High-grade nickel sulphide deposits at Lanfranchi occur as ribbon-like shoots at the base of high magnesium komatiite lava flows or channels. The shoots and high-magnesium lava flows occupy channel structures developed in the underlying Lunnon (footwall) basalt. Above the high-magnesium komatiite flows is a thick sequence of progressively less magnesium-rich komatiite flows. Ten channel structures are recognised at Lanfranchi of which six have been mined historically.
Historically, the majority of the ore has been mined via long-hole open stoping, which is a highly mechanised and low cost method. Using this method, access to the top and bottom of the ore block is established with tunnels, a slot raise is created, and holes are then drilled to blast the ore block. Once the ore block has been blasted and extracted, the stopes are filled with paste (tailings and cement mix) to stabilise the void and allow extraction of adjoining ore blocks.
Under Panoramic’s ownership and over a ten year mining period between 2005 and 2015 (until the mine was placed on care and maintenance), Lanfranchi produced a total of 3.85Mt of ore at an average grade of 2.45% Ni for 94,196t Ni.
Any ore produced from the Lanfranchi Project is processed through the BHP Billiton Nickel West Kambalda Nickel Concentrator under the Ore Tolling and Concentrate Purchase Agreement until February 2019.
In January 2015, the company announced it had intersected three significant zones of high-grade nickel sulphide mineralisation down-plunge of the Schmitz orebody (Lower Schmitz) in drill hole SMT373A:
- 6.10m @ 5.73% Ni from 482.90m
- 6.80m @ 5.02% Ni from 525.30m
- 6.50m @ 6.11% Ni from 550.54m
These intersections are only ~300m from the existing Deacon development. EM anomaly modelled as a single highly-conductive 300 x 100 conductor, open to the south and the latest drilling extends EM 100m to the north.
The development of the access drive from the existing Deacon orebody was completed in August 2015 to allow Resource drilling which has also been completed.
A Maiden Resource of 131,000t @ 5.1% Ni for 6,700t Ni contained was announced in the March 2016 Quarterly Report. A plan and sectional view, showing the shape of the Resource are presented below.
Deacon Channel Extension
The Deacon channel is the largest known channel in the Lanfranchi system. The Deacon channel is open at depth, with EM surveys indicating a number of large off-hole conductors down-plunge of the known mineralisation. A drill program to test the identified EM conductors down-plunge at Deacon intersected some significant mineralisation including:
- HS692 24.0m @ 1.42% Ni
- HS711 14.77m @ 1.71% Ni
- HS713C 3.23m @ 4.28% Ni
Panoramic will continue to drill test down-plunge of the Deacon Channel when suitable drilling positions are available.
In January 2012, Panoramic discovered a new zone of mineralisation down-plunge of the Skinner Orebody, known as the Jury-Metcalfe Zone. The zone remains open both up and down plunge and is readily accessible from the existing Schmitz decline. Results from the initial drilling include:
- 39.50m at 1.79% Ni (SMT221)
- 34.18m at 1.93% Ni (SMT226)
- 46.72m at 1.84% Ni (SMT227)
Maiden Jury-Metcalfe Resource was released to the market in March 2013 for 323,000t @ 1.98% Ni for 6,395t Ni.
In addition to the Jury-Metcalfe Discovery, three of the drill holes intersected thin, moderate grade, semi massive to massive sulphide nickel mineralisation on the same ultramafic-footwall basal contact that hosts the Schmitz orebody further to the east. Results are as follows:
- 3.49m at 2.15% Ni (SMT224)
- 5.77m at 4.12% Ni (SMT228)
- 1.14m at 5.81% Ni (SMT229)
The discovery of the Jury-Metcalfe zone and Lower Schmitz re-affirms the highly mineralised nature of the region and the potential for new deposits to be discovered.
The Lanfranchi orebody is one of the higher grade orebodies in the Lanfranchi system, with downhole EM surveys indicating the Lanfranchi orebody continues with depth.
Drilling of the West Lanfranchi structure during FY2012 intersected high-grade mineralisation on the orebody contact approximately 20–30m below the Lanfranchi 17,000 ore drive. Assay results included:
- LAN218 13.66m at 9.31% Ni
and 10.35m at 11.74% Ni
- LAN219 5.60m at 4.29% Ni
and 12.59m at 7.60% Ni
- LAN220 9.32m at 6.30% Ni
In FY2012, a drill-drive was developed to enable drill testing of the Lanfranchi deposit to 300 metres down-plunge of the existing resource and also follow-up the exciting West Lanfranchi results.
Ongoing drilling has expanded the Lanfranchi Resource to 10,200t Ni.
Cruickshank is an undeveloped nickel sulphide deposit located six kilometres north-east of Lanfranchi in the vicinity of the overturned Northern Dome. In 2010/11, Panoramic undertook an infill and extensional drill program of Cruickshank. The results of the drilling program not only upgraded the resource to 2.63 million tonnes grading 1.28% Ni for 33,560 tonnes Ni contained, but provided valuable structural knowledge of how the Cruickshank mineralisation interacts within the Northern Dome. The results indicated that the Cruickshank deposit has been folded and that with new, better positioned surface drill holes, the central higher grade core of the Cruickshank deposit may be intersected further down-plunge on the underside of the Northern Dome overturned fold structure.
Cruickshank remains a relatively underexplored and exciting prospect in the Northern Dome region of Lanfranchi.
The Northern Dome is a region approximately 6km north of the Lanfranchi channel systems. Structural mapping indicates that the Lanfranchi channels have undergone a folding event and that the channels are repeated to the north. Exploration drilling along the northern dome to date has indicated that the folded basal contact is mineralised in parts and shows geological signatures similar to the southern Lanfranchi system which is currently being mined.
The Northern Dome is an exciting exploration region with the prospect that the mineralised Lanfranchi channels may be repeated further to the North.