classified as andesites. Hawaiite occurs exclusively in the older outcrops, basanite only in parasitic vents and mugearite only on the lower sector of the volcano. Despite this, most of the volcano is believed to consist of mafic rocks with only about 10–15% of felsic rocks, as the upper visible portion of the volcano could be resting on a much larger buried base. The parasitic vents probably make up less than 1% of the edifice. Ice-lava interactions produced hyaloclastite, palagonite and sideromelane. No major changes in magma chemistry occurred during the last 40,000years but some variation has been recorded. All these rocks appear to have a common origin and define an alkaline–peralkaline suite. Phenocrysts include mainly plagioclase, with less common olivine and titanomagnetite; apatite has been reported as well. The magmas appear to have formed through fractional crystallization at varying pressures, and ultimately came from the lithosphere at depth, that was affected by subduction processes over 85million years ago. Eruption history The volcano was active in the late Quaternary. Radiometric results reported in 1988 include ages of less than 360,000years for rocks in the caldera rim and of less than 240,000years for volcanic rocks on the flanks. In his 1990 book Volcanoes of the Antarctic Plate and Southern Oceans LeMasurier gave 310,000±90,000years old as the oldest date for samples tested, citing unpublished K-Ar dates, but in a 2016 review of dates for Mount Takahe LeMasurier reported that none were older than 192,000years. A 2013 paper also by LeMasurier reported maximum ages of 192,000years for caldera rim rocks and of 66,000years for lower flank rocks. The entire volcano may have formed in less than 400,000years or even less than 200,000years, which would imply a fast growth of the edifice. Rocks aged 192,000±6,300years old are found at the summit caldera, implying that the volcano had reached its present-day height by then. Early research indicated that most of Mount Takahe formed underneath the ice, but more detailed field studies concluded that most of the volcano developed above the ice surface. The ice surface has fluctuated over the life of Mount Takahe with an increased thickness during marine isotope stages 4 and 2, explaining why units originally emplaced under ice or water now lie above the ice surface and alternate with lava flow deposits. These elevated deposits were emplaced about 29,000–12,000years ago while the lava delta-like deposits are between about 70,000and 15,000years old. After it