Moyale Graphite Deposit, Ethiopia
The Moyale Graphite deposit located 750km south of the Ethiopian Capital, Addis Ababa, on the southern border of Ethiopia with Kenya at latitude 3° 33’ 11’’N and longitude 39° 00’ 13’’E. The deposit is approximately 6km west of Moyale town at a location known as Edessa. The general environ is mostly a low land area elevated at around 1,200m above sea level.
The Moyale graphite deposit was mapped and trench sampled by the Ethiopian Institute of Geological Survey (EIGS) in the 1990’s with analysis, petrographic and metallurgical work conducted in Norway by the Norwegian Geological Survey (NGU). A review of all previous work was conducted for Montero by a NI43-101 Qualified Person and describes the deposit as having favorable characteristics for development as compared to other global flake graphite deposits.
These are as follows:
- An average grade of 8% Graphitic Carbon (Cg) returned from trench sampling: between 7 -11% Cg with 80% of samples submitted from trench sampling (n=253 samples in 42 trenches) averaging 8.3% Cg.
- Graphite distribution of 40% Jumbo flake and 28% Large flake of the in-situ rocks as determined from thin section image analysis. The Jumbo flakes are favourable having a length >300µm (+48 Tyler Mesh) which corresponds with Extra Large flakes ("Jumbo"). The Large flakes fall within the Large flake category (-300+180 or -48+80 Tyler Mesh). Extra Large/Jumbo and Large flake graphite concentrates with purity of 90-96% carbon can attract a significant price premium.
- Initial trial bench-scale indicate recoveries of up to 94-95% of rougher concentrates. The deposit is very amenable to conventional graphite beneficiation processes and the initial trial bench-scale flotation tests were conducted at the NGU indicating that rougher flotation concentrates grading up to 71% C (Carbon) can be achieved with graphite ores ground to ~400µm. The recoveries of 94-95% of rougher concentrates are well above 80-90% more common of other flake graphite deposits. For most hard rock flake graphite deposits 2-3 stages of grinding and 4-6 cleaner flotation stages are required to upgrade the in-situ ore of 5-10% to a marketable concentrate grade of 90-95%C.
- The Moyale deposit is open at depth and along strike with exposure at surface in wide zones of mineralisation from 6m to 60m in true thickness and displays a favourable dip (~450). Access is reasonable and labour is readily available.
- A polygonal resource (non NI 43-101) was completed by the EIGS which estimates 460,000 t of contained graphite (Cg) to a depth of 20-40m based on 253 composite samples (2-3m) conducted in 42 trenches during the mid-1990s. This historic estimate was based on a cross sectional area methodology for trench profiles assuming a vertical depth of 40m for mineralization for Area 1 and 20 m for Areas 2 and 3.
- Key characteristics of the deposit are noted in the table below:
|Area||Grade (%Cg)||Flake Size||No. Lenses||Av. True Thick (m)||Strike Length (m)||Continuity|
|Area 1||8-10||Med Coarse||2 - Main||18-35||500 - 700
(Open to W)
|Uniformly thick continuous along strike for 100’s metres|
|Area 3||5-11||Fine||2 - Main||6-30||1350
(Open to E)
|Uniformly thin continuous along strike – grades generally erratic and increases in grade to south-east|
|Area 2||7-14||Coarse||Multiple||7-60||100 - 550||Generally Discontinuous along strike|
The Moyale area is situated within the north-eastern branch of the Proterozoic Mozambique Belt which extends from Kenya north through to Ethiopia and the horn of Africa into Arabia. Three major divisions of the Mozambique Belt are present in southern Ethiopia (Lower, Middle and Upper Complexes), differentiated by characteristic contrasts in lithology, metamorphism and structural style. Meta-sedimentary rocks (graphitic phyllites, biotite schists and meta-calcareous rocks) in the Adola area form the uppermost unit of the Upper Complex in southern Ethiopia. The rocks of the Moyale region are correlated with the lower part of the Upper Complex and are regarded as Neoproterozoic in age.
The graphite bearing schists of the Moyale graphite deposit are hosted within a sequence of amphibolite, feldspar-quartz-mica schists, granodiorite and quartzites. Intrusive pegmatite dykes have intruded and may be concordant or discordant to the host sequence. Importantly the rocks appear to have reached a peak metamorphic grade of mid-upper amphibolite facies although a subsequent retrograde event appears to have a greenschist facies overprinting assemblage. Rocks are locally strongly deformed displaying tight isoclinal folding, crenulation cleavage development. Faulting has also disrupted and offset some of the graphitic horizons. There are three main areas of graphitic units that collectively comprise the Moyale graphite deposit. Flake graphite occurs as disseminations within the graphitic units.
A phased evaluation program of data verification, ground truthing, trenching/pitting and resampling, metallurgical test work and core drilling has been proposed leading to preparation of a NI 43-101 Compliant Resource and Preliminary Economic Analysis.