Tigray's Harvest Project is located 600 kilometres north of Ethiopia's capital city of Addis Ababa. It is located in the highly prospective Asmara Mineral Belt in the southern part of the Arabian Nubian Shield (ANS), 90 to 140 kilometres southwest of the Debarwa and Emba Derho volcanogenic massive sulphide (VMS) discoveries in Eritrea and SE of the Bisha deposit. Bisha is now a producing gold-copper-zinc-silver mine with over 25 million tonnes at 1% copper and 0.7 grams per tonne gold of ore in reserves. Vein-related gold deposits are also typical of the ANS, including the giant >13 million ounce Sukari deposit in Egypt, the one million ounce gold discovery at Koka-Zara in central Eritrea and the 140,000 ounce per year gold producer at Lega Dembi in southern Ethiopia.
Tigray acquired a 70% interest in the Harvest Project in 2011 through a joint venture with Ezana Mining Development, a private Ethiopian company. Harvest comprises six contiguous exploration concessions covering approximately 199 square kilometres, including Terakimti, Nefasit, Igub, Midre Felasi, Hamlo and Adi Nebried.
The Harvest Project contains multiple trends of copper-gold-silver-zinc rich VMS systems and numerous artisanal bedrock gold workings on its six exploration licences. Until recently, the ground has not been subject to modern exploration. Exploration by Tigray in 2011-2013 has included drilling 84 diamond drill holes testing four prospects for a total of 17,765 metres, a heli-borne VTEM, magnetic and radiometric survey, ground gravity and electromagnetic (EM) surveys, over 90,000 surface soil, stream and rock chip samples, and regional to detailed geological mapping. State of the art technologies, such as a Niton handheld XRF unit used for real-time base metal assay of drill core and surface geochemical samples, has allowed exploration to advance at a rapid rate.
The most advanced prospect on the Harvest Project is Terakimti, where over 70 diamond drill holes have been completed, with peak results of 73.80 metres of 3.80% copper, 1.30 grams per tonne gold and 14 grams per tonne silver, including 36.45 metres of 6.01% copper, 1.69 grams per tonne gold, 19 grams per tonne silver and 1.31% zinc in hole TD004. Significant base and precious metal mineralization has been intersected in the majority of drill holes completed.
Drilling at Mayshehagne, approximately 3.3 kilometres south of Terakimti, has intersected 20.70 metres of 4.97% copper, 1.10 grams per tonne gold, 31 grams per tonne silver and 8.20% zinc from 24.00 metres, including 12.80 metres of 7.72% copper, 1.70 grams per tonne gold, 50 grams per tonne silver and 12.70% zinc (hole HD002).
A single drill hole at VTEM09, approximately 5 kilometres ENE and along strike of Terakimti, has intersected 10.69 metres of 3.47% copper, 4.20 grams per tonne gold, 91 grams per tonne silver, and 3.69% zinc from 19.81 metres, including 3.06 metres of 5.75% copper, 8.00 grams per tonne gold, 107 grams per tonne silver, and 0.70% zinc (hole TVD001).
Tigray is developing a number of grass roots to advanced prospects across the Harvest Project, including VTEM anomalies defined during a 1,500 line kilometre heliborne VTEM survey in April 2012 and a number of stream sediment and soil geochemical anomalies. Numerous bedrock artisanal gold workings along the Ruwa Ruwa trend have recently been located, mapped and sampled in preparation for drilling.
Drilling at Terakimti has defined a substantial VMS system with four stacked lenses of massive sulphide. The masssive sulphide has significant oxide gold near surface and the system remains open down plunge.
The Terakimti prospect has been drill tested at 40 by 40 metre to 40 by 80 metre drill spacings, and drilling has defined multiple copper-gold-silver-zinc-rich stacked lenses over an 800 metre strike length. The VMS lenses are hosted within a sequence of intermediate volcanic rocks and basalt in the hanging wall. Exhalative siliceous iron formation occurs at the periphery of the mineralized zone, with jasperoidal alteration of basalts present in the hanging wall. Numerous quartz-eye porphyry dykes intrude the centre of the mineralized system and may be responsible for partial upgrading of mineralization through recrystallization. Mineralized lenses and associated alteration have a moderate east-northeast plunge and remain open down plunge.
The system currently consists of four main stacked lenses containing copper-gold-silver and variable zinc:
- The Southern Lens is up to 50 metres wide, 360 metres long, and 170 metres high and is open down plunge. This mineralization has a massive pyrite base up to five metres thick, and appears to be a mound-shaped lens with stringers in the footwall. It is supergene upgraded as it is exposed at the southern end of the Terakimti system. The best intercept in primary sulfide is 73.85 metres grading 3.77% copper, 1.31 grams per tonne gold, 14 grams per tonne silver, and 0.72% zinc from 57.45 metres in hole TD004. Weathering of the lens has provided gold enriched oxide mineralization, including 8.8 metres grading 9.19 grams per tonne gold and 78 grams per tonne silver in hole TD029;
- The Central Lens sits above the Southern Lens and is up to 14 metres wide, 400 metres long, 150 metres high and is open down plunge and down dip. This lens is well banded to massive, tabular, and has several narrower (but high-grade) lenses sitting above it. The highlight hole in primary sulfide from the Central Lens is hole TD011, which intersected 15.2 metres grading 2.61% copper, 1.84 grams per tonne gold, 43 grams per tonne silver, and 6.77% zinc from 181.75 metres. Supergene enrichment is indicated in drill hole TD023 with 12.0 metres of 2.18 grams per tonne gold and 68 grams per tonne silver from 51.2 metres, including 4.0 metres of 5.68 grams per tonne gold and 157 grams per tonne silver.
- Mineralization in the Northern Lens is separated from the Central Lens by a porphyry dyke. The Northern Lens is up to 20 metres wide, 320 metres long, 120 metres high and is open down plunge. This lens is also well banded and contains high-grade gold gossan in the oxide zone. The highlight hole in supergene to primary sulfide from the Northern Lens is 20.85 metres grading 5.67 % copper, 1.48 grams per tonne gold, 17.59 grams per tonne silver and 0.77% zinc from 38.75 metres in hole TD008. High grade supergene enrichment is indicated in multiple holes, including TD053 with 6.12 metres of 27.2 grams per tonne gold and 13 grams per tonne silver and TD034 with 29 metres at 3.4 grams per tonne gold and 11 grams per tonne silver; and
- The Lower Zinc Lens was intersected in several drill holes. Hole TD040 intersected 3.5 metres grading 23% zinc and 1.5% copper from 239.2 metres. This mineralization may provide a lead-in to additional mineralization.
An airborne VTEM survey has identified a strong EM conductor 5.3 kilometres east-northeast and directly along strike of Terakimti. Reconnaissance evaluation at the VTEM09 anomaly has located malachite (copper carbonate) stained gossan coincident with the EM anomaly .Additional on-ground exploration work has been completed for advancing the target to drill ready.
The VTEM09 airborne EM anomaly is located on the Terakimti concession approximately 5.3 kilometres east-northeast of Terakimti, and comprises a strong bedrock EM conductor over 200 metres strike associated with several malachite-rich gossan outcrops. Four trenches (up to 1.5 metres deep and 103 metres long) were completed over 160 metres of strike length at 40m spacing in late 2012 yielded the following intercepts, from northeast to southwest:
- 10 metres at 3.85 grams per tonne gold, 26 grams per tonne silver, 0.84% copper and 0.67% lead, including 5 metres at 7.27 grams per tonne gold, 45 grams per tonne silver, 0.65% copper and 1.14% lead. This intercept is within a broad copper-rich zone averaging 74.85 metres at 0.43% copper.
- Trench 031 - 2 metres at 9.58 grams per tonne gold, 161 grams per tonne silver, 0.21% copper and 0.78% lead
In 2013, a single drill hole at VTEM09 intersected 10.21 metres of 3.16% copper, 3.97 grams per tonne gold, 87 grams per tonne silver, and 3.82% zinc from 20.29 metres, including 2.82 metres of 5.61% copper, 7.48 grams per tonne gold, 102 grams per tonne silver, and 0.72% zinc (hole TVD001).
The high-grade copper and precious metal enriched VMS mineralization intersected by TVD001 compares favourably with the metal tenor encountered at the Terakimti and Mayshehagne discoveries, and marks the third significant VMS discovery made at Harvest. This drill intersection discovery at VTEM09 continues to highlight the base and precious metal endowment of this region of the Arabian Nubian Shield.
Drilling at Mayshehagne, approximately three kilometres south of Terakimti, has defined a high grade VMS shoot over 120 metres strike/plunge, remaining open down down plunge, hosted in a sequence of mafic volcanic rocks with abundant jasperiodal cherts. The discovery adds potential to the project as it proves the presence of a significant new VMS trend.
The Mayshehagne target was identified as a strong bedrock EM conductor from an airborne survey conducted in 2006. Mapping and surface geochemical sampling by Tigray has defined a mineralized zone over a strike of 170 metres that includes several gossans, magnetic ironstone chert, chert breccia, barite and malachite, hosted in carbonate-altered mafic volcanic rocks.. Results from rock-chip sampling returned high-grade assay values ranging from 0.07% to 14% copper, 0.11 to 13.2 grams per tonne gold, up to 56 grams per tonne silver, 0.03% to 1.9% zinc and up to 1.7% lead.
The Mayshehagne prospect has been drilled on four sections over 160 metres of strike. Best results include:
- 20.7 metres of 5.00% copper, 1.03 grams per tonne gold, 31 grams per tonne silver and 8.2% zinc from 24.0 metres, including 12.8 metres of 7.77% copper, 1.62 grams per tonne gold, 50 grams per tonne silver and 12.66% zinc (HD002); and
- 18.0m of 3.23 % copper, 0.95 grams per tonne gold, 22 grams per tonne silver and 3.86% zinc from 60.0m (approximately 35 m below surface), including 5.45m of 7.05% Cu, 1.24 grams per tonne Gold, 46grams per tonne Ag and 6.53% Zn from 62.0 m.
The high-grade massive sulfide body remains open down plunge and down dip to the northeast, and the alteration and volume of disseminated and stringer-style sulfide is increasing to the northeast.
Gold and copper soil anomalies are present over 1.6 kilometre strike at the Nefasit prospect, approximately 20 kilometres east-southeast of Terakimti. The anomalies are associated with narrow VMS gossan outcrops and highly sulphidic porphyry bodies with minor bedrock artisanal workings.
Ten diamond drill holes were drilled in 2010 and 2012 to test VMS potential on the Nefasit prospect. Two holes intersected significant zones of massive sulphide, with peak results including:
- 3.0 metres at 2.34% copper, 1.41 grams gold per tonne, and 22.7 grams silver per tonne in hole 09HND004, from 52.15 metres; and
- 3.0 metres at 0.68% copper, 1.31 grams gold per tonne, and 5.4 grams silver per tonne in hole 09HND001, from 71.93 metres.
Medadib is located on the Nefasit prospect, approximately 24 kilometres east-southeast of Terakimti. Multiple northeast trending gossans are associated with a 900 metre gold soil anomaly returning >20 parts per billion gold. The gossans are hosted in a hornfelsed (metamorphosed) felsic volcanic/sedimentary sequence intruded by multiple types of granite and porphyry. Peak results from trenching across the gossans include 4 metres at 1.85 grams per tonne gold. One vertical RC hole completed by Ezana in the late 1990s intersected 18 metres at 2.72 grams per tonne gold and 5.0grams per tonne silver.
RUWA RUWA GOLD TREND
The Ruwa Ruwa gold trend is located on the Terakimti Concession 1.5 kilometres west of the Terakimti VMS trend. Ruwa Ruwa is defined by a high-order soil gold anomaly and numerous artisanal bedrock gold workings over a seven kilometre strike length. The largest bedrock workings and most advanced targets are Lihamat and Adi Goshu. At Lihamat, extensive artisanal bedrock workings occur over a strike length of 225 metres and the mineralized zone is up to 50 metres wide with shafts up to 15 metres deep. Visible gold is mined in numerous quartz veins in a coarse-grained quartz sericite altered quartz porphyry. The porphyry has intruded into a sequence of mafic and felsic volcanic rocks and banded iron formation.
At Adi Goshu, deep mine workings (>20 metres) are present on quartz veins over a 100 metre strike length on two trends up to 20 metres wide. Soil geochemical sampling has defined a 500 metre long >100 parts per billion gold soil anomaly with five samples assaying > 1.0 grams per tonne gold.