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Magnetic anisotropy of the Redenção granite,eastern Amazonian craton (Brazil):Implications for the emplacement of A-ty pe

plutons

ARTICLE in TECTONOPHYSICS · OCTOBER 2010

Impact Factor: 2.87 · DOI: 10.1016/j.tecto.2010.07.018

CITATIONS

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6 AUTHORS, INCLUDING:

Sérgio P. Neves

Federal University of Pernambuco

38 PUBLICATIONS 916 CITATIONS

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Ricardo I F Trindade

University of São Paulo

146 PUBLICATIONS 1,972 CITATIONS

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Roberto Dall'Agnol

Vale Institute of Technology

93 PUBLICATIONS 1,340 CITATIONS

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Paulo de Barros Correia

Federal University of Pernambuco

6 PUBLICATIONS 88 CITATIONS

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All in-text references underlined in blue are linked to publications on ResearchGate,

letting you access and read them immediately.

Available from: Sérgio P. Neves

Retrieved on: 11 March 2016

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Review Article

Magnetic anisotropy of the Redenção granite, eastern Amazonian craton (Brazil):Implications for the emplacement of A-type plutons

Davis Carvalho de Oliveira a,d,⁎, Sérgio Pacheco Neves b, Ricardo I.F. Trindade c, Roberto Dall'Agnol a,Gorki Mariano b, Paulo Barros Correia b

a Group of Research on Granite Petrology, Instituto de Geociências, Universidade Federal do Pará (UFPA), Caixa Postal 8608, 66075-100 Belém, PA, Brazilb Department of Geology, Universidade Federal de Pernambuco, 50740-530 Recife, PE, Brazilc Institute of Astronomy, Geophysics and Atmospheric Sciences, University of São Paulo, 05509-090 São Paulo, Brazild Geology College, Campus II of Marabá, UFPA, Folha 17 Qd 04 Lt especial, 68505-080, Nova Marabá, Marabá, Brazil

a b s t r a c ta r t i c l e i n f o

Article history:

Received 10 July 2009Received in revised form 27 July 2010Accepted 29 July 2010Available online 12 August 2010

Keywords:

AMSFerromagneticMagnetiteA-type granitesAnorogenicAmazonian craton

A magnetic fabric study was performed on the Redenção pluton in an attempt to understand its emplacementhistory. The Redenção pluton is part of the 1.88 Ga, anorogenic, A-type Jamon suite that intruded 2.97–2.86 Ga-oldArchean granitoids of the RioMaria Granite-Greenstone Terrane in the eastern Amazonian craton (northern Brazil).Previous gravitysurvey indicates that the pluton is a 6 km-thick, tabular intrusion. It is characterized by a concentricdistribution of facies, with rings of seriated and porphyritic granite that cut across the main facies of even-grainedmonzogranites. The whole set is intruded by leucogranites that occupy the center of the pluton. Petrographicexamination, magnetic susceptibilities, coercivity-spectra and thermomagnetic curves indicate that the magneticfabric is primarily carried by coarse-grained multidomain magnetite. This is reinforced by the coincidence of magnetic susceptibility and remanence anisotropy principal axes. The absence of solid-state deformation featuresandthe lowanisotropy degrees indicate thatthe magneticfabricis magmaticin origin.The magnetic fabricdisplaysasystematicpattern, withall facies,includingthe rings ofporphyritic granite, being characterized byconcentric,gentlydipping foliations associated with gently plunging lineations. Only the central leucogranitic facies shows a slightlydiscordantpattern with steeplydippingfabricsat itsnortheasternsector.An emplacementmodelbyverticalstacking

of successive magma batches is proposed for the construction of the Redenção pluton, which reconciles the tabularshape of the intrusion, the petrographic and geochemical zoning, and the magnetic fabric pattern. Initially, twomagma batches were emplaced as sills. First the even-grained monzogranite, then the seriated and porphyriticgranites,whichformedby minglingof a leucograniticmeltwith thehostbiotite-monzogranitic magma asattested bygeochemical data and eld evidence. The nal shape of the pluton was acquired after the intrusion and ination of the central leucogranite giving raise to the concentric pattern of facies in map view.

© 2010 Elsevier B.V. All rights reserved.

Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 282. Geological setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

2.1. Regional context . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

2.2. Shape and facies distribution of the Redenção pluton . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 282.3. Magmatic evolution of the Redenção pluton . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

3. Magnetic anisotropy study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293.1. Sampling and measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293.2. Magnetic mineralogy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303.3. Anisotropy of magnetic susceptibility (AMS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323.4. Anisotropy of anhysteretic remanence (AAR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

4. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374.1. Signicance of magnetic fabrics in the Redenção pluton . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Tectonophysics 493 (2010) 27–41

⁎ Corresponding author. Group of Research on Granite Petrology, Instituto de Geociências, Universidade Federal do Pará (UFPA), Caixa Postal 8608, 66075-100 Belém, PA, Brazil.Tel.: +55 94 2101 5900; fax: +55 94 2101 5901.

E-mail address: [email protected] (D.C. de Oliveira).

0040-1951/$ – see front matter © 2010 Elsevier B.V. All rights reserved.

doi:10.1016/j.tecto.2010.07.018

Contents lists available at ScienceDirect

Tectonophysics

j o u r n a l h o m e p a g e : w w w. e l s e v i e r. c o m / l o c a t e / t e c t o

http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://dx.doi.org/10.1016/j.tecto.2010.07.018http://dx.doi.org/10.1016/j.tecto.2010.07.018http://dx.doi.org/10.1016/j.tecto.2010.07.018mailto:[email protected]://dx.doi.org/10.1016/j.tecto.2010.07.018http://www.sciencedirect.com/science/journal/00401951http://www.sciencedirect.com/science/journal/00401951http://dx.doi.org/10.1016/j.tecto.2010.07.018mailto:[email protected]://dx.doi.org/10.1016/j.tecto.2010.07.018http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-


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4.2. Emplacement model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374.3. On the AMS of A-type granites: reduced vs. oxidized plutons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

5. Summary and conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

1. Introduction

The end of the Paleoproterozoic Era and the entire MesoproterozoicEra were characterized by intense magmatic activity in different cratonicareas of the world. The rapakivi granite suites and associated rocks of theFennoscandian Shield (Haapala and Rämö, 1992; Rämö and Haapala,1995;Amelinet al.,1997;Eklundand Shebanov,1999)andNorthAmerica(Emslie, 1991; Frost etal.,1999;Anderson andMorrison,2005) are typicalexamples of rocks formed during these Proterozoic magmatic events.Similar magmatic events have also been identied in the Amazoniancraton (Dall'Agnol et al., 1999a, 2005; Bettencourt et al., 1999).

Rapakivi granites and related “anorogenic” granites have becomean important tool for modeling Precambrian intraplate crustalprocessesand global-scale lithospheric evolution. An origin associatedwith crustal anatexis promoted by magmatic underplating is generallyaccepted for these rocks (Huppert and Sparks, 1988; Rämö andHaapala, 1995; Dall'Agnol et al., 1999a). However, their tectonicsetting has remained an issue of controversy. Classic Proterozoicrapakivi granites are associated with mac dike swarms, normallistricshear zones, and thinned crust (Rämö and Haapala, 1995). They arefound as multiphase plutons which intrude into a crust that predatesthem by some hundred million years (e.g., Rämö and Haapala, 1995;Rämö et al., 2002; Dall'Agnol et al., 2005). This suggests an extensionaltectonic setting and “anorogenic” origin, i.e., lack of direct associationwith convergent processes (Hutton et al., 1990; Haapala and Rämö,1999 and references therein). However, other authors have suggestedthat rapakivi granites could be related to distal orogenesis (Nyman etal., 1994; Nyman and Karlstrom, 1997; Åhäll et al., 2000).

Rockfabricsprovide a wealth of informationon the emplacement and

deformation mechanisms of plutons and their tectonic settings (e.g.Paterson and Vernon, 1995; Bouchez et al., 1990). However, very fewfabric studies have been carried out on A-type granites, possibly becausethey are often even-grained and isotropic, without visible crystalorientations (Bonin, 1986). Several studies have shown that the low-eld anisotropy of magnetic susceptibility (AMS) technique can providefabric information for weakly deformed or apparently undeformedplutons from various tectonic settings, and with different compositionand mineralogy (Bouchez, 1997). However, few AMS studies have beenperformed on A-type plutons thus far (Geoffroy et al., 1997; Ferré et al.,1999; Bolle et al., 2002). Here we report results of a magnetic fabric studycarried out on the Redenção pluton (eastern Amazonian craton). TheRedenção plutonis representative of the Paleoproterozoic oxidized A-type Jamon suite (~1.88 Ga old), which is hosted by granitoid rocks of the

Archean Rio Maria Granite-Greenstone terrane (Oliveira et al., 2005). Theoxidized A-type granites, in opposition to thereducedA-typegranites, aremagnetite-bearingandformedin moderatelyoxidizingconditions aroundthe nickel/nickeloxide oxygenbuffer(Dall'Agnol andOliveira, 2007). Thiscontribution aims to investigate the emplacement mechanisms involvedin the construction of the Redenção pluton with implications forunderstanding the transport and emplacement of large amounts of felsicmagma through a granitic Archean crust.

2. Geological setting

2.1. Regional context

The Redenção granite is situated in the eastern border of the

Central Amazonian province, in the Amazonian craton (Tassinari and

Macambira, 2004; Fig. 1a). This tectonic domain was stabilized at theend of the Archean and remained stable until 1.88 Ga whengeneration and emplacement of oxidized A-type granites of the Jamon suite and associated mac and felsic dikes occurred (Dall'Agnolet al., 1994, 1999b, 2005). These A-type intrusions postdate theirArchean country rocks by ca. one billion years (Macambira and Lafon,1995; Rämö et al., 2002; Dall'Agnol et al., 2005) and took place~150 Ma after the last major Paleoproterozoic Trans-Amazoniancompressional event recorded in the Maroni-Itacaiúnas province(Fig. 1; Delor et al., 2003; Rosa-Costa, 2006; Rosa-Costa et al., 2006).The emplacement of the Jamon suite granites is thought to be linkedto asthenospheric upwelling and magma production in the mantle,followed by partial melting of the lower continental crust induced byheat provided by underplating of mantle magmas (Dall'Agnol et al.,2005). The resulting melts ascended in the crust and were emplacedas high-level granite complexes. The occurrence of NNW–SSE diabaseand composite felsic–mac dikes coeval with the Jamon suite (Figs. 1and 2) suggests crustal extension oriented approximately ENE–WSWduring pluton emplacement. The 1.88 Ga A-type granite plutons andstocks of the Carajás province also occur along a belt that follows thegeneral trend dened by the dikes (Fig. 1b), suggesting that theiremplacement may have been controlled by the same regional stresseld.

2.2. Shape and facies distribution of the Redenção pluton

The Redenção pluton is usually isotropic in the eld (Fig. 3a) withlocal development of magmatic foliation at its borders. At themicroscope, igneous textures are perfectly preserved (Fig. 3b), except

for local effects of subsolidus alteration such as sericitization andmartitization. The intrusion is subcircular and remarkably discordant,cross-cutting the WNW–ESE structural trend of the host Archeangranitoids (Fig. 2). External contacts are sharp with angular xenolithsof theArco Verde Tonalite (TTG association)commonlyobservednearthe border of the pluton. Inside the pluton, petrographic facies aredisposed along near-concentric zones (Fig. 2), even though thecontact between facies at outcrop scale is often obscured because of local compositional zoning and magma mingling. The less evolvedrocks are equigranular, coarse-grained biotite+hornblende monzo-granites, with enrichment in amphibole±clinopyroxene cumulates atthe southern part of the pluton. Coarse-grained (hornblende)-biotitemonzogranites are dominant in the northern, eastern, and westernborders of the pluton. Coarse- to medium-grained seriated and

porphyritic biotite monzogranites dene annular structures in thecentral and southern sectors of the pluton and intrude the coarse-grained biotite monzogranite (Fig. 2). In the central part of the pluton,evolved leucogranites dene a nearly circular stock, 10-km indiameter that cut-across the even-grained monzogranites, theseriated and the porphyritic facies. Thenal intrusive episode consistsof aplitic dikes with NE–SW and NNW–SSE orientations, parallel tothe main fracture systems observed in the pluton and its countryrocks.

The 3D shape of the Redenção pluton was estimated by forwardmodeling of the residual gravity anomaly obtained after removal of aregional eld from the Bouguer anomaly (Oliveira et al., 2008). Theintrusionshows a tabular shape,with its horizontal diameter of 25 kmbeing much larger than its depth of 2 to 6 km (Fig. 4). A gravity

minima located in the northeast sector of the outcropping area

28 D.C. de Oliveira et al. / Tectonophysics 493 (2010) 27 –41

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indicates the thickest zone of the pluton (its ‘root’) which is thus off-centered relative to the facies distribution (Fig. 4a). Because of thatthe intrusion model presents an asymmetric 3D shape with a stronggradient in its northeastern border and a smooth decrease in pluton'soor depth towards the other borders (see proles in Fig. 4b).

2.3. Magmatic evolution of the Redenção pluton

Geochemical modeling shows that the magmatic evolution of theRedenção pluton was dominantly controlled by fractional crystalliza-tion of early mineral phases, including amphibole±clinopyroxene,andesine to calcic oligoclase, ilmenite, magnetite, apatite, and zircon(Oliveira et al., 2009). Locally, clinopyroxene–hornblende enriched

monzogranites of cumulate origin were identied. The biotitemonzogranite and the less evolved hornblende–biotite monzogranitewere likely produced by fractional crystallization of the same magmabatch. But the leucogranites that occupy the center of the intrusionhave a different source and cannot be explained by fractionalcrystallization of the parent biotite monzogranite magma. Minglingprocesses between these two magmas, the biotite ±hornblendemonzogranite and the leucogranite, account for the geochemicalcomposition of seriated and porphyritic biotite monzogranites fordifferent degrees of interaction. The geochemical evidence isconrmed by eld relationships showing magma mingling relationsbetween coarse-grained biotite monzogranites and leucogranites(Fig. 3a). There is also local evidence of mingling between the lessevolved, mac-rich varieties and the comparatively more evolved

porphyritic and seriated granites.

3. Magnetic anisotropy study

3.1. Sampling and measurements

Anisotropy of magnetic susceptibility (AMS) is particularly welladapted for the study of granitic rocks like the Redenção Granite,which contain mineral shape-preferred orientations that are too weakto be measured by conventional methods. Oriented samples wereobtained from 127 distinct stations separated by 1–2 km (Fig. 2). Atleast three oriented cores, 7 to 9 cm long and 2.54 cm in diameterwere collected from each station using a gasoline-powered portabledrill. In the laboratory, samples were cut into 2.2 cm high specimensusing a diamond-coated wheel saw. Each core provided two or three

specimens, yielding a total of 729 specimens.The specimens were analyzed usinga Kappabridge KLY-4S (AGICO,

Brno, Czech. Republic) susceptibility meter using the spinner mode,whose sensitivity is 2×10−8 SI. For eighteen sites, comprising allpetrographic facies and distributed along all sectors of the pluton(Fig. 2), we have also measured the anisotropy of anhystereticremanence (AAR). While the AMS represents the contribution of allminerals, including ferromagnetic, paramagnetic and diamagneticphases, the AAR is dened by the ferromagnetic phases only, thusisolating the contribution of ferrimagnetic minerals to the magneticfabric of the rock. AF demagnetization and anhysteretic remanenceacquisition were performed with a LDU-AMU (AGICO) demagnetizer/magnetizer and remanence was measured with a JR6A magnetometer(AGICO), housed in a magnetic eld-free room in the Laboratório de

Paleomagnetismo, University of São Paulo. The magnitude and

Fig. 1. (a)Sketch mapof theAmazoniancraton(modied fromTassinari and Macambira, 2004). Central Amazonian province:1—Carajás metallogenic province;2—Xingudomain; indetail twoexposed partsof the Amazonian craton — the Guiana shield in the north and the Central Brazil shieldin the south. (b) Geological map of the Rio MariaGranite-GreenstoneTerrane showing the distribution of the Paleoproterozoic A-type granites of the Jamon suite (modied from Almeida et al., 2006).

29D.C. de Oliveira et al. / Tectonophysics 493 (2010) 27 –41

http://-/?-http://-/?-https://www.researchgate.net/publication/250273890_Geology_geochemistry_and_magmatic_evolution_of_the_paleoproterozoic_anorogenic_oxidized_A-Type_Redencao_granite_of_the_jamon_suite_eastern_amazonian_craton_Brazil?el=1_x_8&enrichId=rgreq-a7ed8b95-66ae-415c-810a-19212f7a0188&enrichSource=Y292ZXJQYWdlOzIzMzc5NTkyNztBUzoxMDI4MDYxMTk3ODAzNjVAMTQwMTUyMjI5NzgxMQ==https://www.researchgate.net/publication/250273890_Geology_geochemistry_and_magmatic_evolution_of_the_paleoproterozoic_anorogenic_oxidized_A-Type_Redencao_granite_of_the_jamon_suite_eastern_amazonian_craton_Brazil?el=1_x_8&enrichId=rgreq-a7ed8b95-66ae-415c-810a-19212f7a0188&enrichSource=Y292ZXJQYWdlOzIzMzc5NTkyNztBUzoxMDI4MDYxMTk3ODAzNjVAMTQwMTUyMjI5NzgxMQ==https://www.researchgate.net/publication/250273890_Geology_geochemistry_and_magmatic_evolution_of_the_paleoproterozoic_anorogenic_oxidized_A-Type_Redencao_granite_of_the_jamon_suite_eastern_amazonian_craton_Brazil?el=1_x_8&enrichId=rgreq-a7ed8b95-66ae-415c-810a-19212f7a0188&enrichSource=Y292ZXJQYWdlOzIzMzc5NTkyNztBUzoxMDI4MDYxMTk3ODAzNjVAMTQwMTUyMjI5NzgxMQ==http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-https://www.researchgate.net/publication/250273890_Geology_geochemistry_and_magmatic_evolution_of_the_paleoproterozoic_anorogenic_oxidized_A-Type_Redencao_granite_of_the_jamon_suite_eastern_amazonian_craton_Brazil?el=1_x_8&enrichId=rgreq-a7ed8b95-66ae-415c-810a-19212f7a0188&enrichSource=Y292ZXJQYWdlOzIzMzc5NTkyNztBUzoxMDI4MDYxMTk3ODAzNjVAMTQwMTUyMjI5NzgxMQ==http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-


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orientation of the principal axes of the AAR ellipsoid were determinedfor each specimen after anhysteretic remanence acquisition along sixdifferent orientations with a peak eld of 50 mT and a biasing eld of 100 μ T following the procedure described in Trindade et al. (2001).

Before AAR measurements samples were AF demagnetized at a peakAF eld of 100 mT. Statistical evaluation of the magnetic anisotropy inindividual sites was obtained using the methods of Jelínek (1978),implemented in the ANISOFT program package (Hrouda et al., 1990).Each station is characterized by the mean anisotropy parameters of aminimum of ve specimens, whose representation is an ellipsoid withthree orthogonal principal axes: K 1≥K 2≥K 3 for AMS and A1≥ A2≥ A3for AAR (Tables 1 and 2).

In addition to the oriented magnetic anisotropy samples, largeblock slabs were collected for sixty-ve sites, covering all facies, formineralogical analysis with special attentionto the iron oxides. Modalcount of oxides, mac and felsic minerals were compared to themagnetic susceptibility of the slabs measured with a SI-1 suscept-ometer (Sapphire Instruments). Transmitted and reected light

microscopy as well as coercivity spectra and thermomagnetic curvescomplemented the magnetic mineralogy study. Remanent coercivityspectra were obtained with a LDU-AMU (AGICO) magnetizer and a JR6A magnetometer (AGICO). Thermomagnetic curves were mea-sured from −195 to 700 °C with a CSL-CS3 furnace coupled to aKappabridge KLY-4 (AGICO).

3.2. Magnetic mineralogy

Magnetite is the main opaque phase in the Redenção granite. Itforms euhedral to subeuhedral crystals up to 0.5 mm in size, usuallyassociated with apatite and zircon, and being included into earlycrystallized phases such as andesine, calcic oligoclase and amphibole(Fig. 3c). Magnetite is a near liquidus phase in the granites of the

Jamon suite (Dall'Agnol et al., 1999c). Therefore, it records the high

temperature evolutionof themelt.Lateron, this phase wasaffectedbythe gradual decrease of temperature and re-equilibrated mostly byoxi-exsolution generating intergrowths between pure magnetite andcomposite, sandwich or trellis ilmenite (Fig. 3d). Finally, late

subsolidus local oxidation processes generated martite along theborders of some magnetitegrains (Fig. 3e). This process occurred in allfacies of the Redenção granite but was more intense in the moreevolved leucogranites.

The mean bulk susceptibility, K=[(k1+k2+k3)/ 3], from investigat-ed core specimens ranges from 0.26×10−3 SI to 32.0×10−3 SI with anaverage value of 11.3× 10−3 SI (Table 1). K is higher in the hornblende–biotite monzogranite with a mean of 18.5×10−3 SI and decreases fromthe coarse-grained biotite monzogranite (12.7×10−3 SI) and seriatedbiotite monzogranite (12.6×10−3 SI), to the porphyritic biotite monzo-granite (9.1× 10−3 SI), andto theleucogranites(6.8× 10−3 SI). Since themagnetic susceptibility of magnetite is two orders of magnitude higherthan that of any ferromagnesian mineral and the contribution of paramagnetic silicates should not exceed 5×10−3 SI (Rochette et al.,

1992),the K values reect essentiallyvariations in theprimarymagnetitecontent of the different granitic facies and the intensity of secondaryreplacement of magnetite by martite. This is further corroboratedby thecomparison of modal analyses of mineral phases with the magneticsusceptibility of rock slabs. Magnetic susceptibilities in these samplestypically increase for higher opaque contents and decreases with quartzand K-feldspar contents (Fig.5). ThehighestK values are concentrated inthe southern part of the pluton and decrease towards the center of theintrusion, the lowest K values being found in the leucogranites, wheremac modal content are the lowest and magnetite martitization is moreintense (Fig. 3e).

Thermomagnetic curves for one sample of each petrographic faciesare presented in Fig. 6. These curvesconrm the magnetic mineralogydeduced from petrographic observations and are consistent with the

high magnetic susceptibilities observed across the Redenção granite.

Fig. 2. Detailed geological map of the Redenção region showing the areal distribution of granitic facies of the pluton and the sampling sites (modi ed from Oliveira et al., 2009).


http://-/?-https://www.researchgate.net/publication/226150835_Statistical_processing_of_anisotropy_of_magnetic_susceptibility_measured_on_groups_of_specimen?el=1_x_8&enrichId=rgreq-a7ed8b95-66ae-415c-810a-19212f7a0188&enrichSource=Y292ZXJQYWdlOzIzMzc5NTkyNztBUzoxMDI4MDYxMTk3ODAzNjVAMTQwMTUyMjI5NzgxMQ==https://www.researchgate.net/publication/226150835_Statistical_processing_of_anisotropy_of_magnetic_susceptibility_measured_on_groups_of_specimen?el=1_x_8&enrichId=rgreq-a7ed8b95-66ae-415c-810a-19212f7a0188&enrichSource=Y292ZXJQYWdlOzIzMzc5NTkyNztBUzoxMDI4MDYxMTk3ODAzNjVAMTQwMTUyMjI5NzgxMQ==http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-https://www.researchgate.net/publication/250273890_Geology_geochemistry_and_magmatic_evolution_of_the_paleoproterozoic_anorogenic_oxidized_A-Type_Redencao_granite_of_the_jamon_suite_eastern_amazonian_craton_Brazil?el=1_x_8&enrichId=rgreq-a7ed8b95-66ae-415c-810a-19212f7a0188&enrichSource=Y292ZXJQYWdlOzIzMzc5NTkyNztBUzoxMDI4MDYxMTk3ODAzNjVAMTQwMTUyMjI5NzgxMQ==https://www.researchgate.net/publication/250273890_Geology_geochemistry_and_magmatic_evolution_of_the_paleoproterozoic_anorogenic_oxidized_A-Type_Redencao_granite_of_the_jamon_suite_eastern_amazonian_craton_Brazil?el=1_x_8&enrichId=rgreq-a7ed8b95-66ae-415c-810a-19212f7a0188&enrichSource=Y292ZXJQYWdlOzIzMzc5NTkyNztBUzoxMDI4MDYxMTk3ODAzNjVAMTQwMTUyMjI5NzgxMQ==https://www.researchgate.net/publication/250273890_Geology_geochemistry_and_magmatic_evolution_of_the_paleoproterozoic_anorogenic_oxidized_A-Type_Redencao_granite_of_the_jamon_suite_eastern_amazonian_craton_Brazil?el=1_x_8&enrichId=rgreq-a7ed8b95-66ae-415c-810a-19212f7a0188&enrichSource=Y292ZXJQYWdlOzIzMzc5NTkyNztBUzoxMDI4MDYxMTk3ODAzNjVAMTQwMTUyMjI5NzgxMQ==https://www.researchgate.net/publication/226150835_Statistical_processing_of_anisotropy_of_magnetic_susceptibility_measured_on_groups_of_specimen?el=1_x_8&enrichId=rgreq-a7ed8b95-66ae-415c-810a-19212f7a0188&enrichSource=Y292ZXJQYWdlOzIzMzc5NTkyNztBUzoxMDI4MDYxMTk3ODAzNjVAMTQwMTUyMjI5NzgxMQ==http://-/?-http://localhost/var/www/apps/conversion/tmp/scratch_2/image%20of%20Fig.%E0%B2%80http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-


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All samples are characterized by a marked Verwey transition at low-temperatures at around −150 °C. High-temperature curves arealways reversible and present a strong decrease in magneticsusceptibility at around 570–580 °C that typies pure magnetite.Most of the curves also present a fraction of magnetic susceptibilitydecay between 580 and 700 °C, attributed to the secondary martitethat partially replaces magnetite. Only one of the analyzed samples,from the porphyritic biotite monzogranite (RED76), does not showevidence of hematite. It is worth noting that the size of mostmagnetite crystals observed at thin sections are well above the critical

size of the single-domain to multi-domain magnetite transition (see

Dunlop and Ozdemir, 1997), suggesting that the anisotropy of magnetic susceptibility is not affected by the inverse fabrics of tinysingle-domain magnetite grains (e.g., Potter and Stephenson, 1988).This is further substantiated by the remanent coercivity spectraobtained for ve specimens from the three main facies, where allsamples show a peak at the low remanent-coercivity window of 0–10 mT (Fig. 7), which is typical of coarse-grained multidomainmagnetite. Nevertheless, the fact that these curves do not reach thebase of the diagram indicate that part of the remanence is carried byanother magnetic phase, probably martite, which has a strong

remanent coercivity and is spared from the effects of the 100 mT

Fig. 3. Textural aspects of the Redenção pluton: (a) magma-mingling features between seriated biotite monzogranite (sBMzG) and coarse-grained biotite monzogranite (cBMzG);(b) microscopic aspect of monzogranite with perfectly preserved igneous texture (subhedral plagioclase, absence of solid-state deformation and recrystallization in quartz); (c)clinopyroxene-bearing hornblende-enriched monzogranite with amphibole showing relic clinopyroxene core (corona texture), where magnetite forms euhedral to subeuhedralcrystals included in these early crystallized phases; (d) oxi-exsolution process generating intergrowths between pure magnetite and trellis ilmenite, with development of martite

(grey traces); (e) oxidation process generating martite along the borders of magnetite crystals in leucogranites. Abbreviation: Op — opaque minerals; Mt — magnetite; Mrt —martite; Ilm T — trellis ilmenite; Cpx — clinopyroxene; Amp — amphibole; Pl — plagioclase; Qz — quartz; Fk — potassic feldspar.


https://www.researchgate.net/publication/216826924_Rock_magnetism_Fundamentals_and_frontiers?el=1_x_8&enrichId=rgreq-a7ed8b95-66ae-415c-810a-19212f7a0188&enrichSource=Y292ZXJQYWdlOzIzMzc5NTkyNztBUzoxMDI4MDYxMTk3ODAzNjVAMTQwMTUyMjI5NzgxMQ==https://www.researchgate.net/publication/216826924_Rock_magnetism_Fundamentals_and_frontiers?el=1_x_8&enrichId=rgreq-a7ed8b95-66ae-415c-810a-19212f7a0188&enrichSource=Y292ZXJQYWdlOzIzMzc5NTkyNztBUzoxMDI4MDYxMTk3ODAzNjVAMTQwMTUyMjI5NzgxMQ==https://www.researchgate.net/publication/248810700_Single-domain_particles_in_rocks_and_magnetic_fabric_analysis_Geophysical_Research_Letters?el=1_x_8&enrichId=rgreq-a7ed8b95-66ae-415c-810a-19212f7a0188&enrichSource=Y292ZXJQYWdlOzIzMzc5NTkyNztBUzoxMDI4MDYxMTk3ODAzNjVAMTQwMTUyMjI5NzgxMQ==https://www.researchgate.net/publication/248810700_Single-domain_particles_in_rocks_and_magnetic_fabric_analysis_Geophysical_Research_Letters?el=1_x_8&enrichId=rgreq-a7ed8b95-66ae-415c-810a-19212f7a0188&enrichSource=Y292ZXJQYWdlOzIzMzc5NTkyNztBUzoxMDI4MDYxMTk3ODAzNjVAMTQwMTUyMjI5NzgxMQ==http://-/?-https://www.researchgate.net/publication/248810700_Single-domain_particles_in_rocks_and_magnetic_fabric_analysis_Geophysical_Research_Letters?el=1_x_8&enrichId=rgreq-a7ed8b95-66ae-415c-810a-19212f7a0188&enrichSource=Y292ZXJQYWdlOzIzMzc5NTkyNztBUzoxMDI4MDYxMTk3ODAzNjVAMTQwMTUyMjI5NzgxMQ==https://www.researchgate.net/publication/216826924_Rock_magnetism_Fundamentals_and_frontiers?el=1_x_8&enrichId=rgreq-a7ed8b95-66ae-415c-810a-19212f7a0188&enrichSource=Y292ZXJQYWdlOzIzMzc5NTkyNztBUzoxMDI4MDYxMTk3ODAzNjVAMTQwMTUyMjI5NzgxMQ==http://localhost/var/www/apps/conversion/tmp/scratch_2/image%20of%20Fig.%E0%B3%80http://-/?-http://-/?-http://-/?-


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peak AF eld used in our experiments. In the leucogranite sampleRED31C, where martitization is stronger, this phase comprehendsalmost half of the total remanence.

3.3. Anisotropy of magnetic susceptibility (AMS)

The shape of AMS ellipsoids was characterized using the degree of anisotropy, P =k1/k3, that indicates the intensity of preferred orien-tation of magnetic minerals, and the shape factor, T =2ln(k2/k3)/ln(k1/k3)−1, thatindicatesthe shape of theAMS ellipsoid( Jelínek, 1981).P varies from 1, corresponding to an isotropic sample (0% anisotropy,sphere) upwards. The T parameter variesfrom−1 forprolate(perfectlylinear magnetic fabric, i.e. k2=k3) through 0 (neutral) to +1 for oblate(perfectly planar magnetic fabric, i.e. k1=k2).

The anisotropy degree in the Redenção pluton is low (Table 1 andFig. 8), with most sites presenting values below 1.10, and does notcorrelate with petrographic domains. Sites with P N1.10 are onlyfound in four sites at the southwestern border of the pluton (sitesRED55,RED57, RED59 andRED62). Thepreponderanceof low P valuesis consistent with petrographic observations showing a lack of solid-state deformation in the constituent minerals of the differentpetrographic facies (Fig. 3). The shape of the AMS ellipsoids varieswidely within the pluton. The site mean shape parameter for all faciesranges from −0.93 to 0.93, with oblate ellipsoids (T N0) being slightlymore abundant than prolate ones (Table 1, Fig. 8). Contrary to theother facies where no clear tendency in the ellipsoid shape can bedened, seriated biotite monzogranites and porphyritic biotitemonzogranites show a strong prevalence of oblate fabrics with

average T values of 0.39 and 0.12, respectively (Table 1).

The AMS directional data of Redenção was screened to eliminatemagnetic foliations and lineations with strong scatter. Using the errorestimates from Jelínek's (1978) statistics, we set a limit of 35° in errorellipses for site acceptance. Magnetic foliations and lineations witherror ellipses higher than 35° were completely discarded for furtherstructural analysis. Considering all petrographicfacies,82% of magneticfoliations and 87% of magnetic lineations passed the screening limit of 35° in error ellipses.From these,62% of foliations and63% of lineationspresent tightly-grouped anisotropy axes with errors below 25°.Seriated biotite mozogranites present particularly well-dened fabricswith errors below 15° for foliations and lineations on most sites(e.g., sites RED16, and RED92 in Fig. 9). The strong coherence withinalmost all sitesand between neighboring sites attests to the robustnessof magnetic lineation and magnetic foliation patterns in the pluton.

Fig. 10 shows AMS foliation and lineation maps after theelimination of scattered fabrics. Magnetic foliations and lineations of coarse biotite mozogranite and hornblende–biotite monzograniteshow a clear concentric pattern in map view. All lineations in thesefacies have gentle plunges (b30°). Gently dipping foliations, with dipsbelow 40°, are also dominant in all sectors where these facies occur,except for the northeastern sector where foliations dip steeply andshow consistent NW-strikes parallel to the contact with the host-rocks. Seriated and porphyritic biotite monzogranites, which crop-outforming annular structuresalso showa concentricpattern of magneticfoliations that systematically dip outwards with shallow to moderateplunges. Magnetic lineations in the seriated biotite monzogranitehave shallow plunges towards NW or SE. Magnetic lineations in theporphyritic biotite monzogranite plunge gently, outward of the ring-

pattern distribution of this facies. In contrast to the other facies,

Fig. 4. The 3D shape of Redenção pluton obtained after inversion of a residual gravity anomaly. (a) Contour lines (in km) show the thickness of the granite pluton across itsoutcropping area and the location of proles A–A′ and B–B′. (b) Observed gravity (squares) and calculated Bouguer anomaly (continuous lines) obtained from the modeling of theresidual anomalies associated with the modeled geometry of the pluton (from Oliveira et al., 2008). Proles A–A′ and B–B′ outline the shape of the pluton. They also show the dip of magnetic foliation (black bars) and an interpretation at depth of the contacts between facies (thin lines).


https://www.researchgate.net/publication/223024006_Characterization_of_magnetic_fabric_of_rocks?el=1_x_8&enrichId=rgreq-a7ed8b95-66ae-415c-810a-19212f7a0188&enrichSource=Y292ZXJQYWdlOzIzMzc5NTkyNztBUzoxMDI4MDYxMTk3ODAzNjVAMTQwMTUyMjI5NzgxMQ==https://www.researchgate.net/publication/223024006_Characterization_of_magnetic_fabric_of_rocks?el=1_x_8&enrichId=rgreq-a7ed8b95-66ae-415c-810a-19212f7a0188&enrichSource=Y292ZXJQYWdlOzIzMzc5NTkyNztBUzoxMDI4MDYxMTk3ODAzNjVAMTQwMTUyMjI5NzgxMQ==https://www.researchgate.net/publication/223024006_Characterization_of_magnetic_fabric_of_rocks?el=1_x_8&enrichId=rgreq-a7ed8b95-66ae-415c-810a-19212f7a0188&enrichSource=Y292ZXJQYWdlOzIzMzc5NTkyNztBUzoxMDI4MDYxMTk3ODAzNjVAMTQwMTUyMjI5NzgxMQ==http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-https://www.researchgate.net/publication/237635121_Gravimetric_radiometric_and_magnetic_susceptibility_study_of_the_Paleoproterozoic_Redencao_and_Bannach_plutons_eastern_Amazonian_Craton_Brazil_Implications_for_architecture_and_zoning_of_A-type_granit?el=1_x_8&enrichId=rgreq-a7ed8b95-66ae-415c-810a-19212f7a0188&enrichSource=Y292ZXJQYWdlOzIzMzc5NTkyNztBUzoxMDI4MDYxMTk3ODAzNjVAMTQwMTUyMjI5NzgxMQ==https://www.researchgate.net/publication/237635121_Gravimetric_radiometric_and_magnetic_susceptibility_study_of_the_Paleoproterozoic_Redencao_and_Bannach_plutons_eastern_Amazonian_Craton_Brazil_Implications_for_architecture_and_zoning_of_A-type_granit?el=1_x_8&enrichId=rgreq-a7ed8b95-66ae-415c-810a-19212f7a0188&enrichSource=Y292ZXJQYWdlOzIzMzc5NTkyNztBUzoxMDI4MDYxMTk3ODAzNjVAMTQwMTUyMjI5NzgxMQ==https://www.researchgate.net/publication/237635121_Gravimetric_radiometric_and_magnetic_susceptibility_study_of_the_Paleoproterozoic_Redencao_and_Bannach_plutons_eastern_Amazonian_Craton_Brazil_Implications_for_architecture_and_zoning_of_A-type_granit?el=1_x_8&enrichId=rgreq-a7ed8b95-66ae-415c-810a-19212f7a0188&enrichSource=Y292ZXJQYWdlOzIzMzc5NTkyNztBUzoxMDI4MDYxMTk3ODAzNjVAMTQwMTUyMjI5NzgxMQ==https://www.researchgate.net/publication/223024006_Characterization_of_magnetic_fabric_of_rocks?el=1_x_8&enrichId=rgreq-a7ed8b95-66ae-415c-810a-19212f7a0188&enrichSource=Y292ZXJQYWdlOzIzMzc5NTkyNztBUzoxMDI4MDYxMTk3ODAzNjVAMTQwMTUyMjI5NzgxMQ==http://-/?-http://localhost/var/www/apps/conversion/tmp/scratch_2/image%20of%20Fig.%E0%B4%80http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-


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Table 1

Parameters of AMS for individual sampling sites.

Site (n) Localization Scalar data Direction of principal axes Facies

UTM coordinate K m (10−3SI ) P T K 1 α 95 (k1) K 2 α 95 (k2) K 3 α 95 (k3)

Hornblende–biotite monzogranite

RED09 (6) 595759 9096278 20.2 1.034 0.023 143/19 32.4/11.1 247/36 26.0/17.0 31/47 29.1/11.4 HBMzGRED10 (6) 595316 9094950 25.7 1.063 0.214 106/24 28.0/12.0 14/6 25.6/9.8 271/66 18.6/11.3 HBMzGRED12 (6) 598171 9090301 13.0 1.043 0.393 131/12 29.8/12.3 238/53 30.4/21.7 32/33 23.6/12.3 HBMzGRED17 (5) 607270 9094443 24.6 1.025 −0.055 31/1 30.2/10.9 122/39 35.8/9.0 299/51 37.6/27.4 HBMzGRED18 (12) 604802 9092932 21.1 1.046 0.180 100/16 30.9/6.0 195/17 30.9/19.8 329/66 19.9/6.3 HBMzGRED57 (7) 588343 9098352 24.7 1.106 −0.023 244/49 12.3/6.9 149/5 16.8/11.3 55/41 16.6/8.1 HBMzGRED59 (6) 589291 9097736 18.7 1.101 0.190 130/6 23.1/10.7 222/19 25.2/15.25 24/70 20.5/13.5 HBMzGRED61 (6) 591151 9094722 16.9 1.069 0.059 133/11 19.8/18.2 228/25 20.7/10.7 20/62 19.0/11.5 HBMzGRED62 (9) 591945 9093615 13.9 1.198 0.893 224/33 21.1/4.9 119/21 21.0/5.8 2/49 6.2/5.2 HBMzGRED63 (6) 592316 9095703 12.3 1.069 0.173 145/19 14.4/7.8 240/14 14.9/11.0 5/66 13.1/9.9 HBMzGRED64 (6) 592208 9102490 20.9 1.021 −0.400 22/28 33.3/16.3 273/32 72.8/25.1 144/46 72.7/16.3 HBMzGRED65 (6) 590824 9099114 31.9 1.093 0.440 308/5 29.9/3.7 212/49 29.5/11.8 42/40 11.9/6.7 HBMzGRED74 (7) 593168 9093397 21.4 1.049 0.223 161/15 19.7/11.2 254/11 21.3/14.3 19/72 18.5/11.0 HBMzGRED75 (7) 593748 9092659 25.6 1.057 −0.334 117/12 18.9/10.5 216/37 26.6/12.7 12/50 26.4/15.3 HBMzGRED78 (7) 597905 9090715 12.2 1.060 0.402 255/14 35.5/7.1 138/60 35.6/12.5 352/25 13.7/7.8 HBMzGRED79 (7) 599343 9090712 11.8 1.041 −0.225 276/27 31.8/15.5 84/63 28.7/27.1 183/5 29.6/19.5 HBMzGRED82 (7) 603294 9092454 18.5 1.032 −0.270 102/17 17.1/12.2 200/24 31.5/10.4 341/60 29.4/12.0 HBMzGRED83 (5) 605929 9093768 10.9 1.035 0.127 225/13 22.3/9.4 128/28 12.1/10.2 336/58 23.7/6.0 HBMzGRED87 (6) 599584 9116264 17.1 1.053 −0.185 97/34 17.5/8.2 241/50 27.4/12.9 354/18 25.2/8.1 HBMzGRED101 (7) 604119 9091684 10.0 1.013 −0.108 295/12 45.9/27.3 197/33 62.6/46.0 42/54 63.1/23.0 HBMzGRED104 (6) 607484 9091338 18.0 1.048 −0.147 82/16 26.1/9.7 185/40 35.8/17.4 335/46 32.1/11.6 HBMzG

RED106 (5) 607832 9095882 19.5 1.056 0.275 75/75 22.4/4.8 245/15 23.0/7.9 336/2 20.8/7.5 HBMzGRED108 (5) 609090 9097384 20.5 1.051 0.201 188/24 31.2/10.5 86/25 35.3/26.1 316/54 31.9/9.6 HBMzGRED121 (6) 604126 9094847 14.9 1.047 −0.156 55/21 19.3/4.9 324/4 30.6/13.4 223/69 28.2/4.7 HBMzGRED125 (5) 599470 9092770 17.4 1.036 −0.366 89/14 23.4/9.4 214/67 28.2/14.8 354/18 22.8/9.8 HBMzG

Coarse biotite monzogranite

RED02 (5) 593510 9109399 7.4 1.050 0.746 313/30 67.6/22.0 211/20 67.1/1.8 93/52 40.3/9.2 cBMzGRED20 (5) 590221 9111872 7.5 1.075 −0.238 238/16 16.9/10.0 351/55 25.4/11.3 138/31 25.2/15.5 cBMzGRED21 (5) 592987 9112235 7.6 1.032 0.814 206/37 78.3/13.6 87/33 78.3/31.4 329/36 30.1/5.7 cBMzGRED23 (9) 603880 9107562 16.1 1.057 −0.392 116/15 23.2/9.2 210/17 29.8/9.3 346/67 31.5/14.9 cBMzGRED37 (7) 590998 9109463 13.8 1.042 −0.692 14/42 41.3/10.3 267/18 41.2/10.1 160/43 14.3/8.4 cBMzGRED38 (5) 591084 9106454 13.5 1.051 −0.119 27/19 12.4/5.0 251/65 12.3/9.4 123/16 10.6/1.6 cBMzGRED39 (5) 591632 9105163 6.9 1.030 −0.042 43/48 35.0/11.1 293/17 46.8/20.7 189/37 39.0/10.0 cBMzGRED40 (5) 593662 9109949 4.3 1.027 0.274 223/12 19.8/12.8 337/62 20.0/0.3 127/25 16.4/8.8 cBMzGRED41 (5) 593653 9105619 9.5 1.052 0.900 89/71 74.1/5.2 237/16 74.1/16.0 330/10 16.5/5.1 cBMzGRED42 (6) 593068 9103870 22.7 1.059 0.076 293/25 33.3/12.1 163/54 34.8/1.9 35/24 12.9/12.2 cBMzGRED43 (6) 592788 9101936 7.4 1.042 −0.248 327/63 18.9/16.4 229/4 25.5/9.8 138/26 21.2/17.4 cBMzG

RED44 (5) 595080 9100150 10.7 1.053 0.388 222/10 42.0/7.5 129/14 32.4/8.5 348/73 19.7/8.6 cBMzGRED45 (5) 600221 9113528 8.5 1.045 −0.582 266/1 30.2/20.3 358/53 60.2/19.5 175/37 60.2/37.3 cBMzGRED46 (5) 599912 9112393 12.6 1.049 0.233 277/30 50.8/18.1 17/16 50.8/20.4 131/55 21.9/17.8 cBMzGRED47 (6) 593606 9112314 10.6 1.034 0.079 252/22 22.6/4.7 4/43 36.9/17.6 143/39 35.0/3.4 cBMzGRED48 (6) 592720 9113268 8.9 1.051 0.290 85/33 36.6/27.3 191/24 45.8/32.3 310/48 30.4/19.1 cBMzGRED49 (5) 592663 9114344 6.5 1.046 −0.892 60/45 22.7/15.5 296/29 84.7/11.0 187/30 84.7/22.3 cBMzGRED50 (5) 604752 9113795 6.0 1.049 0.280 278/0 40.4/17.4 9/74 45.6/20.7 188/17 26.4/6.7 cBMzGRED51 (5) 603897 9114964 10.3 1.092 0.622 131/4 40.8/12.6 224/31 43.6/21.7 36/59 22.3/12.5 cBMzGRED52 (5) 604750 9112904 14.2 1.044 0.242 125/60 43.1/6.4 293/30 45.6/20.8 26/5 30.2/17.1 cBMzGRED53 (6) 587407 9104711 10.1 1.066 0.377 168/67 50.3/17.9 337/23 50.8/20.1 69/4 27.3/10.5 cBMzGRED54 (5) 588753 9104309 17.6 1.049 0.243 210/12 18.7/8.7 94/64 21.2/17.0 305/23 22.7/7.5 cBMzGRED56 (6) 587584 9101025 8.9 1.053 −0.137 116/28 21.4/13.6 290/62 36.0/16.7 25/3 30.3/18.2 cBMzGRED66 (5) 591042 9100926 10.4 1.085 −0.479 150/8 12.4/9.9 21/78 33.9/6.1 242/10 30.9/9.7 cBMzGRED70 (6) 593180 9099017 6.5 1.075 0.353 196/23 20.8/14.6 293/14 18.4/9.7 52/62 19.8/3.6 cBMzGRED84 (7) 604045 9112476 13.4 1.074 −0.415 130/4 10.6/3.9 23/79 19.8/4.8 221/11 19.9/8.9 cBMzGRED85 (5) 603224 9114873 11.2 1.045 −0.841 118/23 14.6/5.7 16/27 78.9/5.7 243/54 78.9/14.3 cBMzGRED86 (5) 600958 9114939 13.8 1.096 0.436 120/17 16.7/4.9 220/29 18.2/7.1 4/56 12.2/7.8 cBMzGRED88 (6) 597429 9110740 12.1 1.044 0.020 276/54 24.4/16.8 54/29 23.7/20.3 156/20 24.0/19.4 cBMzGRED93 (5) 609672 9110036 7.18 1.008 0.568 201/72 83.9/52.8 345/15 83.8/51.4 77/10 62.2/34.1 cBMzGRED94 (6) 609455 9109054 11.2 1.050 0.215 150/67 25.7/20.5 324/23 41.4/15.5 55/2 30.4/18.5 cBMzGRED95 (6) 609906 9105644 8.4 1.045 0.047 162/0 20.1/1.6 71/74 20.8/17.6 252/16 19.6/5.9 cBMzGRED96 (6) 610729 9104321 7.4 1.047 −0.031 129/17 29.5/20.2 13/54 31.5/17.7 229/30 26.1/13.9 cBMzGRED97 (6) 612626 9102788 6.7 1.049 0.100 353/34 37.0/9.8 155/54 38.2/23.3 257/8 27.0/14.7 cBMzGRED99 (6) 601533 9111867 11.3 1.050 −0.532 103/8 11.2/6.7 8/31 55.7/6.7 206/57 35.7/10.5 cBMzGRED107 (5) 608019 9097633 13.4 1.016 −0.643 13/33 30.0/26.1 211/55 65.0/27.0 109/9 35.5/13.6 cBMzGRED109 (5) 606244 9110198 17.8 1.049 −0.441 138/8 20.1/10.4 45/18 25.2/9.1 249/70 27.6/15.1 cBMzGRED110 (5) 604167 9099024 8.4 1.070 0.818 49/30 74.5/3.9 140/1 74.5/1.8 232/60 10.4/0.5 cBMzGRED113 (5) 591003 9112289 6.8 1.056 −0.167 190/4 24.5/8.0 83/77 55.0/23.9 281/13 55.1/6.3 cBMzGRED114 (5) 593726 9111270 12.6 1.051 0.041 275/28 40.0/9.6 175/19 38.8/36.3 55/56 36.8/23.8 cBMzGRED115 (5) 597461 9111661 16.7 1.051 0.044 248/29 18.2/12.0 25/53 17.7/9.8 145/20 14.3/7.7 cBMzGRED116 (5) 596030 9115073 18.6 1.119 0.040 263/5 30.4/3.5 10/75 33.0/1.4 171/14 16.0/3.6 cBMzGRED117 (5) 597221 9113596 12.7 1.047 0.358 272/15 30.3/1.0 178/17 37.4/26.6 40/67 29.2/16.1 cBMzGRED119 (5) 603308 9098227 13.9 1.032 −0.115 22/20 35.0/24.0 117/14 37.8/27.0 239/65 35.0/13.2 cBMzGRED122 (6) 601953 9094607 8.2 1.059 0.414 331/21 12.7/2.5 237/9 14.6/9.3 126/67 12.4/2.9 cBMzG

(continued on next page)



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magnetic foliationsin the central leucogranite show dominantlysteepdips. They form a ring pattern in its northeast contact with the coarse-grained biotite monzogranite, but in other sectors they have variabletrends and do not dene a clear pattern. Magnetic lineations in thisfacies trend dominantly NW–SE, showing steep to moderate plunges

in the northeast sector of the pluton and gentle plunges elsewhere.

3.4. Anisotropy of anhysteretic remanence (AAR)

The AAR is controlled exclusively by the ferromagnetic phases(e.g., Jackson, 1991). In order to further restrict the selection of fabriccarriers we have obtained the AAR within a limited coercivity

window, between 0 and 50 mT, which gather the preferred

Table 1 (continued)

Site (n) Localization Scalar data Direction of principal axes Facies

UTM coordinate K m (10−3SI ) P T K 1 α 95 (k1) K 2 α 95 (k2) K 3 α 95 (k3)

Seriated biotite monzogranite

RED01 (5) 600338 9111648 16.3 1.069 0.481 337/18 6.4/1.9 73/19 7.1/2.9 207/64 4.7/2.1 sBMzGRED03 (9) 593776 9108210 15.5 1.053 0.679 272/27 48.5/6.1 14/21 48.6/17.0 136/54 17.8/6.1 sBMzGRED14 (7) 606351 9106276 0.9 1.078 0.036 156/53 14.8/3.7 310/34 19.2/9.0 49/12 15.7/4.2 sBMzGRED16 (6) 606824 9100843 10.8 1.113 0.603 140/10 20.0/4.1 47/14 20.0/5.3 263/73 5.5/4.3 sBMzGRED22 (7) 602538 9109347 12.2 1.050 0.308 121/8 22.4/5.0 28/20 27.1/6.1 232/69 18.9/4.2 sBMzG

RED92 (6) 597483 9105138 13.3 1.071 0.234 309/19 21.5/8.1 41/5 21.9/9.5 145/70 13.6/4.0 sBMzGRED100 (6) 599238 9111995 12.1 1.063 0.450 302/24 14.6/5.5 43/25 17.4/6.1 173/55 12.1/4.4 sBMzGRED118 (5) 598442 9111997 13.8 1.039 0.114 309/32 15.2/7.5 65/36 19.9/10.8 190/38 17.8/4.9 sBMzGRED127 (6) 605929 9108562 6.8 1.064 0.596 129/45 8.4/4.5 5/30 10.5/3.5 255/31 8.1/3.2 sBMzG

Porphyritic biotite monzogranite

RED11 (5) 598428 9091151 5.8 1.030 0.265 83/3 35.1/20.9 173/16 39.1/11.3 341/74 26.6/16.9 pBMzGRED13 (5) 595629 9097778 12.7 1.042 0.366 156/16 60.2/4.8 255/28 60.1/42.9 40/57 43.2/9.2 pBMzGRED15 (7) 608122 9102546 7.1 1.067 −0.158 161/4 21.1/4.9 69/30 27.1/12.3 259/60 21.9/5.2 pBMzGRED55 (5) 588873 9103080 6.4 1.220 −0.271 215/21 7.5/0.9 123/6 13.9/6.1 18/68 13.9/4.4 pBMzGRED58 (11) 588957 9098934 9.8 1.071 0.065 153/2 30.1/13.8 63/4 30.8/25.2 274/86 26.5/12 pBMzGRED60 (9) 590144 9096076 8.6 1.085 0.441 343/4 11.0/4.3 74/16 12.7/2.2 238/74 7.1/4.6 pBMzGRED71 (6) 592747 9096899 14.0 1.096 0.371 154/18 35.1/7.5 251/21 37.1/11.8 29/61 19.6/6.8 pBMzGRED72 (9) 594709 9098431 10.0 1.060 0.450 227/27 22.5/13.5 128/18 23.3/13.6 8/57 18.3/8.5 pBMzGRED76 (9) 594511 9091890 7.3 1.055 0.079 308/8 9.7/5.8 214/24 9.0/7.6 55/65 9.4/7.8 pBMzGRED77 (6) 596161 9090873 3.5 1.061 0.003 323/74 27.6/7.0 68/4 29.3/17.8 159/16 21.5/9.0 pBMzGRED80 (5) 600813 9091016 9.7 1.047 0.444 141/6 30.4/17.1 140/5 36.0/33.2 11/82 35.1/24.0 pBMzG

RED81 (6) 602222 9091719 11.1 1.038 0.085 165/64 27.6/5.4 296/17 29.4/17.0 32/18 21.4/6.8 pBMzGRED98 (5) 611743 9105762 8.8 1.048 0.202 119/9 25.4/14.0 18/50 30.2/6.0 215/38 26.4/19.7 pBMzGRED102 (5) 607460 9094010 7.8 1.026 0.034 118/45 30.6/19.8 226/17 36.0/30.8 332/40 35.2/8.3 pBMzGRED103 (6) 608406 9093025 7.5 1.051 −0.068 239/6 17.0/4.4 132/72 15.1/9.5 331/17 9.9/9.1 pBMzGRED105 (5) 605863 9091741 11.9 1.048 −0.658 100/4 16.2/10.9 206/78 61.5/15.2 10/12 61.6/9.4 pBMzGRED120 (6) 604834 9096412 9.0 1.038 −0.926 159/60 30.1/11.0 66.1/1.7 81.8/15.9 335/30 81.8/28.2 pBMzGRED123 (5) 598496 9095075 8.7 1.081 0.931 241/10 81.0/4.6 142/43 81.0/1.8 341/45 7.5/4.2 pBMzGRED124 (6) 597672 9096152 11.9 1.083 0.444 209/34 28.8/0.8 305/9 29.6/0.7 47/55 17.7/1.0 pBMzGRED126 (5) 596715 9092100 12.3 1.062 0.384 281/7 25.9/6.9 185/41 27.3/1.5 19/49 10.3/6.9 pBMzG

Leucogranites

RED04 (6) 593797 9106352 2.4 1.024 −0.417 325/25 14.5/8.0 219/30 32.4/13.2 88/49 30.4/9.4 sLMzGRED05 (6) 594289 9106216 0.9 1.030 0.428 346/5 40.1/8.6 83/53 40.4/26.0 253/36 35.0/15.5 sLMzGRED06 (5) 594459 9106478 5.6 1.065 −0.629 322/36 10.7/1.5 217/20 37.4/5.6 104/48 36.8/1.1 sLMzGRED07 (5) 595682 9105178 12.6 1.038 0.250 166/24 52.9/2.0 329/65 53.6/1.8 73/6 27.0/0.7 sLMzGRED14 (7) 606351 9106276 0.9 1.078 0.036 156/53 14.8/3.7 310/34 19.2/9.0 49/12 15.7/4.2 sLMzGRED19 (5) 601389 9098025 11.3 1.024 0.502 161/48 56.6/21.4 314/39 56.6/32.6 55/13 34.7/5.3 sLMzGRED24 (11) 603542 9106580 10.7 1.060 0.153 111/48 28.8/22.7 350/25 30.6/25.1 243/31 30.9/19.6 sLMzGRED25 (5) 603475 9104369 4.7 1.049 0.222 144/49 21.1/4.9 326/41 24.6/15.4 235/1 22.5/9.6 sLMzGRED26 (5) 603167 9103479 8.5 1.036 0.596 189/12 32.1/10.0 64/70 34.9/8.0 282/16 22.2/5.6 sLMzGRED27 (6) 602860 9102927 5.4 1.037 −0.177 160/21 31.1/14.2 342/69 27.1/16.3 250/1 30.0/24.7 sLMzGRED28 (8) 601910 9102684 11.5 1.052 0.681 21/6 26.0/5.4 114/27 26.5/12.5 280/62 17.3/5.7 sLMzGRED29 (8) 601602 9101579 9.3 1.033 −0.116 135/15 29.1/4.6 227/7 36.7/24.3 340/73 34.1/7.5 sLMzGRED30 (8) 601570 9100903 7.2 1.072 0.182 114/22 18.5/13.6 205/1 22.6/13.5 296/68 22.2/9.7 sLMzGRED31 (8) 601230 9099798 4.7 1.038 0.029 181/65 19.1/9.2 302/14 29.2/15.6 37/20 28.7/9.1 sLMzGRED32 (5) 600498 9100537 2.6 1.030 −0.329 140/12 10.7/9.2 41/37 36.5/5.4 244/50 35.3/7.9 sLMzGRED33 (7) 599215 9101830 0.8 1.039 0.729 297/45 59.0/10.3 126/45 59.0/7.3 31/4 12.7/9.6 sLMzGRED34 (5) 598600 9102154 10.3 1.035 0.202 187/25 30.6/15.9 277/1 35.8/21.4 9/65 29.6/15.7 sLMzGRED35 (5) 601390 9102654 10.7 1.043 0.004 212/14 19.8/9.4 113/31 26.7/8.7 323/56 29.3/13.0 sLMzGRED36 (6) 600565 9103147 4.5 1.053 0.103 166/13 13.8/4.8 69/31 13.4/6.6 276/56 10.5/9.7 sLMzGRED67 (6) 597198 9103308 6.7 1.030 0.204 338/23 23.9/7.3 210/55 24.1/4.3 79/25 8.0/4.3 sLMzGRED68 (5) 596920 9101866 0.5 1.054 0.432 157/32 5.4/2.7 325/57 7.6/2.3 64/6 6.6/2.9 sLMzGRED69 (5) 596367 9100792 15.2 1.042 −0.682 132/17 29.1/14.8 231/28 67.3/22.8 14/56 57.1/13.3 sLMzGRED73 (9) 592618 9093736 4.8 1.070 0.169 301/0 12.5/6.5 211/24 13.7/8.3 32/66 11.1/4.4 sLMzGRED89 (6) 597334 9109327 6.4 1.056 0.048 231/83 16.1/5.7 332/1 16.2/6.2 62/7 8.6/3.8 sLMzG

RED90 (5) 597483 9107638 0.5 1.039 0.654 165/14 17.2/3.6 279/59 17.0/10.9 67/27 11.2/4.7 sLMzGRED91 (6) 597483 9106138 8.3 1.048 0.462 49/71 34.8/7.3 269/15 44.9/9.4 175/12 11.1/7.0 sLMzGRED111 (6) 602439 9106429 17.0 1.076 0.178 110/51 22.9/11.8 298/39 30.3/18.8 205/3 28.1/11.5 sLMzGRED112 (7) 600819 9107262 12.9 1.061 −0.098 310/78 26.6/14.6 100/10 38.5/7.4 191/6 30.3/14.7 sLMzG

Site name; number of specimens measured (n); longitude, latitude — UTM; K m = mean magnetic susceptibility (10−3) of the stations in SI unit [ K m=(k1+k2+k3)/3]; P = total

anisotropy of the magneticsusceptibility (P =k1/k3); T = Jelínek's (1981) AMS ellipsoidshape parameter[ T =2ln(k2/k3)/ln(k1/k3)−1]; K 1 = trendand plunge of magnetic lineation(in degrees); K 2 = trend and plunge of the intermediate anisotropy axis; K 3 = trendand plungeof thepoleof the magnetic foliation; e xy are the semi-angle (measuredin degrees) of condence ellipses of AMS axes from Jelínek's (1978) statistics. Facies abbreviations: B — biotite; H — hornblende; MzG — monzogranite; L — leuco; c — coarse, even-grained; s —medium- to coarse- grained seriated; p — porphyritic; e — medium-, even-grained.


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Table 2

Parameters of AAR for individual sampling sites.

Site (n) Scalar data Direction of principal axes Facies

P T A1 e13–e12 A 2 e12–e23 A3 e13–e23

Hornblende–biotite monzogranite

RED57 (5) 1.214 −0.555 241/60 23.9/4.1 143/5 34.7/11.1 50/29 35.2/11.1 HBMzGRED61 (5) 1.082 −0.252 125/34 43.1/34.7 243/35 42.1/22.0 4/37 36.4/21.8 HBMzGRED62 (6) 1.346 0.894 164/39 79.0/12.0 263/11 79.0/7.0 5/48 13.0/5.0 HBMzGRED83 (5) 1.077 −0.221 213/6 34.5/11.5 118/34 50.7/7.1 312/55 49.0/15.9 HBMzGRED101 (5) 1.071 0.229 214/47 43.0/20.7 316/11 64.7/30.6 56/41 39.4/27.5 HBMzGRED108 (5) 1.106 −0.761 178/34 31.2/8.6 79/14 78.9/30.3 330/53 78.9/9.0 HBMzG

Coarse biotite monzogranite

RED53 (5) 1.234 0.066 48/69 13.4/5.0 151/5 21.6/11.5 243/21 20.9/3.4 cBMzGRED84 (5) 1.140 −0.244 299/9 25.8/6.3 167/76 37.7/22.6 31/11 36.3/6.4 cBMzGRED94 (5) 1.288 0.777 129/55 67.6/7.4 342/30 67.4/7.2 243/15 19.5/6.1 cBMzGRED96 (5) 1.090 −0.007 115/27 35.0/27.9 354/45 31.7/20.9 224/32 32.6/20.3 cBMzGRED114 (5) 1.123 0.086 261/47 55.2/16.7 146/21 54.2/47.6 40/35 48.5/25.6 cBMzG

Seriated biotite monzogranite

RED03 (5) 1.081 0.616 270/13 71.5/16.7 3/9 71.4/30.5 126/73 33.3/14.1 sBMzGRED16 (5) 1.184 0.367 133/8 33.2/3.7 42/12 33.6/9.2 256/75 11.7/4.0 sBMzGRED92 (5) 1.198 −0.284 267/18 30.1/10.6 1/11 40.6/24.9. 119/69 38.4/12.1 sBMzGRED14 (7) 1.110 0.195 152/67 24.2/14.6 324/22 23.1/15.9 55/3 26.6/18.5 sBMzG

Porphyritic biotite monzogranite

RED72 (5) 1.134 0.573 222/35 54.1/13.2 113/24 54.0/34.0 357/45 34.3/13.5 pBMzGRED76 (5) 3.010 −0.027 191/30 64.0/30.0 316/46 66.0/44.0 82/29 55.0/33.0 pBMzG

Leucogranites

RED31 (5) 1.065 0.195 166/56 44.8/26.6 315/30 44.5/24.3 53/14 32.1/16.1 sLMzG

Site name; number of specimens measured (n); P = total anisotropy of the magnetic susceptibility (P =k1/k3); T = Jelínek's (1981) AMS ellipsoid shape parameter [T =2ln(k2/k3)/ln(k1/k3)−1]; A1 = trendand plungeof magnetic lineation(in degrees); A2 = trend and plunge ofthe intermediate axis; A 3 = trendand plungeof thepoleof magnetic foliation; e xyare the angular size of condence ellipses from Jelínek's (1981) statistics; facies abbreviations: B — biotite; H — hornblende; MzG — monzogranite; L — leuco; c — coarse, even-grained; s — medium- to coarse-grained seriated; p — porphyritic; e — medium-, even-grained.

Fig. 5. Relationships between magnetic susceptibility (K ,×10-3 SI) and modal compositions of the Redenção pluton. (a) opaque minerals, (b) mac minerals, (c) hornblende,

(d) quartz+K-feldspar contents vs. K (Oliveira et al., 2002).


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orientation of the coarse-grained multidomain magnetites only( Jackson et al., 1988; Trindade et al., 2001). It must be rememberedthat even though magnetite strongly dominates the magneticsusceptibility of a rock, the anisotropy of magnetic susceptibilitymay be strongly inuenced by the other phases. In addition, the AMSis always potentially affected by the inverse fabrics of single-domainmagnetites (e.g., Potter and Stephenson, 1988; Ferré, 2002). InRedenção, the different petrographic facies comprise paramagneticphases (biotite and hornblende) in addition to magnetite and martite.Thus, isolating the anisotropy contribution of coarse-grained magne-tites by low-coercivity window AAR can give some insight into theminerals that control the AMS fabric in the pluton.

The AAR ellipsoid obtained for eighteen sites from Redenção are

shown in Table 2. The anisotropy degree for AAR ellipsoids is always

higher than the AMS for the same sites (compare Tables 1 and 2). Thisarises mainly due to the higher intrinsic anisotropy of the remanenceof ferromagnetic carriers when compared to their magnetic suscep-tibility ( Jackson, 1991). On the other hand, the T parameter for AAR and AMS are quite similar for most sites indicating that the shape of AMS ellipsoid is reproduced in the AAR fabrics.

Fig. 9 shows AMS and AAR results for nine sampling sites. The AMSand AAR fabrics are coaxial for almost all sites thus attesting to thedominant role of coarse-grained multidomain magnetite in deningthe magnetic fabric in these rocks. Some sites show strikingly similarorientation of anisotropy axes, irrespectively if these sites havetightly-grouped fabrics (RED16, RED62, and RED83) or show largerscatter (RED94). This indicates that the dispersion in the AMS fabrics

of thesesites are not related to the inuence of other magnetic phases

Fig. 6. Thermomagnetic curves from −195 to 700 °C for selected samples from the different facies of the Redenção granite. Arrows indicate heating and cooling curves in the high-temperature experiments. VT: Verwey transition, MT: magnetite Curie temperature, HT: hematite Néel temperature. Curves are corrected from CS3 and CSL furnace effects.


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but reect primarily the scatter in magnetite grains orientation in therock. Some sites, however, show signicant differences in fabricorientations for some samples. The worst case is site RED31 for whichsignicant differences are observed in most samples. We speculatethat in these examples, which correspond to a minority of oursampling sites, the AMS fabric is controlled by magnetic phases otherthan magnetite, possibly martite, as suggested by the strong high-coercivity fraction observed in the coercivity spectrum of sampleRED31C (Fig. 7). If this is the case, we expect these effects to bestronger for sites from the more evolved leucogranite facies wheremartitization is more frequent.

4. Discussion

4.1. Signi cance of magnetic fabrics in the Redenção pluton

In the Redenção pluton, the magnetic fabric is controlled mostlyby coarse-grained magnetite. In granitic rocks with K values above5×10−3 SI, the AMS probably results dominantly from the shapeanisotropy of magnetite grains (e.g., Archanjo et al., 1995; Grégoireet al., 1998; Ferré et al., 1999). Here this is further attested byAAR measurements that have principal axes coaxial with the AMSellipsoids for most of the analyzed samples. These AAR ellipsoidscorrespond to the low-coercivity window of 0 to 50 mT, beingcontrolled only by the coarse-grained multidomain magnetite grains.Petrographic evidence shows that these grains are early-crystallizedaccessory minerals and may therefore potentially record all stages of magma deformation. Giving the lack of subsolidus deformation and

recrystallization textures in thin sections (Fig. 3), we can assume thatthe AMS fabric pattern was formed exclusively in the magmatic state.Magnetic lineations correspond to the dominant stretching directionin a magma body, which may result from emplacement-relatedprocesses, magma chamber dynamics, regional deformation or acombination of these (e.g., Paterson et al., 1998; McNulty et al., 2000;Bennetal.,2001;Nevesetal.,1996,2003;Záketal.,2005 ). Syntectonicplutons are characterized by coherent, unidirectional magneticlineations at the pluton scale (e.g., Bouchez et al., 1990; Archanjoet al., 2002). In contrast, the Redenção pluton shows a well-denedconcentric pattern of magnetic lineations suggesting that magmadeformation was controlled by emplacement and magma chamberprocesses, being not related to a major orogeny or syn-emplacementregional deformation, in agreement with the “anorogenic” tectonic

setting attributed to the Jamon suite (Dall'Agnol et al., 2005).

4.2. Emplacement model

A model of emplacement forthe Redenção plutonmust accountforits tabular shape, the dominantly shallowly dipping foliations andlineations, and the concentric arrangement of fabrics and petrograph-ic facies. Recent development in granite emplacement studies showsthat most plutons ascend in the crust as dikes and spread horizontallyto form sills at a certain depth due to crustal heterogeneities, rotation

of principal stress directions (least compressive stress becomesvertical) or buoyancy control (Kavanagh et al., 2006; Annen, 2009;Menand, in press). The sub-horizontal fabrics (Fig. 10) and the tabularshape of Redenção derived from a gravity survey (Fig. 4) arecompatible with that expected from the amalgamation of sills at acertain crustal level.

We propose an intrusion model in which the Redenção plutonformed by the amalgamation of sills emplaced through three majorpulses (Fig. 11). Geochemical data shows that the porphyritic biotitemonzogranites of Redenção can be explained by different degrees of

Fig. 7. Remanent coercivity spectra for selected samples of the Redenção granite. Thespectra were obtained for 10 mT windows up to 100 mT. Note the strong plateau ataround 45% remanence in sample RED31C showing the strong contribution of high-coercivity magnetic phases, such as martite, to the total remanence.

Fig. 8. (a) Variation of the magnetic fabric intensity (P) with the bulk magneticsusceptibility (K in SI) in the individual specimens of the Redenção pluton. (b) AMSellipsoid shape parameter (T; Jelínek, 1981) versus anisotropy degree (P) plot for

Redenção pluton specimens.


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interaction between the equigranular, coarse-grained biotite monzo-granite and leucogranitic magmas (Oliveira et al., 2009). Local

mingling features observed in the eld between the different faciesindicate the coexistence in a partially molten state of differentmagmas batches at the present erosion level and suggests that theintermediate composition of some faciesmight have been acquired, atleast partially, due to magma interactionduring or after emplacement.

Emplacement of Redenção started with coarse-grained (horn-blende)-biotite monzogranites (Fig. 11a), as indicated by cross-cutting relations between facies. They show a compositional zoningfrom north to south, with the less evolved types occupying thesouthern sector of the pluton. The feeding zone for this rst magmabatch was likely placed in the northeastern, the thickest sector of thepluton, where magnetic foliations and lineations are steep. Swarms of mac, intermediate and felsic dikes with NW–SE trends and coeval tothe Redenção granite intrude the country rocks (Silva et al., 1999;

Dall'Agnol et al.,

Tectonophysics2010bom(1)

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