Pachamama Resources Ltd. ("Pachamama" or the "Company") announces positive results from preliminary metallurgical work on the Company's 50%-owned Rio Grande copper-gold-silver project located in Salta Province, Argentina. The Rio Grande project is a 50/50 joint venture between Pachamama and Regulus Resources Inc. ("Regulus", TSX.V - REG) with Regulus acting as the operator.
Mineralization at the Rio Grande project contains significant quantities of both copper and gold and has been completely to partially oxidized to depths of 350 m or more with minimal remobilization of copper (please refer to companion news release for Rio Grande initial resource estimate). Below these depths, the mineralization is associated with a chalcopyrite dominant, low pyrite sulphide assemblage. A series of preliminary metallurgical tests have been completed to determine potential for recovery of both metals and thereby provide a context for evaluation of a concurrent initial resource estimate. The test work consists of single and sequential leaching tests for copper and gold, gravity separation tests for gold, and flotation-concentration studies. Test work was completed on both oxidized and primary sulphide mineralization.
The test work was conducted by ALS Chemex in Chile (ALS), Resource Development Inc. (RDI) in Colorado and SGS Minerals Services in Ontario (SGS), all leading analytical and metallurgical firms serving major and junior mining companies with global resource projects. Highlights of the studies include the following:
Mr. John M. Leask, President and CEO of Pachamama commented as follows:
"The initial metallurgical test results at the Rio Grande project indicate the gold recoveries are very good in both oxide and sulphide mineralization. Copper also leaches well but may be somewhat lower in areas with mixed oxide/sulphide. Acid consumption on oxide and mixed oxide will likely be high based on these tests. The purpose of the tests was to determine if both copper and gold could be recovered using conventional flotation/concentration leaching. The work indicated both leaching and conventional flotation recover both metals.
From the testwork completed to date, two processes require further investigation. The first is cyanide leaching using SART (Sulphidation, Acidification, Recycling, and Thickening) to recover most of the gold and significant quantities of copper. The second process would be conventional flotation with acid leaching of the concentrate tails for more oxidized mineralization to allow recovery of both copper and gold. Additional testwork will be executed on fresh drill core taken from the current program."
Summary of Metallurgical Test Work
A series of metallurgical studies were completed on coarse reject samples from diamond drill core holes completed in 2005/2008 at the Rio Grande project (no additional drilling was completed at the project in 2009/2010). The coarse reject samples had been stored in sealed bags in dry conditions. Drilling that is currently underway will provide fresh core sample for future test work. Composite samples were prepared utilizing multiple drill intercepts to produce samples representative of average mineralization grades and degrees of oxidation. The following metallurgical studies were completed in this phase of test work and results are discussed below:
Gold Cyanide Leach Tests and SART - SGS
The results of cyanide leach bottle roll tests and SART (Sulphidation, Acidification, Recovery and Thickening) processing of leach solution at SGS indicate rapid leach time, very good gold recoveries, and good recovery of cyanide soluble copper and cyanide using the SART process. Cyanide bottle roll tests (48 hours, 40% solids, 1g/l NaCN, K80 approximately 75 microns) were conducted on four samples of oxide or transition mineralization and three of these samples were selected for SART testing.
Sequential Sulphuric Acid - Cyanidation Leach tests for Copper and Gold - RDI
A total of 22 composite samples of coarse rejects from drill core were submitted to RDI for sequential sulphuric acid - cyanidation bottle roll leach tests. Twenty of the samples represented oxide or transitional oxide-sulphide material and two of the samples were sulphide material. The samples were first subjected to sulphuric acid leaching (72 hours, 40% solids, 10 g/l acid, P100 - 150 mesh) and subsequently to cyanidation leaching (48 hours, 40% solids, 1 g/l NaCN). A summary of the results obtained follows:
Gravity Tests - RDI
Gravity concentration tests were conducted to determine if sufficient coarse free gold exists to warrant this processing technique. The Gemini concentrates captured 13-42% of the gold from representative composite samples of oxide, transitional oxide-sulphide and sulphide material. However the gold grade of the concentrates (9-30 g/t, with one sample of 72 g/t Au) was not sufficiently high for direct smelt. Hence, gravity concentration will only be of potential value if used in the grind circuit along with conventional flotation processing.
Flotation Tests - RDI Labs
Two representative bulk composite samples for oxide and transitional oxide-sulphide material were subjected to a total of 10 rougher concentrate flotation tests to evaluate variation in grind size and reagents. The results of these studies are summarized below:
Qualified Persons and QAQC
All of Regulus' exploration programs and pertinent disclosure of a technical or scientific nature are prepared by, or under the direct supervision of, Wayne Hewgill, P.Geo, and Regulus' President, who serves as the qualified person (QP) under the definitions of National Instrument 43-101.
This news release has been reviewed by John M. Leask, P.Eng., President and CEO of the Company, and a Qualified Person ("QP") as defined by National Instrument 43-101 (Standards of Disclosure for Mineral Projects).
On behalf of the Board of Directors,
"John M. Leask"
John M. Leask, P.Eng.
President & CEO
For more information please contact us at (604) 681-4462 or see the Company's website at
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