With 89 holes representing over 14,000 metres of drilling completed on the Corani silver discovery in Peru and a resource estimate due out in early March, Bear Creek Mining (BCM-V, BCEKF-O) continues to expand the boundaries of both the Corani and Corani Este zones, while opening up a new gold zone to the south.
Results are in hand for another 18 holes into the bulk-tonnage prospect, which is situated high in the upper slopes of the Andes in southern Peru. Two zones of silver-rich mineralization — Main Corani and Corani Este, are exposed along separate ridges, roughly 500 metres apart.
There are 63 holes completed to date in the Main Corani zone; 49 of those holes show a weighted average of 86 grams per tonne (or 2.5 oz. per ton) silver, 1.35% lead and 0.4% zinc across an average thickness of 63 metres. The Main Corani zone extends over a strike length of 1,500 metres, and remains open to the north, laterally and at depth. Recent drilling included several infill holes on the south end — holes 39, 39A and 42 — designed to establish the limits of mineralization in the hanging wall of the main structure. Instead, all three holes intersected multi-oz. silver-lead mineralization, further expanding the system to the west.
These holes intercepted: 106 grams (3.1 oz.) silver and 1.08% lead across the top 66.5 metres of hole 39, including 24 metres of 175 grams (5.1 oz.) silver and 1.1% lead; 65 grams (1.9 oz.) silver, 1.01% lead and 0.1% zinc over the first 83.5 metres of hole 39A; and 113 grams (3.3 oz.) silver, 1.61% lead and 0.1% zinc in the upper 60 metres of hole 42.
At the moment, Bear Creek is focused on building access across the steep and challenging terrain in order to further test the structurally controlled mineralization that disappears under a thickening wedge of post-mineral cover to the north and west.
The Corani Este zone lies directly across from the northern end of the Main Corani zone, separated by a small drainage valley. The 25 holes completed to date into the side of the cliff have returned a weighted average of 100 metres true thickness grading 112 grams (3.26 oz.) silver, 0.98% lead and 0.6% zinc. Bear Creek is stepping out on the north end of the zone by drilling a fence of typically three holes every 100 metres. Recent drilling has expanded the Corani Este zone 200 metres to the north where it still remains open. The mineralization is now traced for at least 650 metres along strike. The northern and eastern portions of Corani Este are covered by younger post-mineral tuffs, which has created some access problems.
Results from the most northerly fence of holes on Corani Este, include 161 metres of 48 grams (1.4 oz.) silver, 1.04% lead and 0.42% zinc, right from surface in hole 37B, which was oriented at minus 80 facing the valley. Angled at minus 70, towards the hill side, Hole 37 intersected 146 metres averaging 82 grams (2.4 oz.) silver, 0.89% lead and 0.19% zinc, including 40 metres of 144 grams (4.2 oz.) silver, 1.3% lead and 0.6% zinc near the bottom zone.
Hole 37A was drilled out under the eastern cover at an angle of minus 50, returning 158 metres of 96 grams (2.8 oz.) silver, 0.52% lead and 0.12% zinc from surface, including a higher-grade 40 metres of 175 grams (5.1 oz.) silver, 0.5% lead and 0.1% zinc near the bottom of the zone. A 2-metre-wide, high-grade structure containing 456 grams (13.3 oz.) silver, 0.55% lead and 0.56% zinc was encountered at 188 metres down-hole.
Bear Creek is currently opening up access to the east side to test the higher-grade extensions under the post-mineral cover.
With four rigs turning at Corani, Bear Creek has been working at defining the limits of both Corani and Corani Este, while completing the required infill drilling for a resource calculation.
The Corani project, 160 km directly southeast of the city of Cusco, covers 36 sq. km of high, steeped terrain and U-shaped valleys at elevations of 4,600-5,100 metres. It’s about a 6-hour drive along paved and unimproved roads from Cusco.
Bear Creek can earn a 70% interest in the project from Rio Tinto (RTP-N) by making a series of escalating payments totalling US$5.4 million over three years. Upon earn-in, Rio Tinto will have a one-time right to either maintain a 30% working interest or sell it outright to Bear Creek for US$5 million. Bear Creek’s earn-in is also subject to success payments, in addition to a claw-back provision. Should economic resources exceed 10 million oz. gold-equivalent, Rio Tinto could reacquire a 60% stake by reimbursing Bear Creek 300% of its exploration expenses and carrying the junior through to production. This threshold is the equivalent of roughly 600 million oz. silver.
In early January, Bear Creek announced that previously reported results from early metallurgical test work were incorrect. The early test work performed by Plenge laboratories in Lima, Peru, under the supervision of Dawson Metallurgical Laboratories, had shown silver recoveries of 95% for oxide and 76% for mixed oxide-sulphide mineralization in drill core samples. To confirm that work, Dawson Metallurgical conducted its own bottle-roll leach tests in Salt Lake City, Utah, which indicated recoveries for oxide material in the order of 55% to 70%, more in line with expected recovery rates.
Metallurgical test work is continuing, with a greater emphasis on flotation or a combination of leaching and flotation to address the increasing proportion of sulphide versus oxide component of the deposit. The objective is to enhance the project through lead and zinc recoveries.
Further value in the project may lie in a separate gold target, some 3 km along strike south of the Corani silver zones. Two of the early trenches in this area returned 66 metres of 0.3 gram gold in T-4, and 90 metres averaging 1.9 grams gold (including 32 metres of 5 grams) in T-2. The two trenches are about 200 metres apart on a north-south striking structure that is traced for about 1 km.
An initial three holes were drilled from the same site at different angles to test the continuity below the higher-grade T-2 trench. These holes returned intercepts of: 32 metres grading 3.6 grams gold, 24 grams silver and 0.7% lead; 28 metres of 4.1 grams gold, 27 grams silver and 0.9% lead; and 26 metres averaging 3 grams gold, 38 grams silver and 0.6% lead.
In the latest batch of results, Bear Creek stepped out to the north where a fence of two holes tested the lower-grade T-4 trench, hitting 24 metres of 0.51 gram gold, 10.3 grams silver and 1.1% lead in hole 40A, plus 16 metres of 0.6 gram gold and 0.2% lead in hole 40B.
Stepping out in the opposite direction, 100 metres south of T-2, a fence of three holes intercepted 24-26 metres of 1.14-1.74 grams gold, 75-130 grams silver and 0.8-1.4% lead. Bear Creek has one rig focused on testing the 1-km-long, gold-rich structure at 100-metre intervals.
“We continue to advance steadily towards increasing the size of the deposit, calculating an interim resource, and establishing and optimizing the metallurgical flow sheets on the various process alternatives,” Bear Creek president Andrew Swarthout said in a statement. “Our objective remains to aggressively bring the project to a scoping study stage by mid-year.”
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