Magnetic properties of rocks from the southern Coromandel

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Turner, G.M.; Kellett, R.L.; Caratori Tontini, F.; Stagpoole, V.M.; Christie, A.B. 2017 Magnetic properties of rocks from the southern Coromandel. Lower Hutt, N.Z.: GNS Science. GNS Science report 2017/25 35 p.; doi: 10.21420/G27K51


Abstract: Magnetic properties have been measured in 33 samples of Miocene to Pliocene age volcanic rocks from the southern Coromandel Peninsula, Waikato region. These new data, combined with data from 191 existing samples, provide a comprehensive set of magnetic susceptibility data on andesites, dacites, rhyolites, ignimbrites, and some sedimentary rocks that can support the interpretation of airborne magnetic surveys in the region. The new analysis includes measurements of the remanent and induced magnetisations that indicate an influence of polarity reversals of Earth’s magnetic field on the geophysical response of some of the volcanic deposits. Additional thermal demagnetisation, of a subset of samples, provides insight into the mineralogy of the remanence bearing magnetic grains and the effects of alteration on them. (auth)