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Aug 2014 - Australia's New Age

Australia's New Golden Age of Discovery

In his presentation at Diggers 2014, Evolution's Jake Klein showed a figure of gold discoveries over the period from 1990 to 2013, under the caption "Gold discoveries increasingly rare". The figure showed that ~>40mozpa was being discovered from 2001 to 2009, and then only ~15moz in 2010 and 2011, and since then almost nothing.

However, that is now not quite true with Gold Road's Gruyere gold discovery in October 2013 at Yamarna attaining an in-pit resource in only ~9months of 3.84moz (96.9mt @ 1.23g/t, out of a possibly >4moz [visual-looking] resource) in August 2014.

At Diggers 2014, Gold Fields gave a presentation on their new Invincible gold discovery in the shadow of their St Ives plant at Kambalda, with a unspecified 2013 resource of 1.33moz (9.2mt @ 4.5g/t). Gold Fields claimed in their presentation to have made the discovery hole in 2012, and achieved a maiden underground and open-cut inferred resource of 247koz in only 8 months (2.3mt @ 3.3g/t), as reported in December 2012.

And then there's Barrick's new mega-long diamond drillhole, currently being drilled E-W ~3km to 4km south of the Super Pit, which is apparently twinning a historical WMC drillhole that was originally drilled by Roy Woodall. Roy was overheard telling the Barrick geologists (after his tea-break photo shoot on 6 Aug) what mineralisation and units they should encounter along the drillhole. The mega-hole is being drilled looking for a deeper repetition of Kalgoorlie's Golden Mile, and if successful, could be a "game-changer" for Kalgoorlie.

David Reed in his summation speech at the Diggers Dinner on 6 August, made a veiled reference to the Barrick drillhole when he stated that Diggers delegates may return next year to find that he has drilled a hole under the marquee where the dinner was being held.

However, if the other mineral discoveries are included, then Australia appears to be entering into a "Golden Age of discovery" aided with WA's co-funded drilling scheme.

The discoveries started with the unique (for Australia) Sandfire's DeGrussa copper deposit in 2009, followed by Doray's Andy Well in 2009, and then Sirius' (SIR.ax) Nova-Bollinger Ni-Cu deposit (also unique for Australia) in 2012, and Gold Road's (GOR.ax) Gruyere in 2013.

Just ahead of Diggers (in July 2014), Sirius reported 3 potential new discoveries in the Fraser Range with a deeper EM plate at Nova, look-alike near surface mineralisation at Crux and Centauri, and the Taipan discovery at Polar Bear near Norseman. Whether Taipan is a new style of mineralisation or simply remobilised copper and PGEs in a Widgie-style komatiite lava-flow nickel orebody has yet to be determined (see pages XX of this issue of Paydirt).

While Gold Road is waiting for assay results from its possibly similar looking Toto prospect south of Gruyere (and that is still all in only 1 of the possible 10, ~20km long goldfields that GOR has identified along the Yamarna belt, with Corkwood to the north, being the next goldfield that was expected to be tested).

And the Fraser Range appeared to be bubbling with a number of nearology "hopefuls" such as Enterprise (ENT.ax), Rams (RMR.ax), or Rox (Rox.ax) (to mention just a few) of snagging another Nova (like Sirius). Although a number of the intersections only appeared to be close to the ~0.5%Ni background mineralisation level of the Fraser Range, and as Sirius has shown, the EM plates do not always "work" there. 

As Gold Fields continues exploring along the ~22km long mineralised Speedway Trend that has been discovered extending SE on strike from Invincible South (laterally displaced west ~500m from Invincible), through Valkyrie, Sandalwood South, Heracles and Incredible, and then to the further laterally western displaced Icarus, Orpheus and Pandora as shown in the Figure.

With a $50m exploration budget for the coming year, the Speedway Trend and the acquisition of Darlot, Lawlers and Granny Smith from Barrick, the market is baffled as to why Gold Fields appears to have retrenched most of its successful and highly experienced exploration team.

As Ian Murray of Gold Road remarked in his presentation "Following the closure of Gold Fields' Exploration Division, Justin Osborne joined Gold Road and together with some of his Gold Fields' colleagues took the Gruyere discovery through to a maiden in-pit resource of 3.84moz (on which preliminary pit shells have already been undertaken) within less than a year (actually just over 9 months). Without Justin and his colleagues, that could not have been achieved".

It is an incredible achievement involving over 20 diamond drillholes up to 600m long. In fact 38.1km have been drilled (~26.4km RC & 11.7km diamond) from 2 RC (Raglan) rigs & 5 diamond (Terra) rigs with ~31000 assays (Intertek) and all for less than $7m. As Justin commented in his presentation he arrived on site at Yamarna on 14 October 2013 as Gruyere was discovered and thought "How easy is this".

Justin also commented that the Gruyere discovery to 3.84moz has been achieved at a record cost of <$2/oz (probably the lowest in the industry), with 400koz discovered per month or 13.5koz/day or 560oz per (24-hour) day. And within the resource, ~41% is in the measured and indicated category being to a depth of ~150m from surface. Gruyere is BFMC - big, fat & minimal cover (~3m to 4m), inferring a low strip ratio.

At the next Diggers (August 2015), Nick Holland may receive another vote of thanks - this time from Morrie Goodz of MacPhersons (MRP.ax), because Phil Brown (a Ghanaian, was retrenched in ~June/July 2014) from the Gold Fields exploration team that discovered Invincible, and was subsequently snapped up by MacPhersons. The Invincible discovery is in Black Flag sediments as are MRP's Boorara goldfield and to some associated degree, the Nimbus silver-zinc mine.

The information for the Invincible discovery was mostly derived from pictures taken by ERA of the Gold Fields presentation (while in the Diggers audience on 5 August), of the core at the booth the following morning, 6 August, and speaking to Phil on site at Nimbus, etc.

Phil said that when he joined Gold Fields' St Ives operation in 2007, he was told that ~70% of the mines are in the dolerite. A geochem programme was undertaken over the whole area in ~2009/10 and anomalism was picked up over the Black Flag sediments area, well outside of the dolerite. Aircore drilling of the target area in ~2010 using lake mounted rigs (Invincible is under a salt lake) intersected ~30m to 40m of lake sediments and the important magnetic lignite pathfinder layer, averaging ~3m to 7m thick (thicker in the south).

Detailed aeromag was subsequently flown, highlighting the possible structures, and causeways were then constructed to drill the potential orebody. RC drilling commenced in ~2011 to a depth of ~150m commencing from south to north, over a ~2km strike length from the major Alpha Island fault that displaces the strata south of the fault, ~500m laterally and obliquely to the west.

It seems that the discovery RC drillhole was ~6m @ ~5g/t in Black Flag black shale/mudstone ~130m downhole in 2011, but the recognised discovery diamond drillhole (in altered mudstone?) was in early 2012. It appears to be another example of diamond drilling unravelling the interpretation of the mineralisation. Since then, the ~2km length has been peppered with drillholes mostly to a depth of ~250m below surface, to result in the long-section of the main central shoot shown in the Figure.

Typical Invincible ore was described in the booth as occurring in massive breccia-shear zones with quartz + plagioclase + carbonate + pyrite +/-pyrrhotite +/- chlorite +/- sericite in a host rock of Black Flag mudstone that has been foliated and strongly altered to albite, with pyrite as shown.

In cross-section there are apparently at least 3 main lodes of which the main central lode is up to ~20m wide within up to a ~70m thick black shale/mudstone zone; that has the Merougil Creek sediments / conglomerates as a western hangingwall (HW), and the Black Flag sandstone (sst) - conglomerate and/or andesite as an eastern footwall (FW).

In the long section shown of the central lode in the Figure, there are ~3 southerly plunging higher grade ore shoots (which according to the Figure are ~110m to 200m thick). The uppermost shoot apparently averages ~7g/t while the two lower shoots average ~5g/t.

However, the grades may have been top-cut, as the recent ~1km long deep drillhole shown in the Figure, intersected 26m @ 6.5g/t & 21m @ 12.8g/t in the lower shoot at a depth of ~800m, there are a number of >50g-m and >100g-m colour-coded intercepts shown in the Figure's upper ore shoot, and there was a material amount of visible gold in a piece of the drill core in the booth.

The current 2013 unspecified resource of ~1.33moz (9.2mt @ 4.5g/t : being 6.2mt @ 4.7g/t open-pit & 3mt @ 4.0g/t underground) at A$1570/oz with an unspecified open-pit reserve of 3.7mt @ 4.1g/t for 492koz at A$1370/oz, goes to a modelled depth of ~400m. However, there are those two intersections at ~800m deep, inferring continuity at depth. There have been 363 RC drillholes for 59.2km (avg 163m) & 145 diamond drillholes for 30.2km (avg 208m) using 15km of causeways.

To the north, the conglomerates and andesites become further apart (than 70m) and the mineralisation becomes more diffused/dispersed. While to the south beyond the fault, the initial strike length appears to be possibly ~ 400m as shown in the presentation's section and plans.

Extensive mining studies have been undertaken on Invincible and approvals are apparently well advanced for mining commencement/pre-strip in December 2014 and transportation to the plant in MQ2015, with the waste being used to backfill older pits. The initial pit is ~2km long x 350m wide x 150m deep, with expected high recoveries of ~67% gravity & 93% after an ~8-hour leach.

The Invincible discovery is a classic example of "Gold is where you find it, not where it is supposed to be", and there have been many examples that I have encountered, such as the mineralisation in distant sediments at Hill50 on acquiring Mt Magnet, or the Agincourt's Calais discovery outside of the tram-tracks perception of where orebodies were only supposed to exist at Wiluna.

Adding to the new and potential discoveries are the re-interpretations, such as Macphersons' (MRP.ax) Nimbus silver-zinc mine near Kalgoorlie, Mutiny's (MYG.ax) Deflector Cu-Au-Ag VMS at Gullewa, Cassini's (CZI.ax) Nebo-Babel nickel prospect in the Musgraves, and Dacian's (DCN.ax) possible Wallaby gold look-alike in syenites at its Jupiter prospect near Laverton.

Only two months' ago at the end of May 2014, the vulcanologist expert, Ray Cas reviewed the drill core at MRP's Nimbus and showed that the Nimbus silver-zinc deposit appears to have been formed in a subterranean dacitic volcano (in the Goldfields [Kalgoorlie] stratigraphy). Many have stated that theoretically the silver-zinc vms-style mineralisation (and volcano) should not exist, but it does.

The MRP geologists subsequently re-logged the entire Nimbus drillhole database and showed that the past ~18-year focus on epithermal breccias, appears to have been misguided. If anything Alistair Cowden's original interpretation - that of an undersea volcano (which we recall from the original Archaean (was AHG.ax) presentations in about 1995), appears to have been the closest interpretation.

Now that the MRP geologists have a justifiable model, potential extensions are being made NW and SE on strike, together with additional lodes in some of the previous "gaps", between the lodes, as shown in their recent presentations.

In their Diggers' presentation on the ~20km NE/SW striking mineralised trend that contains Nebo-Babel, Cassini showed that there appears to be a higher grade near surface core as illustrated by Nebo's discovery drillhole of 26.6m @ 2.45%Ni, 1.78%Cu & 0.74g/t PGE+Au

In the Goode News column of the July 2014 issue of Paydirt, the LSG "clock" showed the Australian market at the start of its "Boom" period. Now, New exploration discoveries in Australia may also be entering a "Boom" period.

Disclosure and Disclaimer : This article has been written by Keith Goode, the Managing Director of Eagle Research Advisory Pty Ltd, (an independent research company) who is a Financial Services Representative with Taylor Collison Ltd.

Figure 1. Gold Fields' Invincible discovery's central shoot at St Ives, KambaldaGDNaug14-1

  • Written by: Keith Goode
  • Friday, 01 August 2014