Sunridge mine plan merges Asmara North deposits

Vancouver-based junior Sunridge Gold (SGC-V) combined four polymetallic deposits at its Asmara North project in central Eritrea, Africa, into a centralized-mill mine model for a feasibility study it released in early May.

Asmara North is composed of the Emba Derho, Debarwa, Adi Nefas and Gupo deposits, which jointly contain measured and indicated resources totalling 1 billion lbs. copper, 2.1 billion lbs. zinc, 506,000 oz. gold and 18.6 million oz. silver.

Emba Derho is the largest-tonnage deposit in Sunridge’s portfolio, with 1.7 million tonnes grading 1.06 grams gold per tonne in its gold oxide zone, 1.6 million tonnes grading 0.94% copper in its copper supergene zone, 50 million tonnes grading 0.8% copper in its copper-rich primary zone and 17 million tonnes grading 2.8% zinc in its zinc-rich primary zone.

Debarwa’s oxide zone holds 1.1 million tonnes grading 2.38 grams gold, and its copper supergene zone carries 1.4 million tonnes averaging 5% copper and 1.4 grams gold, while Gupo is a periphery gold deposit with 952,000 tonnes carrying 1.53 grams gold.

Adi Nefas is a zinc-copper-gold prospect hosting 1.8 million tonnes grading 3.3 grams gold, 1.8% copper and 10% zinc, as well as a 115 grams silver credit.

According to Sunridge’s prefeasibility study, its four Asmara North properties carry a net present value (NPV) of US$555 million with a 27% internal rate of return at a 10% discount rate. The valuation assumes an initial capital expenditure totalling US$489 million, with average costs clocking in at US$25.78 per tonne.

The study models average annual production at 57 million lbs. copper, 1.8 million lbs. zinc, 415,000 oz. gold and 11 million oz. silver over a 15-year mine life, including additional mine-expansion capital for a second and third phase totalling US$69 million.

“The outcomes have certainly exceeded our expections,” says Sunridge president and CEO Michael Hopley. “We are particularly pleased that the study has outlined an operating scenario in which all four deposits of the Asmara project are developed in an integrated way, with all ore being processed in a single-centralized mill near the Emba Derho deposit.”

Sunridge’s mine plan involves processing three separate ore types — copper and zinc oxides, as well as copper supergenes — using a common crushing and ball mill, as well as high-pressure grinding rolls and three individual circuits.

Phase one focuses on the copper supergene ore from Debarwa and Emba Derho at a 2-million-tonne per year throughput rate under flotation recovery, including a by-product gold credit.

Phase two incorporates the primary copper and zinc ore from Emba Derho, Debarwa and Adi Nefas at a rate of 4 million tonnes per year, while the third phase involves a carbon-in-pulp plant processing 1.6 million tonnes of gold ore from Gupo and stockpiled gold caps at Emba Derho and Debarwa.

Compared to a preliminary economic assessment filed in 2009, Sunridge’s new plan carries two-fold benefits for the company. The integrated-mill scenario extends mine life by around five years, with original projections pegging Asmara North operations at 10 years. Sunridge’s new plan increases the project’s NPV by 58%, from an original valuation of US$324 million.

Sunridge was greeted with a muted market reaction following the release of its prefeasiblity study. Company shares dropped 6%, or 2.5¢, with 668,700 units trading hands en route to a 38¢ close. Sunridge had US$5.5 million cash-in-hand to end April, with 117 million shares outstanding and a US$44-million presstime market capitalization.