Geology and age of Solander Volcano, Fiordland, New Zealand

The Solander Islands are the eroded remnants of a once much larger volcanic complex, the only known subduction-related magmatism on the Pacific-Australia plate boundary south of New Zealand. The largest island, Hautere, preserves an eruptive sequence of subaerial adakitic andesite domes and related block and ash flows, followed by a phase of phreatomagmatic deposits. Ar-Ar plagioclase ages, detrital U-Pb zircon ages, and magnetostratigraphic data from Hautere indicate that magmatism probably occurred in the interval 100-350 ka. In contrast, an andesite dome on nearby Little Solander Island gives an age of 20-50 ka. Local hydrothermal activity is manifested as orange-colored alteration and tuffisite dikes. There is no evidence, at least in the small preserved remnants of the Solander Islands, for tectonic uplift or subsidence; most of Solander Volcano was eroded away during Late Pleistocene marine planation.