Midas Gold has resumed its resource optimization drill program at the Stibnite Gold Project, Idaho, US.
In addition, Midas Gold reported results from holes completed in late 2016 as part of this program, which has the goal of improving, expanding and de-risking the mineral resources defined in the December 2014 preliminary feasibility study ("PFS") before commencing a feasibility study ("FS"); all three of these goals were achieved with these latest results.
Assay results have been received for two drill holes completed at the southern end of the Yellow Pine deposit and a third drill hole completed in the central portion of the same deposit.
Hole MGI-16-415 intersected substantially higher grades than were anticipated (based on legacy underground exploration drilling from the 1940s), while MGI-16-416 was angled obliquely, but missed the target area and will need to be re-drilled at a slightly different angle in order to intersect the target. Hole MGI-16-417 targeted an area with little Midas Gold data, intersected slightly higher grades than anticipated, and verified the location of an important post-mineral structure.
“These latest drill results realized all three of Midas Gold’s goals for its resource enhancement drill program at the Stibnite Gold Project: expanding the mineral resource, improving confidence in the geological model, and improving margin by identifying higher grade material within the proposed pit limits,” said Stephen Quin, President & CEO of Midas Gold Corp. “Hole MGI-16-415 successfully extended the limits of known high-grade gold-antimony mineralization over 50m to the south, in an area within the limits of the 2014 PFS mineral reserve pit limits, but which had been treated as development rock in the PFS. Hole MGI-16-417 generally verified the mineral resource and provided important structural constraints on mineralization.”
Drilling in 2017, which recently commenced, will be focused on the Yellow Pine deposit, initially following up on encouraging results from MGI-16-414 and MGI-16-417. Additional shallow inclination drill holes are planned to obtain additional data beneath the historical pit lake and to improve understanding of geological controls on high-grade gold and antimony mineralization.
South Yellow Pine Drilling
The Monday Tunnel was driven in 1928-1932 from the south end of the Yellow Pine Pit along the trace of the Meadow Creek Fault Zone (“MCFZ”), the District scale structure that forms the eastern boundary of the Yellow Pine ore-body. In the 1940s, eight small diameter underground core holes financed by the US Government’s Defense Minerals Exploration Agency were completed in this area, focused on exploration for antimony and tungsten. The 2014 PFS geologic model for the southern section of the Yellow Pine deposit was partially based on this legacy underground drilling and the mineralization was modeled as inferred mineralization and subsequently treated as development rock in the 2014 PFS economic model. Drill hole MGI-16-415 returned gold grades approximately twice those carried as inferred mineralization in the 2014 PFS block model (3.12g/t Au in current drilling versus 1.6g/t Au predicted) with substantially higher antimony grades as well. The drill hole intercept was approximately 30% shorter than was predicted in the block model and the differences are likely due to better core recovery and sampling methodology in the modern-era drilling versus the older legacy drilling.
“This higher-grade gold and antimony mineralization at the south end of the Yellow Pine deposit represents an economically attractive resource expansion target within and immediately adjacent to the proposed open pit and warrants additional drilling,” said Mr. Quin.
The second drill hole, MGI-16-416, was drilled in a more southerly direction, sub-parallel to the target zone, but did not penetrate the mineralized corridor of the Meadow Creek Fault Zone. Historical drilling from surface and in legacy underground workings in this area suggest this hole just missed the target. Additional drilling is being considered to intersect and extend the known limits of the mineralized zone farther to the south.
Central Yellow Pine
Drill hole MGI-16-417 was drilled to obtain additional information beneath the historical Yellow Pine pit in order to replace legacy data and to test for continuity of an important post-mineralization fault in the deposit. The drill hole generally confirmed the grades estimated in the 2014 PFS block model, returning approximately 5% higher gold grades, as well as higher antimony grades. Sub-economic inferred mineralization in the footwall of the post-mineralization fault was not confirmed, which has no impact on project economics.
High Grade Antimony Mineralization
Both MGI-16-415 and MGI-16-417 intersected multiple sets of narrow, high grade antimony veins within broader zones of lower grade stockwork and disseminated gold mineralization. These vein intersections and their orientations are consistent with newly developed geologic concepts for the Yellow Pine deposit that are based on Midas Gold work and age dating studies conducted by researchers at the Idaho Geological Survey and U.S. Geological Survey. This work suggests that the antimony vein systems have overprinted earlier, more disseminated, gold mineralization may be related to a separate mineralizing event. The implications, confirmed by the oriented core data from these holes, also indicate more focused drilling at appropriate orientations may provide evidence for continuity to these high-grade stibnite vein systems, which can run multi-percent antimony, and could enhance project economics.