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dc.contributor.authorGeuna, S. E.
dc.contributor.authorMcEnroe, Suzanne
dc.contributor.authorRobinson, Peter
dc.contributor.authorEscosteguy, L.D.
dc.date.accessioned2018-03-23T12:42:10Z
dc.date.available2018-03-23T12:42:10Z
dc.date.created2013-06-19T11:18:45Z
dc.date.issued2008
dc.identifier.citationGeophysical Journal International. 2008, 175 (3), 925-941.nb_NO
dc.identifier.issn0956-540X
dc.identifier.urihttp://hdl.handle.net/11250/2491943
dc.description.abstractDevonian magmatism in the Eastern Sierras Pampeanas (Córdoba, Argentina) is represented by elliptical, porphyritic, batholithic, late- to post-orogenic monzogranites emplaced in a metamorphic—plutonic basement. Two groups of Devonian granitoids are distinguished: (1) metaaluminous to weakly peraluminous, hornblende-biotite bearing granitoids, and (2) peraluminous, biotite-(muscovite) bearing granitoids. Groups 1 and 2 are characterized by accessory phases of sphene-magnetite with high susceptibility, and ilmenite-(monazite-uraninite) with low susceptibility, respectively. The magnetic assemblage of the Group 2 Achala Batholith, predominantly paramagnetic, is the subject of this paper. Forty-three sites were sampled in the Achala monzogranite. Overall, it is weakly magnetic, with a mean magnetic susceptibility of 1.5 × 10−4 SI. Twenty-one sites showed titanohaematite as the magnetic carrier of a stable remanence. The titanohaematite is an accessory mineral and contains exsolved disc-shaped intergrowths of ilmenite. The weak magnetism of Achala monzogranite facies contrasts with the magnetic character of other Devonian porphyritic, batholithic monzogranites in the region. The virtual absence of magnetite, together with the presence of exsolved titanohaematite and Mn-ilmenite indicate crystallization and cooling under more oxidizing conditions. Oxidizing conditions continued into the subsolidus, causing late-stage reactions of ilmenite host grains to ilmenite + rutile+ haematite, and titanohaematite to ilmenite-poorer haematite + rutile. These reactions resulted in low susceptibility values and a strong reduction of natural remanent magnetization (NRM) intensities. Thermal demagnetization, up to 620–640 °C, isolated steeply dipping, dual-polarity remanence directions. The coincidence of the Achala paleomagnetic pole with the 380–360 Myr segment of the Gondwana Apparent Polar Wander Path and the U-Pb zircon age implies that the remanence was acquired soon after emplacement.nb_NO
dc.language.isoengnb_NO
dc.publisherOxford University Pressnb_NO
dc.titleMagnetic petrology of the Devonian Achala Batholith, Argentina: titanohaematite as an indicator of highly oxidized magma during crystallization and coolingnb_NO
dc.typeJournal articlenb_NO
dc.typePeer reviewednb_NO
dc.description.versionpublishedVersionnb_NO
dc.source.pagenumber925-941nb_NO
dc.source.volume175nb_NO
dc.source.journalGeophysical Journal Internationalnb_NO
dc.source.issue3nb_NO
dc.identifier.doi10.1111/j.1365-246X.2008.03964.x
dc.identifier.cristin1035215
dc.description.localcode© 2008 The Authors Journal compilation © 2008 RAS. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.nb_NO
cristin.unitcode194,64,90,0
cristin.unitnameInstitutt for geovitenskap og petroleum
cristin.ispublishedtrue
cristin.fulltextoriginal
cristin.qualitycode2


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