Origin of fluids in the shallow geothermal environment of Savo, Solomon Islands.

Savo is a recently emergent volcano. An active geothermal system has been present for at least 50 years, expressed at the surface by numerous hot springs, fumaroles and steaming ground. Samples of water and steam were collected from geothermal features and non-thermal springs and wells, and representative samples of altered rocks and precipitates were collected from geothermal areas. Analysis of the waters for anion, cation and stable isotope composition shows that the waters discharging at the surface fall into two groups Reoka type fluids have the high sulfate, low pH, and enriched δ18O and δD values typical of steam heated acid sulfate waters, where shallow groundwater is heated by rising steam and gas. Isotopically light H2S is oxidised in the near surface environment to produce the sulfate content. Rembokola type fluids have chemistry distinct from the Reoka type fluids, despite the two being found within close proximity (