Nevsun Resources (TSE: NSU, NYSE: NSU) has lifted the resource estimates at its Bisha and Harena deposits in Eritrea.
The firm owns 60% of the high grade Bisha mine in Eritrea, which has over nine years' reserve life.
Bisha and Harena remain open at depth and further drilling is ongoing this year, the company highlighted.
An underground scoping study for both deposits has also been positive and further investment is warranted, the group said.
Measured and indicated resources at Bisha district now contains 959 million pounds of copper, 3.56 billion pounds of zinc, 840 thousand ounces of gold, and 46 million ounces of silver.
Meanwhile, inferred resources at Bisha now contain 426mln pounds of copper 1.16 billion pounds of zinc, 531,000 ounces gold, and 18mln ounces silver.
There was a 15% increase to Harena primary indicated resources, now at 3.7 million tonnes at 0.86% copper, 3.1% zinc, 0.6 g/t gold and 27 g/t silver and a 69% increase to Harena primary inferred resources, now 10.9 million tonnes at 1.45% copper, 4.0% zinc, 1.0g/t gold and 41 g/t silver.
Nevsun chief Cliff Davis said: "Our drilling at Harena continues to produce significant increases in the total resource available for the Bisha operation.
"We anticipate that further drilling will continue to grow the deposit at depth.
"Our exploration drilling was also successful in discovering new massive sulphide mineralization at Asheli, highlighting the prospectivity of the Bisha District to host additional resources."
Davis added: "The underground scoping study demonstrated the potential to extend Bisha Main life by transitioning to underground mining in the future and the potential to provide additional feed to the Bisha mill from a Harena underground mine.
"In 2016, we will further assess these opportunities through additional investment."