When RT bought Pebble from Tech-Cominco in 2001 for a paltry 14 million at the cyclical low for commodities, Tech estimated, after drilling 100 holes, that they had an inferred resource of 1 billion tonnes. NDM added 4 billion tonnes by drilling farther to the east. They hit the jackpot when Rebagliati’s drilling discovered the East Zone, which added 6 billion tonnes of much better grades, for a total resource of 11 billion tonnes (12 tons). They discovered yet another zone, the East Graben, which RT is now calling the Far East Zone, which is at the easternmost boundary of the East Zone. The one hole that has been drilled into the East Graben hit 289 meters of 1.24% Cu before being lost in the fault. As you can see from the screenshot, the grades get richer, the deeper one drills. DDH 6348 has not been included in the resource calculations. There won’t be further exploration of the East Graben until a road is built into the area. It is very expensive to helicopter in drill rig.
There is an excellent likelihood that the orebody continues to the east of DDH 6348 because the fault was a post-mineralization event, i.e, the minerals were deposited before the fault occurred.
From the chart it looks like the mineralization of DDH 6348 starts at about the 1300 foot level after drilling through the overburden at a grade of 1.20 % CuEQ. This is very good news because it indicates that from the open pit where the orebody lies at surface (outcrops), it descends at a very shallow angle (or “downdips”), judging from the distance from the open pit to DDH 6348. If the orebody plunged sharply, it would make mining it much more expensive, and there comes a point when mining at great depths becomes impossible or uneconomic because the intense heat at depths requires elaborate AC and ventilation equipment. Some South African gold mines, however, are mining at a depth of over 12,000 feet. mining-technology.com/featu...
Because open pit mining is much more economic than underground mining and is capable of a greater throughput—the amount of mineralized material that goes through the mill—the first expansion will certainly be into the East Zone by expanding the open pit in that direction and deepening it to follow the orebody. The PAG TSF will not be backhauled to the open pit for a very long time because the open pit will be in operation for a very long time. The second expansion will likely bring on board an underground mine somewhere to the east, and that will be probably be mined using block caving, the underground equivalent of open pit mining. The mill capacity will be increased, as will the capacity of the power plant. Cantor foresees that Pebble will ultimately have a throughput of 360,000 tpd, twice the current mine plan. The East Zone and the East Graben lies in the Upper Tularik Creek watershed, so that drainage area will no longer be off limits.
By way of comparison, Taseko’s Gibraltar mine near Williams Lake, BC, is also a porphyry deposit, but it has only a 90,000 tpd throughput.
There is an excellent likelihood that the orebody continues to the east of DDH 6348 because the fault was a post-mineralization event, i.e, the minerals were deposited before the fault occurred.
From the chart it looks like the mineralization of DDH 6348 starts at about the 1300 foot level after drilling through the overburden at a grade of 1.20 % CuEQ. This is very good news because it indicates that from the open pit where the orebody lies at surface (outcrops), it descends at a very shallow angle (or “downdips”), judging from the distance from the open pit to DDH 6348. If the orebody plunged sharply, it would make mining it much more expensive, and there comes a point when mining at great depths becomes impossible or uneconomic because the intense heat at depths requires elaborate AC and ventilation equipment. Some South African gold mines, however, are mining at a depth of over 12,000 feet. mining-technology.com/featu...
Because open pit mining is much more economic than underground mining and is capable of a greater throughput—the amount of mineralized material that goes through the mill—the first expansion will certainly be into the East Zone by expanding the open pit in that direction and deepening it to follow the orebody. The PAG TSF will not be backhauled to the open pit for a very long time because the open pit will be in operation for a very long time. The second expansion will likely bring on board an underground mine somewhere to the east, and that will be probably be mined using block caving, the underground equivalent of open pit mining. The mill capacity will be increased, as will the capacity of the power plant. Cantor foresees that Pebble will ultimately have a throughput of 360,000 tpd, twice the current mine plan. The East Zone and the East Graben lies in the Upper Tularik Creek watershed, so that drainage area will no longer be off limits.
By way of comparison, Taseko’s Gibraltar mine near Williams Lake, BC, is also a porphyry deposit, but it has only a 90,000 tpd throughput.
