Gran Colombia said 2018 drilling extended the Deeps Zone to more than 700m along strike, with an average width of about 165m, and remaining open at depth and to the east. It also discovered a higher-grade zone with grade constantly above 2.5 grams per tonne of gold. Highlights included 35.25m grading 3.09g/t gold and 8g/t of silver.
"We remain very encouraged by the progress we are making in the evaluation of the underground mining expansion opportunity at our Marmato project," said executive chairman Serafino Iacono in a statement.
The new high-grade zone will continue to be drilled in 2019 as the primary target zone for expansion of underground mining operations, which is the focus of a preliminary economic assessment to be completed later this year.
The 2018 drilling campaign was completed in March and comprised 24 holes totaling 9,460m. It tested a block 400m high by 700m long below Level 21, currently the deepest level of the producing mine at Marmato.
A separate underground drilling programme undertaken in 2018 within the existing mining operation tested a block within the higher-grade zone, which will be developed and placed into production later this year.
An 8,000m 2019 infill drilling campaign began in March within the same block and has been designed to further delineate and extend down plunge the higher-grade zone, as well as convert the remaining inferred resources within the higher-grade block to indicated resources.
Gold mineralisation in the Deeps Zone is structurally controlled and hosted in narrow quartz veinlets related to a sinistral transpressional shearing system. Gran Colombia says it is characterized by very narrow veinlets of quartz-pyrrhotite-bismuth tellurides-free gold with minor amounts of pyrite and chalcopyrite. The high-grade intercepts are related to a higher veinlet density.
Gran Colombia produced 24,951oz at Marmato in 2018 from a small underground mine. The company has spent recent years refocusing its exploration efforts on the potential to develop the mine to exploit deep mineralisation after abandoning an earlier concept of developing an openpit mine.
Shares in Gran Colombia Gold (TSX:GCM) opened almost 2% higher at C$3.43 Friday valuing the company at $162 million. Its share price has increased 16% so far this year.