Magnetic techniques for ascertaining the nature of iron oxide grains in basalts

Abstract

Qualitative techniques are described by which the domain nature and magnetite-maghemite oxidation state of the iron oxides in basalts may be rapidly identified through measurements of hysteresis and susceptibility over a wide temperature range. Detailed studies made on different suites of basalts have revealed that their magnetic properties in most cases can be explained only on the basis of single-domain behaviour. Also it has been found that the observed variations in these properties between basalts are usually best explained by differences in the position the iron oxide minerals in the different samples occupy along the magnetite-maghemite oxidation chain. These observations suggest that the role of titanium usually found in association with iron oxides in basalts is to subdivide the grains physically rather than to form solid solutions of titanomagnetites or titanomaghemites. Some implications of these results to basalt formation and the magnetic anomalies such rocks could cause are discussed.

          ARK: https://n2t.net/ark:/88439/y055011

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