dolerite dykes, page-9

Yes, I agree, the dolerites could conceivably provide a heat source to drive hydrothermic convection cells. I believe more and more that many deposits are the result of one (or more) remobilisation(s) of existing mineralisation. This is followed by possible re-deposition at economic concentrations, often along structures, conducive lithologies and/or chemical interfaces (such as mineralising fluids reaching the sea floor from below).

An interesting 'remobilised' example is the Avebury Nickel deposit discovered in 1998 in West Tasmania. The ore deposit formed via hot sulphur-arsenic rich fluids emanating from the underlying Heemskirk Granite intersecting and scavenging nickel from nickel rich ultramafic host rocks. The faults that provide the fluid pathways, and those that control the location of the host rock are likely to represent the site of higher Ni grades.
Avebury is essentially a 'new', previously unrecognised deposit style, which immediately increased the nickel prospectivity of the surrounding tenements.

Maybe the Doolgunna dolerites have some analogies with the Heemskirk Granite?