Geology and geochronology of the Sub-Antarctic Snares Islands/Tini Heke, New Zealand

A groundbreaking geological map and radiogenic isotope data reveal the Sub-Antarctic Snares Islands/Tini Heke, New Zealand, are composed primarily of the Snares Granite (c. 109 Ma) intruding Broughton Granodiorite (c. 114 Ma). The study identifies schistose rafts within the granite, suggesting a meta-igneous origin, and confirms no conclusive metasedimentary rocks exist despite sillimanite-bearing mica-rich schists on Rua. Deformation occurred between 95–109 Ma, overlapping with extensional ductile shear zones on Stewart Island. Additionally, basaltic dykes indicate volcanic activity across all Sub-Antarctic island groups, with larger islands capped by peat and gravel deposits.

Scott, J., Turnbull, I., Sagar, M., Tulloch, A., Waight, T., & Palin, J. (2015). Geology and geochronology of the Sub‐Antarctic Snares Islands/Tini Heke, New Zealand. New Zealand Journal of Geology and Geophysics, 58(2), 202–212. Portico. https://doi.org/10.1080/00288306.2015.1023810