Magnetic susceptibility and partial anhysteretic remanence anisotropies in the magnetite-bearing granite pluton of Tourão, NE Brazil

Trindade, R. I.; Raposo, María Irene Bartolomeu; Ernesto, Márcia; Siqueira, Roberto

doi:10.1016/s0040-1951(99)00220-6

Cited by 63 publications

(47 citation statements)

References 49 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Além disso, Rochette (1987) propôs o valor de 0,3x10 -3 SI como o limite inferior para caracterizar a contribuição ferromagnética em granitos (l.s.). Todavia, há granitos, como por exemplo o Plúton Tourão -RN, onde a contribuição é essencialmente paramagnética e apresenta valores acima deste limite (Trindade et al, 1999). Considerando este intervalo, o PC apresenta um caráter predominantemente ferromagnético com K médio de 12,571x10 -3 SI.…”

Section: Resultados Asmunclassified

Modelo de alojamento do Plúton Cupira, Província Borborema (NE Brasil)

Miranda

Mariano

Correia

2016

Geol. USP. Sér. Cient.

View full text Add to dashboard Cite

Recebido em 8 de abril de 2015; aceito em 25 de maio de 2016Resumo O Plúton Cupira está localizado no Domínio Sul da Província Borborema, possui área aflorante de aproximadamente 300 km 2 e forma ovalada com leve alongamento na direção E-W. Com objetivo de determinar o modelo de alojamento do plúton e os alinhamentos magnético-estruturais, foi realizada a integração inédita de estudos de anisotropia de suscetibilidade magnética (ASM) e magnetometria. Os dados de ASM mostram que a susceptibilidade total apresenta variação de 0,105x10 -3 SI a 34,618x10 -3 SI, indicando caráter ferromagnético. O grau de anisotropia varia de 1,06 a 1,272 e apresenta correlação positiva com a susceptibilidade total. O parâmetro de forma varia de -0,802 a 0,897, com preponderância de elipsoides oblatos sobre prolatos, refletindo trama magnética planar. A maioria das lineações magnéticas possuem direção NE-SW, com caimentos suaves a fortes para NE e para SW. A foliação magnética varia de NE a NNE, com mergulhos moderados a fortes (30° a 86°). A porção central do corpo tem foliações magnéticas e magmáticas essencialmente concêntricas, com mergulhos fortes para o centro do plúton, associadas à lineações com caimento forte, sugerindo ser a zona de alimentação magmática. Os alinhamentos magnéticos reforçam as direções estruturais evidenciadas pela ASM. Estes dados favorecem a proposição de modelo de alojamento do Plúton Cupira a partir de uma zona de alimentação magmática central, com fluxo do magma distribuído de forma concêntrica, com geometria de intrusão similar a um lopólito.Palavras-chave: Anisotropia de Susceptibilidade Magnética (ASM); Foliação magnética; Lineação magnética; Magnetometria; Província Borborema. AbstractThe Cupira pluton, located in the southern domain of the Borborema province in the Garanhuns subdomain, crops out for approximately 300 km 2 . It is oval in shape and is slightly elongated in the E-W direction. In order to establish an emplacement model and to obtain structural-magnetic alignments, an integration of Anisotropy of Magnetic Susceptibility (AMS) and magnetometry data was carried out. AMS data show that total susceptibility ranges from 0.105x10 -3 SI to 34.618x10 -3 SI, indicating a ferromagnetic character. The degree of anisotropy varies from 1.06 to 1.272, with positive correlation with the total susceptibility. The shape parameter varies from -0.802 to 0.897, with predominance of oblate over prolate ellipsoids, reflecting a dominantly planar magnetic fabric. The magnetic lineations are distributed mainly in the NE-SW direction, with gentle to strong plunges to NE and SW. The magnetic foliation trends vary from NE to NNE, with moderate to strong dips (30° to 86°). The central portion of the pluton has concentric inward dipping foliations associated with strongly plunging lineations, suggesting a central magmatic conduct. The magnetic alignments corroborate with the structural trends obtained by AMS. These data favor the proposition of an emplacement model for the Cupira Puton from a central magmatic con...

show abstract

Section: Resultados Asmunclassified

Modelo de alojamento do Plúton Cupira, Província Borborema (NE Brasil)

Miranda

Mariano

Correia

2016

Geol. USP. Sér. Cient.

View full text Add to dashboard Cite

show abstract

“…To check a possible composite nature of the AMS fabric, difference between AMS and anisotropy of partial anhysteretic remanent magnetization (partial AARM) was compared. In general, AMS fabrics and partial AARM tensors are similar unless there is a composite fabric (Aubourg et al, 1995(Aubourg et al, , 2000Werner and Borradaile, 1996;Robion et al, 1999;Rochette et al, 1999;Trindade et al, 1999). In practice, a composite fabric may cause distinctively different directional patterns among AMS, soft partial AARM, and hard partial AARM (Aubourg and Robion, 2002).…”

Section: Source Implicationmentioning

confidence: 99%

Magnetic Fabrics and Source Implications of Chisulryoung Ignimbrites, South Korea

Hong

Doh

et al. 2016

Front. Earth Sci.

View full text Add to dashboard Cite

The anisotropy of magnetic susceptibility (AMS) of late Cretaceous ash-flow tuffs in Chisulryoung Volcanic Formation, southeastern Korea was studied to define the primary pyroclastic flow azimuth. AMS data revealed a dominant oblate fabric with a tight clustering of k 3 (minimum axis of magnetic susceptibility) and shallow dispersal of k 1 (maximum axis of magnetic susceptibility) and k 2 (intermediate axis of magnetic susceptibility). Dominance of oblate fabrics indicates clast imbrications imposed by compaction and welding. Flow azimuth inferred from AMS data indicates the nearby intrusive welded tuff (IWT) as the source of calderas for ignimbrites. Such an inference is supported by geologic investigations, in which the IWT displays eutaxitic textures nearly parallel to its subvertical contacts. The results are compatible with a unique prolate fabric and an anomalously high inclination observed for the IWT, possibly produced by rheomorphic flows as the welded tuff is squeezed along the rough-surfaced dyke walls due to agglutination.

show abstract

“…However, since it has been shown that ferromagnetic and paramagnetic materials may both have low bulk susceptibility values (Trindade et al, 1999), the relation between bulk susceptibility and magnetic behaviour must be considered with caution. Therefore, we performed further investigations on 20 samples : 4…”

Section: Rock Magnetic Propertiesmentioning

confidence: 99%

Evolução estrutural e térmica de um batólito sin-cinemático no orógenos Neoproterozóico Araçuaí (leste do Brasil)

Mondou¹

View full text Add to dashboard Cite

AcknowledgementsMy first acknowledgments are for my two co-directors, Marcos Egydio-Silva, and Alain Vauchez, which permitted me to realize this work. I thank them to took me in a country that I enjoyed discover with them, especially during the field missions. And a special thank for their patience and their disponibility during the preparation of this manuscript and for their comments and reflexions in general.A great thank to Maria Irene Raposo who initiate me to the rock magnetism and help me to complete most of the experiments. Thank you for the discussions about sciences and other.I thank the correctors Ricardo Trindade and Jean-Luc Bouchez for accepting to criticize this work, and the others board members Jérôme Bascou, Maria-Helena Hollanda and Andréa Tommasi for their participation to the reflexion.I also thank all those who participated to this work, people from Geoscience Montpellier and from the Instituto de Geociências.Of course, I thank my family who supported me in my choices. My friends, from Brazil and France, for the precious moments of relaxation. And finally, thank you Lara, your support during this experience has been the greatest help I received. AbstractThe allochtonous domain of the Neoproterozoic Araçuaí belt involves large amounts of magma, widespread partial melting, granulitic facies and high geotherm, characterising this belt as a hot orogen. The Galiléia tonalitic suite, emplaced within host metasediments and deformed at magmatic state, represents a huge batholith that strongly influenced the mechanical behaviour of this middle crust. The anisotropy of magnetic susceptibility (AMS) measured through this batholith and used as a petrofabric proxy, combined to a detailed magnetic mineralogy investigation, permitted to characterize the paramagnetic behaviour of the Galiléia suite and therefore to highlight a complex 3D strain deformation. The observed structures developed within the viscous magma resulted from a combination of tangential tectonics induced by the compression, and gravitational forces arising from the load of the overlying crust. The kinematics of the batholith is compatible with that already described for ductile rocks of hot orogens. U/Pb dating on zircons and monazites together with 40 Ar/ 39 Ar dating on amphiboles, muscovites and biotites permitted to define the thermal evolution of the Galiléia batholith and its host metasediments and constrain the timing of the deformation. The Galiléia batholith emplaced during an important magmatic, tectonic and thermal event at ~580 Ma. Temperature remained high during the first ~50 Ma of the thermal evolution, promoting a seemingly constant deformation of the batholith at magmatic state during several tens of millions years. Such high temperature conditions and stable deformation kinematics during protracted periods of time are supposed to be characteristic of hot orogen. The slow cooling rate of ~10°C/Ma evidenced after ~500 Ma probably indicate a very slow exhumation probably only conducted by erosion. ResumoA faixa Araçuaí, ...

show abstract

Magnetic susceptibility and partial anhysteretic remanence anisotropies in the magnetite-bearing granite pluton of Tourão, NE Brazil

Cited by 63 publications

References 49 publications

Modelo de alojamento do Plúton Cupira, Província Borborema (NE Brasil)

Modelo de alojamento do Plúton Cupira, Província Borborema (NE Brasil)

Magnetic Fabrics and Source Implications of Chisulryoung Ignimbrites, South Korea

Evolução estrutural e térmica de um batólito sin-cinemático no orógenos Neoproterozóico Araçuaí (leste do Brasil)

Contact Info

Product

Resources

About