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Age dependent variation of the magnetic fabric of dike swarms and implications for the volcanic structure of ocean islands: the example of the Maio Island, Cabo Verde archipelago

2025-08Journal article Open access
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datacite.subject.fosCiências Naturais::Ciências da Terra e do Ambiente
dc.contributor.authorMoreira, Mário
dc.contributor.authorMata, João
dc.contributor.authorMadeira, José
dc.contributor.authorRepresas, Patricia
dc.contributor.authorMartins, Sofia
dc.date.accessioned2025-09-17T15:51:55Z
dc.date.available2025-09-17T15:51:55Z
dc.date.issued2025-08
dc.description.abstractABSTRACT: Magnetic fabric analysis of dikes is a powerful technique when assessing magma transfer processes. This study presents an integrated analysis combining magnetic susceptibility and anisotropy of magnetic susceptibility, magnetic mineralogy, geochemistry and new 40Ar/39 Ar dating of dikes intruding formations ranging from the Lower Cretaceous to the Miocene on the island of Maio, in the Cabo Verde archipelago. We show that the dikes, dated at ≈9.2 Ma, intruding the younger Miocene Casas Velhas formation, display a Ti-rich titanomagnetite composition, higher whole-rock TiO2 content and very high magnetic anisotropy. They are clearly distinguished from the dikes, ranging in age from ≈9.3 to 11.3 Ma, intruding older formations, which show a predominantly Ti-poor titanomagnetite composition with multiple magnetic phases, lower whole-rock TiO2 concentration, higher range of magnetic susceptibilities and very low anisotropy. Magnetic fabric is predominantly normal with no significant imbrication relative to the dike margins. Numerical analysis of fabric shows a dominant coaxiality between the magnetic lineation and the preferred orientation of opaques and phenocrystals suggesting that magnetic lineation is, therefore, the proxy of the magmatic flow axis orientation. Based on the orientation of the magnetic fabric, we infer that magmatic flow within the studied dikes is predominantly vertical. The differences observed between the younger dikes and all other dikes may be related to magma sourced from distinct magma chambers. One, probably shallow, underneath the Casas Velhas fm in the southwest of the island, which would explain the very high values of magnetic anisotropy and the inferred vertical flow, and another located in a central position in the island, responsible for the dikes intruding the older formations. The location of such magma reservoirs and the dikes ages suggest a hypothetical migration with age of the magmatic sources that fed the dikes from the central part of the island to the southwest region. The magnetic and mineralogical heterogeneities of the dikes intruding older Lower Cretaceous formations may also be a result of a wider age range of the intrusions.eng
dc.identifier.citationMoreira, M., Mata, J., Madeira, J., Represas, P. & Martins, S. (2025). Age dependent variation of the magnetic fabric of dike swarms and implications for the volcanic structure of ocean islands: the example of the Maio Island, Cabo Verde archipelago. In: Geophysical Journal International, 2025, vol. 243 (1), pp. 1-24. https://doi.org/10.1093/gji/ggaf293
dc.identifier.doi10.1093/gji/ggaf293
dc.identifier.issn1365-246X
dc.identifier.urihttp://hdl.handle.net/10400.9/6061
dc.language.isoeng
dc.peerreviewedyes
dc.publisherRoyal Astronomical Society
dc.relationInstitute Dom Luiz
dc.relation"CV-PLUME" An investigation on the geometry and deep signature of Cape Verde mantle plume
dc.relation.hasversionhttps://academic.oup.com/gji/article/243/1/ggaf293/8225763
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/
dc.subjectMagnetic susceptibility
dc.subjectMineralogy
dc.subjectPetrology
dc.subjectAtlantic Ocean
dc.titleAge dependent variation of the magnetic fabric of dike swarms and implications for the volcanic structure of ocean islands: the example of the Maio Island, Cabo Verde archipelagoeng
dc.typejournal article
dspace.entity.typePublication
oaire.awardTitleInstitute Dom Luiz
oaire.awardTitle"CV-PLUME" An investigation on the geometry and deep signature of Cape Verde mantle plume
oaire.awardURIinfo:eu-repo/grantAgreement/FCT/6817 - DCRRNI ID/UID%2FGEO%2F50019%2F2019/PT
oaire.awardURIhttp://hdl.handle.net/10400.9/6060
oaire.citation.endPage24
oaire.citation.issue1
oaire.citation.startPage1
oaire.citation.titleGeophysical Journal International
oaire.citation.volume243
oaire.fundingStream6817 - DCRRNI ID
oaire.fundingStreamConcurso para Projectos de I&D em todos os Domínios Científicos - 2006
oaire.versionhttp://purl.org/coar/version/c_970fb48d4fbd8a85
person.familyNameMata
person.familyNameRepresas
person.givenNameJoão
person.givenNamePatricia
person.identifierI-3352-2012
person.identifierA-8080-2008
person.identifier.ciencia-id4312-8A60-15E3
person.identifier.ciencia-id901F-FDE9-581F
person.identifier.orcid0000-0001-5769-7708
person.identifier.orcid0000-0002-2987-2836
person.identifier.scopus-author-id7102806167
project.funder.identifierhttp://doi.org/10.13039/501100001871
project.funder.nameFundação para a Ciência e a Tecnologia
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