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Jun 2018 - Sampling Sandstone

Soil Sampling Works at Sandstone

On 13 & 14 June 2018, Alto (AME) reported the progress of its soil sampling program at its mostly wholly owned Sandstone goldfield and discovery of a ~1.3km x 1.3km anomaly south of the Bull Oak open-pit, of which ~30% of the assays have values >30ppb. The actual distribution reported includes 42 assay samples between 31 & 100ppbAu, 17 from 101 to 300ppbAu and 3 >300ppbAu. The significance of >300ppb and the cluster in the >200ppb area shown in the figure is that from what I recall, an ~300ppb gold-in-soil anomaly usually inferred that it could/should result in a gold mine, as illustrated by the Plutonic gold mine having been based on a ~300ppb gold anomaly.

Of course soil sampling for gold is not new. However what is new is the low cost fast method in which it can now be achieved. Alto required ~3000 soil samples to be collected on varying grids (depending on perceived geology and structures) of mainly 100m x 200m, and 200m x 400m in their ~800 sq km goldfield, which was achieved in 30 days (mostly in the month of April 2018) at the rate of 100 ready to be assayed samples per day.

As described in the JORC 2012 notes with Alto’s 13 June announcement, soil samples were taken from 20cm to 50cm below surface at the designated grid spots by XM Logistics Pty Ltd (using people on 2 quad bikes at the rate ~A$1500 to $2000/day). The samples were then screened in field (using sieves) to achieve a ~1kg sample of the 0.9mm to 1.6mm fraction, which was bagged, labelled and photographed together with its gps position. The labelled sample bags were then sent in bulker bags to MinAnalytical’s labs for mass spectrometry analysis, with the results then entered into excel spreadsheets.

How Alto came up with this approach was that it had taken them ~ 2 years to rebuild an understanding of the geology of the Sandstone goldfield and what had and had not been done/explored. It was actually a not too dissimilar approach and effect on its share price that Gold Road undertook for ~2 years and then resulted in GOR’s Gruyere discovery in its Yamarna greenstone belt.

Initially Alto produced its own geological plan of the Sandstone goldfield, as the original plan that Troy was using did not appear to even correlate with Google Earth (admittedly the freely available Google Earth was still in its infancy when Troy closed its plant in ~2010).

That resulted in 5 main camp-style target areas, and the initial focus on the Vanguard-Indomitable “Mafic-Terrane”, and then the extensive soil sampling program completing the gaps in the patchwork quilt of historic soil sampling, followed by the current aircore and then follow-up RC. Most company owners (starting with WMC) of the Sandstone goldfield have undertaken some soil sampling of parts of the goldfield, but often been thwarted by not holding a neighbouring tenement.

As part of the gradual review, Alto’s chief geologist, Changshun Jia produced a powerpoint presentation on the discovery of Troy’s Bulchina ore deposit, highlighting its discovery from soil sampling. Further soil sampling by Troy caused a change in the interpreted direction of the mineralisation, and ultimately the discovery of the orebody. More importantly, it showed that soil sampling in the Sandstone goldfield worked in delineating and producing mineralization.

Let’s face it, geology appears to be all about trying to find a correlation between one of the possible method layers that can be applied, and an ore deposit. For Sandstone that appears to be soil sampling.

In the Alto presentation to the AMEC Conference released on 14 June, there is a reference to a 3km x 3km gold-in-soil anomaly also south of Bull Oak, and the ~2km diameter Stingray area.

Stingray is a completed undrilled (by any means) area north of an excised alluvial mining area, and was probably ignored because it is demagged (demagnetized) probably due to a pole-swap period. However, demagged areas are increasingly coming under the spotlight by various exploration and producing companies, possibly since Jundee lies in a demagged area. At Stingray extensive BIF outcrop (possibly parasitically folded) can be physically seen, but it is effectively “invisible” in mags because it is demagged, and probably lends itself to soil sampling (where practical).

It has been remarked by international geos that the standard of geology and geological techniques and new advanced equipment (eg the photon analyser, etc) applied in WA is the highest in the world, well ahead even of Canada. It could well be that soil sampling may attain a revival now that it is simpler, faster and less costly than it was historically.

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 State One Stockbroking (AFSL 247100).

Figure. Alto’s Soil Assays from its Hancocks Mining Area South of the Bull Oak open-pit, at Sandstone.paydirt jun2018

  • Written by: Keith Goode
  • Saturday, 30 June 2018

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