Geochemistry of Ground and Thermal Waters in the Ngawha Area and Elsewhere, Northland, New Zealand

Abstract

Most groundwaters in Northland are of ambient temperature neutral to alkaline and of type. Their chemistry is apparently determined by the lithologies through which they move, in particular the Permian-Jurassic basement which contributes B, and Li. There are also waters high in Ca-Mg hosted by the overlying sedimentaryrocks. Several waters may contain a component of connate water and a few near the coasts probably obtain some of their from seawater. The geothermal system at Ngawha itself contains alkali chloride water which is slightly acid. The system has a high gas content, largely which migrates at least 15 km. Both the gas and heat disseminated fiom the geothermal system influencegroundwater chemistry in theperipheral areas.