This statement in this article: The massive accumulations of...

This statement in this article:

The massive accumulations of sulphides show up very well in geophysical surveys because they are both denser and more conductive than the surrounding rock, making VMS deposits a relatively easy geophysical exploration targets ....

makes it seem quite simple, but we know that it is anything but (simple).

Talisman said this on 7/7:

The effectiveness of DHEM is dependent on many factors. Estimated off-hole coverage is influenced by the size and nature of mineralisation and the continuity of any potential conductive body of mineralisation. Talisman believes the DHEM undertaken to date on the Springfield tenements to be a useful tool for searching for large orebodies within a 100 to 200 metres radius of a surveyed drill hole, but has reduced effectiveness and coverage for smaller, fractured mineralised orebodies.

M Hawke and others said this in 2010:

Down‐hole electromagnetic (DHTEM) surveying showed the “DeGrussa” conductor to be relatively small; however, follow‐up fixed loop and moving loop surface electromagnetic surveys identified the presence of a significantly larger underlying conductor referred to as “Conductor 1”. Spectacular high‐grade copper‐gold intersections through Conductor 1 have elevated DeGrussa to one of the most significant copper discoveries in Australia in recent years. DHTEM surveying has been used to complement the diamond drilling program in defining the extent and geometry of the deposit, as well as to explore for possible extensions to the known mineralisation. This method was also instrumental in the discovery of a third body of copper‐gold massive sulphides at depth, referred to as “Conductor 4”.

We know that TLM when drilling Monty (it was named Monty by TLM, not SFR, as was Homer too - the area is called Springfield ) missed the deposit that SFR later found by only about 90ms. SFR found it by doing a DHEM in a TLM hole and so were led to the deposit that way. These are extracts from the May 2015 anns re 2 DHEMs:

1. # 11 May: The hole, TLDD0002A, will test a subtle, but discrete, late-time EM target identified by a high-powered down-hole electromagnetic (DHEM) survey completed by Sandfire on historical Talisman diamond drill-hole SPD021.
   
   # 15 May: Sandfire have advised Talisman that a high-powered DHEM survey undertaken on TLDD0002A has identified a highly conductive late-time anomaly approximately 15 metres off-hole potentially indicative of an accumulation of mineralised massive sulphides. ... - bingo!
   So, it can be seen that DHEM does help, and even work, but it takes excellent geophysical analysis coupled with other critical things such as geochemistry from drilling to find the target. I have put bold type for the words that I see as important.
   This is what AUR plans on doing, and it fits in with what has happened before in the eastern part of the Bryah:
   .............further drilling is being planned to test the for a mineralised system below the base of oxidation and ultimately vector towards a potential fresh sulphide source both geochemically and with DHEM surveys.