Yes they can. If you watch this video by Dr Quinton Hennigh he discusses the geology of Fosterville in Bendigo in Victoria, which was formed together with Siren Gold's Alaxander RIver, Big River and Lyell deposits in NZ. He is comparing to his own Queensway deposit in Canada, which was also formed at the same time, when Canada was much closer to Australia and NZ(which were joined).
Some interesting comments below by Dr Hennigh. The High grade Swan zone at Fosterville contains ~3million Oz of gold, in purple below, compared to all that green area that contained only 1million ounces.
If you look at the formation of Fosterville, the deposit it does thicken and get to an extremely high grade the deeper it goes.
You can see the Alexander River image on the left, and how deep Fosterville runs into the Earth. The entire drilling of Alexader River sits within that small box in the Fosterville image on the RHS.
