I have to agree with you on the contamination idea doesn't really seem convincing.
There are some 'blown up" diamond drill bits in my collection of a lifetime in exploration [I took a photo but it won't load properly
]. They are pretty obvious in the core tray and to the drillers who have to pull the rods to replace a damaged bit. To smear that much cobalt over 10s of meters is very unlikely.
Esso results do show sniffs of gold so there is a chance that is real and the cobalt suss or real too.
Having just put out a tome on contamination it appears to come down possibly to a batch issue for the high grade samples. If that is the case then one possibility is a calibration error of say 5-10 fold for that particular batch meaning there is cobalt but the grade may be less than the results say.
Don't want any of the negative ideas to be true and I will shut up now.
GLTAH
(20min delay)