From what I understand the UG operation at Hill 50 closed in 2007 and mining had reached a depth of 1,500m when it closed. I'm not sure where the Hill 50 Deep resource lies in terms of the depth of the existing mine workings but given the name I'd expect it lies deeper then the final workings (can anyone clarify?). You'd imagine that the costs in restarting this mine after all that time won't be small as there would likely be significant damage to all the subterranean infrastructure due to years of the mine being flooded. You would probably need to replace all the electrical and ventilation infrastructure and given the depth (ie length of cabling, ventilation system etc) the costs would not be small.
The bulk of the actual gold mineralisation in the Hill 50 mine from what I understand occurs where banded iron formations (BIFs) typically >20m thick (of the Sidar Formation) are cut (fractured) by north-northeast to northeast striking faults at locations known as the Boogardie Breaks. The fractures allowed fluids to enter the rock and the magnetite (iron) in the BIFs was replaced by massive gold-bearing pyrite – pyrrhotite ore, with pyrrhotite being the dominant sulphide at depth and at the centre of the ore zones. The sulphide rich mineralised zones are said to have formed stratabound plunging pencil shaped shoots that can be detected from inside the mine using EM techniques. I don't know the typical size of these shoots, maybe someone else knows, but average grades of about 10g/t were common.
Hill 50 is one of the deeper and better quality UG gold mines to have been mined in WA so that's why I get excited about the potential RMS has to uncover another one of these BIF style ore bodies that just keeps on giving. I don't know much about the Water Tank Hill deposit but it is also recorded as hosted in BIF so it could have the potential to show similar characteristics to Hill 50. The smaller resource at WTH seems shallower and easier to access than Hill 50 Deep so that's why I imagine it's being developed first.
Eshmun
RMS Price at posting:
47.0¢ Sentiment: Hold Disclosure: Held
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