Cu and Ni are more conductive than Fe, but pyrrhotite (and/or...

Cu and Ni are more conductive than Fe, but pyrrhotite (and/or pyrite) is generally the dominant sulphide even if Ni and Cu are present. The pyrrhotite's greater volume will contribute more to the overall EM response. The presence of Ni/Cu may make things a bit more conductive, but overall it might not be a significant difference. Whether it is massive, disseminated, etc has more effect.

5000 S/m is a high number. A prior announcement had 3950 S/m for a similarly located conductor. These are good targets for massive/semi-massive sulphides. But look at CUL, they have just drilled pyrite (with minor pyrrhotite) and the conductors were modelled in the 4000-4800 S/m range. I tend to be grounded with low expectations and would only back the truck up with stupidly high numbers that would be a miracle to find.

Tried to find a case study with some sulphide/siemens variations. The one below is a bit old, but gives a summary for Amorac and Waterloo, which are only 300m apart, but two different settings. Amorac has 10,000 S/m from massive pyrrhotite (0.1% Ni). Waterloo has 20,000 S/m for a massive sulphide with high Ni. Most of Waterloo's nickel sulphides are disseminated/matrix with a wide range of moderate S/m values.
https://www.tandfonline.com/doi/pdf/10.1071/ASEG2004ab105?needAccess=true