Drilling by
First Quantum put 13 drill holes into Lufua, a new prospect pinpointed by a reconnaissance soil survey. Nine of the holes encountered significant copper mineralization in metamorphosed fine-grained sedimentary rocks of the Katangan series.
All but one of the holes were drilled vertically into the prospect in an area where previous soil sampling had outlined a zone of soils with copper contents exceeding 500 parts per million. The drill holes encountered variable weathering thicknesses, which may be controlled by faults in the host rock.
The mineralized intersections ranged from 17.5 to 164.7 metres in length, and total copper grades ranged from 0.7% to 2.33%. The principal initial exploration interest is in oxide material with acid-soluble copper mineralization; acid-soluble copper grades in oxide material fell in the range 0.37% to 3.12%.
Oxide zones, carrying grades of 0.87% to 3.42% total copper and 0.57% to 3.12% soluble copper, ranged in length from 13.3 to 61.2 metres. Mixed oxide-sulphide material, in zones of 4.3 to 85.1 metres length, showed grades of 0.7-2.34% total copper and 0.38-1.86% soluble copper.
Sulphide mineralization graded from 0.5% to 3.49% copper, with negligible acid-soluble copper; such material would likely have to be treated in a conventional mill. The sulphide mineralized zones ran anywhere from 2 to 138 metres in core length.
Primary mineralization at Lufua occurs in quartz-dolomite veinlets that carry chalcopyrite, and in later quartz-dolomite-chalcopyrite-bornite veins. There is also disseminated chalcopyrite accompanied by potassic and albitic alteration in the host rocks.
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