A selective procedure for absolute paleointensity in lava flows

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Abstract

[1] We present a compilation of experiments of absolute paleointensity using double heating protocols on very recent lava flows from Hawaii, La Réunion, the Canary islands and Santorini. The existence of a sharp distribution of grain sizes carried by a single mineralogical phase always yielded successful determinations of paleointensity that deviate by less than 10% from the actual field value. Thus, a rapid decrease of at least 70% of the initial magnetization over a narrow range of temperatures prior to the Curie point combined with a unique mineralogical phase define an optimal situation for obtaining reliable estimates of absolute paleointensity. Consequently, we suggest that stepwise standard thermal demagnetization of companion specimens should be routinely performed prior to paleointensity experiments. Not only do these measurements provide important information about the characteristic magnetization, but they indicate which samples are appropriate for paleointensity experiments, which increases the success rate to almost 100%.

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