Origin of Mineral Springs of the East Coast, North Island, NZ

Abstract

Strongly mineralised waters emerge as warm and cold springs from parts of a Cenozoic accretionary prism which extends along the East Coast of the North Island. The chemistry of these waters is consistent with them having been derived from connate sea water in deeply-buried sediments and is distinct from springs other parts of the prism and elsewhere in New Zealand. Most of these mineral springs are associated with three, long-wavelength, magnetic anomalies which modelling suggests are caused by deeply-buried ophiolite bodies within the prism or by seamounts on the top of the subducted Pacific Plate underlying the prism. It postulated that these deep-seated bodies have facilitated the dewatering of marine sediments from deep within the prism or from the subducted plate. This "devolved sea water" has then risen, been modified by contact with overlying sediments and mixed with near-surface meteoric waters, before emerging at the mineral springs.