TORONTO, ONTARIO--(Marketwire - Aug. 16, 2012) - Malbex Resources Inc. (TSX VENTURE:MBG) is pleased to report final results from column leach testing of Rojo Grande mineralization from the Company's Del Carmen Norte gold-silver (Au-Ag) project in San Juan province, Argentina. Average gold recoveries of nearly 80% in static columns show there is good potential to use heap leach cyanidation to process Rojo Grande mineralization. Heap leaching is generally considered to be a lower capital and operating cost alternative to traditional milling, vat cyanidation or other methods of gold extraction.
Seven composite samples weighing approximately 200 kilograms each and representative of grade, mineralogical and spatial variations within the inferred resource at Rojo Grande were subjected to individual column testing at McClelland Laboratories, Inc. in Sparks, Nevada. Two feed sizes (12.5 mm (half-inch) and 6.3 mm (quarter-inch)) were tested for each composite. Average recoveries for all column tests were 79.8% for gold and 35.7% for silver. Testing indicates that the composites are amenable to simulated heap leach cyanidation and show limited sensitivity to crush size (12.5 mm composites average 78.6% gold recovery with 6.3 mm composites averaging 80.9% gold). The column tests show higher gold recoveries for quartz-alunite hosted mineralization (average 85.3%) compared to silicified material (average 75.6%). Gold recovery rates are reported as "moderate to fairly rapid". The Rojo Grande mineralization is oxidized with few visible sulphide minerals and very low "sulphide sulphur" analyses in silicified composites while quartz-alunite composites contain up to 0.83 weight % "sulphide sulphur".
"We're very encouraged by the results of this phase of comprehensive metallurgical testing. The Rojo Grande mineralization is shown to be amenable to standard heap leaching cyanidation techniques. Heap leach operations are generally cheaper, faster to engineer and can be built in a fraction of the time when compared to grind-CIP plants." said Joe Hamilton, CEO of Malbex.
McClelland Laboratories, Inc. of Sparks, NV conducted heap leach cyanidation tests, on both agitated (bottle roll) and larger static columns, in order to determine gold and silver recoveries, rates of recovery, reagent consumption and sensitivity of cyanidation to feed size. Additional tests were conducted to determine parameters for agglomeration, load/permeability and modified acid base accounting static acid rock drainage (ARD) potential. The latter two tests along with mineralogical and gold deportment studies were conducted by third party contractors. The McClelland metallurgical report will be available at www.malbex.ca/reports.
Further information about Del Carmen Norte, including maps, sections and a complete assay table may also be accessed at www.malbex.ca/Projects/Del_Carmen.
About Del Carmen Norte
The 151 km2 Del Carmen concession package is located near the southern end of the El Indio Gold Belt, and hosts two high sulphidation epithermal gold-silver alteration systems. The Del Carmen Norte hydrothermal alteration system covers approximately 9 km2. The second, less exposed, high sulphidation epithermal system at Del Carmen Sur is some 5 km to the south.
Del Carmen Norte consists of a strongly altered, sub-horizontal sequence of andesitic volcanic rocks that are cut by numerous faults. Volcanic and/or hydrothermal breccias appear to be selectively silicified with mineralization hosted by silicification and quartz-alunite alteration between less favourable argillic (quartz-kaolinite) alteration in volcanic lithologies. Steep structures and the margin of dacite domes appear to have also strongly influenced hydrothermal fluid flow within the volcanic sequence. High-sulphidation alteration is therefore zoned outward by the combination of both lithological and structural controls.
About the Rojo Grande deposit
The Rojo Grande deposit has the following characteristics:
- Disseminated, very fine-grained mineralization that is
- hosted in two ore types: 1) silicified breccias and pervasive silicification and 2) quartz-alunite alteration;
- shallow, locally outcropping; and
- strongly oxidized, with metallurgical testing showing the resource is amenable to heap leach processing.
- Contains a pit-constrained inferred resource of 25.4 million tonnes grading 1.0 g/t gold and 13.3 g/t silver.
Each composite was created by combining selected intervals of quarter core (i.e., half sampling of previously sampled half core) to make samples representative of the two types of mineralization (silica, quartz-alunite) that comprise the inferred resource at Rojo Grande. The average calculated grade for four silica zone composites is 1.03 g/t gold and 19.8 g/t silver; that for three quartz-alunite composites is 1.31 g/t gold and 16.7 g/t silver. Fire assays of the composites by McClelland are in good agreement with calculated averages. The intervals selected in September 2011 span the then-known horizontal and vertical extent of vuggy silica and silicification (silica zone) and the underlying quartz-alunite alteration from over 90% of the twenty-three drill holes that defined the inferred resource at Rojo Grande.
Static leach tests were conducted in 15 centimetre by 3 metre columns at two feed sizes: 80% passing 12.5 mm and 80% passing 6.3 mm. The average gold recovery for the fourteen column leach tests is 79.8% with a range from 60.0 to 88.9%. Gold recovery rates are reported as moderate to fairly rapid with test leach cycles ranging from 66 to 151 days. Leaching of two silica composites was incomplete suggesting some material may require a long leach cycle. Gold leach rate profiles commonly flattened after 30 or more days of leaching. Cyanide consumption is low to moderate with the lab reporting that consumptions should be lower in commercial production. Lime and cement requirements for agglomeration appear to be low to moderate to maintain pH control and stability in loading tests that simulate 20 m and 40 m high stacks.
Malbex Resources Inc. is a gold exploration company led by experienced management and directors with projects in Argentina and Peru. In April 2010, Malbex made a near-surface, gold-silver oxide discovery at Del Carmen in Argentina. Released in September 2011, the National Instrument 43-101-compliant, inferred mineral resource estimate for the Rojo Grande deposit at Del Carmen measured 25.4 million tonnes grading 1.00 g/t gold and 13.3 g/t silver for 816,600 ounces of contained gold and 10.9 million ounces of contained silver. Further drilling was conducted during the 2011-2012 field season which extended the known mineralization. The Del Carmen project is located in the El Indio Gold Belt which contains more than 35 million ounces of gold in current reserves and past production, including Barrick's Veladero mine and Pascua-Lama project. For more information, please visit www.malbex.ca.
Peter Stewart, PhD, Vice-President Exploration of Malbex Resources Inc., is a Professional Geoscientist in the Province of Ontario, and is the Qualified Person as defined by NI 43-101 responsible for the technical information presented in this news release.
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