The Ngovayang Project is located in the southwestern region of Cameroon, West Africa and covers approximately 2,970km² comprising three exploration permits. The permits are considered prospective for iron ore in the form of magnetite and direct shipping ore (DSO), along with gold mineralisation.
Following a period of due diligence involving field reconnaissance and a 2,566km² aeromagnetic survey, Legend exercised its right to acquire 90% of Camina SA and the Ngovayang Project (ASX Announcement: 5 February 2010). Camina, its consultants and advisors have substantial experience and expertise in dealing with mineral projects, infrastructure and government relationships in Cameroon.
The Ngovayang Project is well served by access infrastructure including rail and road networks to and from the port city of Douala (see location map), which will greatly assist the exploration phases of work and potentially facilitate a start-up production transport system to port.
The Ngovayang Project contains a NE-SW trending package of Archaean to Proterozoic age gneiss, (with varying magnetite content), amphibolite, quartzitic metasediment, along with felsic and ultramafic/mafic intrusives. Legend completed an extensive aeromagnetic survey over the Project revealing that magnetic units occur on a larger scale than previously known information indicated, confirming the iron ore prospectivity of the Project.
Eighteen target areas were identified from the survey and are shown in the figure below.
Ngovayang Project – Target Areas over Aeromagnetic Image
Field reconnaissance involving geological mapping and geochemical sampling where appropriate has been completed over all eighteen areas. Based on the results of this work, eight areas have been followed up with diamond drilling (namely; Hill 464, Alpha, Hill 335, Hill 419, Melombo North, Melombo West, Melombo East and Plateau, all of which intersected magnetite gneiss. To date, 101 diamond drillholes for a total of 7,267m have been completed, with 62 of these holes focussed on the Melombo East and Plateau prospects, see below for further detail.
Melombo East Prospect
Phase 1 diamond drilling has been completed at the Melombo East prospect, comprising 34 holes (DH042-075) for a total of 2,349.25m. The drilling has focussed on a large (6km x 1.5km) complex aeromagnetic feature, targeting areas with outcropping magnetite gneiss and supported by geophysical modelling. An “Exploration Target” of 300-500Mt @ 16-40% Fe was estimated for Melombo East, based on the geophysical modelling with input from drilling and geological mapping, (ASX Announcement 23 November 2011).
Metallurgical testwork on three drillholes indicated; high iron weight recoveries and that a high iron concentrate with low impurities was achievable (ASX Announcement 28 February 2013).
Melombo East – Drillhole Locations and Results over Aeromagnetics
Significant iron grades and thicknesses of magnetite gneiss have been identified at Melombo East and are shown in the table below.
Metallurgical testing was completed on drillcore samples of banded magnetite gneiss from three diamond drillholes (DH044, 058, 061), see Photo 1. The drillholes are considered representative of the magnetite mineralisation observed at Melombo East and were selected based on a combination of iron grade, intersection thickness (36.02-83.02m) and location within the prospect.
Photo 1: DH044, 146.52–149.98 End of Hole
The key points from the testing are summarised below, with further details provided in the following three tables:
- A blast furnace grade concentrate with low impurities can be produced at (P80) 55 micron.
- Average grade at (P80) 45 micron is: 69% Fe, 2.1% SiO2 and 1.22% Al2O3.
- Low phosphorous 0.006% and low sulphur 0.042%.
- Average weight recovery of 33.5% and iron recovery of 87.2% from 26.5% Fe head grade.
- Similar magnetite liberation response was seen from all three samples, which are spread across 4km, see Figure 1.
- Magnetite is the main form of iron in the samples/deposit.
- Samples respond to conventional magnetic separation techniques and should produce a filter cake for on-site pelletising or pelletising abroad
Drilling utilised an Ingetrol man portable diamond drilling rig – HQ and NQ core sizes.
Co-ordinates: Universal Transverse Mercator WGS84, Zone 32, Northern Hemisphere.
Individual samples of nominal 4m intervals from each drillhole were crushed to -3.35mm and split/mixed to form composite samples representative of each of the three drillholes. The head assays for these composite samples are presented below.
Assay Method Fe, SiO2, Al2O3, P, S, TiO2 by fusion XRF – Amdel Limited, Perth. LOI – Loss on Ignition at 1,000C determined gravimetrically.
Each composite sample was subjected to grind liberation testing using a laboratory rod mill and low intensity magnetic separation, as well as Davis Tube testing. All samples produced a good blast furnace grade type magnetite concentrate at a grind size of 80% passing (P80) 55 micron. Actual measured concentrate grades at (P80) 45 micron are shown below.
Assay Method Fe, SiO2, Al2O3, P, S, TiO2 by fusion XRF – Amdel Limited, Perth.
LOI – Loss on Ignition at 1,000C determined gravimetrically.
The results of this testwork are encouraging, as they indicate that the magnetite can be readily separated with high iron weight recoveries ranging between 30% and 40%. The testing also returned a high iron concentrate grade with low impurities and it is highly unlikely that this material will require any form of flotation.
Golder Associates (Golder) were engaged by Legend to conduct a full review of the Ngovayang Iron Ore Project commencing in September 2012, including a site visit by a senior geologist experienced in magnetite. As part of the review, a detailed assessment of Melombo East was undertaken, involving the relogging of numerous drillholes and the review and acceptance of the prospect scale geological model.
Based on the geological model and results from the metallurgical testwork, Golder completed a high level optimisation report on the potential return for Melombo East. The report has demonstrated the robust nature of the prospect, with several optimisation scenarios indicating substantial cash flows before capital and other considerations.
Golder have also provided recommendations on future work programmes at the project, including the appropriate level of drilling required to bring Melombo East to a JORC compliant Inferred Resource status.
At the Plateau prospect, 26 holes for 1,793m have been completed, along six NW-SE trending traverses spaced 500-600m apart with holes every 100m along the traverses. The drilling was testing a 2.5km portion of a regional 10km linear aeromagnetic feature associated with outcropping magnetite gneiss displaying a NE-SW strike and 400-600 NW dip.
Plateau Prospect – Drillhole Locations over Aeromagnetics
A generalised stratigraphic sequence has been observed on all five traverses and comprises (from top to bottom); magnetite gneiss, overlying garnet gneiss with magnetite gneiss bands of varying thickness, and a footwall unit of silicified quartz-biotite gneiss. The drilling has also confirmed the moderate NW dip of the package and demonstrated relatively good correlation between holes on section.
Drillholes DH076-079, 088, 090 and 092, which intersected significant downhole thicknesses of magnetite bearing gneiss (54.2m-100.4m) were sampled in their entirety over nominal 4m composite intervals and submitted for a standard iron ore suite of elements. Full analytical results were received and are summarised below.
The drilling originally focused on the Eseka region in the north of the Project and included programmes at the Hill 464, Alpha, Hill 335 and Hill 419 prospects. Drillholes generally intersected a sequence of up to 10m of ferruginous saprolite overlying a highly oxidised package of alternating garnet gneiss and magnetite gneiss followed by a basal unit of siliceous biotite gneiss. Positive confirmatory assay results included: 33.8m @ 29.6% Fe in NESD011 at Alpha and 98m @ 28.8% Fe in NESD022 at Hill 419, (ASX Announcement 12 May 2011).
Preliminary Davis Tube Recovery (DTR) test work from a drillhole at the Alpha prospect confirmed the high grade magnetite potential of the Ngovayang Project, (ASX Announcement: 14 March 2011). The following tables show the results of the Stage 1 and Stage 2 DTR test work
Drilling activities then moved south to the Melombo North and Melombo West prospects, again targeting large aeromagnetic features coincident with topographic highs. Two diamond drillholes at the Melombo North prospect returned significant grades and thicknesses associated with magnetite gneiss; 91.2m @ 23.1% Fe in hole NMELD002 and 105.4m @ 29.5% Fe in hole NMELD007, (ASX Announcement: 18 July 2011). Drillholes at Melombo West returned; 53.05m @ 22.6% Fe in NMLWD001 and 125.98m @ 16.3% Fe in NMLWD002. Six of the seven holes drilled reported magnetite of similar character and tenor to the results previously announced from the Alpha, Hill 335, Hill 419 and Melombo North prospects, (ASX Announcement: 15 August 2011).