Relationship of paleosubduction regime and prospectivity of an epithermal gold field,coromandel, new zealand

The volcanic rocks of the Coromandel Peninsula, North Island, New Zealand, were formed during a late Miocene convergence of the Pacific and Indo-Australian plates. The consequence of varying convergence velocity at the subducting plate margin is tensional regimes and basement collapse between 17–21 Ma and again at 3 Ma. The regions of basement collapse may be expected to be more fractured and might be anticipated to allow the penetration of late-stage magmatic fluids more easily. The distribution of high- chloride hot springs in the region is consistent with this notion. Recent discovery of economic quantities of gold deposited in geothermal wells at Broadlands (Ohaaki) and Wairakei in the nearby Taupo volcanic zone suggests, by analogy, that Coromandel gold may have been similarly transported. If so, then gold mineralization prospectivity may be expected to vary in a way similar to the regional variation in the chloride content of hot springs. On this basis the northernmost Coromandel would appear to be even more highly mineralized than the southern portion, where most of the large producing mines have been sited to date.