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Kurmuk Project - Dish Mountain, Ashashire |
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Ethiopia |
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Au
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
Available as Full Text for direct download or on request. |
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The Kurmuk Gold Project comprises two separate deposits, Dish Mountain and Ashashire 11 km to the south, located in western Ethiopia, ~750 km WNW of Addis Ababa and 65 km NNW of the town of Asosa.
Gold mining in the region, but not in the immediate project area, dates back 6000 years to when it was a key source of gold to the ancient Egyptian empire. An exploration licence over the Dish Mountain area was granted to Ariab Mining in May 2007, and transferred to a company called AME in November of the following year. Regional stream sediment sampling in 2008 identified gold anomalies which were followed up by rock chip sampling and detailed mapping in 2009. Trenching and RC drilling in 2010 confirmed gold mineralisation and was followed by drilling to test its strike and depth potential. In May 2017, Allied Gold Corp. took control of AME and the project, but after a scoping study in 2019, concluded that additional economic mineralisation was required to justify project development.
A large exploration licence covering the Ashashire area had been granted to Golden Star Resources in 1995 who drilled 30 diamond holes into prospects within the licence area. These returned disappointing results, consistent with those of the drilling conducted in the same area by the Ethiopian Institute of Geological Surveys in 1994. Further exploration by a number of companies, including interpretation of satellite imagery, magnetic and airborne radiometric data, geological mapping and rock sampling led to the drill testing of known, and delineation of new, prospects. From 2011 to 2014, Aurigin Resources, in joint venture with Gold Fields outlined several high priority areas, which included Ashashire. Aurigin acquired full ownership of the licence from Gold Fields in 2015 and focused its work on resource drilling at Ashashire, which included 5000 m of diamond and RC drilling. The company subsequently exhausted it's funds and relinquished the ground. In 2019, Allied Gold Corp. took control of the Ashashire area and commenced drilling to prove sufficient resources to add to, and make the Dish Mountain deposit a viable project.
Geological Setting and Mineralisation
The Kurmuk Project falls within the western section of the north-south trending Tulu Dimtu Shear Belt which cuts Neoproterozoic volcano-sedimentary rocks of the Arabian-Nubian Shield at the northern end of the East African Orogen/Mozambique Belt. The Tulu Dimtu belt is characterised by a sequence of metasedimentary rocks interlayered with mafic to ultramafic volcanic and intrusive rocks, all of which have been metamorphosed to upper greenschist/amphibolite facies during the closure of the East African Orogen between the east and west Gondwana cratonic blocks. The Kurmuk Project deposits lie within the western part of this shear belt, and are similar to other gold mineralisation in the belt, which is associated with major regional fault and fracture systems.
See the separate Arabian-Nubian Shield record for regional location and setting.
The Dish Mountain deposit lies within a NE-trending volcano-sedimentary succession that is composed of four main lithofacies, which are, in porder of abundance:
• Foliated mafic igneous rocks composed of meta-pyroclastics, lavas and intrusives that strike NE and dip moderately to the NW.
• Foliated metasedimentary rocks that are intercalated with the meta-volcanic lithofacies and are composed of either:
- predominantly quartz and mica with lesser feldspar and chlorite, and variable carbonate-bearing siliciclastic rocks that are dominantly pelites and phyllites, with lesser, psammo-pelite and psammites;
- lesser chemical sediments that are marker horizons, and range from silica- to carbonate-dominant.
• Variably deformed ultramafic rocks.
• Syn to post tectonic intrusives rocks, ranging from gabbro, diorite and tonalite to granite.
Faulting within this suite mostly strikes NE, parallel or sub-parallel to the regional structural fabric.
The gold mineralisation at Dish Mountain is interpreted to have been emplaced peripheral to a mafic dominant, but bimodal eruptive centre, mainly
characterised by tuff and ash pyroclastics, with lesser lavas, punctuated by periods of low energy sedimentation. The deposit occurs as a sigmoidal, lozenge shaped body in plan, interpreted to be hosted within dilational zones associated with a major NE-trending thrust, known as the 'Dish Mountain Fault'. Gold mineralisation is associated with late-stage, discordant, extensional, quartz > dolomite >> pyrite veins with lesser chlorite and tourmaline, and adjacent dolomite-muscovite-pyrite selvages within broader dolomite-muscovite alteration haloes that may also be anomalous in gold. These vein sets typically range from 1 to 10 m in thickness and occur as stacked arrays.
Three main mineralised lode orientations have been recognized:
• West-dipping lodes that lie on the eastern side of Dish Mountain, associated with the interpreted Dish Mountain Fault;
• Sub-vertical chert lodes; and
• Flat-lying lodes.
Both the west-dipping and flat lying lodes are composed of 2 to 5 cm thick quartz veins that are laterally extensive, and structurally repeated to form 5 to 10 m thick stacks of these veins that are separated by pelites. The chert bodies are sub-vertical, composed of massive banded silica and quartz
that are up to 10 m wide and strike for several hundred metres to be truncated by a fault near the centre of the deposit.
The Ahashire deposit is located about 11 km south of Dish Mountain within the same NE-trending volcano-sedimentary succession, which locally comprises:
• A footwall sequence of steep, SE-dipping, mafic-dominated volcaniclastic rocks with jasperoidal and chert horizons, and numerous thin granite and tonalite intrusive bodies;
• A siliciclastic sediment-dominated package of fine-grained psammites, pelites and psammo-pelites with minor carbonate interbeds, separated by mafic units;
• A hangingwall sequence that is mafic-dominated, comprising chloritic siltstone and basalt.
In plan, the gold deposit occurs as a series of linear bodies that follow ridge crests. As at Dish Mountain, the gold mineralisation is associated with late-stage, discordant, quartz > dolomite >> pyrite veins with lesser chlorite and tourmaline veins with dolomite-muscovite-pyrite selvages within within broader dolomite-muscovite alteration haloes that may also be anomalous in gold.
The key controls on mineralisation are interpreted to be:
• Competency contrast boundaries, where mineralisation is hosted in zones that are typically associated with granitoid lenses or the margins of mafic bodies, adjacent to less competent schistose siliclastic rocks that typically dip steeply to the NW; and
• Mineralised quartz veins oriented sub-perpendicular to the steeply dipping lithofacies, where the dominant vein set dips shallowly to the WNW.
The Ashashire deposit is interpreted to be a late-stage, structurally controlled, sheeted-vein gold system with minor stockwork veining. The defined gold system, as at 2023, is restricted to a 2.5 km long, 200 m wide and 10 to 20° aligned, corridor of mineralisation that has been segmented by several major oblique sinistral shear zones. Individual lode segments are hosted in a variety of rocks including lower greenschist facies mafic and sedimentary rocks and granite dykes. Three main mineralised segments have been outlined, Perch, Gin Dish and Scorpion, separated from each other by regional NNE trending shear zones.
As detailed above, gold mineralised veins are accompanied by intense muscovite-dolomite-pyrite ±chlorite selvages and a proximal to distal intense carbonate alteration halo. Locally, lithological controls and faults are important in controlling the formation of vein arrays, and possibly their grade (e.g., mafic rocks may correspond to higher grades) and the plunge of ore systems. Vein arrays predominantly dip at 20 to 45°WNW (Groves and Francis-Smith, 2020).
Reserves and Resources
The NI 43-101 compliant Mineral Resource estimates at Kurmuk as of 31 December 2022 (Earl et al, 2023) were:
Measured + Indicated Mineral Resources
Dish Mountain - 26.4 Mt @ 1.71 g/t Au;
Ashashire - 29.58 Mt @ 1.78 g/t Au
TOTAL - 55.98 Mt @ 1.78 g/t Au, for 95.7 tonnes of contained gold.
Inferred Mineral Resources
Dish Mountain - 6.85 Mt @ 1.78 g/t Au;
Ashashire - 2.89 Mt @ 1.53 g/t Au
TOTAL - 9.75 Mt @ 1.70 g/t Au, for 16.6 tonnes of contained gold.
Proved + Probable Ore Reserves
Dish Mountain - 26.7 Mt @ 1.10 g/t Au;
Ashashire - 26.0 Mt @ 1.13 g/t Au
TOTAL - 52.8 Mt @ 1.53 g/t Au, for 80.8 tonnes of contained gold.
The information in this description is drawn from: Earl, A., Andrew, M., Cunningham, G., Theron, P. and Craig, S., 2023 - The Kurmuk Gold Project, Ethiopia; an NI 43-101 Technical Report prepared for Allied Gold Corp and Mondavi Ventures Ltd (to be renamed Allied Gold Corporation) by Datamine Australia Pty. Ltd. (Snowden Optiro), 129p.
The most recent source geological information used to prepare this decription was dated: 2023.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
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