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Rock magnetism and microscopy of the Jacupiranga alkaline-carbonatitic complex, southern Brazil

dc.contributor.authorAlva Valdivia, Luis Manuel
dc.contributor.authorPerrin, Mireille
dc.contributor.authorRivas Sánchez, María De La Luz
dc.contributor.authorGoguitchaichvili, Avto
dc.contributor.authorLópez Loera, Héctor
dc.contributor.authorLopes, Omar Ferreira
dc.contributor.authorBonás, Thiago Bastos
dc.identifier.citationAlva-Valdivia, L.M., Perrin, M., Rivas-Sanchez, M.L. et al. Rock magnetism and microscopy of the Jacupiranga alkaline-carbonatitic complex, southern Brazil. Earth Planet Sp 61, 161-171 (2009).
dc.description.abstract"This study of the Cajati deposit provides evidence that the ore was neither purely hydrothermal, nor volcanic in origin, as previous workers have proposed. The ores were formed from magnetite-rich magmas, hydrothermally altered and intruded at an indicated crustal depth in excess of 500 m. The mineralogical and textural association between magnetite and magnesioferrite in the carbonatite, and between the titanomagnetite and magnesioferrite-Ti mineralization in the pyroxenite of hedenbergite, seems to be analog mineralizations strongly related to the ionic substitution of Fe2+ by Mg. Relatively high Q ratios (≥5) for Jacupirangite-pyroxenite may indicate a thermo remanent magnetization (TRM) by the ore during post-metamorphic cooling, however it can also be developed from chemical remanent magnetization (CRM). Vector plots for the pyroxenite samples show reasonably linear and stable magnetic components. The intensity decay curves show that only two components of magnetizations are likely present. Continuous susceptibility measurements with increasing temperature show that the main magnetic phase seems to be magnetite. Maghemite is probably produced during the cooling process. Susceptibility recorded from low temperature (liquid nitrogen (-196°C)) to room temperature produces typical curves, indicating Verwey transition of magnetite. Hysteresis parameters point out that nearly all values fall in a novel region of the Day plot, parallel to but below magnetite SD + MD mixing curves."
dc.rightsAttribution-NonCommercial-NoDerivatives 4.0 Internacional
dc.subjectJacupiranga complex
dc.titleRock magnetism and microscopy of the Jacupiranga alkaline-carbonatitic complex, southern Brazil
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Attribution-NonCommercial-NoDerivatives 4.0 Internacional
Except where otherwise noted, this item's license is described as Attribution-NonCommercial-NoDerivatives 4.0 Internacional