I think you've all misread the 4Km comment. Your interpretation...

I think you've all misread the 4Km comment. Your interpretation of the comment is that the local source is 4km away.

Read it again - what they said is:

"These indicators are interpreted as having not travelled more than four kilometres, which demonstrates a local source."

My interpretation is that, because the mineral indicators have not travelled more than 4km it means there is a local source.

They're not saying the local source is 4km away or 400m away or 40m away. They are just confirming that there is a local source. No more no less.

JC