boddington gold mining centre at Goongarrie, and to parts of the Ardea Zeus prospect at Big Four, which both trend around 330˚. Like these prospects, the mineralisation may well be stretched along sheared stratigraphic contacts, but also localised on minor cross-cutting structures.
Compilation and interpretation of historic data continues with records sourced for the Half Mile Reef located near the centre of Ardea’s Windanya tenure, indicating that between 1897 and 1906, 23,480 tonnes of ore were mined from an underground operation, producing 12,993 ounces of gold. This indicates a recovered gold grade of 17.2 g/t.
Compilation of historical data, including old mine plans and a long section, along with detailed interpretation of geophysical datasets was used to complete detailed geological interpretation and design a first phase RC program aimed at locating near surface gold mineralisation with open pit mining potential around high-grade plunging reefs extending from historically mined areas and remnant stope selvedge mineralisation. As a first test of Ardea’s geological model, 11 RC holes were completed for 1,196m to determine the orientation and controls on gold mineralisation around Half Mile Reef.
Ardea’s 2020 drilling has confirmed that the Half Mile Reef structure and parallel lode structures occurs at the contact of a Mafic Complex, the Mt Ellis Gabbro with the underlying Big Dick Basalt (high Mg basalt at Half Mile). The shear host is typically 50-100m drill width, although historically mined lodes were typically narrow with stope widths around one to four metres. There is a Footwall Reef which may coalesce with the main Half Mile lode structure. Additionally, there is an upper, hanging wall lode in basalt at the Mt Ellis Gabbro contact.
During early 2021 Ardea’s first diamond drill hole was completed to a depth of 862m, with up to 50% of the drilling costs to be refunded by the State Government as part of Ardea’s successful Exploration Incentive Scheme application. The hole was planned as a deep stratigraphic hole, targeting the down plunge extents of the Half Mile Reef and another 10 subparallel interpreted structures.
Observations from the drill hole logging indicate that the regolith profile consists of a mottled zone leading into goethitic upper saprolite which transitions into a ferruginous saprolite and a green lower saprolite. Between 87m to 204m the rocks are heavily faulted. The faulting is generally comprised of large zones (up to 26m) of primarily clay only material with mylonitic zones either at the base or top of the fault. Often there is quartz veining within the clay zones with sericite and biotite mica within the veins and manganese staining. Multiple mafic units have been intersected, along with zones of disseminated sulphide and quartz veining.
Assay results received during March to June 2021 Quarter have not defined any significant gold mineralisation with path finder elements currently being assessed.
Moriaty Gold and Nickel Sulphide Prospects
The Moriaty tenements, at the eastern margin of the Highway nickel laterite project are located immediately north of the GNCP tenements within the BTZ. Detailed compilation of over 50 years of historic exploration has been completed, including assessment of old mines department reports, plans and drill logs, the open file drill hole database, nickel sulphide petrology and legacy EM survey information. All historic data has been digitised by Ardea and compiled into a GIS platform with detailed geological interpretation continuing. A number of nickel sulphide and gold exploration targets have been defined, including an interpreted extension of the Mount Pleasant Sill that has seen limited historic exploration. This layered mafic complex will be one of several targets for future exploration.
The exploration data and structural review also identified GNCP process water exploration targets within bedrock structures, upon which tenure was applied for.
Big Four Gold Prospect
The Big Four gold prospect is located within the BTZ south of Goongarrie and offers an exceptional gold exploration opportunity for Ardea with high gold grades apparent in shallow geological settings. Limited historic mining around the 1920s to 1930s recovered 571.5t of ore for 10.53kg Au (~339oz Au), at an average grade of 18.4g/t Au. This gold occurrence cropped out at surface so was discovered by prospectors. Most of Ardea’s tenure is covered by shallow alluvial cover and/or the development of a laterite profile which obscures the underlying gold potential.
The most recent Ardea drill results from the Big Four area, as well as reassessed historic data, shows that strong, laterally extensive gold anomalism is present beneath the full 20km strike length of the nickel-cobalt orebodies of the GNCP. The exceptional thickness and grade of the GNCP laterite is interpreted to be directly attributable to deep and intense weathering along BTZ bedrock shear structures, particularly at the eastern contact of the Walter Williams Formation (WWF) laterite host rock with the stratigraphically overlying Siberia Komatiite.
Infill and extensional drilling completed by Ardea in January 2020 and historic data collated by the Company has enabled estimation of an Inferred Mineral Resource being 178kt at 2.7g/t gold for 15,300oz gold (0.5g/t Au cut off).
This result provides proof of concept of the gold mineralisation potential of the BTZ within Ardea’s GNCP, which elsewhere is concealed by Quaternary sediments and the overprinting nickel laterite profile.
Metallurgical composites have been prepared from the RC drill samples and are currently undergoing metallurgical testwork, confirming gravity and cyanide leach recoverable gold (no refractory gold identified). Once completed, the total gold recoveries will be available to advance discussions on monetising the Big Four Gold deposit.
Ghost Rocks Gold Prospect
Three main prospect areas have been defined at Ghost Rocks, being the Lady Isobel gold prospect, the Twelve Mile base metal prospect and Ghost Rocks Southeast gold and nickel prospect. Soil auger drilling, rock chip and geological mapping data have been used to generate drill targets around historic gold workings at Lady Isobel. A first phase drilling program targeting quartz veins subject to historic mining is planned to be completed in Q1, 2020.