The geology of Ruapuke Island


Webster, J. G. (Jennifer Gaye)


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Ruapuke Island lies to the north-east of Stewart Island in Foveaux Strait. The area mapped consists mainly of dioritic rocks with small amounts of older gabbro and hornblende hornfels. A region of heterogeneous diorite is formed by partial assimilation of hornblende hornfels by dioritic magma. Trondhjemite, hornblende gabbro, granodiorite dykes and pegmatite veins have been examined and mapped where size permits.
Metamorphosed flows, dykes and volcanic sediments of the hornblende hornfels, and the gabbro pluton, are correlated with the Brook Street and Eglington volcanics, probably forming part of an extensive Permian volcanic arc.
Diorite and hornfelsic rocks are cut by basic dykes of hornblende-andesite composition, some of which have been intruded into hot dioritic magma. Field relations and petrography suggest that diorite emplacement may have taken place in more than one phase. Intrusive activity probably extended from late Permian into the Triassic. Devereux, McDougall and Watters (1968) have dated a tonalite from South Point by potassium-argon mineral dating at 217 m.y.s.
Whole rock chemical analyses and mineral analyses of Ruapuke rock types have been compared to published analyses of Stewart Island and South Island contemporary rocks.

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149 p. : ill. (xome col.), maps ; 30 cm.


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POLYGON ((168.462727735000044 -46.730259451999984,168.552406605000101 -46.73348425599994,168.547053688000119 -46.809635908999951,168.547048378000113 -46.809703277999972,168.45793118600011 -46.806536944999948,168.46263629200007 -46.730255980999971,168.462727735000044 -46.730259451999984))




Webster, J. G. (Jennifer Gaye), “The geology of Ruapuke Island,” Otago Geology Theses, accessed October 24, 2020,

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