|Location||Bendigo Region, Victoria, Australia|
|Development Stage||Reconnaissance AC drilling|
|Acquired||Staked in 2017 and since expanded|
The 100%-owned Pyramid Hill Gold Project is a district scale holding comprising an extensive 5,190km² area located in northern Victoria, Australia. The Project encapsulates approximately 60% of the northern Bendigo Zone, which is covered by variable Murray Basin cover, and is one of the most exciting, underexplored high-grade gold provinces worldwide.
The Project comprises three key districts centred around the northern Bendigo Zone: the Muckleford, Mt William and Percydale areas.
- The central Muckleford Area extends to the north-west of the high-grade historic >22Moz @ 15g/t Au Bendigo Goldfield.
- The Mt William Area extends to the north-east of one of the world’s highest-grade producing gold mines, the >8Moz Fosterville Gold Mine owned by Kirkland Lake Gold (NYSE / TSX: KL | ASX: KLA).
- The Percydale Area is located north-west of the historic St Arnaud Goldfield within the Stawell Zone.
The region has extensive established infrastructure including HV power, sealed roads and rail. There are currently two commercial scale mining operations in the region at Fosterville and Stawell.
The Murray Basin covered northern Bendigo Zone has largely flat topography and in most areas the primary land use is agriculture. Chalice has access agreements in place with private land owners where necessary to conduct exploration and drilling into the underlying Bendigo Zone geology.
The Bendigo Zone of Victoria has produced >60Moz of high-grade gold. The region has been mined since the mid nineteenth century, however is now capturing global attention once again, largely due to Kirkland Lake Gold’s new ultra high-grade discoveries at depth at Fosterville.
Historically, all gold production in the region has come from fields with outcropping geology (easy to find), such as Bendigo (~22Moz @ 15g/t Au); Ballarat (~14Moz @ 12g/t Au) and Castlemaine (~6Moz @ 13g/t Au).
The "Gold Undercover1' initiative by the Victorian Government estimated a potential ~32Moz (P50 mid case) of undiscovered gold beneath Murray Basin cover in the northern Bendigo Zone.
|No. of significant goldfields undercover||15||25||32|
|Undiscovered gold endowment (Moz)||9||32||58|
- Monte Carlo simulation model used to extrapolate known gold endowment in outcrop areas into the 7,000km2 northern Bendigo Zone undercover
- Model limited to 1km depth and ignored potential undiscovered gold in outcrop zones
- Model was created prior to the epizonal ultra high-grade gold discovery at depth at Fosterville, hence is likely to be conservative
Limited undercover exploration by previous explorers over the last two decades has confirmed the Bendigo Zone geology extends to the north, however it remains poorly explored presenting a significant opportunity for new large-scale, high-grade gold discoveries.
The region has two significant undercover discoveries thus far; Four Eagles (Catalyst Metals and Hancock Prospecting JV) was discovered in 2011 and Tandarra (Catalyst Metals and Navarre Minerals JV) was discovered in 2007. Both discoveries are in advanced exploration stage and demonstrate that undercover exploration can be successful.
REGIONAL GEOLOGY AND MINERALISATION
The Bendigo Zone is located within the Lachlan Fold Belt, one of the major components of the Tasman Fold Belt System. Geologically, the Bendigo Zone is located between the Avoca and Mount William Faults which separates the Stawell Zone to the West and the Melbourne Zone to the East and is largely composed of turbiditic sediments (typically sandstones and shales) of the Castlemaine Group which is host the majority of gold deposits.
The Stawell and Bendigo Zones were deformed during the Benambran Orogeny, a lengthy interval spanning the Late Ordovician (c.460-444Ma) and Silurian (c.444-419Ma). The Melbourne Zone by contrast escaped this Ordovician-Silurian deformation and continued to receive sediment until it was eventually deformed during the Middle-Devonian (c.380-370Ma) during the Tabberabberan Orogeny.
The structural style across the Bendigo Zone is relatively uniform, controlled by relatively simple east-west oriented compression and characterised by simple, upright, tight chevron folding. Widespread post-tectonic plutonism occurred during the Early Devonian (c.410-400Ma) which played only a very minor role in deformation across the region and is not associated with any significant gold events.
Orogenic gold deposits within the Bendigo Zone are diverse and often complex but share similar origins and geological characteristics. Mineralisation was episodic during the Ordovician-Silurian periods (460-420Ma) driven by crustal heating during the Benambran Orogeny, from the beginning of fold development to late stage tectonic faulting.
The surface footprints of major gold deposits in the district are commonly narrow but strike extensive and can occur over multiple kilometres. Typically, major deposits are located within the hanging walls of, but distal to, major crustal scale structures which are themselves not mineralised. These regional structures have been interpreted from 2D seismic surveying completed by Geoscience Australia and provide an important structural framework for exploration activities.
At the deposit scale, high-angle secondary reverse faults and dilational cross structures served as conduits for the mineralising fluids. In addition to the fault-controlled mineralisation, where accommodation occurs at the apexes of tight fold hinges, mineralisation can occur as stacked ‘saddle’ or ‘trough’ reefs as commonly seen within the Bendigo area.
Chalice is targeting large-scale, high-grade gold deposits, and commenced its regional scale greenfield exploration program in mid 2018. Due to the variable and in some cases poorly mapped cover depth and predicted economic constraints, Chalice’s initial focus is on areas with <150m of cover.
The Company has adopted a systematic approach to undercover exploration, utilising the high quality regional geophysical, geological and geochemical datasets generated by the Victorian Geological Survey and previous explorers.
Regional soil sampling, ground gravity geophysics as well as predicted structural corridors were initially used for targeting the first phase of reconnaissance drilling on widely spaced drill lines (3-7km apart). The Company sourced a multi-purpose, high-capacity AC/RC drill rig for the initial phase of reconnaissance drilling. This rig has been very successful in reaching the target basement in >95% of drill holes and is a very cost-effective reconnaissance exploration tool.
~39,000m of reconnaissance AC drilling was completed over the 2018/2019 season and this initial phase of exploration was designed to provide reconnaissance-level shallow drill testing of targets defined from a combination of soil geochemistry, gravity and structural interpretation. The results of this initial phase of drilling are now being utilised to identify areas of anomalous gold and associated pathfinder elements providing potential vectors to large-scale gold mineralised systems.
A ~24,500m Phase 2 reconnasissance air core (AC) drill program commenced in late Q3 2019 as a follow up to targets identified from Phase 1 drill testing.
Three new large-scale targets have been outlined in the Muckleford Area following the completion of Phase 1 drilling.
The Ironbark, Karri and Beech Targets contain shallow drill intercepts of anomalous gold and/or pathfinder metals from within the highly weathered top of the basement directly beneath the Murray Basin cover. Drilling has mostly intersected Castlemaine Group sediments, which are the main host rock to gold deposits in the Bendigo Zone, as well as other prospective rock types including diorite intrusives. The intersection of anomalous gold within basement shows that gold is likely sourced from primary mineralisation:
- Ironbark Target shallow gold intersections up to 1.1g/t Au under 35-75m of Murray Basin cover, within a ~380m diameter diorite intrusion, coincident with a large >5ppb gold-in-soil anomaly (Walhalla-Woods Point style target).
- Karri Target shallow gold intersections up to 0.66g/t Au over ~15km of strike, under 50-70m of Murray Basin cover, ~20km west of Four Eagles (typical Bendigo style target).
- Beech Target outlined by highly anomalous As and Sb (gold pathfinders) in basement, ~25km north-west of Bendigo (~22Moz Au) along the Sebastian Fault.
Similar shallow, anomalous gold intercepts on wide-spaced drill lines has led to significant gold discoveries under cover by other explorers in the region.
Phase 2 drilling is currently underway in the Muckleford area, and is designed to test these promising targets. Assays have been received for 4,038m of AC drilling completed to sate at the Ironbark target, and results indicate an extensive gold and arsenic footprint. Anomalous gold has been intersected in shallow drilling over an area of ~500m x 500m, both within weathered diorite and overlying Castlemaine Group sediments.
Future Work - Ironbark
An additional 3,000 - 5,000m of AC drilling is planned for the Ironbark Target in Q4 2019 (Phase 3) to in-fill and extend drill coverage on several existing drill sections and to step-out along strike to further refine the footprint of gold anomalism and to test structural zones of interest. Planning for a follow-up diamond drilling has also commenced.
The Pyramid Hill Gold Project was staked in late 2017 and is 100% owned.
1) Lisitsin, V., Olshina, A., Moore, D.H. & Willman, C.E., 2007. Assessment of undiscovered mesozonal orogenic gold endowment under cover in the northern part of the Bendigo Zone. GeoScience Victoria Gold Undercover Report 2, Department of primary Industries.
iAdapted from Arne, D.C., House, E. & Lisitsin, V., 2008. Lithogeochemical haloes surrounding central Victorian gold deposits: Part 1 – Primary alteration systems, Gold Undercover Report 4. Department of Primary Industries, Victoria.