Great post there Poodle, resonates well with me and crux of your post is why I initially invested in DRE and will continue to hold at least for the foreseeable future. So, my perspective and subsequent rationale is very much based on that long term view of backing DRE’s exploration ability across a range of projects.
“If we have covered not even 10% of the planned drilling so far, yeah it may pinch and swell, grade and TREO ratios may vary and there is a lot of unknowns but given what we have found so far and how much more is to be explored I feel pretty comfortable where we are at, the targets we have set ourselves and the chances for finding better /more REE”Agree!
Have also been thinking about this for a while now, and it is easy to lose sight of the project scale, and potential opportunities that brings – as well as the challenges of effective exploration. Clearly there is a lot to be said for boot-on-the-ground style exploration...it got them onto Yin. But for that to be effective there needs to be a methodology of prioritisation – DRE have shown the benefits of the radiometrics as a first-pass regional targeting method. No doubt they will be combining that along with the magnetics, mapping and other available datasets.
On the theme of regional targeting and value through exploration – there is a useful case study in HAS, or at least one that I found interesting anyway.
In 2012 HAS commissioned an airborne HyMap survey – the results are no longer private, and anyone can access the data. There have been multiple posts already on spectral mapping from various satellite platforms (ASTER, sentinel, Landsat etc) which show potentially useful proxies for regional target gen.
Hymap is true hyperspectral, being collected at 5m spatial resolution and including 126 different bands across the full VNIR and SWIR spectrum at an average resolution of ~15nm. Compare that to a multispectral system like sentinel-2 which is collected at 10-60m spatial resolution and only incudes partial coverage of the VNIR/SWIR spectrum via 12 bands with spectral resolutions ranging from 15 to 175nm).
In essence what that means is that with hyperspectral data you can more definitively discriminate between different minerals using multiple diagnostic absorption features that is simply not possible to do using multispectral data.
So, the benefit of true hyperspectral over satellite-based multispec systems is twofold… both in terms of spatial resolution (i.e. pixel size) but also spectral resolution (i.e. focus).
HAS acquired this data in 2012, and then it took them a few years to properly process the results, level4 processing didn’t occur until 2015. The interesting aspect is looking at the known (mapped/drilled) ironstone resources before the survey and then again after the survey…….not even before the survey but before it was properly processed in 2015.
When HyVista was contracted to process the hyperspectral data in 2015 HAS was sitting on approx. 6.8 Mt @ 1.52% TREO from Frasers, Simons Find, Bald Hill and Yangibana North. In fact, the extent of these known REE ironstones was provided as a training/truthing layer for the spectral processing.
The figure below shows the survey outline (blue), known REE ironstones (red) and the generated targets (yellow), with DRE’s current tenure in black just for reference.
If we then compare those yellow targets highlighted in 2015 with the 2021 pit outlines (magenta) in the image below, can see the additional mineralised areas of Yangibana, Auer and Auer north that this survey had identified (not saying it was based solely on this, usually it’s multiple factors)...but it likely helped. BTW....they also picked Yin! Or at least the northern end of it (see left lower corner).
There is a whole stack of different mineral and ternary combinations that have been used to map lithology, alteration, mineral chemistry (Mg-OH and Al-OH etc) and ultimately target/identify REE-ironstones. Some work better than others and it’s a case of using multiple inputs, then ground truthing. Neodymium oxide also has a unique spectral signature, the difficulty comes in trying to resolve that at very low concentrations or signal to noise ratio relative to the more dominant weathering minerals.
Nevertheless when you look at the HyMap neodymium pseudocolour mineral map over the C1-C5 area it does show a discrete high towards the southern end where it is yet to be drilled. Also, interestingly it doesn’t show anything over the main C3 area. Personally I wouldn’t read too much into it…but lets see what the drilling shows.
The muscovite abundance map also lights up over what we now know as Yin and the southern part of Y3. Possibly indications of increased hydrothermal fluid flow.
Unfortunately, the HyMap survey doesn’t extend down to C6 area….im intrigued what it would show, especially as it does have a distinct SWIR response in the Sentinel-2 data. In any case, it highlights the potential application of hyperspectral mapping, and I wonder if DRE has plans to increase the coverage.
Also, interesting that C6 shows up as a coincident gravity and magnetic anomaly, especially given the gravity is very wide-spaced stations.
GLAH - as always just my thoughts, please dyor.
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