TORONTO, ON--(Marketwired - April 07, 2016) - Marathon Gold Corporation ("Marathon" or the "Company") (MOZ.TO) announced today that it has received encouraging positive gold extraction results from bottle roll cyanide leach tests carried out on mineralized material from the Leprechaun and Marathon Deposits. This is first stage testing of material from the Valentine Lake project to assess the ores amenability to heap leaching technology. Thibault & Associates Inc. (an independent process chemical engineering firm) is engaged to carry out Marathon's 2016 metallurgical test work program. They report a gold extraction of 73.6% on minus 0.25" crushed core samples after 96 hours of bottle roll cyanide leach testing. Core from the Marathon and Leprechaun deposits had similar gold leachability characteristics and the data suggests that an increase in gold extraction may be possible with additional leaching time. The bottle roll tests indicated that the core samples from each deposit are amendable to heap leaching and short column tests are underway to assess gold leachability at a coarser crush size.
Highlights:
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The sample material was composited from half core samples that were within 150 meters of surface. These samples were within the pit shells of the Marathon and Leprechaun Deposits and were selected to represent as closely as possible the characteristics of the mineralization making up each resource. The core samples were un-oxidized. Oxidation is rarely present at Valentine Lake except in fractures near surface, so this material demonstrates very good leach potential for fresh rock.
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The Marathon and Leprechaun material was treated separately. The bottle roll and column samples were composited for a target grade of 1.5 g/t Au. The head grades for the metallurgical tests samples from the Marathon and Leprechaun deposits was determined to be, 1.73 g/t Au and 1.95 g/t Au respectively. Increases in grades from the core assays used to compose the metallurgical samples are consistent with the presence of coarse gold, which is common in each of the deposits found to date at the Valentine Gold Camp.
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The cyanide extraction of gold for the Marathon and Leprechaun bottle roll leaching tests was 73.6% after 96 hours with a 50% extraction of gold in the first 22 hours. The high leachability of gold on crushed ore justifies short column leach testing on ore at various crush sizes.
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The bottle roll tests were discontinued after 96 hours, even though gold was still being recovered, because there was sufficient data to proceed with more definitive column tests. The bottle roll test results by themselves indicate that heap leaching may be a viable process to use at the Valentine Lake project.