In its first venture outside Spain,
In October, Rio Narcea acquired an exploration licence covering the 440-sq.-km Penedono property in northern Portugal. Gold mineralization in old underground workings is said to occur in 13 parallel, granite-hosted quartz veins that range from 0.5 to 2.2 metres in width and up to 1 km in length.
So far Rio Narcea has resampled portions of four veins — named Filons 1, 2, 3 and 7.
The best results came from channel sampling in the upper levels of Filon 3, where one zone graded 30 grams gold per tonne over a length of 72 metres and an average width of 1.6 metres. Re-assaying of all samples at Reno-based Barringer Laboratories yielded a grade of 26.1 grams gold over the same interval.
Assay results from the first levels of Filons 1 and 2 were also encouraging, with a 77.7-metre portion of Filon 1 averaging 4.5 grams gold over a 1.7-metre width, and a 106-metre portion of Filon 2 averaging 9.3 grams gold over an average width of 0.7 metre.
The underground workings at Penedono total 4,100 metres, with the deepest development being found in Filon 3, where only the upper two of four levels have been mined. Rio Narcea says earlier reports of sampling in the two lower levels indicated that neither the grade nor the width of the structures decreases at depth.
With all but the first levels of Filons 1, 2, and 3 being flooded, any additional sampling will require dewatering of the lower levels.
Drilling on the project has been tentatively scheduled for the last quarter of 1999 following completion of trenching and soil geochemical surveys.
Based on past work, the Penedono veins are estimated to contain 1.5 million tonnes grading 8.3 grams gold, equivalent to 400,000 contained ounces, to a depth of 160 metres.
Rio Narcea’s metallurgical testing indicates that the Penedono ore is non-refractory and that recoveries ranging from 85% to 95% can be achieved through flotation and leaching.
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