Geology of northern White Island, Southern Victoria Land, Antarctica
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White Island is a uniquely basanitoid-basanitic volcano in a chain of Cenozoic volcanic islands that parallel the western edge of the West Antarctic Rift System. Glaciatjon and possibly landsliding has eroded the island which, as shown by magnetic surveys, extends several kilometres further to the north under the ice sheet. Two main vent types were identified, lava-shields and maars, formed during a variety of eruption styles ranging from surtseyan to strombolian. All but one sample was found to be basanite, the other rock, a basanitoid, has more groundmass plagioclase and is less enriched in incompatible trace elements. Both rock types are inferred to have resulted from small amounts of partial melting possibly in the spine! lherzolite stability zone (25-60 km). The basanitoid resulted from slightly higher degrees of partial melting than the basanite, but based on Zr/Nb ratios all samples are cogenetic. Up to 50% crystal fractionation has occurred within the basanite spectra. Based on paleomagnetic dating, the island was found to be at least 0.78 my old, approximately four times the age of the single previous K-Ar date of 0.17 Ma (Kyle 1981). The extended age range is more compatible with lithospheric flexure models in the area whicli imply volcanic loading occurred between 1.4 Ma and 11 Ma (Aitkin 2003), and indicates that the island was active for a minimum of 0.6 my. The island occurs in an area of the West Antarctic Rift System (the Erebus Volcanic Province, Southern Victoria Land) interpreted as being a transtensional accommodation zone. This section of the rift boundary is marked by a change in orientation of the Transantarctic Mountains, and has acted as a tectonically separate block to the rest of Victoria Land for the last 800 my. During that time, the area that is now the Erebus Volcanic Province experienced two main tectonic regimes, the Ross Orogeny and the plume-related West Antarctic Rift System. At both times the area is associated with distinctly alkaline magmatism. Geophysical and modelling data indicate that the crust beneath the Ere bus Volcanic Province is very thin (- 20 km) and that Cenozoic uplift may have been localised in Southern Victoria Land, which may be part of the reason that the volcanics have such an alkali-rich signature.
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xi, 121 leaves : col. ill. ; 30 cm.
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OU geology Identifier:
2004Coulter
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Citation
Coulter, Roseanne F., “Geology of northern White Island, Southern Victoria Land, Antarctica ,” Otago Geology Theses, accessed February 7, 2025, https://theses.otagogeology.org.nz/items/show/425.