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Título: | Mineralogical control on the magnetic anisotropy of lavas and ignimbrites: a case study in the Caviahue-Copahue field (Argentina) |
Autor(es): | Moncinhatto, Thiago Ribas Haag, Maurício Barcelos Hartmann, Gelvam André Savian, Jairo Fransciso Poletti, Wilbor Sommer, Carlos Augusto Caselli, Alberto Tomás Ferreira da Trindade, Ricardo Iván |
Fecha de publicación: | 23-oct-2019 |
Editorial: | Oxford University Press |
Citación: | Moncinhatto, Thiago R., Haag, Maurício B., Hartmann, Gelvam A., Savian, Jairo F., Poletti, Wilbor y et al. (2019). Mineralogical control on the magnetic anisotropy of lavas and ignimbrites: a case study in the Caviahue-Copahue field (Argentina). Oxford University Press; Geophysical Journal International; 220 (2); 821-838 |
Revista: | Geophysical Journal International |
Abstract: | Anisotropy of magnetic susceptibility is a petrofabric tool used to estimate the alignment of minerals at the site-scale, the imbrication between the magnetic foliation and the emplacement surface being an indicator of flow direction. However, despite numerous studies examining the flow direction in pyroclastic deposits and lava flows, the effect of magnetic mineralogy and the domain state of ferromagnetic phases on the magnetic fabric remains poorly understood. This paper describes the magnetic mineralogy and its influence on the magnetic fabric of Plio-Pleistocene lava flows and ignimbrites of the Caviahue-Copahue Volcanic Complex in the Andean Southern Volcanic Zone, Argentina. Rock magnetism, anisotropy of magnetic susceptibility and anhysteretic remanent magnetization and petrographic observations were performed on 30 sites of the volcanic complex. Results revealed the extrusive and pyroclastic rocks present varied magnetic mineralogy, formed in different stages of the magmatic evolu- tion. Magnetic mineralogy variations strongly affect the anisotropy of magnetic susceptibility data in volcanic rocks and associated ignimbrites, providing ‘scattered’ fabrics when late Ti- rich titanomagnetite phases dominate the fabric, and ‘inverse’ or ‘intermediate’ fabrics when single-domain grains are present. ‘Normal’ fabrics are typically found when early crystallized pure magnetite is present. Our results highlight the complexity in the interpretation of magnetic anisotropy data in volcanic rocks and ignimbrites. |
Resumen: | Anisotropy of magnetic susceptibility is a petrofabric tool used to estimate the alignment of minerals at the site-scale, the imbrication between the magnetic foliation and the emplacement surface being an indicator of flow direction. However, despite numerous studies examining the flow direction in pyroclastic deposits and lava flows, the effect of magnetic mineralogy and the domain state of ferromagnetic phases on the magnetic fabric remains poorly understood. This paper describes the magnetic mineralogy and its influence on the magnetic fabric of Plio-Pleistocene lava flows and ignimbrites of the Caviahue-Copahue Volcanic Complex in the Andean Southern Volcanic Zone, Argentina. Rock magnetism, anisotropy of magnetic susceptibility and anhysteretic remanent magnetization and petrographic observations were performed on 30 sites of the volcanic complex. Results revealed the extrusive and pyroclastic rocks present varied magnetic mineralogy, formed in different stages of the magmatic evolu- tion. Magnetic mineralogy variations strongly affect the anisotropy of magnetic susceptibility data in volcanic rocks and associated ignimbrites, providing ‘scattered’ fabrics when late Ti- rich titanomagnetite phases dominate the fabric, and ‘inverse’ or ‘intermediate’ fabrics when single-domain grains are present. ‘Normal’ fabrics are typically found when early crystallized pure magnetite is present. Our results highlight the complexity in the interpretation of magnetic anisotropy data in volcanic rocks and ignimbrites. |
URI: | https://academic.oup.com/gji/article-abstract/220/2/821/5603748?redirectedFrom=fulltext https://rid.unrn.edu.ar/jspui/handle/20.500.12049/5127 |
Identificador DOI: | https://doi.org/10.1093/gji/ggz483 |
ISSN: | 0956-540X 1365-246X |
Aparece en las colecciones: | Artículos |
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2020 Moncinhatto et al.pdf | 10,93 MB | Adobe PDF | Visualizar/Abrir |
Este documento es resultado del financiamiento otorgado por el Estado Nacional, por lo tanto queda sujeto al cumplimiento de la Ley N° 26.899
Esta obra está bajo una Licencia Creative Commons Atribución-NoComercial-CompartirIgual 4.0 Internacional.