The Black Range Project (124km2) includes multiple, largely untested, targets over approximately 100 kilometres of Stavely Arc volcanics, including the Eclipse, Lexington, Glenlyle and Pollockdale prospects. The volcanics within the Project area are mostly concealed by more recent cover rocks. Small windows of basement exposure have led to the discovery of a number of copper and gold prospects such as Eclipse, Lexington and Pollockdale.
The Stavely Arc is recognized as a series of volcanic rocks deposited within a continental margin arc setting, similar to the Andes in South America and host to some of the world’s largest known porphyry copper deposits.
Historic work programs, completed by Navarre, have targeted large volcanic-hosted massive sulphide (VHMS), porphyry copper – gold and epithermal deposits within the region and have successfully intercepted mineralized units within defined geological settings.
Review and research by Navarre has concluded that the area of potential mineralisation is large, as a 4km long volcanic basin has been defined and is modelled to have potential for Cu / Au and base metal sulphide mineralisation. A series of geophysical surveys and geochemical reviews have confirmed anomalous zones and exhibiting high levels of hydrothermal alteration.
The Black Range Project is located within the Mount Stavely Volcanic Complex (MSVC), considered an analogue of the Mt Read Volcanics in Tasmania, which is host to:
- Mount Lyell (1.8Mt Copper / 2Moz Gold)
- Rosebery (1.1Mt Lead / 820kt Zinc / 115kt Copper / 110Moz Silver / 2Moz Gold)
- Henty (1.2Moz Gold)
The MSVC is classified into the Grampians – Stavely Zone in western Victoria. The Moyston Fault separates the Delamerian Grampians – Stavely Zone, to the west, from the Lachlan Fold Belt containing the Victorian goldfields to the east. West of the Moyston Fault are fault-bounded belts of Mount Stavely Volcanics within a sequence of quartz-rich turbidites (Glenthompson Sandstone) deforming during the Late Cambrian period to form the basement of the Grampians-Stavely Zone.
The Dalamerian rocks are unconformably overlain by an Ordovician-Silurian shallow marine to fluvial sequence of the Grampians Group. The Mount Stavely Volcanics consists of a basal ultramafic unit and then a suite of andesitic lavas at the base of the pile, conformably overlain by felsic volcanics/tuffs, shales and sandstones, with plugs of tonalite and rare slices of ultramafic rocks.
The Black Range Project captures three fault-bound segments of the Stavely Arc volcanics. The Project area includes the advanced Eclipse prospect where a supergene blanket of enriched copper (chalcocite) mineralisation is developed above widespread copper, gold and zinc mineralisation, interpreted to be associated with a potential volcanic-hosted massive sulphide source.
In 2014, Navarre undertook an induced polarisation (IP) geophysical survey which highlighted a large anomaly beneath the shallow chalcocite mineralisation that is also coincident with a gold-in-soils anomaly. The IP target zone was wide and extended under areas of cover adjacent to the chalcocite mineralisation that had been confirmed by a prior series of reverse circulation drill holes. A portion of this target has had a small diamond drill program (3 drill holes for 1,497m) completed to depth and anomalous gold, copper and other base metals have been intercepted. Within the diamond drill core, clasts of massive sulphides were noted indicating the possible proximal nature of the works to more in situ ores deposited within a VHMS. All drill holes were limited to the area of chalcocite outcrop, and as such did not test many areas with cover rocks and as such was limited in its scope. Further work is required to determine size and extent of the mineralisation and to define further exploration targets.
On completion of the Transaction, the Company will undertake exploration, pre-feasibility studies and bankable feasibility studies on the Black Range Project in order to demonstrate the commercial viability of a mining operation. The Company will also undertake appropriate due diligence and pursue suitable transactions on identified projects that meet the Company’s growth strategy, with a view to growing the Company’s asset portfolio. Such identified projects will be synonymous with the Company’s main undertaking of mineral exploration and development.
Set out below are the high level indicative key steps (in chronological order) as part of the Company’s strategy to establishing a mining operation at the Black Range Project:
- preliminary on ground exploration activities (including sampling, trenching mapping and geochemical surveys);
- establish an initial Inferred JORC compliant resource from existing geological data in Year 1;
- 1st and 2nd year drilling campaigns;
- establish an initial JORC compliant resource.
Recent diamond drilling at the Eclipse Prospect targeted historic supergene chalcocite mineralisation to identify the primary sulphide source of copper mineralisation. An IP survey was conducted over the prospect area and three diamond drillholes were undertaken to test a coincident chargeability high.
Drilling identified VHMS style polymetallic mineralisation concentrated on three stratigraphic horizons, Horizons A, B and C. Mineralisation occurs as stratiform style VHMS mineralisation favouring shale beds or is clustered around rhyolite domes in the eastern portion of the project area. Massive sulphide clasts were observed in epiclastic units at various locations in drillhole ED003 which suggest massive sulphide mineralisation is more widespread than primary examples intersected in the vicinity of drilling.
- Felsic bimodal volcanics showing a westward progression from felsic to mafic dominated mixed sequence stratigraphy.
- Massive sulphide mineralisation and clastic sulphides with chalcopyrite and sphalerite representation.
- Syn-sedimentary sulphide mineralisation intersected in ED001 and ED003 is progressively becoming more concentrated towards the north.
Evidence of a northward progression from a high energy to low energy depositional setting.
- Widespread acid alteration dominated by chlorite and sericite development.
- Strong lithogeochemical anomalism indicating proximity to potential economic mineralisation, including Na depletion.
- Alteration appears concentrated within three main target zones, with Zone B showing a footwall alteration halo of approximately 100m thickness. This feature is typical of sub-seafloor replacement type VMS deposits such as Rosebery and Hercules in western Tasmania.
- High resolution airborne magnetic data shows a regional V-shaped feature containing the Eclipse prospect. It is reasonable to consider this as a graben feature younging to the west to guide future exploration activities.
EL4590 was granted 14th February 2007 for 767 graticules and has undergone 4 partial relinquishments in 2009, 2011, 2014 and 2017. The remaining area of the tenement is 124 graticules which are primarily focused on regional magnetic defined extensions of the Stavely Arc Volcanic Belt in the region. The tenement is due for renewal on 14 February 2022.
The annual expenditure commitment for the remainder of the licence term is $77,000 per annum.
Resource Base plans to convert the EL into a retention licence, granting up to a further 10 years.
- EL4590 which forms the Black Range Project will expire in 2022, with continuing exploration to be completed under a Retention License.
- The Retention Licence is a “halfway” tenement between an Exploration and a Mining Licence, providing the tenement holder with up to a further 10 years to complete the exploration works.
- Application for a Retention Licence requires a small existing resource (which is currently the case within the Eclipse location – Cu/Au near surface resource), and a “Mineralization Potential” report to be submitted with a proposed budget for the exploration works planned.
- Development of a small JORC compliant inferred resource and the “Mineralization Potential” report can be completed in a matter of weeks and would form part of the preliminary exploration works being undertaken by Resource Base.
- Submission would be prior to the relinquishment of the Exploration Licence – this ensures continuity of ownership and exploration works.
- As all conditions can be met there is no expectation for any delay with the granting of a Retention Licence for a period of time that would match the budgeted works submission.
First Geophysical Survey
On 18 November 2021, Resource Base announced that it had completed its first Gravity and IP/Resistivity Geophysical survey programs at the Black Range Project (EL4590).
The Preliminary results from the Gravity and IP/Resistivity geophysical survey programs identified numerous target areas to be tested.
Plans are underway for initial investigation using air-core drilling which aims to confirm:
- Bedrock geology hidden below shallow transported cover and Grampians Sandstone units;
- The presence of slight geochemical anomalies over geophysical targets; and
- Vital geological and mineralogical data for planning the maiden diamond drilling program.
The survey programs were designed to test the priority target area between the Eclipse and New Moon prospects, over Mt Stavely Volcanic Complex (MSVC) rocks which host the Eclipse prospect. Preliminary results have identified a number of IP and Resistivity features which will be targeted in the search for copper, zinc, lead, gold and silver and tested in due course as part of the Company’s broader exploration strategy.
Initial Results & Targets
Induced Polarisation (IP) surveys are utilised in the search for Volcanic Hosted Massive Sulphide (VHMS) and Porphyry style deposits for their ability to map the distribution of metal-sulphide minerals hundreds of meters below the ground surface.
Preliminary gravity data has been received and has proven useful in understanding geology of the Eclipse Prospect area, particularly under Grampians Sandstone cover and when combined with magnetic data it has been important in understanding the IP/Resistivity data.
Combined interpretation of IP/Resistivity, Gravity and Magnetic geophysical data sets has identified a new zone of interest on the western margin of the Eclipse Basin, see the following figures.
This area appears to be a transitional zone where significant changes in the chemical composition of volcanic rocks occur and there is transition from volcanic to sedimentary geological processes. These features are commonly important in the formation of VHMS deposits.
As the following figures show, within this volcanic-sedimentary zone there are a number of highly anomalous IP and Resistivity features, potentially related to accumulations of metal sulphide minerals and volcanic derived hydrothermal alteration.
Given the known association of metal sulphides and hydrothermal alteration to VHMS and Porphyry deposits and the location of these geophysical anomalies in this transitional basin margin setting, these targets are considered extremely interesting.
Figure 7 demonstrates intense IP targets shown as coloured iso-surfaces located in the volcanic to sedimentary transition zone of the inferred volcanic graben structure. This is an important geological setting for development of VHMS mineralisation, making these targets a very high priority for bedrock drill testing. Magnetic features related to volcanic rocks shown as red wireframe. Map grid values shown are GDA94 MGA54 datum.
Figure 8 shows coherent, linear resistivity anomalies paralleling geological strata. Resistivity targets shown as coloured iso-surfaces located in the volcanic to sedimentary transition zone of the inferred volcanic graben structure are highly encouraging. Magnetic features related to volcanic rocks shown as red wireframe. Map grid values shown are GDA94 MGA54 datum.
Geological and project-wide reviews have been conducted by Crawford (2010), McNeill (2012), and Holliday (2014). Each of the project reviews are detailed and comprehensive in nature and consider the project area in the context of geological setting comparability to the Mt Read Volcanic Belt of western Tasmania, and exploration target deposit styles for porphyry Cu exploration or VHMS exploration strategies. Each review lists exploration activities conducted and historic drilling and sampling at the time of reporting.
A lithological assessment was conducted by McGilvray (2020) which established a stratigraphic column and aided in identification of volcanogenic basin architecture based on current drilling with confirmation of a VHMS deposit style to mineralisation.
McNeill (2012) and Holliday (2014) each conducted a thorough review of geophysical surveys and data completed over the eclipse prospect area with recommendations to advance the understanding of the area further.