Variation of magnetisation on White Island, New Zealand

Abstract Measurements of the magnetisation of andesitic rocks from White Island have been combined with an interpretation of an aeromagnetic survey of the island to show the high variability of magnetisation in the rocks. Sampling of the rocks on White Island shows that, as expected, fresh andesitic lavas are highly magnetised (up to 20 A/m) whilst the phreatomagmatic deposits and altered andesites are weakly magnetised ( 10 A/m, occur in three settings. They form a ring around the outside of the crater floor; there is a group of them between Shark Bay and Troup Head in the east of the island; and ther...