Progressing towards a decision to re-start operations at Savannah
The Savannah sulphide rich nickel, copper and cobalt orebody is hosted by the layered mafic-ultramafic Savannah Intrusion which is enveloped by aluminous metasediments and para-gneisses of the Tickalara Metamorphics. The Savannah Orebody is mostly confined to a marginal norite unit up to 40 metres thick developed above the base of the intrusion. Areas of massive, matrix and disseminated sulphide mineralisation, dominated by pyrrhotite, chalcopyrite, pentlandite and minor pyrite occur throughout the marginal norite unit.
Prior to the development of the Savannah Open Pit, the marginal norite unit outcropped as a prominent 250 metre long limonite-goethite gossan with fresh sulphide mineralisation developing approximately 20 metres below surface. At approximately 500 metres below the surface, a significant sub-horizontal fault, the 500 Fault, cuts the orebody and offsets it 200 metres to the northwest. Mineralisation above the 500 Fault is referred to as the “Upper Zone” and below the 500 Fault as the “Lower Zone”.
The majority of the ore was mined via long-hole open stoping, which is a highly mechanised and low cost 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 vertical slabs off 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. The minimal waste material mined is either stockpiled underground or trucked to surface.
The process plant at Savannah comprises a single stage crusher, SAG mill, flotation, thickening and filtering stages to produce a bulk nickel, copper, cobalt concentrate. Metallurgical recoveries average 86-89% for nickel, 94-97% for copper and 89-92% for cobalt. The plant was originally designed for a throughput of 750,000 tonnes per annum, but has consistently outperformed the design specifications. Recent plant trials indicate the plant can operate at in excess of 1 million tonnes per annum.
The Savannah concentrate is contracted for sale to the Jinchuan Group of China until April 2020. The terms of the Extended Concentrate Sales Agreement for 100% of the concentrate from the Savannah Project are similar to the terms of the original Concentrate Sales Agreement signed in 2003, and are considered by Panoramic to be very competitive in global terms.
The Contract is currently suspended while the Project is on care and maintenance.
In 2009/10, Panoramic reported on the Lower Zone Ore Reserve below the 500 Fault and that the Lower Zone orebody was truncated by a fault structure (the 900 Fault) at approximately 900 metres below surface. Resource definition drilling has extended the mineralisation significantly to the north and west above the 900 Fault.
Below the 900 Fault & Western Splay
Ongoing exploration around the Savannah ore body above and below the 900 Fault have led to an upgrade in the Savannah Resource. A maiden Resource of 905kt @ 1.65% Ni for 14,900t Ni was announced by the Company in August 2015.
In early 2014, the Company announced it had intersected 89.3m @ 1.6% Ni and followed it up with another promising hit of 33.7m @ 1.56% nickel at Savannah North. A successful resource drilling program undertaken during 2015 provided an interim Resource estimate of 3.15Mt @ 1.75% Ni for 55,200t Ni. Both the Upper and Lower Zones of the Savannah North mineralisation are open to the east and west and could stretch for more than two kilometres. A major upgrade in Resource increased to 175,100t Ni was announced in August 2016. Combined Resources at Savannah now 218,300t Ni, 99,100t Cu and 14,900t Co metal contained.
Potential 2km strike at Savannah North
Resource Open – Savannah North Resource drilling programs have not closed off the mineralisation. Potential strike length of the Upper Zone is ~2km based on the large, highly conducting on-hole EM responses identified in surface drills holes SMD164, Section 5400mE and SMD167 SMD 167A, Section 5100mE. Only half of the potential Upper Zone mineralisation has been tested by resource drilling. The Lower Zone Resource remains open down dip to the northwest.
It is the Company’s intention to resume exploration activities in 2018, including drill testing four under-explored layered mafic-ultramafic intrusions located near Savannah. The impetus and focus of the 2018 exploration program is being driven by the results of a series of recently completed Panoramic / Minerals Research Institute of WA (MRIWA) funded research projects with CSIRO Mineral Resources. The aim of the research projects, which commenced in 2015, was to improve the Company’s understanding of the petrography, mineralogy, geochemistry and geochronology of the Savannah Style layered mafic intrusions and the origin and emplacement mechanisms of their parental melts.
A number of other mafic/ultramafic intrusive bodies occur at the Savannah Project
- Dave Hill
- Subchamber D
- Frog Hollow
Little or no modern exploration has been conducted on these intrusions. Previous drilling by Panoramic has demonstrated that both Dave Hill and Wilsons host disseminated/blebby magmatic nickel-copper sulphide mineralisation. Past drilling has been minimal and has not tested the most prospective basal parts of these intrusives.
- Dave Hill – one 700m deep and five shallow core holes
- Wilsons – one core and seven shallow RC holes
- Subchamber D – one core hole
- Frog Hollow – never been drilled
The research conducted by CSIRO Mineral Resources on Subchamber D, Dave Hill and Wilsons concluded that all three intrusions were emplaced at the same time and by the same magmatic event that was responsible for the emplacement of the mineralised Savannah and Savannah North intrusions. Consequently, the CSIRO considers all three intrusions to be highly prospective for Savannah Style magmatic nickel-copper sulphide mineralisation. The Frog Hollow intrusion, which has never been drill tested, was not part of the CSIRO research project but is included in the Company’s 2018 exploration plans based on its many geological similarities with the other Savannah Style intrusions.
The Copernicus Project is located 50 kilometres south of the Savannah Project.
The host unit of the Copernicus nickel sulphide deposit is the layered mafic-ultramafic Copernicus Intrusion. The intrusion, which has an overall gabbroic composition, is enveloped by amphibole rich meta-sediments and para-gneisses of the Tickalara Metamorphics. It outcrops as a lens-shaped body with maximum dimensions of 600 metres along strike by 100 metres thick. It dips moderately to the west and has a pronounced northward plunge of approximately 40 degrees. Sulphide rich nickel, copper and cobalt mineralisation at Copernicus is confined to a discreet cumulate-textured meta-pyroxenite unit located within the Copernicus Intrusion. The pyroxenite unit is lens-shaped and dips west and plunges north with the Copernicus Intrusion. The sulphide mineralisation is preferentially developed at the northern end of the pyroxenite unit where it forms sulphidebearing cumulates rich in pyrrhotite-chalcopyrite-pentlandite and pyrite. Sulphide textures vary from net (matrix) textured mineralisation containing 5-10% sulphides to coarse-grained blebs and massive sulphide-rich stringer mineralisation, containing upwards of 50-70% sulphide. The mineralised pyroxenite has a maximum thickness of 35 metres and a down dip extent of between 100-150 metres. The down-plunge (strike) dimension to the north has been drilled over a strike length of 750 metres.
The orebody was mined using conventional open cut methods, involving drilling, blasting and excavation using contractors.
The open pit operations re-commenced in December 2014 and were completed in April 2016. The ore was trucked to Savannah where it was blended and processed with Savannah ore producing a nickel, copper, cobalt concentrate.
The concentrate was sold to the Jinchuan Group of China under the same terms as the Savannah Project.