I had been doing some research on Yarawindah and then this AEM data was announced and plugged it in to see how it fit previous exploration.
Firstly, mini taste of exploration in the Wheatbelt of WA.
There has been a moderate amount of exploration here mostly since the late 1960's but not a large amount of success to show for it. There has been Boddington and Darling Range bauxite along the western margin but elsewhere gold, nickel, copper, iron exploration has only produced some gold mines of which Westonia is the largest.
This image shows some of the major prospects/mines but is
by no means complete. Tampia and Bindi are both well explored with Jorc resources that put them IMO closest to possible mid-long term relatively large scale production if they can get over all the hurdles. Much more could be said but too speculative and not appropriate here.
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Secondly, previous exploration is summarised in this 2016 wamex open file 107852.
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Some extracts:
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Prior exploration goes back to the 1970s. The 1996 regional geology map shows a major NNW/SSE structure near Yarawindah which may be something that tweaked Dr Hronsky's interest in the area. Babel/Nebo, Karlawinda and Tropicana were results from this type of thinking at WMC in the 1990s.
Some images of previous exploration in the report:
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Some grid lines are still visible on google earth because this area is a ridge and not suitable for cropping:
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Thirdly, how does the AEM relate to previous work and google earth images. I have limited resources so overlaying images does result in minor errors which hopefully are not too significant for the purpose of this exercise. 100+- meters is possible.
Images of the original AEM channel 39 map and a photo shopped version where I have removed the background and hopefully no significant anomalies.
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To overlay this modified image on other maps all that seems available are the property outlines which do not always seem to be consistent with older maps such as the magnetics. The location of numbered anomalies to this CZI image looks adequate....
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Overlaying google earth, magnetics:
Mag and approx CZI numbered AEM:
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Photo shopped AEM on magnetics - approximate.
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Finally what do all these images mean? Note the final bulleted point and DYOR there is a lot available in open files on WAMEX.
AEM measures conductance and with today's instrumentation and multi channel read outs Geophysists have a better idea of what may or may not be a good = economic conductor. Some basic rules of thumb, in no particular order or necessarily complete, for an exploration geo of my vintage:
- The later time anomalies tend to be related to better conductors but depth and ground conditions mean close examination is necessary. All the lettered anomalies are ambiguous and would require detailed examination - most seem to have failed at this stage with the possible exception of A and D. "Weak" anomalies could be a reflection of deeper targets - F and H perhaps???
- check for cultural anomalies (power/water lines, buildings etc.) - anomaly D above fits this description but IMO given the channel 39 and the size of the anomaly relative to the shed it may be real.
- Check for fault structures, drainages, saline rich areas - Anomalies E and G are probably of this type and there may be some drainage aspect to the A to B area.
- Related to the last point AEM can be quite good for finding underground water. Perhaps used for this purpose at the WMP and definitely elsewhere though probably more as an add on to mineral exploration.
- What if any correlation is there to other surveys? A conductor/anomaly is more likely to be prospective if it correlates to magnetics, gravity, geochem etc. IMO the numbered CZI anomalies/conductors are at best peripheral to magnetics and relatively short (<=300m). Not a great observation as Ni/Cu massive sulphides usually have a magnetic signature. Ground truthing with EM, magnetics and perhaps gravity Vs (or with follow up) aircore?/RC drilling will be needed.
- All the AEM data needs to be examined - Only Ch39 available for comment.
- Don't let geologist's try to interpret geophysics!!
Previous explorers in the Yarawindah area appear to have missed some of these anomalies as this appears to have been the first large scale AEM survey and perhaps they focused on airborne magnetic targets for IP and EM.
A lot of work to do at Yarawindah with odds of finding something good - statistically low but worth a good try.
GLTAH
