Now about 500 to 1,000 metres to the northwest of the discovery zone, in the centre of the system, Erdene has reported its most consistent high-grade gold results yet on the project in a series of northerly trending epithermal veins in the Union North and South zones, together targets with a roughly kilometre-long strike length (see maps and cross section below). Erdene”s latest trenching campaign centres on a series of parallel epithermal veins in Union North, where last year Erdene had drilled a single drillhole – number 46 – into a geophysical anomaly and hit 9 metres @ 4.4 g/t gold, 11.6 g/t silver, 1 percent lead and 0.8 percent zinc.
Erdene”s recent trenches centre around that intercept and cover about 150 metres of strike. They confirm and considerably expand surface gold mineralization around the intercept, showing high-grade gold mineralization in multiple veins across widths in the 5- to 20-metre range (near true width) and at grades in the 3 to 10 g/t Au gold range, along with significant – and sometimes high grade – lead and zinc, as well as some silver mineralization.
Of particular note is a vein that Erdene trenched in the western part of Union North zone that appears not to have been hit at depth in drillhole 46 (less than 100-metre depth). To concentrate here on gold grades in the new trenches, Erdene reports, from south to north on roughly 50 metres spacings: 7 metres @ 2.5 g/t gold; 8 metres @ 4 g/t Au; 19 metres @ 8.9 g/t Au, including up to 20.2 g/t Au over 7 metres; and 18 metres @ 1.8 g/t Au, including 5 metres @ 6 g/t Au.
This vein lies about 50 metres west of another, similar vein in terms of grade and width that Erdene had already hit in drillhole 46 (i.e. 9 metres @ 4.4 g/t gold.) At surface, trenching showed continuity of similar grades to the drillhole intercept, with 12 metres @ 5.3 g/t gold and roughly 1.8 percent combined lead-zinc. Another 50-odd metres east of the vein, Erdene also trenched 15 metres @ 1 g/t Au, similar to a drill intercept 25 metres below of 8 metres @ 1.1 g/t Au.
While trenching is notorious for bias to higher grades – field technicians may either knowingly or unknowingly cherry pick high-grade mineralization – the consistency of grade between drilling assays and surface trenching suggest Erdene sampling was not obviously biased. Indeed, taking questions from Mineweb on Thursday Erdene geologists noted that heavily altered mineralization at Altan Nar does not show visible gold, making it more difficult for field crews to be selective.
So far the high-grade Union North zone is fairly modest in known extent and depth. But at this stage of the discovery there is considerable room to grow with tentative indications that high-grade gold mineralization continues to the south. Erdene also dug a single trench at Union South about 600 metres south of Union North, reporting very similar grades with 10 metres @ 4.5 g/t Au along with 8.9 g/t Ag and 2.2 percent Pb.
To note, Erdene had already poked a drillhole midway in between the Union South and the Union North zone and come up empty handed. But Erdene geologists are of the mind that the drillhole missed its target. In the drillhole, Erdene had targeted epithermal quartz veins at surface showing colloform and crustiform textures, common to epithermal systems.
But Erdene geologists say they have found geophysics – which was not used to target the drillhole – the better guide at Altan Nar. That suggests Erdene, exploration wise, hasn”t ruled out further high-grade gold mineralization along a fairly substantial strike length of roughly 750 metres. No guarantee there, of course.
