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Mining News: Porphyry experts join junior at Pyramid Chilean miner Antofagasta partners with Full Metal on Alaska Peninsula property; drilling cuts thick zones of copper mineralization Shane Lasley Mining News
With copper-gold-molybdenum intercepts up to 500 meters thick and a location near tidewater on the Pacific Rim, Full Metal Minerals Ltd.’s Pyramid Project on the Alaska Peninsula is shaping up as a significant copper deposit.
Chilean copper producer Antofagasta Minerals S.A. joined the junior to explore Pyramid earlier this year and the partners launched an initial 1,668-meter drill program at the porphyry copper-gold-molybdenum project in August.
Antofagasta Minerals, a subsidiary and the mining division of Antofagasta plc, owns and operates three copper mines with a total production of 442,500 metric tons of copper and 7,800 metric tons of molybdenum in 2009. The company’s vice president of exploration, Pepé Perelló, is considered to be one of the world’s top porphyry experts.
The exploration, funded by Antofagasta as part of its option to earn a 51 percent interest in the Southwest Alaska property, targeted a deposit previously examined with shallow drilling in the 1970s. Some 1,695 meters of historical drilling produced a pre-NI 43-101 resource of 125 million tons grading 0.40 percent copper and 0.025 percent molybdenum in a near-surface zone at the 37,296-hectare, or 92,160-acre, project.
Drilling five widely spaced holes, Antofagasta and Full Metal encountered 300-meter- to 500-meter-thick zones with grades comparable to the historical resource with the final two holes cutting higher grade copper and molybdenum mineralization.
Full Metal CEO and Vice President of Exploration Rob McLeod said he does not anticipate upgrading the resource at Pyramid until at least the end of 2011. The historical drilling in combination with the broad mineralization encountered this year establishes that a big porphyry copper system exists at the project. The next step for the partners is to find higher grade zones within the bigger system.
“It’s clearly a big porphyry system, and the key is to try to find some higher grades within that broader 0.3 percent to 0.6 percent copper envelope,” McLeod told Mining News.
Five for five All five holes drilled in 2010 intersected copper mineralization from the time the drill bits cut bedrock to the bottom of the holes. This wide-spaced drilling covered a 900-meter-by-750 meter-area within a 2,000-by-1,000-meter zone of surface mineralization.
PY10-01, the first hole drilled by the Pyramid partners, cut copper mineralization from bedrock at 32 meters to the bottom of the hole at 500 meters. This 467.6-meter intercept averaged 0.27 percent copper, 0.02 percent molybdenum, and 0.06 percent gold (0.41 percent copper-equivalent). Within this was a 388-meter interval averaging 0.46 percent copper equivalent and a 57.7-meter higher grade zone grading 0.65 percent copper-equivalent.
“We drilled five holes out there and all of them are very well mineralized starting at surface and some seem visually to be better grade than this first hole,” Full Metal CEO Rob McLeod told Mining News after results from hole 1 were reported in September.
“There is significant supergene enrichment, which is pretty rare to get in Alaska, so metallurgically that bodes well,” he added.
McLeod’s eye for copper mineralization turned out to be accurate. All four of the subsequent holes cut significant mineralization, with three of them returning better grades than hole 1.
PY10-02 drilled about 700 meters south of hole 1 cut 352 meters starting at 4.6 meters averaging 0.34 percent copper, 0.08 g/t gold and 0.01 percent molybdenum (0.44 percent copper equivalent). Included in this intercept was a 56-meter higher grade zone averaging 0.65 percent copper equivalent.
PY10-03, collared 800 meters southwest of hole 1, was the weakest of the five holes. Hole 3 cut 297.3 meters grading 0.20 percent copper, 0.05 g/t gold and 0.004 percent molybdenum (0.25 percent copper equivalent). A 74-meter zone within this intercept averaged 0.49 percent copper equivalent.
Holes PY10-04 and PY10-05, collared from the same set up about 230 meters east of hole PY10-01, seem to be vectoring in on a higher grade region of the large mineralized system. Hole 4, drilled toward the south, cut the highest molybdenum grades of the season and hole 5, drilled to the north returned the best copper grades of the program.
Starting at 9.7 meters, hole 4 cut 289 meters grading 0.30 percent copper, 0.08 g/t gold and 0.03 percent molybdenum (0.52 percent copper equivalent). Included within this longer intercepts was a 48-meter zone grading 0.80 percent copper equivalent.
Hole 5 intersected 194.8 meters containing 0.63 percent copper, 0.14 g/t gold and 0.02 percent molybdenum (0.82 percent copper equivalent). Starting at 20 meters this hole cut a 72-meter zone averaging 0.96 percent copper equivalent.
McLeod told Mining News that hole 5 was still cutting 0.05 percent copper mineralization when the hole was terminated due to reaching the end of the US$1.5 million budget allocated for 2010 by Antofagasta.
Early days In addition to drilling Full Metal and Antofagasta geologists completed geological mapping of the main target area at Pyramid, an exercise that was challenging due to the inclement weather of the Southwest Alaska island arc that separates the Pacific Ocean from the Bering Sea.
This mapping identified multiple hydrothermal centers within an oval-shaped 2,300-meter-by-1,400-meter extent of phyllic and potassic alteration zones.
“We did get a good portion of the main target area mapped, but certainly not the peripheral areas – this thing is still wide open for expansion. There are multiple porphyry centers, multiple hydrothermal events that have overprinted each other, so it is still early days in understanding the whole system out there,” McLeod explained.
To further their understanding of Pyramid, the partners are anticipating an aggressive follow-up exploration program for 2011.
McLeod said Antofagasta and Full Metal geologists will be meeting during the Alaska Miners Association annual convention in Anchorage to begin hammering out an exploration plan for next year.
The geologists, which will include exploration vice presidents Perelló and McLeod, plan to fly out to the Pyramid exploration camp to re-examine the core during the early November meeting in Alaska.
Pyramid is but one prospect on the 1.4 million acres of Native-owned lands being explored by Full Metal on the Alaska Peninsula and Aleutian Islands. The junior has an exploration agreement with Aleut Corp., an Alaska Native Regional Corporation, to explore the length of island arc that extends some 1,000 miles into the Pacific.
“It’s a great location and the Aleut Corporation is a great partner to have,” McLeod said.
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