Laboratory investigation of remanent magnetisation in some rocks from New Zealand and Antarctica

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Hunt, T.M.; Mumme, T.C.. 1977 Laboratory investigation of remnant magnetism in some rocks from New Zealand and Antarctica. Wellington: DSIR, Geophysics Division. Report / Geophysics Division 125 68 p.

Abstract: Results are given of storage, alternating field (a.f.), and thermal demagnetisation tests on samples of peridotite and serpentite from Dun Mountain, New Zealand. The samples were more resistant to thermal demagnetisation than to a.f. demagnetisation. In an attempt to determine the amount of dextral shear on the Indian-Pacific plate boundary in New Zealand, igneous rocks of Cretaceous age were collected from several localities on the West Coast of the South Island and their magnetic properties investigated. None of the rocks had an identifiable, stable, thermal remanent magnetisation. Basalts from the Morgan Coal Measures at Roa Mine possess strong secondary components of magnetisation. The magnetisation in olivine basalts from Kowhitirangi Hill and in lamprophyre dikes from the Hohonu Range is mainly isothermal remanent magnetisation, and no primary thermal remanence could be identified. Basalts and andesites from the Takitimu Mountains were also found to have a large component of isothermal remanent magnetisation. Measurements of the directions of remanent magnetisation in basalt boulders within the Mawson Diamictite Formation from Shapeless Mountain, Antarctica, were made to determine the temperature of formation of the diamictite. The measurements indicate the formation was not emplaced at low temperatures and is not a tillite, and that it is probably a volcanic breccia emplaced at a temperature of 300 - 600deg C. Basalt of the Sledgers Formation from Carryer Glacier, northern Victoria Land, Antarctica, has a strong, stable, remanent magnetisation.