Pacific Rim bullish over Luicho tests

Junior Pacific Rim Mining (PFG-T) has tabled encouraging results from bottle-roll tests of samples collected from its Luicho gold project in southern Peru, while noting that sampling has confirmed the vertical continuity of mineralization.

The project centres on 10-sq.-km parcel of land in a mountainous region of Parincochas province, 540 km southeast of Lima, between Arequipa and Nazca.

In March, three bulk samples of non-carbonaceous mineralization grading 1-2 grams gold per tonne were collected from underground workings and subjected to four bottle-roll tests. The tests were performed at crush sizes of minus 2 inches, minus 1 inch, minus 0.5 inch and minus 5 mesh (about 3/16 inch).

Results indicated gold recoveries of 94%, 89% and 87% for the minus-5 mesh material; 90%, 84% and 93% for the minus-0.5-inch material; 91%, 73% and 68% for the minus-1-inch material; and 89%, 71% and 68% for the minus-2-inch material.

“These results have greatly exceeded our expectations and clearly indicate that Luicho mineralization will be heap-leachable with excellent recoveries,” says Pacific Rim CEO Thomas Shrake, who adds that geological mapping of the site is nearly complete.

Metallurgical results reportedly confirm the presence of free gold in open spaces and fracture fillings. Cyanide and lime reagent consumption was low to moderate.

Two types of metallurgically distinct rock have been identified at Luicho: carbonaceous and non-carbonaceous. The less abundant carbonaceous mineralization is present in the uppermost 10 metres of the sandstone unit and is probably derived from the overlying shale unit.

Two bulk samples from the carbonaceous mineralization were collected and tested at four crush sizes. Recoveries ranged from 19% to 61%. Bottle-roll tests are typically not accurate for carbonaceous mineralization, and so Pacific Rim plans to perform column-leach tests to improve recoveries. These test will be conducted at crush sizes of minus 1 inch and minus 0.5 inch. In addition, the company is looking for a site to test-leach a half-tonne sample of low-grade, run-of-mine material.

Geologically, the property is an adularia-sericite, low-sulphidation epithermal prospect. The target area is related to a complex series of converging right-lateral strike-slip faults that have created a broad corridor of fracturing and brecciation. The major structural feature is the north-southerly striking Luicho fault, which bounds the western side of the corridor in the south and central areas. A secondary series of northeasterly trending faults has created a broad zone of fracturing and brecciation. Mapping indicates that high-angel faulting is the main control of mineralization.

In addition, the company has collected 1,033 two-metre-long continuous chip channel samples from the structural corridor; this brings the total number of samples collected to 6,535 with an average grade of 1.52 grams gold per tonne. The samples represent individual rock samples together with 194 channel samples composed of two or more individual 2-metre-long samples strung together end-to-end.

Of the 1,033 new channel samples, 97 were collected from cliff faces. The samples were collected primarily from the Northeast zone and cover a vertical span ranging from 11 to 25 metres. Assay results from cliff faces include:

4.15 grams gold over 21 metres;

1.4 grams gold over 21 metres;

2.58 grams gold over 17 metres; and

0.81 gram gold over 25 metres.

Pacific Rim has been sampling from three zones — Northeast, Central and South — in the structural corridor.

The average grade of 1,100 samples taken from the Northeast zone stands at 1.33 grams gold, whereas the average grade of samples exceeding a 0.31-gram-per-tonne cutoff works out to 1.87 grams gold.

Of the 2,195 samples taken from the Central zone, the average grade is 3.04 grams gold; when the 0.31 gram per tonne cutoff is applied, the average rises to 4.37 grams.

In the South zone, 636 samples average 2.28 grams gold, whereas the average grade using the 0.31-gram cutoff is 2.37 grams gold.

Sampling is being supervised by Pacific Rim geologists, with assays performed by Bondar Clegg in Vancouver. A check-assay program at the labs of Chemex, also in Vancouver, is ongoing. Metallurgical tests are being carried out by McLelland Labs in Reno, Nev.

The property, which is accessible from the Pan American Highway, sits atop steep and rugged terrain at an elevation of 2,700 metres.

The company is constructing a road leading into the project and intends to begin constructing drill pads shortly. Meanwhile, a 12,000-metre, first-phase drill program is about to get under way.

Pacific Rim has made an initial property payment of US$200,000 and can earn a 100% interest by paying an additional US$400,000 in year one, US$1 million in year two and US$24.2 million in year three. The vendor retains a sliding-scale royalty of 2.5-3.5% on the first 1 million oz. produced and 3% on production thereafter.

Pacific Rim has added to its holdings by staking an additional 60 sq. km in the immediate area.