Ann: Intersections of Bonanza High Grade Gold Plus Visible Gold,EVN-ERM.AX, page-71

It depends on several and various factors. First of all, the primary zone in geological terms is below a supergene zone if one exists.

Then if one exists, the most important factor of course is proving up the quantity and quality of the supergene zone. Then there is the factor relating to how much residual gold remains closer to surface and the level of concentration in that residual gold. That is called the oxidised zone. Then there is the depth of zoning to consider. All up this stuff gets assayed and measured then put into a geostatistical model to establish things like tonnage, g/t of gold, overburden considerations and many others.

Open pit mining is much cheaper than underground mining. The perfect set up is a deposit that is economical to mine open pit in the first stage then in a later stage progresses into an underground mining operation. Sometimes the reverse can happen like is being considered by BHP at Olympic Dam, but that is a rare exception.

Regardless, if a deep deposit in the primary zone proves up an economical ore body then underground mining is viable in the first instance.

Here is the thing that excites me about ERM's exploration and discovery. The Tennant Creek region is renowned for having small to medium IOCG deposits all over the place. That is prosperous for finding a relatively large IOCG deposit that would be a company maker. Additionally, the historic mining in this region has plenty of shaft mining that has only gone down to 50m or so deep. That indicates to me that there is plenty of scope to discover residual gold concentrates close to surface in the oxidised zone and above any supergene enrichment zone. If so discovered, then it would likely be all systems go for open pit mining with follow on underground mining into the primary zone (also called the hypogene zone).

Bottom line and relative to size of the gold supergene enrichment zone then one can say it will be the "icing on the cake". Time will tell. How much time is the golden question though?

Cheers