Are Tokaanu Chloride Waters the Outflow From Ketetahi or Hipaua?

Abstract

Waters discharged at Takaanu-Waihi have the highest c1 (3500 mgkg) and B (100 mg/kg) contents of the Taupo Volcanic Zone. Very high B contents in waters and steam at Ketetahi suggest a possible link. Relative Na-K-Mg and Ca contents of Tokaanu waters cornspond to attainment of water-rock equilibrium at about 230?C. Ketetahi, some 20 km S of Tokaanu, produces highly immature, steam-heated, essentially NH4-S04 waters. The isotopic composition of Tokaanu waters is compatible with derivation from both Ketetahi and Hipaua, another area of intense fumarolic activity some 3 km to the W. At Ketetahi, the inferred B contents of deep waters, however, are much too high, while those at Hipaua are suitable to act as source waters for Tokaanu. Relative CO2, HzS, CH4 contents, and higher hydrocarbons in Tokaanu and Hipaua vapors are very similar, but differ consistently from those of the Tongariro discharges. The close relation between Tokaanu and Hipaua is strongly supported by the isotopic compositions of COz CH4 and He. All three areas, Ketetahi, including Red and Central Crater, Tokaanu-Waihi, and Hipaua appear to be associated with arc-type, probably andesitic magmatism.