Highlights
- Targeted VTEM Diamond Drilling programme penetrates DeGrussa Style mineralised system at the Revere Gold Project
- 3 Holes (1038m) Diamond Drilling complete over 8.5km Target Area
- REV-01 – 400mts
- REV-04 – 302mts
- REV-05 – 336mts
- Portable XRF results indicate up to 5.7% Copper and up to 4.2% Zinc at varying intersections
- Mafic breccia, volcaniclastics and shales with chalcopyrite, sphalerite and pyrrhotite/pyrite intersected in various intervals[1]
- Core currently being prepared for assay
- Expedited Downhole Electromagnetic Survey completed and awaiting results for next drill program
- Additional Drilling Rig mobilisation underway to support accelerated extension of current program
Commenting on the drilling results at the Revere Gold Project, Chief Operating Officer Simon Philips said:
“To drill into such a large mineralised system on our first pass drilling is significant and highlights the potential of the target area. The first three diamond drill holes were designed to test electromagnetic conductors identified as having the potential for Volcanic Hosted Massive Sulphides at depth. The similarities in geological sequences when compared to the Sandfire (ASX: SFR) DeGrussa VHMS deposit is geologically very significant. We look forward to assays and downhole EM surveys to guide us on further testing the system.”
Everest Metals Corporation Limited (ASX: EMC) (“EMC” or “the Company”)is pleased to provide the first update from its deep drilling program, designed to test the copper and gold potential at the Revere Gold Project (“RGP”) in Western Australia.
BACKGROUND
The project is located just off the Great Northern Highway approximately 90km to the northeast of Meekatharra in the Murchison Region of Western Australia and 900km north of Perth. The tenement package size, including the tenements under option cover an area of 82km2. This is comprised of granted tenements E51/1766, E51/1770, P51/3240, P51/3241, and pending applications M51/905, E51/2119, E51/2088 and E51/2088 (Figure 1). The project sits proximal and along strike of the DeGrussa and Monty Copper-Gold mines, just 55km to the southwest.
Figure 1: Revere Gold Project location
The Revere Gold Project is located in the Palaeoproterozoic Yerrida Basin – Doolgunna Formation. The alteration system appears to represent a classic precious metal ductile shear system – the Revere Reef System – that is associated with the Capricorn orogenic event. The historical geochemical anomaly is interpreted to represent hydrothermal mineralisation. Visual observations of the lode material from the Revere Reef indicate that coarse visible gold is contained within gossan iron oxide which forms the matrix of the quartz breccias.
Field assessment by Enterprise Metals (2009-2017), Mineral Commodities (2018-2021), and recent technical review and data interpretation by EMC demonstrated the potential of the Doolgunna formation to host DeGrussa-style Volcanic Hosted Massive Sulphide (“VHMS”) and Plutonic-style orogenic gold deposits. At depth, the anomalous high copper, zinc, and arsenic values indicate the potential for a DeGrussa type copper-gold deposit below the zone of complete oxidisation. Copper and even gold lodes in the region are generally shear hosted shoots, narrow and long, comprised of high-grade lodes. The DeGrussa deposit was discovered in follow up drilling of a zone of oxide gold mineralisation similar to that found at the Revere Gold Project.
The Company carried out remodelling and re-interpretation of the historic geophysical data using up to date technology – the results highlighted the potential of VHMS copper-gold mineralisation within the RGP[2]. The new model targets a discrete conductor that coincides with a discrete magnetic anomaly and suggests possible pyrrhotite mineralisation. Chalcopyrite and sphalerite are not strong conductors, and their conductance mostly depends on concentrations of associated pyrrhotite. The modelled conductive plates identified new target areas adjacent to previously drilled conductors. Data from the VTEM survey indicates that this discrete conductor strikes northeast. The strongly conducting nature of the EM anomalies suggested that they were either massive sulphide or highly graphitic bodies. Considering the anomalies are hosted in a sedimentary package, and the proximity to the target stratigraphy is conformable to reduced facies and could be shale. A Significant conductor was defined immediately north of the Revere Reef, south of DD Reef, and southwest of Tree quartz Reef (Figure 2). The current drilling program is designed to test the separate plate conductors which are considered to be priority targets, a deep hole in each reef system.
Figure 2: Location of three deep holes at Revere Project over EM conductors from VTEM Survey
DRILLING UPDATE
Three diamond deep holes (REV-01, REV-04 and REV-05) for a total of 1038.4 meters completed at Revere Gold Project and sulphide mineralisation intersected in all holes.
In relation to the disclosure of visual mineralisation of base metal bearing sulphides in the core have been included in this release including photos, table and commentary for geological context, the Company cautions that visual estimates of mineral abundance should never be considered a proxy or substitute for laboratory analysis. Laboratory assay results are required to determine the widths and grade of the visible mineralisation (if reported) in preliminary geological logging.
HOLE 1 (REV-01)
The first diamond hole was completed to a depth of 400.1m. REV-01 was located at 7127034mN and 700697mE, approximately 350 meters from the Revere costean. This was the first diamond hole in the tenement package – This was a step-out program of diamond drilling designed to test electromagnetic conductors at depth. Hole REV-01 was inclined at 60 degrees to the southeast (azimuth 115 degrees).
The logging of the first drill core has redefined the stratigraphy within the project area and highlights key stratigraphic horizons within the project area that are known to host DeGrussa-style VHMS copper-gold mineralisation. REV-01 intersected a thick package of interbedded siltstone, sandstone, basalts, mafic breccia, interbedded green-grey shale, graphitic black shale, quartz veinlets containing sulphide mineralisation dominated by pyrrhotite, pyrite, and trace chalcopyrite and sphalerite.
A section in excess of 25m of mafic breccia chlorite-epidote alteration containing pyrrhotite and pyrite and minor chalcopyrite was observed from 305m followed by approximately 58m of graphitic black shales displaying the same mineralisation (Figures 3 and 4). It seems both mafic breccia and sulphide- rich interbedded green-grey shale/ graphitic black shale are the source of the aeromagnetic anomaly.
Figure 3: Examples of field observation of sulphide mineralisation (pyrrhotite, pyrite and chalcopyrite) in diamond hole REV-01 (A: 334m, 0.5% Cu, B:354m, 0.2% Cu, C:346m, 0.3% Cu)
The amount of sulphide and the relative proportions of the sulphide species from metre to metre are highly variable and a detailed estimate of this variability is not possible within the limits of acceptable accuracy (Table 1). The metal grades of the core shall be determined by assay. The sulphides occur as fine disseminations and randomly oriented, penetrative veins and blebs.
Figure 4: An example of mafic breccia with chlorite-epidote alteration and disseminated pyrrhotite/pyrite mineralisation (Rev-01, 313.5 to 315.8m)
HOLE 2 (REV-05)
The second hole was drilled at Tree Reef to a depth of 336.1m. REV-05 was located at 7124896mN and 702500mE, approximately 60 meters northwest of the Tree Revere costean. Hole REV-05 was inclined at 60 degrees to the southeast (azimuth 135 degrees). The first 114m of the hole contains a series of oxidised siltstone with chlorite alteration about followed by 16m of volcanoclastic breccia with a fragment of quartz appearing before 64m of banded basalt. Banded mafic and ultramafic rocks and stromatolite graphitic silicified dolomite with disseminated sulphides and numerous quarts-carbonate veinlets were the last intersected geological unit in this hole. Significate chalcopyrite, pyrite, and pyrrhotite were observed in different intersections over 80m along with sphalerite mineralisation e.g., 1.9% Cu at 280.8m depth, and 5.7% Cu and 4.2% Zn at a depth 314.9m (Figure 5 and Table 1).
Figure 5: Significant mineralisation in REV-05 core, A: disseminated chalcopyrite and sphalerite (314.9m, 5.7% Cu and 4.2% Zn, B: chalcopyrite (280.8m, 1.9% Cu)
HOLE 3 (REV-04)
The third hole was drilled at DD Reef, near the southern boundary fault to a depth of 302.2m. REV-04 was located at 71131140mN and 700630mE, inclined at 60 degrees to the west (azimuth 270 degrees). Breccia zone of quarts-dolomite clasts in a white clay matrix intersected from 115m with numerous disseminated pyrite. Then a massive sulphide (pyrite and pyrrhotite) in the graphitic hydrothermal alteration zone appeared for over 30m (Figure 6). Cu elevated up to 210 ppm and Zn at 440ppm in this section. Well-developed disseminated pyritic zone along chloritized veins and fractures zones placed in dolomite with banded alteration layers intersected from 194 m to the end of the hole. The laboratory assay data of mineralised sections will be reported by the Company.
Figure 6: Significant Massive sulphides (pyrite and pyrrhotite) in graphitic hydrothermal alteration zone in REV-06 core, 162.5-162.9m
PORTABLE XRF RESULTS
Hand-held Olympus Vanta X-Ray Florescence analyser was used to assist in the visual identification of ore mineralogy and lithology. Portable XRF readings were completed on the drill core in various locations to assist with the geological logging. The XRF has highlighted a volume of elevated copper, zinc, and lead mineralisation. Laboratory assays for these holes are pending with results expected to be received by September 2023. Details of REV-01, REV-04 and REV-05, spot pXRF value and estimate of the abundances at each interval are detailed in table 1.
Whilst disclosure of visual occurrences of coarse base metal bearing sulphides in the core have been included in this release, in photos, table 1 and commentary for geological context, the company cautions that the visual identification, estimates of mineral abundance, or point pXRF measurements should never be considered a proxy or substitute for laboratory analyses. Visual estimates also potentially provide no information regarding impurities or deleterious physical properties relevant to valuations provided by laboratory assay. Core cutting and sampling has not been done yet, the Company will update the market when laboratory analytical results become available.
Table 1- Details of diamond drilling completed at Revere, significant intercepts and pXRF results
GEOLOGICAL INTERPRETATION
Mineralisation intersected on all three holes over 8.5km target area at Revere project. Geological logging (lithology, mineralogy, alteration, and structure) of the three drill holes at Revere represent the same stratigraphy Mooloogool Group in the Yerrida Basin that hosted the world class Monty, Taduna and Green Dragon deposits (Figure 7). All of which also have a strong synergetic relationship with the DeGrussa copper-gold deposit. The area being investigated have proved to be highly prospective for sediment or volcanic hosted copper sulphide deposit due to the following key elements:
- The drill target areas are associated with a well-developed and proven near surface hydrothermal and mesothermal gold system (Revere Reef and Tree Reef systems), that potentially reflect an oceanic volcanic rift shear at depth.
- The intersected formation at depth (REV05) represents black turbiditic carbonate rich shales and intrusive tholeiitic basaltic layers in close proximity to volcanic breccia with hydrothermally mobilised copper-sulphides. This formation not only correlates with the above deposits’ host rock but also complies with the classic VHMS target model.
Associated with the above intersected sediments, volcaniclastic breccia, peperitic mafic basalt and turbiditic sediments with chlorite, sericite, graphitic and silicic alterations and disseminated sulphides, rock typical of the other copper deposits in this region. Noteworthy, REV-01 and REV-04 are about 8.5km apart, and the geological similarities of both holes indicate a large mineralisation system may occur at Revere.
Figure 7: Map showing location of Revere deep holes and the historical copper mines in the area including DeGrussa, Monty, Green Dragon and Thaduna
PVC casing was inserted into drill holes to allow for a downhole transient electromagnetic (“DHTEM”) survey. Recently, the DHTEM survey completed, this allowed to search around the holes at depth for any other conductors potentially indicative of massive sulphide mineralisation.
A summary of important assessment and reporting criteria used for this Exploration Results announcement is provided in JORC Table 1 in accordance with the checklist in the Australian Code for the Reporting of Exploration Results, Mineral Resources, and Ore Reserves (the JORC Code, 2012).
NEXT STEPS
- The next stage of drilling will see two new holes at the Revere Reef prospect. The target depth of the hole is approximately 300 metres.
- DHTEM survey results in early August 2023.
- Assays due early September 2023.
[1] In relation to the disclosure of visual mineralisation, the Company cautions that visual estimates of mineral abundance or point pXRF measurements should never be considered a proxy or substitute for laboratory analysis. Laboratory assay results are required to determine the widths and grade of the visible mineralisation (if reported) in preliminary geological logging.
[2] ASX: EMC announcement; Geophysical Modelling Identifies Deep Drilling Targets at Revere Gold Project, dated 7 March 2023
