Couple of points. Olympic Dam is not a porphyry system, it's an...

Couple of points. Olympic Dam is not a porphyry system, it's an IOCG (THE exemplar IOCG). Having said that, while there is a depth limit, porphyries can still make good $ at depth if the grade/tons are there. Good recent example would be Alpala in Ecuador. These things are very difficult to pin down. IP can find a phyllic halo just fine but locating a potassic inner alteration zone (if one exists) is really hard and doing it with one hole would be frankly rediculous good luck. 3 holes might not find a porphyry but if we're lucky it might. If not, we should know if we're in the ballpark and even get a direction towards > heat, which needs at least a couple of holes not one. So nice as it'd be to hit something; not doing so is far from making the project a dud...