This is an interesting idea or concept but I'm not entirely sure it fits under gambling
as presented but a gambling element could be added where odds could be offered into
the system for those who didnt necessarily want to hunt the treasure.
For a geolocated treasure hunt the treasure would have to be substantial to cover
participant travel and accommodation expenses.
The treasure would have to be verified with an escrow or something, or insured?

The gambling element could be odds offered for getting the location correct, the odds
reducing as each clue is revealed for example.
The clues could be eliminating countries or continents therefore killing wagers
so that the scenario doesnt exist that all bets are live until the treasure is found.