AZY (ASX) Ann: Rio Tinto Citadel Farm-in Project 2018 Exploration Update

Originally posted by salpetie: ↑

I liked the Dec 4 announcement by Greatlands and have taken quite a close look to see what can be gleaned from it and previous drilling reports.
This image summarises the first 9 holes.

It is a cartoon with this plan view showing where the collars sit relative to one another plus my estimate of the traces for inclined holes 7 & 9.
To generate the cartoon I crunched data from the announcement to give this table.
This PDF may give access to the active links within this image. HAVIERON COMPARISONS 1-9.pdf

Some observations and musings not in any specific order:
The depth of cover is between 400-440m vertical. Quite uniform from these 9 pierce points.
The target area is not very large but open in several directions and to depth. Geophysics >=1400m!
I couldn't find detailed geological info for holes 1-4. IMO the terminology is being refined now they have 9 holes with over 3 Kms of basement core into a relatively confined area. The rig geo's will be developing a reasonable feel for grades based on chalcopyrite estimates which may or may not continue to show a fairly reasonable correlation with gold.
Grades to date have shown a high level of variability as has been commented on both other posters including me. The 5% Cu and 100+ g/t Au "spot" values have been repeated in holes 1 and 5 so they are beginning to show statistical relevance = real and material to any final resource estimate IMO. Further confirmation from holes 6-9 and it is really game on to see if they can make a mine here.
The general alteration, mineralisation and lithologies for Holes 1-4 is mentioned in the table above. I suspect mafic dykes may be present. Hole 8 may have been drilled into a sub vertical 20??-50m wide intrusive body.
Holes 1-4 were drilled to around 600m with some stopping in low grade mineralisation. Some of these assays at 600+-m are as good as those reported by AZY today! I wouldn't be too surprised if some or all of these holes are extended at some point in the future if it is technically possible. Directional drilling would also be an option that, while expensive, can save re-drilling the top 2-400m when feasible.
At Havieron NCM missed and that is as good as a mile. Greatland's have hit two good holes which, if they go on to putting a mineable resource together, will be seen as a success. NCM a failure or technical success? With respect to today's fairly low key results by AZY the margin between them and Greatlands Havieron 'success' so far is very slim IMO.
How many of the geophysical anomalies will turn out to be mineralised? The positive indications at Havieron suggest most will be tested as budgets become available. Rio will probably show some love there with Eros followed by others. Some very large ones further out in the basin will be deep but how are they producing such signatures with so much cover???
Why are AZY doing aeromagnetics? The proposed surveys do not mention AEM (Airborne Electromagnetics) this time unless I misread the announcement. Havieron is a very distinct magnetic anomaly with a gravity anomaly semi coincident. Airmag is a fairly quick and easy thing to do in comparison to AEM which may be one reason - economics plus the chance to define another Havieron type target???

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Consider the Winu 'success' of Rio.
Did you know that the drill truck for BHP's 1992 program got bogged after hole ANK156? The driller was having a bad day and the geo was tired. So after digging it out hole 157 was drilled elsewhere the next day after a few cold ones.
Not a true story but what if......
Theoretical hole 157 may have just missed.....

Such issues can be the margin between success and failure in exploration.
Rio would not have authorised some 2000m or RC drilling at Folly, GT and MB if they didn't feel there was some chance of success. IMO Winu represents a combination of good geology/geophysics and whatever luck means to stick three holes into a significant deposit at the end of a season. It will be a story the people involved will carry with them for the rest of their lives. Some may even write a paper or book about what their version was. See this example for Olympic Dam's discovery.

One factor for determining BHP's drill pattern, not necessarily hole 157, was that Magnum was recognised for the first time by some phase of this program. Apparent success can distract attention away from the region and suck up energy and budgets.

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A red hot story that may make some wise investors very happy. Exploration success.....?

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A rather tenuous link between these posts comes from this conclusion drawn by PJ Russell after a review of Newmont's and Newcrest' work at Havieron and environs between the late 80's and 1996.
This 2003 WAMEX open file report gives a very good summary of the work done to that date. azy ncm hav a068545_terringa ann 2003 30-1445 -6045_12081986.pdf
It looks like they drilled one more hole and flew some geophysics but the 400+m of cover and only teasing results meant NCM finally surrendered the tenement (again) in 2008/9.

Some images from the above 2003 report and others.

Processed magnetic image.

1996/5 compilation.

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The serendipity of discovery. Great word. NCM came within 200m at Havieron.
They also explored many of the other named magnetic anomalies in the area during the 1990's but Havieron was the most prospective. A summary of probably 1000+ pages of repetitious dense data.