EVIDENCE OF GEOTHERMAL ACTIVITY NEAR THE NAZKO VOLCANIC CONE, BRITISH COLUMBIA, CANADA, FROM WETLAND GEOCHEMISTRY

Two wetlands, informally named the North and South Bogs, near the Nazko volcanic cone, British Columbia, Canada, have carbon dioxide gas seepages, travertine deposits and organic soil mixed with abundant calcium carbonate. A previous study revealed that the carbon dioxide had negative δ ¹³ carbon values and there were traces of methane and helium in the gas suggesting a magmatic and possibly geothermal source for seepages. However, bog water temperatures between 6 and 23 degrees centigrade indicate that a surface discharge of thermal water from depth is unlikely. Analysis of 34 ground and surface water samples collected in and around the bogs by the authors in 2013 revealed that the water is typically alkaline with a high calcium and dissolved carbon dioxide content. Trace element analysis of the ground and surface water samples found elevated lithium and boron levels, but these geothermal pathfinder concentrations were lower than those reported in the thermal water at known geothermal fields. Calcium carbonate and travertine deposits form when calcium in stream water from the dissolution of calcite-rich outcropping basalt reacts with carbon dioxide dissolved in bog water. Elevated nickel up to 44 part per billion in water from the base of a small travertine cone on the edge of the North Bog is most probably derived from the weathering of minerals in soil and glacial sediment surrounding the bog and solution transport in the ground water flowing into the calcium carbonate-organic soil. While a vigorous and continuous carbon dioxide flow from a vent in the travertine cone cannot be directly attributed to a geothermal source, the discharge is evidence of an appreciable gas generation beneath the bogs.