As Yale Encounters Porphyry Deposits in Mexico, a Grand Mystery Unfolds as to its True Nature
By John Hurst
ResourcexInvestor.com
September 26, 2007
A grassroots company no longer, porphyry deposits have encouraged Yale Resources Ltd. (TSX.V:YLL) to expand its La Verde land package in Mexico by 400 hectares. Often a holy grail for explorers, porphyry deposits – all the way from Alaska to Chile – make for great exploration targets. They are typically low grade, promise immense tonnages and create your “As Seen on Google Earth”, open-pit mines.
Yale Resources’ La Verde project, a copper-zinc-silver-gold property located 45 km northwest of Hermosillo, Sonora State, Mexico, has at least six deposits, with workings on them dating back to the early 1900’s.
“We now have known mineralization of potentially economic grades. It’s not a grassroots exploration play. These are deposits and we are going to determine how large they are as quickly as we can,” stated Ian Foreman, the Vancouver company’s geologist-president.
La Verde Grande (The Big Green) is the project’s main deposit. Yale’s first program was done there. Land acquisitions adjoining its northeast corner cover the La Sierrita copper-zinc-molybdenum porphyry that was drilled in early 2000’s by Freeport McMoRan. In its amalgamation with Phelps Dodge, that behemoth chose to leave Mexico and the project was dropped. Another Canadian junior had the project in the 1990s, and dropped it too.
“In each case, the company would drop the property for larger economic reasons, not geological reasons,” Foreman said. “Either the metal prices were too low or the Canadian exchange rate was too high or the world markets were weak…but nobody came to a conclusion with regards to the geological potential of the project, and that was really key for us.
“Freeport-McMoRan drilled eight holes, of which seven are on land that Yale controls. Five of those holes intersected a porphyry. Each of those holes has long intervals of anomalous copper, zinc and molybdenum mineralization. We know that over this four-square-kilometer area, that’s a huge exploration target, and we’ve added a large additional target to the property,” Foreman said.
“So we know that there is a large mineralizing system present. The association between the La Sierrita porphyry and the skarn deposits we are concentrating on at the present, is currently unknown. Is it the source for all the mineralization that has bled into the limestones and created the skarns, or maybe that is indicative of additional porphyry present and maybe the additional porphyry is what is feeding these skarn systems and therefore is a genuine porphyry target on its own.”
The La Verde Grande mine has three principal levels – two of which are about 100 metres in length – and recent field work has identified two additional levels vertically higher, which indicate that there is the potential for additional resources to be defined both up and down dip. The northeast extension of the mine, located 30 metres to the north, has additional workings that continue for another 30 metres along strike. The northeast extension has a second level of workings, located 23 metres below, which have visual mineralization. These were not sampled in previous exploration campaigns but have been sampled by Yale personnel. A three-week rehabilitation program was required before sampling could begin.
A total of 175 samples have been taken and all samples have been submitted to ALS Chemex labs in Hermosillo. Samples were taken every five metres as vertical chip channel samples along the walls of the workings. This sampling program also included initial samples from the historic workings that are all within a radius of 150 metres of the La Verde Grande Mine. In each working, skarn mineralization with visible copper mineralization was encountered.
There has been only very limited drilling done at La Verde. Yale’s exploration strategy for the La Verde Project is that it wants to explore all the targets in the concept that there is a larger mineralizing system present. The technical team and sampling crews will now be moving to the El Picacho prospect, located 900 metres along strike from the La Verde Grande Mine, where work in the early 1900's exposed a breccia with strong copper oxide staining over a 15 metre width.
Trails leading up to the La Tescalama prospect, some 250 metres up the hillside, are being cleared so that the crews will have access. The La Tescalama prospect saw significant historical development as the principal working extends in at least 40 metres and exposed strongly copper mineralized skarn throughout.
“It’s our impression that all previous exploration has tackled these small, high-grade deposits individually,” he stated.
“How are they connected? Are they connected, and if so, what is the key that ties them together? Right now, we are trying to get a feeling for how much mineralization there is. In the La Verde Grande area, there is a mine with three levels of workings; there is an extension off to the northeast with two levels of workings that show the strike length is a deposit in the neighborhood of 150 metres. To us, that already is twice as long as what we understood the deposit to be when we first optioned the property. Now, in just simple exploration, we’ve identified six other small pits or workings that the old-timers had found mineralization, back in the day when they found just something interesting.
“That, to us, indicates that there is genuine exploration potential not just in the 150-metre radius surrounding the mine, but in the surrounding land.”
Much of the site is covered by calcrete, a calcium alteration product up to several metres in thickness and more difficult to explore. All will have to be reckoned with before Yale decides where to drill.
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