Isn't it conventional to use cheaper rc until something of...

Isn't it conventional to use cheaper rc until something of interest is found, or indication of something at depth beyond range of rc Onceover? Unless they say otherwise I'd say safe to assume rc atm. Technical Q: Would a gossan at surface preclude goodies at depth (ie beyond rc), or would you normally expect to see sulphides not much deeper? Doesn't gossan indicate heavily weathered mineralisation so you'd need to get into fresh rock below oxide zone to really see what's behind the gossan mineralisation? Thanks if you can enlighten me.