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Gondwana Research 20 (2011) 782–797

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Gondwana Research

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Paleomagnetism and rock magnetism of the Neoproterozoic Itajaí Basin of the Rio de la Plata (Brazil): Cambrian to Cretaceous widespread remagnetizations of South America

E. Font a,⁎, C.F. Ponte Neto b,1, M. Ernesto b a Instituo Dom Luiz, Universidade de Lisboa, Campo Grande,1749-016, Lisbon, Portugal b Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, São Paulo, Brazil article info abstract

Article history: A detailed rock magnetic and paleomagnetic study was performed on samples from the Neoproterozoic Itajaí Received 8 July 2010 Basin in the state of Santa Catarina, Brazil, in order to better constrain the paleogeographic evolution of the Rio Received in revised form 27 April 2011 de la Plata craton between 600 and 550 Ma. However, rock magnetic properties typical of remagnetized rocks Accepted 28 April 2011 and negative response in the fold test indicated that these rocks carried a secondary chemical remanent Available online 6 May 2011 magnetization. After detailed AF and thermal cleaning, almost all samples showed a normal polarity fi Handling Editor: E. Tohver characteristic remanent magnetization component close to the present geomagnetic eld. The main magnetic carriers are magnetite and hematite, probably of authigenic origin. The mean paleomagnetic pole of the Itajaí Keywords: Basin is located at Plat=−84°, Plong=97.5° (A95=2°) and overlaps the lower Cretaceous segment of the Remagnetization apparent polar wander path of South America, suggesting a cause and effect with the opening of the South Paleomagnetism Atlantic Ocean. A compilation of remagnetized paleomagnetic poles from South America is presented that Rock magnetism highlights the superposition of several large-scale remagnetization events between the Cambrian and the West Gondwana Cretaceous. It is suggested that some paleomagnetic poles used to calibrate the APWP of Gondwana at Rio de la Plata Precambrian times need to be revised; the indication of remagnetized areas in southern South America may Neoproterozoic offer some help in the selection of sites for future paleomagnetic investigations in Precambrian rocks. © 2011 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

1. Introduction components (e.g. Trindade et al., 2004; Rapalini and Sánchez Bettucci, 2008; Tohver et al., 2010, 2011). The timing and kinematic models of the Gondwana superconti- The APWP of Gondwana is well documented from 550 to 500 Ma nent assemblage at the end of the Neoproterozoic is still a matter of (see review in Trindade et al., 2006), the latter representing the time debate (e.g., Yoshida, 1995; Torsvik et al., 2001; Stern, 2002; Meert, of the final assemblage of the supercontinent. However, the 2003; Veevers, 2004; Collins and Pisarevsky, 2005; Squire et al., 2006; 600–550 Ma interval is still poorly constrained (Tohver et al., 2006). Trindade et al., 2006; Yoshida and Upreti, 2006; Paulsen et al., 2007; Recently, a high quality but secondary origin paleomagnetic pole has Yoshida, 2007; Meert and Lieberman, 2008; Vaughan and Pankhurst, been obtained from the Nola dolerite, Central Africa (Moloto-A- 2008; Cordani et al., 2009; Santosh et al., 2009). Several models are Kenguemba et al., 2008) satisfying six of the seven criteria of the Q proposed in the literature but they still deserve more high-quality index of Van der Voo (1990). The remagnetization is associated to paleomagnetic poles to be tested, particularly for South America metamorphism and dated by 40Ar/39Ar on amphibole to 571±6 Ma. . A principal limitation resides in the superposition of This pole gives clues to Gondwana APWP, however only two poles successive large-scale deformational events (from Cambrian to from the (Fig. 9), namely the Sierra de las Cretaceous) that affected the area causing overprints of secondary Animas (SA1, Sánchez-Bettucci and Rapalini, 2002) and Sierra de los magnetization, or the complete resetting of primary magnetic Barrientos (LB, Rapalini, 2006) contribute to the curve. In this way, additional efforts are needed to better constrain the APWP of Gondwana at 600–550 Ma. In this way, in this paper we investigated the Neoproterozoic rocks from the Itajaí basin (Santa Catarina) recently dated at 563±3 Ma and 549±4 Ma (U–Pb dating, ⁎ Corresponding author at: Instituto Dom Luiz, Universidade de Lisboa, Edifício C8, Guadagnin et al., 2010). However, as will be discussed, rock magnetic Campo Grande, 1749-016, Lisbon, Portugal. Tel.: +351 21 75 00 811. E-mail address: [email protected] (E. Font). properties typical of remagnetized rocks and negative response in the 1 Presently at Observatorio Nacional, ON/MCT, Rio de Janeiro, Brazil. fold test indicated that these rocks carried a post-folding remanent

1342-937X/$ – see front matter © 2011 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.gr.2011.04.005 Author's personal copy

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Fig. 1. A) Map of South America and location of the Mantiqueira Province; Geological and structural maps of B) main tectonic terranes in southern Brazil and northeastern Uruguay (modified from Rostirolla et al., 1999); C) eastern Santa Catarina and southernmost Paraná with emphasis on the Itajaí, Camaquã and Campo Alegre basins (modified from Hartmann et al., 2003); D) the Itajaí basin (modified from Rostirolla et al., 1999). Author's personal copy

784 E. Font et al. / Gondwana Research 20 (2011) 782–797 magnetization. In view of these results, and considering that this is a Guaratubinha basins which date 598±29 Ma and 604±5 Ma (U–Pb persistent problem in the Gondwana Neoproterozoic, we then extend zircon; Basei et al., 1998) respectively. our discussion to a larger-scale perspective by presenting a review of According to Macedo et al. (1984) the sedimentary rocks of the remagnetized paleomagnetic poles from South America and by Apiúna region were weakly metamorphosed as indicated by illite discussing the possible mechanisms responsible for the widespread crystallinity data. The Itajaí sediments were silicified without any remagnetization events. Our results question the reliability of the metamorphic foliation, thus preserving their original sedimentary Precambrian paleomagnetic database in South America and identify features (Rostirolla et al., 1999). According to Rigon (1993), early unsuitable geographical areas for future paleomagnetic investigations diagenesis is evidenced by mechanical compaction, hydration and in Precambrian rocks. carbonation reactions and by precipitation of iron and titanium oxides. Mesodiagenesis is characterized by chemical compaction, 2. Geological setting calcite precipitation, illitization, chloritization and late cements (pyrite and titanium oxides). According to Rostirolla et al. (1999), In southeastern Brazil the collision that sutured the Congo, the basin underwent a main late-collisional compressional deforma- Kalahari and Rio de la Plata cratons produced the Ribeira and Dom tion phase followed by an extensional post-orogenic relaxation. The Feliciano orogenic belts. These belts consist mainly of syn- to post- same authors reported that the Perimbó Zone (PFZ), a orogenic magmatic and volcanic rocks with local metasedimentary Precambrian dextral-reverse fault separating the Itajaí foreland successions. A series of isolated ‘basins’, some possibly remnants of a basin from the Brusque Metamorphic Fold Belt, was reactivated as a much larger basin, is found inboard of the older orogenic belts. The left-lateral strike-slip fault during the Paleozoic (Rostirolla et al., Castro, Guaratubinha and Camarinha basins in the Paraná state, and 2003). At the scale of the Dom Felicano Belt, Almeida et al. (in press) the Campo Alegre and Corupá basins in the Santa Catarina state, discriminate at least three deformational events in the Itajaí, Camaquã southern Brazil, record the evolution of the volcanic activity and and Castro basins based on fault orientation data. The first event is sedimentary deposition in the region at the end of the Proterozoic characterized by strike-slip and oblique faults generated by a NE–SW (Fig. 1). compression at the Precambrian–Cambrian boundary in relation to The Itajaí Basin is located in the northeastern portion of the state of the Brasiliano . The second deformational event, more Santa Catarina, and represents an area of 50×25 km elongated in the intense, occurred between the Cambrian and Permian and is N60°E direction. It is limited by thrusts and shear zones from the Santa characterized by a NW–SE compression that caused major strike- Catarina Granulite Complex (Luis Alves Foreland) to the north and by slip and oblique faults that controlled the morphology of the basins. the Brusque fold belt to the south. In the west the basin is capped by The third deformational event is contemporaneous with the em- Paleozoic sediments of the Paraná Basin whereas in the northeast it is placement of Early Cretaceous dykes related to the opening of the covered by Quaternary sediments (Fig. 1). The Itajaí Basin is South Atlantic Ocean which caused a NW–SE extension generating interpreted as a collision-related foreland basin where sediments normal and oblique faults that affected all units. were deposited and deformed between the structural front of the Dom Feliciano fold belt and the proximal flank of the Luis Alves 3. Sampling and laboratory methods cratonic forebulge (Mantovani et al., 1989; Gresse et al., 1996; Rostirolla et al., 1999). However, there is no clear evidence to support Samples for paleomagnetic work were collected near the city of a syn-orogenic origin since no syn-depositional sedimentary features Apiúna in the state of Santa Catarina, Brazil. Sediments of the Itajaí have been observed (Almeida et al., 2010, in press) The sedimentary Basin were mostly collected along the BR-470 road where they show a fill is about 4 km thick, and is attributed to a ramp-type deepwater gentle and progressive southeastward dip. Rhyolites were sampled clastic depositional system (Basilici, 2006). along a local dirt road from Apiúna to Vargem Grande in an area near The Itajaí Group is composed of detrital sediments intruded and the Fazenda Santa Luzia (site 7; Fig. 1). Granites were collected at the capped by granites and rhyolites. Several stratigraphic terminologies Azza quarry to the south of Apiúna city. North of BR-470, rocks of the have been adopted. Pioneer studies divided the stratigraphy of the Itajaí Santa Catarina Granulite Complex crop out as massive high-grade Basin into two formations: the Gaspar Formation (psammitic sequences orthogneiss (site 9). Paleomagnetic sites along the BR470 correspond with minor conglomerate and volcanic rocks) and the Campo Alegre to sites VI–VII–VIII of D'Agrella-Filho and Pacca (1988). Formation (pelitic rythmite beds) (e.g., Silva and Dias, 1981). The In the field cylindrical samples were collected with a gasoline- denomination of Campo Alegre came from Albuquerque et al. (1971), powered rock drill, and when necessary hand samples were taken. who correlated the volcano-sedimentary rocks of this basin with those Sample orientation was performed by both magnetic and solar of the Itajaí Basin. However, some authors suggest that the Campo compasses. From each site (=outcrop) 4 to 9 cylinders were prepared Alegre Basin does not have any stratigraphic similarities with the Itajaí into specimens of 2.5 cm in diameter and 2.2 cm in height. At least Basin (e.g., Ebert, 1971). For this reason we have adopted the more three samples from each cylinder were analyzed resulting in more recent terminology of Rostirolla et al. (1999) who proposed four main than 200 measured specimens. sedimentary facies associations that are classified according to their In order to reduce viscous overprints on the characteristic depositional environment, corresponding to the Gaspar (Facies A) and magnetization, samples were stored in a low-field chamber for the Garcia formations (Facies B, C and D) (Fig. 1). Rhyolites (Apiúna three months. Paleomagnetic directions were obtained after stepwise Rhyolites) and granites (Subida Granite) crop out predominantly in the alternating field (AF) and thermal demagnetizations. Measurements western part of the basin along the Itajaí-Açu River near the city of were performed in a three-axis 2G-cryogenic and a JR6 magnetometer Apiúna. In this area, Facies B is represented by well stratified sediments which are intercalibrated and housed in a magnetically-shielded room dipping gently toward the southeast and cropping out continuously (ambient field b1000 nT). Principal component analysis (Kirshvink, along the BR-470 road (Fig. 1). 1980) was used to determine magnetic components. Fisher (1953) The deposition time for the Itajaí Basin was set in between 563±3 Ma statistics were applied to mean directions. and 549±4 Ma (U–Pb dating, Guadagnin et al., 2010). The older limit is marked by the youngest volcanic zircon grains from sandstones and tuffs, 4. Paleomagnetic results whereas the upper limit corresponds to the intrusion of the Apiúna Rhyolite. On the other hand, Basei et al. (2008) obtained a U–Pb SHRIMP After AF and thermal treatments, 192 samples showed stable zircon age of 584±27 in the lower level of the arkosic succession. These demagnetization patterns with 96% success in revealing a character- ages are younger than those obtained for the northern Campo Alegre and istic remanent magnetization component (Fig. 2). AF cleaning was Author's personal copy

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Fig. 2. Typical stereographic and orthogonal projections and demagnetization plots of the characteristic remanence isolated in the Apiúna rhyolites, the Gaspar Formation sandstones, the orthogneiss of the Brusque complex (embasement) and the Subida granites. Author's personal copy

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Fig. 3. Stereographic projections of sample-based and site-based means; open symbols indicate downward directions. Boxes show mean directions and Fisherian statistical parameters. PDF indicates the present-day field and DF the dipolar field. Individual and mean VGP's coordinates are also provided.

more efficient than thermal treatment for rhyolites and sandstones. applied to both sample- and site-mean directions (Table 2). Because Most samples showed uni-vectorial demagnetization patterns with the test implies that N=N1+N2 (N corresponding to the total of unit northward magnetic declination and upward inclinations of ~40° vectors and N1, N2 are the individual set of data), we used sample- (Figs. 2, 3). Maximum angular deviation (MAD) was in the range 0.9– mean directions with no cut-off angles (i.e., N=117). In both tests, 7 (except for sample 18.F3, MAD=12.4). individual paleomagnetic poles for rhyolites and sandstones share the The Apiúna rhyolites lost most of their remanence below 40 mT common mean at the 95% confidence level. and 250 °C (Fig. 2), suggesting a low coercivity phase as the principal magnetic carrier. After AF cleaning at 170 mT, 30% of the remanence 5. Magnetic mineralogy still remained suggesting an additional contribution of higher coercivity magnetic minerals, probably hematite. Thermal demag- 5.1. Thermomagnetic curves netization of sandstones showed an abrupt remanence decay at 350 °C corresponding to maghemite destruction or to the 280– Low and high-temperature thermomagnetic analyses (χ vs. T°) 320 °C characteristic unblocking temperature of pyrrhotite (Kontny were conducted on more than 30 samples (at least one per site) in et al., 2000; Rochette et al., 2001). Unblocking temperatures Argon-controlled atmosphere using a KLY-4S kappabridge (Fig. 4). between ~500–540 °C and above 600 °C suggests the presence of Initial magnetic susceptibility (at ambient temperature) of rhyolites magnetite and possibly hematite as the main magnetic carriers. The and sandstones is very low (b50 μSI) and higher in granites orthogneisses and the Subida granite samples displayed demagne- (N100 μSI). All rock types showed similar behavior and characteristic tization patterns compatible with low to medium coercive minerals curves are illustrated in Fig. 4. (Fig. 2). Rhyolites present a complex magnetic mineralogy characterized Virtual geomagnetic poles (VGP) based on sample- and site-mean by a mixture of a low-temperature transition phase, with unblocking directions were calculated for both rhyolites and sandstones (Tables temperatures around 100 °C (goethite?), and a population of Ti-poor

1, 2). Best cut-off angles for each data set (Vandamme, 1994) were magnetites (TC =580 °C) and low amount of hematite (TN =680 °C) calculated using the Rotpole software. Due to the relatively low (Fig. 4). Presence of very fine (SP??) magnetite is suggested by the number of sites (only 11) sample-mean directions and corresponding omnipresence of a pronounced Hopkinson peak in both heating and poles are preferable as they allow more reliable statistics. Sandstone cooling curves. Magnetic carriers in sandstones are mainly magnetite, samples gave mean characteristic remanent magnetization (ChRM) of and subordinately goethite. Both sandstones and rhyolites suffered

D=356.1°; I=−35.8° (n/N=43/46, a95 =3.2°) with a correspond- severe mineralogical transformations after heating up to 700 °C, ing paleomagnetic pole located at Long=282.9°; Lat=82.4° corresponding to formation of new magnetite probably from hematite (A95=2.6°). Rhyolites give a mean ChRM of D=0.1°; I=−40.4° inversion or destruction of iron-bearing paramagnetic minerals.

(n/N=64/71, a95 =3.8°) with a corresponding paleomagnetic pole located at Long=312.5°; Lat=86.6° (A95=3.7°). The mean mag- 5.2. IRM analyses netic component and corresponding paleomagnetic pole computed from all samples is D=356.4°; I=−38.4° (n/N=95/117, a95 =2.2°) Isothermal remanent magnetization acquisition curves were and Long=277.5°; Lat=84.0° (A95=2.0°), respectively. obtained for 10 samples at fields up to 1 T; the characteristic To check for the similarity of paleomagnetic poles calculated from behaviors are shown in Fig. 5. All rock types exhibit large variations sandstones and rhyolites we applied the test of McFadden and Lowes of SIRM values in the range of 0.1 to 10,000 mA/m, except for rhyolites (1981) that allows the discrimination between mean directions, that that have quite homogeneous (500–1000 mA/m) SIRM values follow a Fisher distribution, using the N (number of unit vectors), R (Fig. 5A). Rhyolites, sandstones and orthogneiss show a bimodal (length vector) and K (dispersion) parameters (Table 2). The test was distribution of coercivity spectra, and SIRM values do not reach a Author's personal copy

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Table 1 Site-based mean magnetic directions and corresponding VGP's.

Site-based means Lithology Glong (°) Glat (°) n/N Cut-off (°) D (°) I (°) k a95 PLong. (°) PLat (°) A95

Site 1 Rhyolite −49.21 −27.33 4/4 23.9 331.7 −48.1 84.3 10.1 209.6 65.0 12.0 Site 2 Rhyolite −49.21 −27.33 14/15 26.3 355.4 −37.5 49.2 5.7 276.9 82.8 5.8 Site 3 Rhyolite −49.21 −27.32 6/6 34.9 341.3 −34.1 18.7 15.9 242.5 72.2 13.9 Site 4 Rhyolite −49.21 −27.31 6/6 19.0 350.8 −44.5 99.1 6.8 224.8 82.0 6.5 Site 5 Rhyolite −49.21 −27.31 2/2 15.7 354.4 −40.0 167.5 19.4 226.1 82.6 18.0 Site 6 Sandstone −49.22 −27.11 14/14 16.5 355.5 −41.7 122.9 3.6 254.5 85.0 3.2 Site 7 Rhyolite −49.26 −27.26 5/5 24.4 351.1 −32.3 56.6 10.3 269.0 77.5 10.3 Site 8 Rhyolite −49.23 −27.32 12/12 27.7 0.3 −45.4 45.3 6.5 73.3 89.2 6.8 Site 9 Sandstone −49.22 −27.14 22/23 23.2 357.9 −34.6 45.3 4.7 297.4 82.2 3.9 Site 10 Rhyolite −49.22 −27.01 20/21 39.2 21.7 −35.7 11.9 9.9 29.4 69.9 7.8 Site 11 Sandstone −49.21 −27.24 9/9 38.6 352.7 −22.3 13.9 14.3 284.3 73.4 12.1 Site 12 Orthogneiss ––––––––––– Site 13 Granite –––––––––––

Table 2 Palaeomagnetic poles calculated from sample- and site-based mean directions.

Mean Paleomagnetic poles n/N Cut-off (°) D (°) I (°) R k a95 PLong. (°) PLat (°) A95

Site-based mean Rhyolites 8/8 30.2 353.6 −40.5 7.8 42.3 8.6 252.9 82.9 9.7 Sandstones 3/3 17.2 355.3 −32.9 2.9 65.0 15.4 284.1 80.1 10.4 Rhyolite+sandstones 11/11 27.2 354.1 −38.4 10.8 46.4 6.8 263.6 82.3 7.0

Sample-based mean Rhyolites 64/71 35.1 0.1 −40.4 61.3 23.1 3.8 312.5 86.6 3.7 Sandstones 43/46 22.6 356.1 −35.8 42.1 46.9 3.2 282.9 82.4 2.6 Rhyolite+sandstones 95/117 24.8 356.4 −38.4 93.0 44.3 2.2 277.5 84.0 2.0

saturated state at 1 T (Fig. 5B). Granites are characterized by unimodal representing the contribution of the lower coercive phase, while coercivity spectrum with saturation at around 0.1 T (Fig. 5B). concave upward shapes, similar to those observed in igneous rocks, IRM curves were analyzed by cumulative log-Gaussian (CLG) are observed in higher fields suggesting a secondary magnetization. functions using Kruiver's et al. (2001) software. Each magnetic carrier is characterized by its saturation IRM (SIRM), B1/2 and dispersion 5.4. Frequency-dependent magnetic susceptibility parameter (DP). The DP parameter reflects the dispersion of the logarithmic distribution around B1/2 (corresponding to one standard Superparamagnetic particles (SP) are very fine-grained iron oxides deviation and being independent of concentration). For the granite with very low values of relaxation times (b100 s; Butler, 1992). They sample a unique log-Gaussian curve was adjusted while the best are generally produced by authigenesis and are characteristic of fitting for rhyolites, sandstones and orthogneiss involved at least two remagnetized carbonates (Jackson et al., 1992, 1993; Font et al., 2006). components (Fig. 5C). Based on demagnetization and thermomag- At high frequency (4700 Hz) the measurement time is short enough netic procedures we interpret the low and high coercive phases in for these particles to behave as stable SD grains, while at low rhyolites to correspond to a mixture of magnetite and goethite and/or frequency (470 Hz) the measurement time is longer than the hematite. In rhyolites, the high coercive phase contributes to more relaxation time and particles behave as superparamagnetic (SP). than 80% of the SIRM (Fig. 5D). The frequency-dependent magnetic susceptibility is thus expressed by Kfd=[Khf–Klf]/Klf where Khf is high-frequency susceptibility and 5.3. NRM:IRM Klf is low-frequency susceptibility. For remagnetized carbonates characteristic values for the frequency-dependent susceptibility are The comparison of NRM magnitude and demagnetization patterns greater than 5% (Jackson et al., 1993). Kfd values for both rhyolites and with results of saturation IRM provides a good proxy for distinguishing sandstones were obtained using a Bartington MS2 dual-frequency primary and secondary magnetizations (Fuller et al., 1988; Fuller et al., (470 and 4700 Hz), which gave a frequency-dependent susceptibility 2002). In rocks carrying a TRM (thermal remanent magnetization) between 4 and 11%, suggesting a significant contribution of SP the ratio of NRM:IRMs is of the order of 10− 2, smaller values implying particles (Table 3). secondary magnetization (Cisowski and Fuller, 1986). All igneous rocks (rhyolites, granites and orthogneiss) show ratio of NRM:IRMs 5.5. Scanning Electronic Microscopy below the 10−2 boundary, suggesting a secondary origin for the magnetization (Fig. 6). Furthermore, rhyolites and granites exhibit Most of the iron oxides in the sandstone samples are severely concave upward curves that are typical of remagnetized igneous rocks altered (Fig. 7A–F). Amorphous iron can be seen filling fractures or (Fuller et al., 2002). The concave upward shape is due to a mixture of intergranular spaces. Large Energy Dispersive Spectra (EDS) indicate soft multidomain grains carrying the lower coercive remanence, and that iron is frequently associated with hydrothermal elements such as a hard magnetic phase that contributes with a smaller percentage manganese and barium, suggesting important metasomatic processes (Fuller et al., 2002). (Fig. 7B, C and F). In rhyolites, most of the iron oxides are represented Sandstones show NRM:IRM ratios close to the 10− 3 boundary by euhedral authigenic magnetite (without Ti; Fig. 7G). Rare suggesting a DRM origin for the magnetization. However, in these preserved titanomagnetites with exsolution textures are observed, samples, straight NRM:IRM lines are isolated between 0 and 20 mT and show strong heterogeneities in Ti content and eroded forms Author's personal copy

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Fig. 4. Low and high-temperature thermomagnetic curves from rhyolite and sandstones samples; arrows indicate heating and cooling sense.

(Fig. 7H and I) indicating important chemical alteration. The same is remagnetization took place during Cretaceous (Fig. 10). This result valid for granite and orthogneiss samples for which observed iron differs from previous interpretation by Rapalini and Sánchez Bettucci oxides are devoid of titanium and are found filling voids and fractures (2008), who suggested a widespread Permian remagnetization of the (Fig. 7J–O). Rio de la Plata craton. However, based on the presence of dual polarity and because post-tectonic poles for the Cerro Victoria, Yerbal and 6. Field test Rocha formations partially overlap those corresponding to the middle Cretaceous (100 Ma), Late Cretaceous (75 Ma) and Paleogene A fold test was performed on the Gaspar Formation cropping out (50 Ma), the authors do not rule out a Late Cretaceous–Paleogene along the BR-470 road (Fig. 1). A continuous decrease in k-values with age for the remagnetization. When plotting their paleomagnetic data percentage unfolding gives a negative fold test (McElhinny, 1964) (poles CV, Y and R, Fig. 10) on the APWP of Brandt et al. (2009),a pointing to a post-folding magnetization (Fig. 8; Table 4). Permo–Trias age remagnetization is indeed preferred. The same comment is valid for the AV and VF poles (D'Agrella-Filho and Pacca, 7. Discussion 1988). However, the CG pole from the Castro Basin located about 300 km NW of the Itajaí Basin also shows overlap with middle and 7.1. Widespread Cambrian to Cretaceous remagnetization of the Rio de upper Cretaceous (140–110 Ma) mean poles (Fig. 10). la Plata craton The Campo Alegre Basin (CA pole; Fig. 9) is only ~100 km northwest of the Itajaí basin, and it has been correlated in recent Several lines of evidence point to a secondary origin for the literature (Almeida et al., 2010) to the Castro Basin (CG pole). In spite remanence of the Itajaí Basin rocks: i) negative fold test; ii) mixture of of its geographic location between the other two basins (Itajaí and soft (magnetite) and hard (hematite/goethite) fractions to the ChRM Castro) it seems that its volcanic sequence preserved a primary both with high values of Kfd that indicated a significant contribution magnetization. The CA paleomagnetic pole has been treated as a key of superparamagnetic particles; and iii) ubiquity of contamination of pole for the construction of the Neoproterozoic pole path at ~590 Ma primary iron oxides by hydrothermal-linked elements such as Ba and (e.g. Trindade et al., 2006). However, it must be emphasized that the Mn. The coordinates of the paleomagnetic pole calculated from both CA pole (D'Agrella-Filho and Pacca, 1988) deserves re-evaluation. The rhyolites and sandstones are 277.5°E, 84.0°S (A95=2.0), and plot remanent magnetization of the Campo Alegre rocks is carried by both close to the current geographic pole. Once rotated to African magnetite and hematite whose origin was not investigated coordinates using the “tight fit” Euler poles (Trindade et al., 2006), (D'Agrella-Filho and Pacca, 1988). The reliability of the results was the Itajaí pole (IT) is located far away from the APWP of Gondwana for not fully demonstrated by field tests: one of the outcrops is cut by a the 570–500 Ma interval (Fig. 9; Rapalini, 2006; Trindade et al., 2006; rhyolitic dyke that gave no results. However, dubious and inconsistent Moloto-A-Kenguemba et al., 2008), suggesting that the remagnetiza- reported field corrections suggest deeper problems for this result. For tion took place well after the final assemblage of the Gondwana example, D'Agrella-Filho and Pacca (1988) did not mention any supercontinent. structural dip of the lava flows, but bedding corrections were in fact We thus tested several scenarios from Upper Paleozoic to applied; the same paleomagnetic pole (57°S 223°E) was previously Cretaceous times in order to constrain the date of the remagnetization reported by D'Agrella-Filho (1984) who mentioned bedding plane event, using the database compilations of Brandt et al. (2009) and corrections up to 25°. However, some of the field lava attitudes were Font et al. (2009), respectively (Fig. 10; Table 5). In the figure we also inferred from magma flow structures that may not indicate included all available paleomagnetic poles for the Rio de la Plata paleohorizontally (D'Agrella-Filho, 1984). Tentatively we have re- craton, namely La Tinta (LT; Valencio et al., 1980), Sierra de la Animas stored site mean magnetizations to the values previous to dip I (SA1) and II (SA2) and Playa Hermosa (PH) from Sánchez-Bettucci corrections (site mean magnetizations are not given by D'Agrella- and Rapalini (2002), Campo Alegre (CA), Castro Group (CG), Filho and Pacca, 1988) using the field information given by D'Agrella- Acampamento Velho (AV), and Vargas Formation (VF) from Filho (1984)). The site mean magnetizations before tilt correction give D'Agrella-Filho and Pacca (1988). VGPs that plot closer to the Itajaí VGPs; the same can be said for the The Itajaí pole is significantly distant from the Permian poles but Castro rhyolites. Unfortunately the authors did not give more its confidence circle overlaps those of Cretaceous age (Fig. 10). The information to test the remagnetization hypothesis of the CA Itajaí pole is statistically similar to the Lower to middle Cretaceous rhyolites. However, considering the proximity of the Campo Alegre poles at a 63% confidence level (Butler, 1992), suggesting that the Basin with the Itajaí Basin, both covered by the Paraná Magmatic Author's personal copy

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Fig. 5. IRM analyses of rhyolites, sandstones, orthogneiss and granite samples: A) IRM curves in vertical logarithmic scale to illustrate differences in concentration of magnetic carriers; B) IRM in horizontal logarithmic scale to discriminate differences in grain size; C) treatment by the method of Kruiver et al. (2001); D) DP, log B1/2 and contribution parameters obtained from the Kruiver treatment. Author's personal copy

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Table 3 Kfd values.

Samples Kfd (%)

CP.1-A1 10 CP.2-A1 10 CP.3-A1 10 CP.5-B1 11 CP.6-D1 9 Apiúna CP.7-C1 11 Rhyolites CP.8-B1 7 CP.11-A1 5 CP.12-B1 9 CP.13-A1 10 CP.14-A1 11 CP.15-C1 8 CP.16-A1 9 Fig. 6. AF-NRM vs. AF-IRMs diagram showing concave upward shapes typical of Sandstones CP.9-A1 4 remagnetized rocks (Fuller et al., 2002). CP.10-A1 8

Province lavas and cut by the related Cretaceous dykes, it is not unrealistic to suppose that the CA pole also reflects partial or total migration and drainage of ore-bearing fluids. In the Campo Alegre remagnetization under the influence of the Paraná magmatism. A new Basin, kaolin deposits originated in volcanogenic environments and systematic study on the Campo Alegre lavas must be carried out in following an evolutionary sequence from high temperatures (300– order to confirm or refute the hypothesis. 500 °C) to low temperatures (20°–50 °C) hydrothermal facies The paleomagnetic data of the Itajaí Basin presented here together (Biondi et al., 2001). In the Camaquã basin, Cu, Pb and Zn with previous paleomagnetic results (D'Agrella-Filho and Pacca, 1988; mineralization occurs along NW-striking fault zones (Gresse et al., Rapalini and Sánchez Bettucci, 2008) confirm the existence of large- 1996). Diagenetic illites associated with the ore have given K–Ar scale remagnetization events from Permian to Cretaceous that dates of ~550–465 Ma (Bonhome and Ribeiro, 1983). The Itajaí Basin affected the Rio de la Plata craton from Southern Brazil to Uruguay. is rich in Au-rich quartz veins and Pb, Zn and Cu mineralizations, These results allow investigation of: i) the mechanisms that are which are interpreted to result from the reactivation of the Perimbó responsible for the widespread remagnetization event, and ii) fault during the Permian San Rafael Orogen (Biondi et al., 1992). reconsideration of the paleomagnetic database of the Rio de la Plata Unfortunately, the timing of the different mineralizations is poorly craton in the context of the final assemblage of Gondwana. constrained making it difficult to correlate the remanence acquisition (Milani and Ramos, 1998; Almeida et al., 2010; in press). Indeed, 7.2. Mechanisms responsible for the Rio de la Plata craton Cretaceous based on a rigorous study of fault orientations, Almeida et al. (in overprint press) discriminate at least three deformational events in the Itajaí, Camaquã and Castro basins at the Precambrian–Cambrian boundary, Remagnetization of rocks is still poorly understood, but several the Permian and at the Cretaceous. mechanisms have been proposed and documented in the literature. The The Cretaceous was a period of unusually active tectonism during most commonly invoked cause of chemical remagnetization is orogen- which ocean crust formation rate and off-ridge volcanism were related fluids that cause magnetite authigenesis over vast regions (e.g., greater than at any time since (e.g., Larson, 1991; Poulsen et al., 2001; Oliver, 1986; McCabe and Elmore, 1989). Alternatively, authigenic Phipps Morgan et al., 2004). As a result, shallow and deep connections magnetite may be linked to hydrocarbon migration and/or organic between the South Atlantic and North Atlantic Ocean basins opened in matter maturation (e.g., Elmore et al., 1987; McCabe and Elmore, 1989; the Middle Cretaceous (Aptian/Albian; Eagles, 2006; Moulin et al., Brothers et al., 1996; Banerjee et al., 1997; Blumstein et al., 2004; Font et 2010). In South America the opening of the South Atlantic Ocean led al., 2006); to smectite–illite conversion (e.g., Elmore et al., 1993; Hirt et to intraplate deformation that generated normal and oblique faults al., 1993; Katz et al., 2000; Gill et al., 2002; Tohver et al., 2008; Tohver et with a NE–SW extension direction (MacDonald et al., 2003; Moulin al., 2010); or to burial diagenesis and in-situ fluids (e.g., Moreau et al., et al., 2010; Almeida et al., in press). Late Cretaceous alkaline dykes 2005). Recently, paleomagnetic, petrographic and geochemical studies related to reactivation of WNW–ESE faults are compatible with this have shown that major faults can act as conduits for fluids that cause NE–SW extension, as are basic Early Cretaceous dykes related to the chemical remanent magnetization, which, in turn, can be used to date opening of the South Atlantic Ocean (Almeida et al., in press). In the fluid migration events (e.g., Elmore et al., 2002; Blumstein et al., 2005; state of Santa Catarina, southern Brazil, extensional deformation Elmore et al., 2006). However, little is known about the mechanisms resulting from the opening of the South Atlantic Ocean also involved responsible for large-scale magnetic overprint such as those that the reactivation of ancient NE–SW faults such as the Perimbó Shear affected the Rio de la Plata craton during the Cretaceous. Zone (PSZ) limiting the Itajái Basin from the Neoproterozoic Brusque First, we have to consider separately thermal from mechanical/ Complex and the Major Gercino Shear Zone (MGSZ) (Passarelli et al., chemical processes. A thermal remanent magnetization (TRM) is 2010 and references therein). acquired by cooling from above the Curie temperature and is the form In summary, all these observations point to a scenario where the of remanent magnetism acquired by most igneous rocks (Butler, reactivation of major crustal faults during the Cretaceous favored 1992). In our case, maximum demagnetization temperatures for the deformation, fluid circulation and hydrothermal alteration in the ChRMs of both rhyolites and sandstones around 680 °C (hematite) Neoproterozoic basin of the Rio de la Plata craton that could have are too high for these components to have been acquired uniquely by facilitated the observed widespread remagnetization. a thermoviscous overprint (Pullaiah et al., 1975). Alternatively, evidence of hydrothermal alteration point to a chemical origin for the 7.3. Location and age of remagnetization episodes in South America remagnetization. Indeed, most of the sedimentary basins of the eastern Santa Catarina and southern Paraná regions are important The paucity of reliable paleomagnetic poles for South America is sources of ore deposits, indicating that they are favorable to leaching, mostly due to the presence of widespread remagnetization events Author's personal copy

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Fig. 7. Scanning Electron Microscopic observations coupled with Energy Dispersive Spectra analyses: (A–F) Altered iron oxides containing manganese and barium (hydrothermalism) in sandstones; (G–I) authigenic magnetite and altered titanomagnetite with typical exsolution textures in rhyolites; (J–L) authigenic iron oxides filling fractures in Subida granites and (M–O) in orthogneiss.

that affected the plate from the Cambrian to the Cretaceous. A with the localization of remagnetized paleomagnetic poles published paleomagnetic review of where and how these events acted is thus since 1980 (i.e., since Principal Component Analysis; Kirshvink, 1980). necessary. Fig. 11 and Table 6 illustrate the South America continent At early Cambrian, the closure of the Clymene Ocean that separates Author's personal copy

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Table 4 Magnetic directions of samples from site 9 (sandstones) before and after tilt correction (see Fig. 8).

Samples Az. Dip Before tilt correction After tilt (°) (°) correction

D (°) I (°) a95 D (°) I (°)

CB 56A1 110 11 0.40 −33.10 24.30 2.30 −22.70 CB 56A2 110 12 48.50 −37.60 4.00 45.10 −26.90 CB 56B2 265 12 346.50 −22.40 15.30 345.50 −34.30 CB 56C2 223 22 3.60 −21.20 9.30 13.20 −33.80 CB 56D1 270 17 353.40 −16.70 5.70 352.40 −33.60 CB 56D2 270 17 348.80 −15.40 6.90 347.20 −32.00 CB 56 E2 250 24 1.70 −28.50 7.00 10.50 −50.20 CB 56E3 250 24 350.20 −28.70 5.60 354.70 −52.20 CB 56F2 242 20 347.60 −28.60 6.80 352.50 −47.70 CB 56G2 256 26 357.00 −25.60 5.90 1.80 −50.90 CB 56H1 252 26 13.30 −48.50 8.90 44.30 −67.10 CB 56H2 252 26 351.90 −42.00 4.80 1.30 −67.30 CB 56I1 242 29 354.10 −41.30 12.80 16.40 −66.20 CB 56I2 242 29 351.90 −42.00 4.80 13.40 −67.50 CB 56J1 245 41 356.60 −45.10 11.60 58.30 −74.80 CB 56J2 245 41 8.90 −31.90 8.60 43.60 −59.40 CB 56K1 250 27 346.20 −45.70 3.20 354.40 −72.30 CB 56K2 250 27 358.50 −33.50 10.10 10.20 −58.30 CB 56L3 237 28 5.70 −36.10 6.90 28.00 −54.70 CB 56M1 246 31 2.10 −35.90 5.20 23.90 −61.30 CB 56M2 246 31 7.40 −50.40 6.50 54.20 −70.20 CB 56N1 255 27 8.30 −43.00 1.90 30.00 −65.90 CB 56N2 255 27 6.60 −40.50 5.90 24.90 −64.10

Francisco Craton (Fig. 11). Recently, based on 40Ar/39Ar encapsulation dating of mixed authigenic and detrital illite from remagnetized carbonates, Tohver et al. (2010) provide an age of ca. 528 Ma for the initial deformation and remagnetization of the Paraguai Belt. The age of the Paraguai belt overlaps with that of the farther south along the western margin of the Rio de Plata craton, suggesting a coeval closure for the Clymene ocean separating the Amazon craton from the São Francisco and Rio de Plata cratons (Tohver et al., 2010). The Permian was a period of intense acidic volcanism along the continental margin of southwest Gondwana where a magmatic belt Fig. 8. Fold test (McElhinny, 1964) applied on Gaspar Formation sandstones that crops was active at the western margin and emplaced voluminous extrusive out along the BR-470 road (Fig. 1). A continuous decrease in k-values with percentage rhyolitic rocks and granites in Chile and Argentina (23°S–42°S) — the unfolding gives a negative fold test. Choiyoi Complex (Vaughan and Pankhurst, 2008, and references therein). This period of intense volcanism appears to be at least partially coeval with the San Rafael orogenic phase that affected the southwest margin of Gondwana causing uplift and interrupting the Amazon craton from the São Francisco and Rio de Plata cratons sedimentation in areas close to the magmatic arc (Kleiman and was responsible for the remagnetization of the Paraguai belt and the Japas, 2009). The first phase of the San Rafael orogeny involves a Pampean belts (e.g., Tohver et al., 2010). Neoproterozoic carbonates of major event of N–NNW dextral transpressional motions probably the Bambuí and Salitre formations in the eastern part of the São related to oblique (Az. 30°) of the Paleo-Pacific plate Francisco craton yielded remagnetized directions dated to ~520 Ma as (Kleiman and Japas, 2009). A WNW sinistral transpression of the evidenced by the resetting of the U–Pb system by regional-scale fluid second episode of the San Rafael orogeny is associated with an migration, providing a minimum age for the final assemblage of west eastward migration of the magmatic arc at this latitude. To the Gondwana (no. 3 and 4 respectively; D'Agrella-Filho et al., 2000; southeast of Argentina, magmatism and transpression continued to Trindade et al., 2004). A negative fold test was obtained in migrate inland and can be traced from San Rafael to Sierra de la Neoproterozoic bituminous limestones (Guia Formation) close to Ventana, linking the San Rafael orogeny with the Gondwanide the Paraguai belt, Amazonia, and paleomagnetic directions indicated a orogeny of the Cape Fold Belt in South Africa (Kleiman and Japas, date of ~520 Ma for the remagnetization event (pole no. 2 on Fig. 11; 2009). The reactivation of large-scale faults generated by the Permian Trindade et al., 2003). The mechanisms responsible for the remagne- San Rafael Orogeny may have been responsible for the remagnetiza- tization involved organic matter maturation and clay mineral tion of the eastern part of the Rio de la Plata craton, from southern transformation linked to metamorphism and tectonic activity of the Brazil to Central Argentina involving: Sierra Australes (no. 8, Fig. 11; Paraguai thrust and fold belt (Font et al., 2006; Tohver et al., 2010). Tomezzoli and Vilas, 1999; Tomezzoli, 2001) and the Sierra Chica in Two remagnetized poles of possible Cambrian age from the Cerro Argentina (no. 9; Tomezzoli, 2009). Other Permian-age overprints Victoria and Polanco Formations are documented in Uruguay have been suggested in northern Chile (Hartley et al., 1992; Forsythe (Rapalini and Sánchez Bettucci, 2008) suggesting that the Cambrian et al., 1993), Patagonia (Rapalini, 1998) and the eastern Andean remagnetization is probably not restricted exclusively to the Sao Precordillera of Argentina (Rapalini and Vilas, 1991; Rapalini et al., Author's personal copy

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Fig. 9. APWP of Gondwana with tight fit correction from Trindade et al. (2006). New recent palaeomagnetic poles from the Nola dyke (Moloto-A-Kenguemba et al., 2008) and Sierra de los Barrientos (LB; Rapalini, 2006) are also shown as well as the position of the Itajaí pole (IT; this study).

Fig. 10. Orthogonal stereographic projections of palaeomagnetic poles of South America at the Carboniferous–Permian interval (orange) following Brandt et al. (2009) (on the left); and Cretaceous (green) poles for South America using the database of Font et al. (2009) (on the right). Poles CV, Y and R (dark gray) from Rapalini and Sánchez Bettucci (2008) and CG, AV and VF from D'Agrella-Filho and Pacca (1988) are also indicated (light gray).

2000), but a direct link with the San Rafael orogeny has not been made Table 5 Selected palaeomagnetic poles of Fig. 10. (Fig. 11). Prior to the large-scale NW–SE extension, we suggest that a San Selected paleomagnetic poles Plat (º) Plong (º) A95 Rafael Permian Overprint was responsible for the remagnetization of Brandt et al. (2009) the southern part of the Rio de la Plata craton, in Central and Middle Permian–early Trias −80 311 6.9 northern Argentina, Uruguay and Chile as well as the genesis of Early Permian −62.4 347.6 8.1 Permian–Carboniferous −54.3 341 12.4 numerous ore deposits. However, in regions formerly affected by Middle Carboniferous −31.6 317.5 8.3 theParanáMagmaticProvinceandclosetothemajor-scalefaults that border the Dom Feliciano and Ribeira belt (Figs. 1, 11), the Font et al. (2009) Permian remagnetizations if they existed must have been reset in Upper Cretaceous −80.2 345.2 3.9 − the Cretaceous (e.g., the pole of the Itajaí Basin). On the western Middle Cretaceous 89.2 50.9 4.9 Early Cretaceous −86 74.8 1.9 margin of South America, Cretaceous magnetic overprints are also observed in southern Chile associated with the intrusion of the This study Patagonian Batholith dated at 132–120 Ma (Halpern, 1973; Itajaí — sandstones −82.4 103 2.6 Cunningham et al., 1991; Cembrano et al., 1992; Rapalini et al., Itajaí — rhyolite −86.6 132.5 3.7 Itajaí total −84 97.5 2 2001; Rapalini et al., 2008) and in Peru, at around 90 Ma, in relation Author's personal copy

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Fig. 11. Map of South America showing the location of principal remagnetized palaeomagnetic poles and the eventual mechanisms responsible for the acquisition of the corresponding remanence. References of palaeomagnetic poles are indicated in Table 6. PMP: Paraná Magmatic Province; MGSZ: Mega Gercino Shear Zone. Schmidt stereographic projections of individual paleomagnetic pole are also indicated.

to the Peruvian Batholith (May and Butler, 1985; Roperch and took place at the Precambrian–Cambrian boundary and was related to Carlier, 1992). the final assemblage of the western Gondwana that sutured the craton São Francisco-Congo-Rio de la Plata block with Amazonia and West 8. Conclusions Africa. The second, called here the San Rafael Permian Overprint, was responsible for the reactivation of large-scale pre-existent faults that All rocks of the Itajaí Basin recorded a secondary magnetic lead to the formation of important amount of ore deposited in Santa overprint of a chemical origin linked to the reactivation of the Catarina and Paraná state, Brazil, and to the remagnetization of Perimbó Fault system and hydrothermal activity during the Creta- Central to northern Argentina, Uruguay, Southern Brazil and Chile. ceous opening of the South Atlantic Ocean. Comparison of the Itajaí The third one is related to the opening of the South Atlantic Ocean paleomagnetic pole with those of the coeval neighbor basins confirms which was responsible for the remagnetization of the units bordering the existence of widespread remagnetization events that affected the the Dom Feliciano and Ribeira Belt, namely the Itajaí and eventually Rio de la Plata craton from Cambrian to Cretaceous. The first event the Campo Alegre and Castro basins, in Brazil. Author's personal copy

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Table 6 Banerjee, S., Elmore, R.D., Engel, M.H., 1997. Chemical remagnetization and burial Selected palaeomagnetic poles of Fig. 11. diagenesis: testing the hypothesis in the Pennsylvanian Belden formation, Colorado. Journal of Geophysical Research 102, 24825–24841. Code Plat Plong a95 Geological units Reference Basei, M.A.S., Drukas, C.O., Santos, P.R., Osako, L., Arcaro, N.P., 2008. Estratigrafia, idade e proveniência dos sedimentos da Bacia do Itajaí, SC, Brasil. In 44 Congresso Brasileiro − 1 81 97.5 2 Itajaí Basin This study de Geologia. Anais, Curitiba. SBG. 2 −33.1 146.6 3.2 Guia Limestones Trindade et al., 2003 Basei, M.A.S., Citroni, S.B., Siga Jr., O., 1998. Stratigraphy and age of Fini-Proterozoic 3 −33 143 4 Salitre Fm. Trindade et al., 2004 basins of Paraná and Santa Catarina States, southern Brazil Boletim IG-USP, Série 4 −30 141 3.8 Bambuí Fm. D'Agrella-Filho et al., 2000 Científica 29, 195–216. 5 −76.6 291 4.2 Rocha Fm. Rapalini and Sánchez Basilici, G., 2006. Depositional mechanisms and architecture of a pre-early Cambrian Bettucci (2008) mixed sand–mud deepwater ramp (Apiúna Unit, South Brazil). Sedimentary Geology 5 −77 298.4 5.9 Yerbal Rapalini and Sánchez 187, 183–204. Bettucci (2008)) Biondi, J.C., Bartoszeck, M.K., Vanzela, G.A., 2001. Controles geológicos e geomorfoló- 5 −82.6 309 3.9 Cerro Victoria Rapalini and Sánchez gicos dos depósitos de caulim da bacia de Campo Alegre (SC). Revista Brasileira de Geociências 3, 13–20. Bettucci (2008) Biondi, J.C., Scfficket, Bugalho, A., 1992. Processos mineralizadores em bacias tardi- 5 −4.2 163.2 13.8 Cerro Victoria c Rapalini and Sánchez orogênicas 1. Influência das estruturas rígidas na geração dos depósitos da minepar e Bettucci (2008) do Ribeirão da Prata, grupo Itajaí (sc). Revista Brasileira de Geociências 22, 275–288. − 5 3.2 145.8 15.2 Polanco Fm. Rapalini and Sánchez Blumstein, A.M., Elmore, R.D., Engel, M.H., 2004. Palaeomagnetic dating of burial Bettucci (2008) diagenesis in Mississippian carbonates. Utah. Journal of Geophysical Research 109. 6 −34 322 17 Vargas Fm. D'Agrella-Filho and Pacca doi:10.1029/2003JB002698. (1988) Blumstein, R.D., Elmore, R.D., Engel, M.H., Parnell, J., Baron, M., 2005. Date and origin of 6 −61.45 337.46 17 Acampamento D'Agrella-Filho and Pacca multiple fluid flow events along the Moine Thrust Zone, Scotland. Journal of the Velho I (1988) Geological Society of London 162, 1031–1045. 6 −57 223 10 Campo Alegre D'Agrella-Filho and Pacca Bonhome, M.E., Ribeiro, M.J., 1983. Datações K/Ar das argilas associadas à mineralização (1988) de cobre da Mina Camaqua e suas enceixantes. I Simpósio Sul-Brasileiro de – 6 −76 4 12 Castro Group D'Agrella-Filho and Pacca Geologia. Sociedale Brasileira de Geologia, Atas, pp. 82 88. (1988) Brandt, D., Ernesto, M., Rocha-Campos, A.C., dos Santos, P.R., 2009. Paleomagnetism of the Santa Fé Group, central Brazil: implications for the late Paleozoic apparent polar 7 −80 301 5 La Tinta Fm. Valencio et al. (1980) wander path for South America. Journal of Geophysical Research 114. doi:10.1029/ 8 −63 374 4.8 Tunas Fm. Tomezzoli and Vilas (1999) 2008JB005735. 9 −66.5 34 8 Sierra Chica Tomezzoli (2009) Brothers, L.A., Engel, M.H., Elmore, R.D., 1996. The late diagenetic conversion of pyrite to − 10 77 311 4.5 Sierra Grande Fm. Rapalini (1998) magnetite by organically complexed ferric iron. Chemical Geology 130, 1–14. − 11 21 251 9.3 San Juan province Rapalini et al. (2000) Butler, R.F., 1992. Paleomagnetism: magnetic domains to geologic terranes. Blackwell 12 −71 263 10.8 Lila Fm. Forsythe et al. (1993) Scientific Publications, Boston, MA. 319pp.Cembrano, J., Beck Jr., M.E., Burmester, 13 −52 197 8.9 Purilactis Fm. Hartley et al. (1992) R.F.,Rojas,C.,García,A.,Hervé,F.,1992. Paleomagnetism of Lower Cretaceous 14 −42 356.2 5.7 Hoyada Verde Fm. Rapalini and Vilas (1991) rocks from east of the Liquiñe-Ofqui fault zone, southern Chile: evidence of small 15 −24.6 318 12.1 Madre de Dios Rapalini et al. (2001) in-situ clockwise rotations. Earth and Planetary Science Letters 113, 539–551. Archipelago Cembrano, J., Bec, M.E., Burmester, R.F., et al., 1992. Paleomagnetism of lower 16 −83.1 166.7 7 Alto Palena Fm. Cembrano et al. (1992) Cretaceous rocks from east of the liquine-ofqui fault zone, southern Chile — 17 −42.5 337.8 4.2 Hardy Fm. Cunningham et al. (1991) evidence of small insitu clockwise rotations. Earth and Planetary Science Letters – 18 −73.3 359.3 3.4 Puente Piedra Fm. May and Butler (1985) 113, 539 551. 19 −56 15.4 4.4 Chala Fm. Roperch and Carlier (1992) Cisowski, S.M., Fuller, M., 1986. Lunar paleointensities via the IRM(s) normalization method and the early magnetic history of the moon. In: Hartmann, W.K., Phillips, 19 −62.2 3 8.5 Chocolate Volcanic Roperch and Carlier (1992) R.J., Taylor, G.J. (Eds.), The Origin of the Moon. Lunar and Planetary Science Fm. Institute, Houston, pp. 411–424. − 20 39 0.3 6.9 Los Barrientos Fm. Rapalini et al. (2008) Collins, A.S., Pisarevsky, S.A., 2005. Amalgamating eastern Gondwana: the evolution of the circum-Indian orogens. Earth-Science Reviews 71, 229–270. Cordani, U.G., Teixeira, W., D'Agrella-Filho, M.S., Trindade, R.I.F., 2009. The position of the in supercontinents. Gondwana Research 15, 396–407. Considering the paucity of reliable palaeomagnetic data for the Rio Cunningham, W.D., Klepeis, K.A., Gose, W.A., Dalziel, I.W., 1991. The Patagonian de la Plata craton, particularly between 600 and 550 Ma, the present Orocline: new palaeomagnetic data from the Andean magmatic arc in Tierra del Fuego, Chile. Journal of Geophysical Research 96, 16061–16069. study provides indications of probably remagnetized areas in southern D'Agrella-Filho, M.S., Babinski, M., Trindade, R.I.F., Van Schmus, W.R., Ernesto, M., 2000. South America that may help in the selection of geological sites for Simultaneous remagnetization and U–Pb isotope resetting in Neoproterozoic future paleomagnetic studies in Precambrian rocks. carbonates of the Sao Francisco craton, Brazil. Precambrian Research 99, 179–196. D'Agrella-Filho, M.S., Pacca, I., 1988. Paleomagnetism of the Itajaí and Bom Jardim Group from Southern Brazil. Geophysical Journal International 93, 365–376. Acknowledgments D'Agrella-Filho, M.S., 1984. Estudo paleomagnético dos Grupos Itajaí, Camaquã e Bom Jardim. Dissertação de Mestrado. Departamento de Geofísica. IAG-USP, São Paulo, Brasil. 164 p. This work has been supported by CNPq and FAPESP (grants Eagles, G., 2006. New angles on South Atlantic Opening. Geophysical Journal 1996/09619-6 and 06/02965-0). The authors thank Daniele Brandt for International 168, 353–361. technical assistance. A particular acknowledgment is given to Farid Ebert, H., 1971. O Grupo Guaratubinha no norte do Estado de Santa Catarina. In: Congr Bras Geol, 25, São Paulo, 1971. Anais, São Paulo. SBG 2, 153–157. Chemale (UFRGS) for numerous discussion of the geological history of Elmore, R.D., Dulin, S., Engel, M.H., Parnell, J., 2006. Remagnetization and fluid flow in the studied region. We thank Thierry Aigouy, Sophie Gouy and the Old Red Sandstone along the Great Glen Fault, Scotland. Journal of Geochemical Philippe de Perceval (LMTG) for SEM assistance. We also thank Exploration 89, 96–99. Elmore, R.D., Parnell, J., Engel, M.H., Baron, M., Woods, S., Abraham, M., Davidson, M., C. Langereis. This paper has been greatly improved by the critical 2002. Palaeomagnetic dating of fluid-flow events in dolomitized rocks along the reviews of Agusto Rapalini and Arlo Weil, and the helpful advices of Highland Boundary Fault, central Scotland. Geofluids 2, 299–314. the editor Eric Tohver. Elmore, R.D., London, D., Bagley, D., Fruit, D., Guoqiu, G., 1993. 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