Bardoc Tectonic Zone Gold Project ARL 100%
“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. On the basis of the initial results, a 2,600m follow up RC program has been designed, aiming to commence a drill out of the target zone to further define the gold mineralisation grade tenor and geometry.”
— 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 GNCP 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 GNCP is using a systematic multi-disciplinary camp-scale approach to assess the obscured greenstone sequence. For reference, the modelled GNCP 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 north-northwest orientation throughout Ardea’s granted Mining Lease, M29/426.
The Aphrodite North area was identified as a gold target following comprehensive in-house assessment, chiefly from geophysical datasets and the derived structural geological models. Ardea drilled the first regional exploration air core holes into the area in mid-2020 and defined strong gold anomalism. Prior to this, the main targets and their host structures had never been drilled.
Lily Albany is the first gold discovery in the Aphrodite North area by any company and was confirmed by Ardea during late 2020. It is located 3km east of Ardea’s 25km long line of nickel-cobalt laterite deposits that define the GNCP. Lily Albany is a proof-of-concept discovery that resoundingly illustrates the gold fertility of the BTZ within Ardea’s tenure.
In early 2021, 15 resource definition RC drill holes were completed for 2,122m and two diamond drill holes for structural interpretation and geo-mechanics were completed for 365m. The initial diamond hole was cancelled at 64m, following drilling problems and the second hole was completed to 301m. Assay results are still awaited with high demand for assay services continuing to cause delays. Structural data collected from the orientated diamond core hole will be used to refine the geological model once all assay results have been received.
RC drilling at Aphrodite North within the Bardoc Tectonic Zone (BTZ) has 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
The recent Zeus gold discovery (ASX release 9 November 2020) is located around 4km south southwest of the recent Lily Albany gold discovery and is less than 2km east of Ardea’s 25km long line of nickel-cobalt laterite deposits that define the GNCP. Zeus is located on one of the granted GNCP mining leases.
The Zeus discovery comes from a thorough reassessment of historic open file datasets that indicated strong gold anomalism that had not been adequately followed up, as historic drilling orientations were undertaken at a suboptimal orientation to the gold mineralisation trend. Following Ardea’s rigorous in-house reinterpretation and targeting process, a new south-westerly drill direction was defined and gold lode orientations determined.
Ardea assay results 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
Historic assay results include:
- SCR0806: 9m at 4.23g/t Au from 67m (April 1999)
including 1m at 17.50g/t Au from 68m
- SCRC0310: 8m at 3.52g/t Au from 17m (July 1999)
Analysis of historic data and Ardea’s detailed geological interpretation of the area suggests that gold mineralisation around Zeus may extend for over 1,000m of strike length.
Gold anomalism encountered in historic drill holes up to 750m to the northwest and up to 250m to the southeast is consistent with the magnetic datasets and their derived interpretations. These show a distinct NW trending shear zone extending the full length of this trend that cross-cuts the Siberia Komatiite stratigraphy and coincides directly with the historic gold anomalism. Available data indicates that the host shear zone is approximately 50m wide, so the emerging discovery has scale potential and is a priority for follow-up exploration.
Grafter gold prospect
The Grafter gold prospect is an underexplored area, covering 3.7 x 1.5 km in the south-eastern GNCP, 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 hangingwall 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.
A modest “toe in the water” first-pass RC exploration program has commenced at Grafter to test three different types of target (A / Lady Charlotte, B and C), with the knowledge gained to be used to continue to refine the exploration targeting approach on concealed BTZ gold targets. Two RC holes were completed at Lady Charlotte in July 2020. The initial RC result from ABFR0286, 8m at 6.57g/t Au from 24m, is an excellent start to the first round of gold exploration drilling at Grafter. This intercept is interpreted to represent high grade supergene mineralisation, with the primary lode position and orientation to be defined by follow-up RC drilling.
Work is ongoing in the area to better define the controls on gold mineralisation, with initial observations supporting this area as being highly prospective for hosting orogenic gold mineralisation and including:
- As at Lily Albany, Lady Charlotte high grade intercept occurs within a Layered Mafic Complex (LMC).
- As at Big Four and Zeus, there is a diagnostic alkaline intermediate association (assumed to be an intrusive alkaline diorite based on grain size).
- Localised on the north northwest striking regional Brighton Grafters Trend.
The learnings from the first phase drilling program have been included in refining targets for future exploration that will be ranked against other targets to ensure that the Company prioritises the top ranked projects.
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 the March 2021 Quarter 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. The drill hole will be logged in detail, sampled, and dispatched to the assay laboratory. Once results have been received a detailed interpretation can be completed.
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.