LTD-Thellier paleointensity of 1.2 Ga Nova Floresta mafic rocks (Amazon craton)

K.R. Celino, R.I.F. Trindale, Eric Tohver

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    5 Citations (Scopus)

    Abstract

    Absolute paleointensity at 1.2 Ga was obtained on basalts and gabbros from Nova Floresta Formation (Amazon craton, Brazil). Magnetic carriers in these rocks are single-domain to multi-domain pure (to nearly pure) magnetite. They present a strong decrease in remanence after low-temperature demagnetization (LTD) accompanied by an increase in median destructive fields. Incorporation of LTD to Thellier double-heating measurements improved paleointensity estimates and enabled paleofield recovery for otherwise sterile rock samples, giving twenty seven successful determinations for six sites (45% success rate). Site-mean paleofield values are within 4.90 μT and 15.55 μT (mean at 8.37 ± 4.07 μT). These results correspond to a mean VDM of 2.08 ± 0.94 × 1022 Am2, thus increasing the number of low-field determinations that dominate the (still scarce) Precambrian database. Our study exemplifies the need for alternative approaches in the study of ancient rocks (Amazon craton).
    Original languageEnglish
    Pages (from-to)L12306
    JournalGeophysical Research Letters
    Volume34
    Issue number12
    DOIs
    Publication statusPublished - 2007

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