Many low sulphidation epizonal gold and zinc-lead vein deposits within magmatic arcs are situated on basement highs,
and post-date both the main volcanic episode and porphyry copper (gold) mineralization. These features are best
explained by emplacement of a flat batholith a few kilometres beneath each mineral district, as recently demonstrated by
geophysical data in the Baia Mare district of Romania. The batholith provides heat for the hydrothermal system, and
results in extensional faulting both through up-doming of the overlying rocks, and in some arcs through incipient collapse
of the thermally weakened crust under regional extensional stress. More water-rich magmas emplaced at greater depths
could explain some deep epizonal and mesothermal gold deposits situated outside magmatic arcs.