Summary
The chemical compositions of hot waters (260–280°C) tapped by drillholes to depths of approximately 1 km beneath volcanic hydrothermal areas of New Zealand are examined in the light of experimental work on the reaction of volcanic rocks with water at high temperature and pressure. The origin of most of the constituents (magmatic or leaching source) is indeterminate due to the reaction of the hot water with the reservoir rock, and many of the elements are controlled in concentration by solubility and ion exchange equilibria. Water compositions approaching those of natural thermal waters can be produced by the simple reactions of volcanic rock with hot water, but if this is the origin of the natural compositions, the mechanism of operation of a volcanic hydrothermal system is limited to a very slow-moving convection cycle, with a total water output during its lifetime not exceeding the storage volume by more than a small numerical factor. Otherwise, the chemical supply would become exhausted.
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Paper read at the IAV International Symposium on Volcanology (New Zealand), scientific session of Nov. 30, 1965.
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Ellis, A.J. Volcanic hydrothermal areas and the interpretation of thermal water compositions. Bull Volcanol 29, 575–584 (1966). https://doi.org/10.1007/BF02597178
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DOI: https://doi.org/10.1007/BF02597178