Ernest Giles Research Thread13 Apr 2024 15:27
i’m starting a thread on ernest giles given its going to be a focus for exploration and in my opinion is the top target. i'm considering devoting some time to research the ernest giles region in more detail and maybe will produce another video. but for now, i thought i’d post some general information which might be useful.
ernest giles is located in the yilgarn craton, which differs geologically from the paterson and is the dominant host to gold in australia. i’ve heard before that ~70% of gold produced in australia comes from the yilgarn although i can’t find a source on that. in 2013, the yilgarn produced even more gold than the witwatersrand in s africa. this is just to highlight as far as jurisdictions go, you can’t really get better than the yilgarn.
firstly, the yilgarn craton is extremely old, forming between ~3.7 and 2.6 ga (billion years ago). it is split into different terranes by geologists/academics. ernest giles is located in the far eastern and most underexplored part of the craton, the yamarna terrane. the nearest deposits that have a resource or are in production are the gruyere deposit (gold road resources and goldfields jv), tropicana (anglogold) and several deposits in the laverton district (owned by barrick, anglogold ashanti). however, these are located pretty far away so the local geology to ernest giles could be very different. we’ll only know that once enough drill holes go in the ground given there is 0 outcrop and the entire thing is undercover.
the likely deposit type ernest giles falls into is called orogenic gold. this is sometimes referred to as lode gold or mesothermal gold. put simply, orogenic gold deposits form during mountain building events (orogenies) and are often associated with granites and mineralised quartz veins. these veins are emplaced up to 20km depth from the surface. orogenic gold deposits in the yilgarn are often hosted in granite-greenstone belts and are archaean in age. greenstone is just a common term for archaean age, metamorphosed basaltic igneous rocks that are located in narrow basins. several researchers have published ages on the mineralisation that fall between 2.68-2.63 ga, during the waning stages of the orogenic episode that affected the yilgarn. to avoid information overload, i'll save alteration, lithology and geochemical details for another time.
the best orogenic gold systems carry high average grades (>2g/t au) and form large mineralised veins and tightly spaced veins. some orogenic gold deposits such as sunrise dam can be very “nuggety” whilst others like obuasi contain shear zones that host gold mineralisation. common sulphide minerals include ****nopyrite, pyrite, pyrrhotite and more rarely chalcopyrite. gold may occur as visible gold or hosted in pyrite or ****nopyrite. drillholes at ernest giles are less likely to produce continuous, uninterrupted drill intercepts like havieron. instead, we may see intermittent high grade intercepts, representin