Usually that darkness is the result of close spacing of the black lines that are used to connect the places that have the same conductance. Surrounding those black blobs, you'll see that the black lines get closer and closer together. I think it's just a bad image because a much larger one was shrunk down for release to the public. That squashed the black lines together such that none of the coloured regions showed through.

So, that would indicate extremely high conductance. That may or may not be a good thing. Most high-grade nickel sulphide deposits, for example, have moderate conductance.

Regards,
Lar.............................Rece... this explanation from another board as i inboxed Hoov, i was searching for reasons that created this strange image of black spots. I guess my thoughts of an intrusion, gorge or over burden were out in left field. Traps7