isotope geochemistry

Journal of South American Earth Sciences 69 (2016) 131e151

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Origin and evolution of the granitic intrusions in the Brusque Group of the Dom Feliciano Belt, south Brazil: Petrostructural analysis and whole-rock/isotope geochemistry Mathias Hueck a, *, Miguel Angelo Stipp Basei a, Neivaldo Araújo de Castro b a b

~o Paulo, Brazil Geosciences Institute, University of Sa Geosciences Institute, Federal University of Santa Catarina, Brazil

a r t i c l e i n f o

a b s t r a c t

Article history: Received 9 November 2015 Received in revised form 26 February 2016 Accepted 14 April 2016 Available online 16 April 2016

In the southern Brazilian state of Santa Catarina the Dom Feliciano Belt, formed by the tectonic juxtaposition of different crustal blocks during the Brasiliano-Pan African Orogenic cycle, can be divided into three domains. In the central domain, three granitic suites intrude the metavolcanosedimentary ~o Batista (SJBS), Valsungana (VS) and Nova Trento (NTS), from the sequence of the Brusque Group: S~ ao Joa oldest to the youngest. This extensive magmatism, here referred to as granitic intrusions in the Brusqe Group (GIBG), is coeval with the thermal peak in the host metamorphic successions, but postdates its main foliation. A progressive deformation starting from the magmatic stage throughout the cooling history points to the influence of the late stages of deformation recorded in the Brusque Group. The SJBS consists of gray to white leucocratic, equigranular granites, with aluminous minerals such as muscovite, garnet and tourmaline. The porphyritic VS is the largest of the suites and is characterized by its cm-sized K-feldspar megacrysts in a coarse-grained biotite-rich matrix. The granites from the NTS are equigranular, light gray to pink in color and have biotite as the main mafic mineral, but magmatic muscovite, tourmaline and hornblende can occur as well. Geochemically, the GIBG are mildly peraluminous and show a calc-alkaline affinity. Most intrusions have a high REE fractionation, but some SJBS granites show a characteristic pattern with no fractionation and strong negative Eu anomalies (“seagull pattern”). Elevated Sr(i) values, between 0.707 and 0.735, and negative εNd values as low as
24 points to the melting of old evolved crust. The Nd (TDM) ages are scattered between 1.54 and 2.76 Ga, with a predominance of values around 2.0 Ga. The GIBG have a strong crustal signature that most closely connects, within the regional units, to that of the metasedimentary rocks of the Brusque Group and its crystalline basement, the Camboriú Complex. All three suites seem to have been produced during a same regional melting event, but at different crustal levels and reflecting heterogeneities within the same source rocks. Most evidences imply that sedimentary source rocks were especially important to the SJBS, which probably originated in a shallower environment, whilst the VS and NTS represent the melting of deeper crystalline crust, probably sharing some magmatic interaction. © 2016 Elsevier Ltd. All rights reserved.

Keywords: Dom Feliciano Belt Brasiliano Neoproterozoic Granites

1. Introduction Granites, for all its commonness, simple mineralogy and abundance in the continental crust, are produced in many different processes and geologic settings. Thus, the understanding of the

* Corresponding author. Current address: Geoscience Centre, Georg-August€t G o €ttingen, Germany. Universita E-mail addresses: [email protected] (M. Hueck), [email protected] (M.A.S. Basei), [email protected] (N.A. Castro). http://dx.doi.org/10.1016/j.jsames.2016.04.004 0895-9811/© 2016 Elsevier Ltd. All rights reserved.

tectonic history of an area necessarily involves an appreciation of the events that led to the formation of its granitic rocks. It is no different in Brazil, where one of the most striking characteristics of the Neoproterozoic Brasiliano Cycle is the extensive occurrence of granites along its orogenic belts, which have received a great deal of attention in recent years. In the Brazilian State of Santa Catarina, The metavolcanosedimentary Brusque Group and its crystalline basement, the Camboriú complex, constitute the central domain of the Dom Feliciano Belt, a Neoproterozoic orogenic association assembled during the

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formation of West Gondwana in the Brasiliano-Pan African Event (Basei et al., 2000). Both units are intruded by voluminous granitic magmatism, which is closely connected to the thermal apex of the amphibolite-facies metamorphic association. This diverse association of granitic intrusions has been classified, over the years, into different suites according to their affinities (e.g. Trainini et al., 1978; Castro et al., 1999; Basei et al., 2000). Petrologic investigations on these rocks, however, have mostly been limited to smaller-scoped researches, not considering the broad variety of intrusions (Florisbal et al., 2012a). The objective of this paper, therefore, is to interpret the origins and evolution of the granitic intrusions within the Brusque Group considering its diversity and classification into different suites. Besides a characterization of its petrography and structural geology, new geochemical and isotopic data from tenths of samples are presented. Along with these new data, we use previous published data from literature in order to have a broader perspective of the array of rocks. Combining a regional scope with a multidimensional approach accessed by the analysis of a large number of individual plutons, we are able to get new insights on the geologic history that led to the formation of each suite, including the varieties within them, in a closer association with the units that constitute the regional setting. 2. Geological setting The Dom Feliciano Belt (DFB), a lithostructural unit that stretches from southern Brazil to Uruguay for about 1400 km, comprises the southern end of the Mantiqueira Province (Almeida et al., 1981), and represents the result of the tectonic juxtaposition of different crustal blocks during the Brasiliano-Pan African Orogenic Event, culminating in the consolidation of the WestGondwana supercontinent. It has a typical width of ca. 150 km and a NNE trend approximately parallel to the Atlantic coast, bordering, to the west and northwest, Archean to Paleoproterozoic rocks associated to the Rio de La Plata Craton and Luis Alves Microplate. The DFB (Fig. 1) is divided into three distinct domains (Basei et al., 2000). The easternmost (Internal) of them is a granitic belt polis, Pelotas and Aigu which includes the Floriano a Batholiths in the Brazilian states of Santa Catarina (SC) and Rio Grande do Sul (RS) and in Uruguay. All three batholiths comprise a number of intrusions with radiogenic ages scattered between 650 and 580 Ma (Basei et al., 2000; Philipp and Machado, 2005; Florisbal et al., 2012b; Chemale et al., 2012), and at least part of the intrusions are closely related to the development of important shear zones, resulting in rocks with variable degrees of deformation (Bittencourt and Nardi, 2000; Oyhantçabal et al., 2007; Passarelli et al., 2010, 2011a). The central domain of the DFB is the fold-and-thrust Schist belt, an association of deformed volcanosedimentary rocks which went through a greenschist to amphibolite facies metamorphism and is frequently intruded by Neoproterozoic granitic bodies. These litostratigraphic segments are, from north to south, the Brusque Group (SC), Porongos Metamorphic Complex (RS) and the Lavalleja Group (Uruguay). In Santa Catarina, the Brusque Group is mostly arranged according to a NE-SW orientation, in the shape of NWtrending nappes, and records evidence of polyphasic deformational and metamorphic histories, in which the thermal apex, associated to the intrusion of the granitic bodies which are the object of this study, postdates its main foliation (Basei et al., 2011; Philipp et al., 2004). The basement of the Brusque metavolcano-sedimentary sequence is exposed on the northeastern portion of the Central Domain in Santa Catarina, and is known as Camboriú Complex. It is

mostly composed of banded gneisses and migmatites, cross-cut by more than one generation of neosome and granitic injections. These metamorphic rocks were intruded by a large granitic body concordant to its main foliation and characterized by abundant mafic xenoliths, which is named Ponta do Cabeço or Itapema Granite (Lopes, 2008; Peternell et al., 2010; Basei et al., 2013). This basement unit has a long-spanning geologic evolution, with most crust-forming events having taken place in the Archean and Paleoproterozoic, but was ultimately reworked and migmatized in the Neoproterozoic Brasiliano event (da Silva et al., 2005; Basei et al., 2013). The western (External) domain of the DFB consists of foreland basin deposits, placed between the schist belt and the foreland of the Luis Alves and Rio de La Plata Cratons, mostly composed of anchimetamorphic sedimentary and, subordinately, volcanic rocks. This domain includes the Arroyo del Soldado, Piri apolis (Uruguay), ~ (RS) and Itajaí (SC) basins. The latter boast a thickness of Camaqua 4.5 to 7.5 km and has a sedimentation age comprised approximately between 565 and 550 Ma, having subsequently been affected by late thrust tectonics, related to the approach of the Brusque Group (Guadagnin et al., 2010; Basei et al., 2011). All three sectors are separated by tectonic contacts orientated along a NE-SW direction and accompanying that of the belt itself. These structures are collectively referred to as Southern Brazilian Shear Belt by Bitencourt and Nardi (2000). The most significant tectonic structure in the DFB in the state of Santa Catarina is the Major Gercino Shear Zone (MGSZ), which marks the contact between the granite arc of the Florianopolis Batholith and the schist belt of the Brusque Group (Trainini et al., 1978). Its formation encompassed mostly dextral transcurrent shearing, incorporating several individual anastomosed shear zones generally oriented along a NE to NNE axis, controlling the intrusion of a series of granitic bodies (Passarelli et al., 2010; Bittencourt and Kruhl, 2000). It connects to the Cordilheira Shear Zone (CSZ), also known as Dorsal do Canguçu Shear Zone in the literature (e.g. Fernandes and Koester, 1999; Philipp and Machado, 2005), in RS, and to the Uruguayan Sierra Ballena Shear Zone (SBSZ) by means of strong gravity anomalies (Mantovani et al., 1989). This ca. 1.400 km long lineament is interpreted as a lithospheric- scale suture, as evidenced by strongly diverging isotopic signatures on both sides of the shear zone (Basei et al., 2005, 2008; Passarelli et al., 2011a,b). The timing of this suture event, however, is still a matter of discussion. Basei et al. (2008, 2011) and Passarelli et al. (2010, 2011b) place the collision synchronically to the main transcurrent event around 600e610 Ma, whereas Florisbal et al. (2012b) suggests an age older than 630 Ma, in accordance to a postcollisional setting proposed for the intrusion of granitic bodies along the structure by some authors (e.g. Bittencourt and Nardi, 2000; Philipp et al., 2013; Oyhantçabal et al., 2007). 2.1. Granitic intrusions in the Brusque Group (GIBG) The presence of widespread granitic intrusions, comprising more than 40 individual intrusions, is one of the main characteristics of the Brusque Group. They are closely related to the metamorphic evolution of the Central Domain in the Santa Catarina portion of the DFB. Although this magmatism has been recognized since the first regional geologic descriptions, it was first classified into stratigraphic units by Trainini et al. (1978), who proposed the Valsungana and Guabiruba Suites, separating coarse-grained porphyritic varieties from fine- to medium-grained equigranular ones, a definition which is still followed by some authors (e.g. da Silva et al., 2005; Hartmann et al., 2003). Later classifications of the many types of rocks include Caldasso et al. (1988, 1995), who added to the two original suites a third, named Faxinal,

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Fig. 1. Tectonic sketch of the Dom Feliciano Belt (after Basei et al., 2000).

characterized by the presence of amphiboles, and Castro (1997, summarized in Castro et al., 1999), who recognized the presence of W (Sn-Mo)-specialized intrusions in the so-called Catinga Suite and grouped into the Morro Pelado Suite several smaller intrusions in the main Valsungana-type batholith. This later study also recognized some similarities that would distinguish the granites of the northern domain within the Brusque Group from the rest, such as presence of pink K-feldpar phenocrysts, hornblende as rockbuilding or accessory minerals and higher K2O contents. More recently Basei et al. (2000, 2006, 2011), based on the result of 1:100,000-scale mapping of the region, grouped the intrusions ~o Joa ~o Batista, Valsungana and Nova Trento. into three Suites: Sa This approach maintains the definition of the Valsungana Suite for the porphyritic granites and divides the equigranular rocks

traditionally referred to as Guabiruba into two distinct Suites, which include the varieties described by Caldasso et al. (1995) and Castro et al. (1999). This classification holds into account mainly textural and mineralogical criteria, associated to field relationships, and is adopted in this study. The relative chronological organization of the three suites was based on field evidences, such as contact relations and the presence of xenoliths. Most recent geochronological data point to a spectrum of crystallization ages between 610 and 590 Ma (da Silva et al., 2005; Basei et al., 2011; Florisbal et al., 2012b). A review of the available data including new UePb zircon ages is currently in preparation. Fig. 2 locates all the intrusions within a regional geologic map, and Fig. 3 presents the main mesoscopic features of the different suites. ~o Joa ~o Batista (SJBS), The oldest of the three suites is named Sa

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Fig. 2. Central Domain of the Dom Feliciano Belt in Santa Catarina, emphasizing the intrusive suites in the Brusque metavolcanosedimentary sequence. Modified from Basei et al. (2006, 2011).

after the homonymous city located close to the most representative intrusion, and comprises 10 mostly small stocks. With the exception of the Catinga and Tijucas intrusions, referred to as Catinga Suite by Castro et al. (1999), all intrusions are located south of the main Valsungana Batholith. This suite consists of isotropic leucocratic to hololeucocratic, equigranular granites, usually gray to white in color (Fig. 3a). The presence of muscovite as the main mafic mineral is distinctive of this suite, along with the occasional occurrence of other peraluminous accessory minerals such as garnet and tourmaline. Most contacts with the Valsungana

southern Batholith are clear, but some gradation can be seen locally, suggesting a short-timed interval between both intrusions. Tungsten mineralizations on the metasedimentary rocks around the Catinga Granite were once commercially exploited. The Valsungana Suite (VS), by far the largest of the three, consists of two batholiths (Southern and Northern) and four stocks. Its intrusion into the Brusque Group succession generated metamorphic aureoles varying from the greenschist (biotite zone) to upper amphibolite (sillimanite zone) facies (Basei et al., 2011). Near the contact, magmatic apophyses hosted inside the

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~o Joa ~o Batista Granite (SJBS); b) Valsungana Southern Batholith (VS); c) Aspect of the Serra dos Macacos Granite (NTS); d) mafic enclave Fig. 3. Mesoscopic features of the GIBG; a) Sa lia Granite (NTS); f) Gneiss xenolith of the Camboriú Complex inside the Serra dos in the Valsungna Southern Batholith (VS); e) Small xenolith from a VS Granite inside the Nova ita Macacos Granite (NTS).

metasedimentary rocks are common, as much as xenoliths of the latter within the granites. The Suite is characterized by its porphyritic texture, containing cm-sized K-feldspar megacrysts in a coarse-grained matrix (Fig. 3b). Most varieties are leucocratic and gray, but the northern batholith has slightly pink megacrysts. Biotite is the main mafic mineral. The youngest of the three Suites is named Nova Trento (NTS), after the homonymous city located close to its biggest intrusion. It comprises 18 stocks, including those formerly associated to the Faxinal (Caldasso et al., 1995) and Morro Pelado (Castro et al., 1999) suites. These rocks have predominantly light gray to pink colors and a fine- to medium-grained equigranular to seriate texture (Fig. 3c), with occasional coarser-grained, porphyritic varieties. When present, megacrysts are composed of pink K-feldspar. The main mafic mineral is biotite, but magmatic muscovite and, occasionally tourmaline and hornblende occur as well. A distinct feature of this suite is its spatial relationship to the Valsunganatype granites, with most NTS granites intruding inside or around the Southern Valsungana Batholith. Contacts commonly show diffuse gradations, suggesting low temperature contrasts (Florisbal et al., 2012a). The presence of metasedimentary xenoliths and roof pendants from the Brusque Group is common in the VS, along with mafic

microgranular enclaves (Fig. 3d), usually with elongated shapes concordant to the granite's foliation. NTS contains only rare microgranular enclaves, usually with similar composition to the host rock, though poorer in K-feldspar. Xenoliths of the VS Granites within the NTS (Fig. 3e) are rare, but present, attesting its later intrusive nature. When intrusive in the Camboriú Complex, granites from the VS and NTS bear gneissic and migmatitic xenoliths (Fig. 3f). 3. Petrographic aspects Fig. 4 illustrates the microscopic features of the GIBG. ~o Joa ~o Batista Suite 3.1. Sa This suite comprises leucocratic to hololeucocratic rocks, with colors varying between gray and white. The texture is equi- to weakly seriated inequigranular texture, with fine- to medium-sized granulation. The mineralogical composition varies between alkalifeldspar granites, sienogranites and monzogranites. K-feldspar tends to have an irregular shape and inclusions, and they commonly present exsolution lamellae. Plagioclase forms euhedral crystals with composition varying between oligoclase and

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~o Joa ~o Batista Fig. 4. Microscopic features of the GIBG; a) difference between post-magmatic sericite overgrowth in plagioclase crystal and igneous muscovite in the matrix, Sa Granite (SJBS); b) Tourmaline as only mafic mineral, Oliveiras granite (SJBS); c) Garnet as accessory mineral, Catingas Granite (SJBS); d) plagioclase inclusions in K-feldspar megacryst, Valsungana Southern Batholith; e); Euhedral titanite as accessory mineral, Lajeado Alto Granite (VS); f) chlorite alteration in bitotite, with growth of epidote crystals /Nova Trento Granite (NTS). along its cleavage, Indaia

andesine. Quartz characteristically forms relatively large crystals, suggesting emplacement at shallow crustal level. The mafic and accessory mineralogy is heterogeneous in the suite, but is characterized by the presence of igneous muscovite ~o Jo~ and/or tourmaline. In some varieties, such as the Sa ao Batista pluton, euhedral crystals of muscovite comprise up to 7% of the rocks volume (Fig. 4a), while biotite occurs only as accessory. Other varieties, however, such as the Catinga and Tijucas Granites, have both muscovite and brown inclusion-rich biotite as rock-forming minerals. A third variety is distinguished by the presence of tourmaline in volumes as high as 6%, with no micas whatsoever, and includes the Ponta do Engodo and Oliveiras intrusions (Fig. 4b). Tourmaline can also occur as accessory in the other varieties. A distinctive but not ubiquitous accessory is garnet, which occurs as colorless round crystals (Fig. 4c). Trace minerals include Apatite, zircon, allanite and monazite. The late- to post-magmatic mineralogy includes sericite, chlorite, fluorite and, to a lesser degree epidote/clinozoisite. Fluorite ~o Joa ~o Batista may sum up to 1% of the rocks, such as in the Sa pluton. Sericitic alteration of plagioclase is widespread in all rocks (Fig. 4a), with the notable exception of the tourmaline-rich varieties. Biotite, when present, usually suffered chloritization.

3.2. Valsungana Suite Of the three granitic suites intrusive in the Brusque Group, the VS is petrographically the most homogeneous. Its rocks have a distinguished porphyritic texture, characterized by K-feldspar megacryst surrounded by an inequigranular seriated medium- to coarse-grained matrix. Most rocks are leucocratic to mesocratic (color index as high as 15%) and gray, with the exception of pink variations within the northern batholith, owing its color to the Kfeldspar content. The dominant composition varies from Monzogranites and quartz-monzonites to monzodiorites. The K-feldspar megacrysts can measure up to several centimeters in length, and have predominantly tabular shapes, though irregular crystal contacts and many inclusions point to a relatively late crystallization (Fig. 4d). Exsolution lamellae are common. Plagioclase is the most common mineral in the matrix and has a main composition between oligoclase and andesine. Quartz tends to form coarse-grained round crystals. The mafic mineralogy is dominated by red to brown idiomorphic bitote, with amphibole being a rare trace mineral. Other accessory and trace minerals include apatite, zircon, allanite, monazite and titanite, which is especially common in the northern intrusions of the VS, summing

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Fig. 5. Mesoscopic features of the VS: a) magmatic foliation, characterized by euhedral K-feldspar phenocrysts surrounded by undeformed matrix; b) undulation of the magmatic foliation, highlighted and with indication of the axial planes; c) magmatic deformation, as indicated by the presence of euhedral phenocrysts associated to stretched matrix and slightly deformed K-feldpars; d) solid state deformation, concentrated in a shear band.

Fig. 6. Microstructures in the GIBG: a) preserved oscillatory zoning in plagioclase, Valsungana Northern Batholith (VS); b) chessboard pattern in quartz, Indaia/Nova Trento Granite (NTS); c) microfracturing of K-feldspar phenocrysts associated to ductile recrystallization of quartz, Valsungana Southern Batholith (VS); d) protomylonitic foliation surrounding a plagioclast porphyroclast, Valsungana Southern Batholith (VS).

up to as much as 1% and forming crystals as big as 1 mm (Fig. 4e). Late- to post-magmatic minerals are mostly sericite, chlorite, opaque minerals, epidote/clinozoisite, and carbonate, which can be either late-magmatic, growing interstitially, or post-magmatic, concentrated in microfractures.

The sericitic alteration of plagioclase and chloritization of biotite is widespread not only in this suite, but in all the studied granites, and seems to be a combined phenomenon. The intensity of both processes varies among the different intrusions and even within a same pluton, but is always coupled one to another. While

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Fig. 7. The magmatic foliation of the Valsungana Batholiths follow the pluton elongation. The overall orientation of solid-state foliation on both batholiths is subhorizontal.

less hydrothermalized rocks may show only very fine crystals of sericite (usually aligned to the cleavage direction of the K-feldspars) in association to partial substitution of biotite on the crystals' rims, intensively affected granites show big hydrothermal muscovite crystals associated to epidote crystallization, always accompanied by the complete chloritization od these rocks' biotites. 3.3. Nova Trento Suite This suite comprises equigranular to seriated inequigranular rocks, with colors varying from gray to pink. Most granites have medium-sized grains, but granulation variations leads to finer or coarser-grained varieties, some of which even bearing a “porphy/Nova Trento, Faxinal, Gaspar roid” appearance, such as the Indaia ^ nio granites. The main composition is syeno- to and Santo Anto monzogranitic. The biggest crystals in most rocks are composed of K-feldspar, which experienced relatively late crystallization. On porphyroid varieties, potassium feldspar makes up for the phenocrysts and can reach sizes up to 2 cm, usually bearing a pinkish color. Plagioclase commonly forms small crystals, and has a dominantly oligoclasic composition. Quartz has relative irregular shapes and may be interstitial. The main mafic mineral is brown to slightly pale biotite, and hornblende occurs as distinctive mafic phase in the Faxinal and Gaspar granites. Accessories include apatite, zircon, allanite, monazite, muscovite and tourmaline. The two latter occur ~o Batista Suite. The latein a much lesser extent then in the S~ ao Joa to post-magmatic mineralogy includes sericite, chlorite, fine opaque minerals, epidote/clinozoisite (Fig. 4f) and, more rarely, fluorite. 4. Structural aspects The foremost mega- to macroscopic structural characteristic of the GIBG is the elongated shape of most bodies of all three suites. The orientation of the intrusions' long axes is approximately N50E,

parallel to the Brusque Group's foliation and its megafolds. It is also semi-parallel to the direction of the MGSZ and to the maximum elongation axis of its deformational ellipsoid (Basei et al., 2011). On the meso- and microscopic scale (Figs. 5 and 6, respectively), magmatic foliation and solid-state overprint are the main structural feature of the GIBG. They are very rare on the SJBS rocks, which are characteristically isotropic and show only sparse microscopic evidence of low-temperature deformations, but are common on both the VS and NTS. While In the latter the planar structures are rather subtle, the former's porphyritic texture with coarse-grained matrix enhances its fabric, allowing it to be easily recognizable in field. In the GIBG, the magmatic foliation is indicated by the orientation of euhedral feldspar. In the VS, the presence of tabular Kfeldspar phenocrysts surrounded by an undeformed matrix makes this structure particularly evident (Fig. 5a), especially around the intrusions borders. In the central areas of the batholiths, where tabular feldspar are less orderly arranged and isometric crystals are more common, this foliation is more subtle and irregular. Locally, the magmatic foliation can be undulated (Fig. 5b). In thin sections, the oriented crystals preserve igneous characteristics, such as oscillatory zoning in plagioclase (Fig. 6a) and string perthites in Kfeldspar. There is ample evidence that the magmatic flow was accompanied by some degree of deformation of the crystal mush as the temperatures declined, as discussed by Paterson et al. (1989, 1998). In the field, it can be observed in rocks from the VS by the coexistence of undeformed or slightly deformed K-feldspar phenocrysts, associated to stretched biotite in the matrix, forming a regular and aligned fabric (Fig. 5c). This is the main structure in the Northern Valsungana Batholith and in the Camboriú/Rio Pequeno Granite. In the Southern Valsungana Batholith there is a division between its central and SW sections, which show predominantly evidence of pure magmatic foliation, and its NE section, in which the magmatic flow usually shows a synchronic deformation. Microstructures such as the recrystallization of feldspar and the presence of chessboard patterns in quartz (Fig. 6b) further suggest a continuity of deformation from igneous to subsolidus conditions for both the VS and NTS. This has been described in the Camboriú/Rio Pequeno (VS) and Serra dos Macacos Granite (NTS) by Peternell et al. (2010), which also identified optical continuity between quartz from the matrix to that filling cracks in feldspars, another indicator of deformations in the crystal mush (Bouchez et al., 1992). Solid state deformation is widespread on the VS and NTS. It affects the different intrusions heterogeneously, commonly concentrating in small shear bands that are few meters wide (Fig. 5d). It usually has more gentle dips then the igneous foliation, but both may be semi-parallel close to the intrusions' borders. It is characterized by stretching of the original fabric, and in the VS the phenocrysts are commonly sheared. In thin section, microfracturing of feldspars associated to dynamic recrystallization of quartz (Fig. 6c) indicates greenschist conditions. The most deformed rocks can show protomylonitization, with development of anastomosed foliation on quartz, surrounding feldspar porphyroclasts. (Fig. 6d). The orientation of the magmatic foliation, with or without evidence of synchronic deformation, varies throughout both batholiths of the VS (Fig. 7), but generally follows the intrusive contacts, as could be expected. On the Southern Batholith the strike accompanies the intrusions' elongation, which is inflected along its length, going from an approximate N20E direction in its southern tip to ca. N45E trend on the central section and N60E on the northern extremity. The magmatic foliation dips both to S/SE and to N/NW, with a predominance of the first, agreeing well to the

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Table 1 Major and trace element for different granites intrusive in the Brusque Group. Suite

SJBS

Intrusion

~o Jo~ Sa ao Batista

Sample

B-19C

B-20C

72.31 15.16 0.49 0.15 0.73 5.22 4.73 0.13 0.00 0.00 <0.002 0.9 366 12 65.2 22.0 39.1 5.5 24.2 480.7 20 155.9 10.1 38.8 32.0 <8 515.3 122.5 24.2 36.1 79.9 9.26 31.0 5.62 0.51 2.48 0.27 1.03 0.12 0.30 0.06 0.29 0.05 0.7 5.4 28.4 23 5.2 2.5 0.1 0.1 1.4 0.2 3.4 0.01 0.3 0.5

70.42 15.77 0.73 0.25 0.79 4.81 5.40 0.23 0.09 0.01 <0.002 1.3 513 9 57.1 28.9 42.2 6.4 19.9 586.6 22 176.2 10.3 51.2 21.6 <8 581.3 181.4 4.8 50.4 106.8 12.46 43.5 6.37 0.74 2.61 0.28 0.99 0.13 0.30 0.05 0.37 0.04 1.9 0.9 58.8 44 3.4 3.3 0.3 0.2 27.4 0.2 2.8 0.01 0.6 0.5

SiO2 Al2O3 Fe2O3 MgO CaO Na2O K2O TiO2 P2O5 MnO Cr2O3 LOI Ba Be Co Cs Ga Hf Nb Rb Sn Sr Ta Th U V W Zr Y La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Mo Cu Pb Zn Ni As Cd Sb Bi Ag Au Hg Tl Se

% % % % % % % % % % % % ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppb ppm ppm ppm

VS Ponta do Engodo

Valsungana southern Batholit

B-21E

IT-IV-126

B-30

B-31

B-32

B-48

B-50

75.97 12.45 1.37 0.16 0.92 3.50 4.23 0.15 0.00 0.03 <0.002 1.0 176 9 89.7 13.0 23.2 6.3 41.5 336.9 6 59.8 23.4 43.0 18.2 <8 1094.1 145.0 71.4 39.3 83.3 9.38 32.1 7.20 0.50 7.42 1.65 10.15 2.26 7.24 1.24 8.18 1.29 2.6 0.5 15.7 16 3.7 0.5 0.1 0.1 23.1 0.1 8.5 0.01 0.5 0.6

74.24 14.67 0.79 0.06 0.38 5.14 3.81 0.02 0.19 0.03 <0.002 0.6 83 7 75.9 75.7 20.1 1.3 19.0 343.8 2 25.3 15.8 1.5 3.1 <8 608.0 17.9 3.7 1.4 2.5 0.32 1.1 0.39 0.01 0.38 0.11 0.64 0.13 0.32 0.06 0.56 0.08 <0.1 0.9 3.5 <1 33.3 <0.5 <0.1 <0.1 5.6 <0.1 <0.5 <0.01 <0.1 <0.5

71.28 13.52 3.48 0.66 1.65 3.03 4.47 0.49 0.17 0.00 <0.002 0.9 709 4 87.5 6.3 19.2 7.5 31.8 202.8 3 200.7 10.4 35.1 7.3 21 601.0 301.3 51.5 88.7 170.8 18.53 64.4 10.06 1.79 8.30 1.39 7.26 1.55 4.10 0.65 3.77 0.57 3.0 5.9 9.2 56 5.5 0.5 0.1 0.1 0.1 0.1 2.0 0.01 0.6 0.5

69.33 13.98 4.81 0.89 2.60 3.45 3.06 0.70 0.27 0.06 0.003 0.6 440 4 63.0 7.9 22.5 11.4 37.7 174.9 4 198.2 9.0 34.3 4.4 31 406.1 457.4 34.5 76.7 146.1 15.95 53.6 8.91 1.57 7.26 1.20 6.60 1.19 3.40 0.50 2.98 0.45 3.9 8.1 6.1 68 8.4 0.5 0.1 0.1 0.2 0.1 0.5 0.01 0.8 0.7

70.06 14.19 3.34 0.59 1.71 2.99 5.23 0.50 0.18 0.04 0.006 0.9 924 3 76.6 6.7 19.5 7.4 30.9 217.6 4 190.3 9.2 34.9 3.7 15 492.8 311.1 31.5 80.9 159.2 16.91 56.3 8.99 1.61 6.62 1.12 5.84 1.11 2.99 0.46 2.67 0.42 3.9 7.0 8.6 49 11.3 0.7 0.1 0.1 0.1 0.1 1.0 0.01 0.5 0.8

65.08 15.89 4.03 0.82 1.60 3.08 6.91 0.63 0.23 0.00 <0.002 1.3 1621 2 55.4 5.3 20.0 8.9 26.2 194.5 2 315.7 6.4 23.2 2.6 30 330.9 390.3 27.4 63.7 121.4 13.29 45.9 7.52 2.31 5.88 0.98 4.84 0.95 2.66 0.38 2.31 0.37 2.0 8.8 14.2 56 6.2 0.9 0.1 0.1 0.2 0.1 1.1 0.01 0.4 0.5

66.26 16.21 3.45 0.55 2.35 3.91 5.29 0.48 0.17 0.00 0.003 1.0 1282 3 60.7 4.4 23.1 8.0 31.8 176.6 2 257.3 9.5 13.0 3.1 13 409.8 354.9 23.6 47.1 85.4 9.34 35.2 6.01 2.09 5.14 0.87 4.61 0.90 2.31 0.33 1.84 0.28 2.0 6.0 8.0 50 4.6 0.6 0.1 0.1 0.1 0.1 2.4 0.01 0.4 0.5

Valsungana northern Batholit

Camboriú/Rio Pequeno

MAGB-12

MAGB-14 B

MAGB-14 A

MAGB-2.1

74.90 12.80 2.18 0.24 1.22 3.03 4.39 0.40 0.09 0.03 <0.002 0.6 440 3 73.8 4.1 17.5 6.2 16.1 168.9 2 114.9 1.6 42.8 4.5 8 639.0 204.5 25.7 116.3 245.7 24.64 81.6 12.54 1.12 8.57 1.17 5.51 0.84 2.33 0.30 1.95 0.25 1.1 1.7 6.5 34 41.0 0.9 0.1 0.1 0.2 0.1 0.7 0.01 0.4 0.5

68.04 14.62 2.04 0.77 2.62 4.23 3.75 0.40 0.11 0.00 <0.002 3.1 1609 2 76.4 1.6 19.1 4.5 11.9 96.0 2 914.1 1.3 8.7 2.0 27 617.6 146.6 4.8 35.3 68.5 7.65 26.6 4.24 1.12 2.38 0.28 1.06 0.15 0.32 0.05 0.32 0.05 0.1 0.8 8.9 66 43.0 0.5 0.2 0.1 0.1 0.6 0.5 0.01 0.1 0.5

68.63 15.48 1.77 0.56 1.98 4.18 4.64 0.29 0.14 0.02 <0.002 1.7 2111 2 87.4 0.9 21.3 4.9 13.0 104.1 2 1254.2 1.4 8.8 2.6 28 693.9 160.8 5.5 38.0 76.6 8.33 31.0 4.65 1.13 2.57 0.31 1.22 0.17 0.41 0.06 0.34 0.05 0.1 0.3 5.8 54 48.0 0.5 0.1 0.1 0.1 0.1 0.5 0.01 0.1 0.5

69.61 14.33 3.57 0.57 1.86 3.29 5.05 0.50 0.18 0.08 <0.002 0.6 872 3 78.3 3.5 20.2 9.5 17.5 158.3 3 216.7 1.3 15.4 1.6 33 592.6 366.6 23.7 89.1 180.8 19.28 71.1 12.35 1.50 9.54 1.40 6.33 1.01 2.17 0.26 1.49 0.21 1.5 14.6 2.4 47 42.0 0.5 0.1 0.1 0.1 0.1 1.0 0.01 0.5 0.5

NTS Indai a/Nova Trento

Nova lia Ita

Serra dos Macacos

Morro Pelado Rio do Alho

Santo Aleixo

Beija Flor

Morro Pelado

Campo Novo

B-22

B-23

B24B

B-25 B-27B MAGB13.1

MAGB-4.1

B-38 NT-71 B-11

B-16 NT60A

NT-51

NT-63 NT-71

IT-VI-96

73.05 13.43 2.30 0.32 1.21

75.61 12.49 1.61 0.12 0.72

75.30 12.76 1.45 0.12 0.89

72.93 13.46 2.32 0.33 1.27

71.87 14.31 1.95 0.47 1.58

72.88 13.93 1.90 0.34 1.24

72.83 13.71 1.86 0.36 1.04

74.16 13.73 1.25 0.20 0.71

72.93 14.02 1.69 0.28 0.96

74.20 13.62 1.44 0.26 1.24

73.78 13.03 2.33 0.30 1.10

73.12 13.97 1.71 0.27 0.48

72.74 14.10 1.78 0.33 1.08

73.44 13.76 1.55 0.28 0.96

74.91 13.16 1.54 0.24 0.86

72.74 14.10 1.78 0.33 1.08

Detection limit

Mean standard error (%)

0.01 0.01 0.04 0.01 0.01

0.79 0.57 0.43 0.39 0.91 (continued on next page)

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M. Hueck et al. / Journal of South American Earth Sciences 69 (2016) 131e151

Table 1 (continued ) NTS /Nova Trento Indaia

Nova lia Ita

Serra dos Macacos

Morro Pelado Rio do Alho

Santo Aleixo

Beija Flor

Morro Pelado

Campo Novo

B-22

B-23

B24B

B-25 B-27B MAGB13.1

MAGB-4.1

B-38 NT-71 B-11

B-16 NT60A

NT-51

NT-63 NT-71

IT-VI-96

3.31 5.01 0.28 0.11 0.06 <0.002 0.7 442 8 88.4 19.1 21.0 6.0 37.2 364.7 11 119.5 15.8 31.7 11.9 <8 851.6 226.4 30.9 43.6 87.7 9.50 31.0 5.59 0.88 4.62 0.89 4.82 0.98 2.94 0.50 3.12 0.50 11.40 1.1 13.2 47 4.8 0.5 0.1 0.1 0.4 0.1 5.3 0.01 0.9 0.5

3.17 4.99 0.13 0.03 0.00 <0.002 0.9 173 6 136.7 8.0 21.9 5.1 51.3 333.2 11 43.8 24.5 56.4 26.6 <8 989.3 134.2 42.0 32.1 67.9 7.92 29.3 6.26 0.41 5.56 1.06 6.16 1.33 4.16 0.68 4.16 0.68 4.00 0.4 19.4 36 2.7 0.5 0.1 0.1 1.3 0.1 7.0 0.01 0.3 0.5

3.44 4.67 0.11 0.02 0.00 0.002 1.0 125 10 99.4 9.0 19.8 4.2 29.8 306.6 11 43.5 13.6 45.8 15.9 <8 762.7 110.1 50.6 25.2 56.0 6.78 24.8 6.30 0.40 6.25 1.32 8.06 1.66 5.03 0.79 4.99 0.76 1.40 0.5 16.2 36 4.3 0.5 0.1 0.1 0.1 0.1 0.9 0.01 0.5 0.6

3.38 4.69 0.29 0.09 0.00 0.002 1.0 449 10 76.9 12.2 20.7 6.1 31.2 283.0 15 132.5 11.2 44.3 10.5 <8 536.4 219.0 38.5 70.5 138.6 14.71 48.8 8.06 0.88 6.18 1.09 6.26 1.23 3.75 0.59 3.72 0.59 1.40 2.3 13.8 47 10.5 0.5 0.1 0.1 0.2 0.1 0.8 0.01 0.5 0.5

3.34 5.00 0.23 0.08 0.04 <0.002 0.6 2243 2 106.1 1.5 15.4 5.8 15.6 132.3 2 365.2 2.3 20.7 3.2 24 847.7 218.2 14.7 83.9 148.0 13.90 44.7 5.78 1.06 3.58 0.55 2.66 0.51 1.48 0.23 1.46 0.24 0.30 1.9 10.2 34 58.0 0.5 0.1 0.1 0.1 0.1 0.8 0.01 0.2 0.5

3.21 5.27 0.21 0.07 0.04 0.003 0.7 813 6 91.1 5.0 18.6 5.4 29.2 275.6 8 198.1 13.9 19.9 4.8 <8 640.1 195.2 25.2 62.2 117.8 11.67 34.9 5.66 0.85 4.21 0.77 4.22 0.83 2.43 0.41 2.65 0.39 1.40 1.0 13.2 33 7.5 1.6 0.1 0.1 1.1 0.1 2.1 0.01 0.1 0.5

3.20 5.39 0.25 0.07 0.04 0.002 1.0 734 5 69.9 5.3 19.1 5.7 28.4 266.1 4 163.5 11.5 25.3 5.8 11 611.4 203.3 24.5 67.3 128.3 13.18 42.3 6.35 0.93 4.68 0.77 3.83 0.73 2.08 0.33 1.97 0.30 2.00 1.8 7.8 41 6.0 0.5 0.1 0.1 0.1 0.1 8.0 0.01 0.6 0.5

3.38 5.26 0.15 0.04 0.03 <0.002 0.9 489 5 61.1 12.7 18.6 4.2 24.4 273.9 5 136.6 3.1 33.4 8.1 14 484.4 134.5 47.9 78.3 124.4 15.69 53.8 9.59 1.13 8.86 1.31 7.57 1.39 4.10 0.63 4.09 0.66 0.50 0.5 13.8 23 28.1 0.7 <0.1 <0.1 0.5 <0.1 <0.5 <0.01 0.3 <0.5

3.24 5.35 0.19 0.07 0.03 <0.002 1 700 3 80.1 7.0 19.3 5.1 15.6 257.4 4 174.8 2.2 14.2 2.2 15 636.9 173.4 17.6 50.5 96.3 9.50 29.4 4.95 0.71 3.68 0.56 3.04 0.56 1.73 0.26 1.73 0.27 0.20 0.8 7.1 28 34.4 0.6 <0.1 <0.1 0.2 <0.1 <0.5 <0.01 0.1 <0.5

3.39 4.63 0.18 0.05 0.03 <0.002 0.7 697 4 82.9 9.8 19.2 4.7 28.9 228.7 4 153.5 2.8 24.7 4.4 11 663.1 147.1 38.5 64.0 119.1 12.81 42.7 7.82 0.85 6.75 1.09 6.61 1.21 3.85 0.55 3.47 0.50 0.10 2.6 10.9 29 36.9 <0.5 <0.1 <0.1 <0.1 <0.1 <0.5 <0.01 0.4 0.6

3.36 4.53 0.26 0.09 0.06 <0.002 0.9 329 8 85.6 12.1 20.4 6.7 39.3 305.0 12 96.4 15.8 43.2 19.3 <8 704.9 225.1 43.2 53.3 105.5 11.60 40.3 7.26 0.66 6.12 1.20 6.45 1.33 4.16 0.65 3.79 0.60 1.90 1.2 17.2 52 3.5 0.5 0.1 0.1 0.1 0.1 1.9 0.01 0.8 0.5

2.88 5.70 0.21 0.06 0.02 <0.002 1.2 1096 3 115.4 6.6 16.9 5.9 18.1 256.1 4 193.1 2.5 30.4 3.9 21 925.2 197.7 16.3 84.0 152.0 15.00 47.9 6.68 0.89 3.96 0.62 3.11 0.58 1.67 0.27 1.77 0.28 0.40 0.7 11.0 31 62.0 0.5 0.1 0.1 0.1 0.1 0.5 0.01 0.2 0.5

3.35 5.28 0.22 0.08 0.03 <0.002 0.8 726 6 63.4 4.0 18.4 5.2 16.0 233.9 3 196.0 1.9 13.7 5.7 20 490.8 178.1 21.9 47.9 85.7 8.85 28.4 4.73 0.77 3.71 0.57 3.58 0.64 2.09 0.32 2.07 0.32 0.20 0.7 9.3 31 31.8 1.0 <0.1 <0.1 <0.1 <0.1 <0.5 <0.01 <0.1 <0.5

3.36 5.19 0.21 0.00 0.04 <0.002 0.9 558 4 84.4 4.0 18.9 5.6 34.4 257.1 3 154.0 12.0 43.8 4.9 <8 678.3 177.9 28.2 80.5 152.1 15.21 46.4 7.36 0.84 4.85 0.89 4.81 0.95 2.66 0.41 2.40 0.37 2.50 2.5 11.3 49 13.7 0.6 0.1 0.1 0.1 0.1 3.3 0.01 0.4 0.5

vergence direction of the Brusque Group's megafolds. All three sections share a tendency of having steeper dip angles on its borders and slightly gentler dips on the batholiths' center. The magmatic foliation in the Northern batholiths shows no discernible location-dependent variation throughout either length or width. It has a predominantly NE trend, dipping both to NW and SE with a slight dominance of the first. Late solid-state foliation occurs rather homogeneously on both batholiths, with mostly subhorizontal to gently S-dipping orientations. On studying the magnetic fabrics of the Southern Valsungana batholith, obtained by the measurement of the anisotropy of the magnetic susceptibility (AMS) of these granites, Steenken et al. (2007) identified a dome-like structure on the southern tip of the

3.16 5.22 0.16 0.03 0.03 <0.002 0.5 507 3 42.8 8.7 17.9 4.6 19.8 246.9 9 129.5 2.4 33.0 10.2 10 334.8 135.7 46.6 57.6 110.2 11.61 38.4 7.46 0.70 6.60 1.17 7.08 1.49 4.59 0.71 4.31 0.67 0.40 0.5 4.9 31 22.6 0.7 <0.1 <0.1 <0.1 <0.1 <0.5 <0.01 0.4 <0.5

3.35 5.28 0.22 0.08 0.03 <0.002 0.8 726 6 63.4 4.0 18.4 5.2 16.0 233.9 3 196.0 1.9 13.7 5.7 20 490.8 178.1 21.9 47.9 85.7 8.85 28.4 4.73 0.77 3.71 0.57 3.58 0.64 2.09 0.32 2.07 0.32 0.20 0.7 9.3 31 31.8 1.0 <0.1 <0.1 <0.1 <0.1 <0.5 <0.01 <0.1 <0.5

Detection limit

Mean standard error (%)

0.01 0.01 0.01 0.01 0.01 0.002 e 1 1 0.2 0.1 0.5 0.1 0.1 0.1 1 0.5 0.1 0.2 0.1 8 0.5 0.1 0.1 0.1 0.1 0.02 0.3 0.05 0.02 0.05 0.01 0.05 0.02 0.03 0.01 0.05 0.01 0.1 0.1 0.1 1 0.1 0.5 0.1 0.1 0.1 0.1 0.5 0.01 0.1 0.5

0.89 0.77 0.18 0.63 0.30 1.29 e 2.05 e 4.33 2.89 2.51 3.73 5.91 2.27 3.45 3.33 2.18 15.51 4.66 2.31 3.03 3.57 1.53 3.84 4.47 4.01 4.55 4.29 4.69 2.20 4.91 3.30 4.14 3.91 3.32 2.67 5.76 8.15 5.32 8.10 6.52 4.48 9.42 3.94 18.90 5.72 12.58 24.98 12.89 8.91 9.89

batholith. Hence, these authors suggest that the batholith's formation is the result of the connection of a series of ascension paths aligned NE-SW by means of subhorizontal NE-trending flows, as evidenced by the magnetic lineations, possibly related to the late deformational phases of the Brusque Group. 5. Elemental geochemistry 28 samples from different intrusions associated to all three suites were analyzed for this study. The samples were prepared in gicas the laboratories of the Centro de Pesquisas Geocronolo ~o Paulo University (USP) and analyzed in the (CPGeo) in the Sa ACME Analytical Laboratories LTD, in Vancouver, Canad a, by ICMPS.

M. Hueck et al. / Journal of South American Earth Sciences 69 (2016) 131e151

141

Fig. 8. Harker-type diagrams. Al2O3, Fe2O3, CaO, MgO and TiO2 show negative correlation, whereas Na2O has a discrete positive correlation. Note the presence of distinct compositional fields for each granitic suite, which seem to be connected for the VS and NTS.

Table 1 presents the results. The new results, together with previous data obtained from Castro (1997), Lopes (2008) and Basei et al. (2011), were used in order to integrate the accumulated knowledge and allow a wider and more complete representation of the GIBG. 5.1. Major elements

Fig. 9. A/NK vs A/CNK diagram after Shand (1943). The GIBG are moderately peraluminous, and different suites plot into distinct compositional fields. Symbols as in Fig. 8.

The GIBG cover a relatively wide compositional range, as shown in the Harker-type dispersion diagrams (Fig. 8), with most samples between 64 and 79 wt% SiO2. The exception is the Faxinal Granite, part of the NTS, which has the lowest silica content of all, at 59 wt%, a distinctive outlier among its suite that is also evident in other elemental concentrations, such as Fe2O3, MgO and the trace element TiO2 (the sample was excluded from the SIO2 vs. MgO diagram for clarity, given its anomalous high MgO content). With the exception of this sample, there is a clear difference in the compositional range between the VS (mostly between 64 and 71 wt % SiO2) and the SJBS and NTS (71e79 wt% SiO2). The latter two have a broad overlap, but there is a slight tendency for higher silica values of the SJBS, as compared to the NTS. Most of the diagrams show rather unique compositional variations for each of the three suites, with some overlap between the NTS and SJBS due to their overlapping silica content. Of all three suites, the SJBS shows the most scattered data, reflecting its rather varying mineralogy, whilst the VS and NTS tend to have adjacent, if not continuous, fields.

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Fig. 10. Compositional classification diagrams after Frost et al. (2001): a) SiO2  FeOtot/(FeOtot þ MgO) diagram, most GIBG plot around the transition from ferroan to magnesian granites, with the exception of the strongly magnesian Faxinal Granite; b) SiO2  Na2O þ K2O
CaO diagram, with most granites plotting on the alkali-calcic to calcic-alkalic transition. Symbols as in Fig. 8.

Fig. 11. Harker-type diagrams for trace elements. Sr, Ba and Zr show negative correlation, whereas Rb, U and Th have a discrete positive correlation. Symbols as in Fig. 8.

There is a distinct negative correlation for all three suites between SiO2 and components such as Al2O3, Fe2O3, CaO, MgO, TiO2, and a less pronounced positive correlation between SiO2 and Na2O Naturally, the distribution of samples among different plutons would disqualify these correlations as result of simple fractionized crystallization, as is evidenced by the lack of correlation in some of the diagrams, but it does point to some degree of magmatic interaction, especially between the VS and NTS, which often show close connection in the field, with most NTS intrusion intruding the borders and interior of the Valsungana batholiths. All three suites have a moderately peraluminous tendency ~o Jo~ (Fig. 9), with few exceptions (one sample each of the Sa ao Batista Granite and both Valsungana batholiths) which plot in the metaluminous field. Most A/CNK values are concentrated between 1.0 and 1.1. Despite its characteristic mineralogy, with widespread presence of igneous muscovite and garnet and tourmaline as the common accessory, the SJBS does not seem to have a more pronounced metaluminous geochemistry than the other suites. The

diagram also shows, once more, that the different suites plot into distinct compositional fields, with the NTS in an intermediate position between the VS and SJBS. Regarding the SiO2  FeOtot/(FeOtot þ MgO) classification criteria proposed by Frost et al. (2001), all three suites plot around the transition from ferroan to magnesian granites, though most samples have a rather ferroan affinity (Fig. 10a). The most distinctive exception to this pattern is the Faxinal Granite, which has a pronounced magnesian characteristic. On the SiO2  Na2O þ K2O
CaO classification (Fig. 10b), most samples plot on the alkali-calcic to calcic-alkalic transition, with few samples having an alkalic characteristic, which is typical of the calcalkaline granitic series. As for the empiric compositional fields proposed by these authors for A-type and cordilleran granites, the GIBG as a whole do not fit especially well on one specific field, showing similarities to both. On a detail-scale study on the Camboriú/Rio Pequeno (VS) and Serra dos Macacos (NTS) granites, Florisbal et al., 2012a identified for both intrusions a more evident

M. Hueck et al. / Journal of South American Earth Sciences 69 (2016) 131e151

143

Fig. 12. ORG-normalized spidergrams of analyzed samples after Pearce et al. (1984). Note distinguished concentration variations within the SJBS and less so in the VS and NTS.

A-type signature, which was regarded by these authors as probably linked to melting under low H2O activity. 5.2. Trace elements Harker-type dispersion diagrams of trace element concentrations for the GIBG (Fig. 11) show similar results to those obtained for the major elements. Different suites usually plot into evident compositional fields, which, in the case of the VS and NTS, seem to be continuous. Sr, Ba and Zr show clear negative correlations, whereas Rb, U and Th have the opposite behavior. Multi-element spidergrams normalized to ORG values as proposed by Pearce et al. (1984) are shown in Fig. 12. There is an evident variation of the patterns within the suites, as for in the case of the Ta values, which fluctuate strongly on all three suites. In this

context, the SJBS is the most striking example, with concentrations spreading distinctly in most compared elements. A clear stand-out within the group is the Ponta do Engodo Granite, which is characterized by anomalously low Th contents and depleted normalized values between Ce and Yb. Even within a same pluton, namely the ~o Joa ~o Batista Granite, there are strong compositional variations, Sa such as on the Ta values and the occasional depletion of both Y and Yb. On the other hand, both the VS and NTS have much more consistent signatures, with some notable exceptions. In the case of the VS, there is a distinct compositional pattern to the Northern Batholith, which has positive Ba anomalies and is impoverished in both Y and Yb. The same Ba anomaly is observed in some granites of the NTS in the northern portion of the Brusue Group, a distinction that is further discussed in the REE segment of this section. On the Rb vs Y þ Nb discriminant diagrams of Pearce (1996), the

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intrusive granites in the Brusque Group plot predominantly on the boundary between volcanic arc, within-plate and syn-collisional magmatism, usually associated with post-collisional magmatism (Fig. 13). 5.3. Rare earth elements Chondrite-normalized REE patterns of analyzed samples (Fig. 14) vary throughout the different suites. The SJBS has a twofold behavior. The first pattern, present in all analyzed intrusions and unique to this suite within the studied rocks, shows little to no fractionation and very distinct negative Eu anomalies. Commonly referred to “seagull pattern” in literature, it has been linked to differentiated S-type granites or, alternatively, to REE mobilization due to late-magmatic hydrothermal processes. Both alternatives have petrographic evidences commonly associated to this suite, such as the peraluminous mineralogy and ore-building hydrothermalism (mainly W, subordinately Sn and Mo). The Ponta do Engodo Granite distinguishes itself not only for its “seagull pattern”, but also for having much lower REE concentrations than any other analyzed rock, comparable even to the chondritic standard. ~o Jo~ The second REE-pattern occurs in some samples of the Sa ao Batista pluton and is common to most GIBG in all three suites. It shows moderate to high fractionations with subtle to pronounced negative Eu anomalies, a typical behavior of crustal-generated granites. This is also the predominant pattern in both the VS and NTS, with the exception of a few samples that show no Eu anomalies at all. In the Valsungana suite, this behavior is characteristic of the northern batholith and subordinate for the southern batholith, and it is shared by three granites associated to the NTS: Faxinal, Gaspar and Morro do Boi, all of which occur within the northern domain of the Brusque Group and show positive Ba anomalies, as discussed in the trace element section. This characteristics, together with the common presence of titanite in these granites, suggest that within this northern domain the magmatism underwent more oxidizing conditions (Drake and Weill, 1975), a hypothesis first identified by Castro et al. (1999), possibly causing the distinctions between the northern and southern batholiths of the otherwise quite homogenous VS.

Fig. 13. Rb vs Y þ Nb discriminant diagram after Pearce (1996), indicating a postcollisional setting for the GIBG. Symbols as in Fig. 8.

6. Isotope geochemistry Thirty-one samples were selected for the isotope geochemistry (RbeSr, SmeNd and PbePb) analyses. These correspond to the same rocks analyzed for elemental geochemistry, with the addition of a few samples for which there already was elemental geochemistry data in the literature. All samples were prepared and analyzed in the CPGeo-USP laboratories, according to experimental routines described in Torquato and Kawashita (1994), Babinski et al. (1997) and Sato et al. (1995). Sr and Nd isotopic ratios for the three suites were recalculated with crystallization ages of 600 Ma, a mean value obtained from the available radiometric ages for these rocks (Hueck and Basei in preparation). Most values were published, together with a preliminary analysis, by Basei et al. (2011). The results are presented in Table 2. Two additional analyses from the Serra dos Macacos Granite (NTS) and one from the Camboriú/ Rio Pequeno Granite (VS) from Lopes (2008) were added in the evaluation of the data. A number of samples of the SJBS yielded systematically unrealistic Sr and Nd ratios, evidencing a disturbance of this isotopic system. These values are presented in Table 2, but are not included in the respective figures. It is worth noting that these are the same rocks that yield the distinct “seagull” REE patterns. This could suggest that the same process that caused this distinct pattern, whether high differentiation or late hydrothermal activity, may have also affected the isotopic systems in this samples. Many of the SJBS samples and two of the NTS displayed elevated 147Sm/144Nd ratios and therefore had their TDM ages calculated in a double-stage model. Most initial 87Sr/86Sr values from the SJBS are far higher than for the rest of the GIBG. These ratios, as elevated as 0.7348, outline a distinguished compositional field for this suite in a silica-dispersion diagram (Fig. 15a), suggesting important contribution of upper crust sources. With a different behavior, VS ratios are very well constricted to the interval between 0.7082 and 0.7132, attesting not only the development of a more homogeneous isotopic system, but also its affinity to less differentiated sources, as might be attested by the more intense presence of mafic enclaves. As pointed out in the elemental geochemistry section, the NTS defines a compositional field that is seemingly continual to the VS, suggesting some degree of magmatic interaction. Though the initial 87Sr/86Sr ratios have rather similar values for both suites, there is a gentle but conspicuous increase in the NTS, with values as high as 0.7186, which might suggest a late contamination of upper-crust material. This apparent upper-crust affinity of the NTS, when compared to the VS, is also apparent in a SiO2 vs. εNd Diagram (Fig. 15b), but there is less evidence of a continuous evolution, with poorly aligned data. Another distinct difference between both isotopic systems is the comparatively low εNd values obtained for the SJBS. However, a dominant crustal signature is clear for all three granitic suites, with values between
8.5 and
24. Crossing both isotopic systems, Fig. 16 shows a εSr vs. εNd plot, and compares the obtained data to that of contiguous units of the CDF in SC. As a whole, the GIBG overlap mainly with the compositional fields outlined by the Camboriú Complex and the metapsamitic rocks from the Brusque Group, even if both units define rather ample and scattered fields. There is, however little to no similarities between the studied rocks and those associated both to polis Batholith and to the metabasic rocks within the the Floriano Brusque Group. Fig. 17 presents εNd vs. Time diagrams for the GIBG. TDM ages were calculated after De Paolo (1981) and unrealistically old ages were calculated in a double stage model. There is a distinguished signature for each of the three suites. Younger values come from the SJBS (between 1.54 and 1.91 Ga), which also shows the most

M. Hueck et al. / Journal of South American Earth Sciences 69 (2016) 131e151

145

Fig. 14. Chondrite-normalized REE patterns of analyzed samples. Chondrite standard values after Taylor and McClennan (1985). Most samples show moderate to high fractionations with light to pronounced negative Eu anomalies. Note distinctive “seagull” patterns for most SJBS intrusions and absence of Eu anomalies in the Valsungana Northern batholith (VS) and Faxinal, Gaspar and Morro do Boi Granites (NTS).

scattered values, considering that less samples for this suite yielded satisfactory results. Both the VS and the NTS hint to the

contribution of older crust in its magmatic sources. VS yielded TDM ages between 1.74 and 2.17 Ga, whilst typical values for the NTS

146

Table 2 Whole-rock Sr, Nd and Pb isotopic data for different granites intrusive in the Brusque Group. Suite Intrusion

Sample

Sm

Nd

147

Sm/144Nd

ppm ppm B-19C 5.62 31.0 0.109626 B-20C 6.37 43.5 0.088550 B-21E 7.20 32.1 0.135634 NT-85 5.61 32.6 0.104060 Tijucas NT-76A 10.20 35.5 0.173745 Catinga NT-78 6.57 8.7 0.459292 NT-77 5.31 15.2 0.211247 Ponta do Engodo IT-IV-126 0.39 1.1 0.214394 VS Valsungana S Batholit B-30 10.06 64.4 0.094461 B-31 8.91 53.6 0.100520 B-32 8.99 56.3 0.096559 B-48 7.52 45.9 0.099071 B-50 6.01 35.2 0.103246 Valsungana N Batholit MAGB-14B 4.24 26.6 0.096388 MAGB-14A 4.65 31.0 0.090705 Camboriú/Rio Pequeno MAGB-2.1 12.35 71.1 0.105036 NTS Indai a/Nova Trento B-22 5.59 31.0 0.109041 B-23 6.26 29.3 0.129195 B-24B 6.30 24.8 0.153613 B-25 8.06 48.8 0.099875 B-27B 7.26 40.3 0.108936 lia MAGB-13.1 6.68 47.9 0.084330 Nova Ita Serra dos Macacos MAGB-4.1 5.78 44.7 0.078192 Morro Pelado B-38 5.66 34.9 0.098069 NT-71 4.73 28.4 0.100712 Rio do Alho B-11 7.36 46.4 0.095918 B-16 6.35 42.3 0.090776 Beija Flor NT-63 4.95 29.4 0.101812 Rio do Alho NT-60A 7.46 38.4 0.117476 Santo Aleixo NT-51 9.59 53.8 0.107789 Campo Novo IT-VI-96 7.82 42.7 0.110744

Nd/144Nd εNd (0) εNd TDM Rb Sr 600 Ma Ma ppm ppm

0.511839 0.511777 0.511646 0.511666 0.511507 0.512597 0.511779 0.511998 0.511626 0.511681 0.511645 0.511650 0.511715 0.511543 0.511548 0.511497 0.511542 0.511721 0.511828 0.511490 0.511561 0.510969 0.510958 0.511239 0.511229 0.511195 0.511306 0.511256 0.511317 0.511193 0.511232


15.6
16.8
19.4
19.0
22.1
0.8
16.8
12.5
19.7
18.7
19.4
19.3
18.0
21.4
21.3
22.3
21.4
17.9
15.8
22.4
21.0
32.6
32.8
27.3
27.5
28.2
26.0
26.9
25.8
28.2
27.4


8.9
8.5
14.7
11.9
20.3
20.9
17.9
13.8
11.9
11.3
11.7
11.8
10.9
13.7
13.2
15.2
14.7
12.7
12.5
15.0
14.3
24.0
23.7
19.7
20.1
20.4
17.9
19.7
19.7
21.4
20.9

1761 1541 2323 1915 2654 2688 2514 2272 1810 1834 1819 1853 1832 1950 1854 2173 2191 2201 2187 2082 2161 2455 2354 2387 2459 2402 2159 2445 2760 2683 2703

87

Rb/86Sr

87

Sr/86Sr

87

Sr/86Sr(i) εSr (600 Ma)

480.7 155.9 9.01059 0.80630 0.72920 586.6 176.2 9.73318 0.81086 0.72758 336.9 59.8 16.54388 0.85623 0.71467 321.0 88.0 11.43597 1.55200 1.45415 316.0 37.0 24.94003 0.79890 0.58551 336.0 12.0 87.78262 1.55200 0.80090 278.0 45.0 18.09064 0.82745 0.67266 343.8 25.3 40.78692 1.08377 0.73478 202.8 200.7 2.93328 0.73833 0.71323 174.9 198.2 2.56082 0.73504 0.71313 217.6 190.3 3.32018 0.74088 0.71247 194.5 315.7 1.78653 0.72740 0.71211 176.6 257.3 1.99079 0.72992 0.71289 96.0 914.1 0.30404 0.71079 0.70819 104.1 1254.2 0.24031 0.71135 0.70930 158.3 216.7 2.11852 0.72845 0.71033 364.7 119.5 8.90697 0.79302 0.71681 333.2 43.8 22.44104 0.90312 0.71111 306.6 43.5 20.76878 0.89161 0.71390 283.0 132.5 6.22005 0.77095 0.71772 305.0 96.4 9.23809 0.79767 0.71862 256.1 193.1 3.85147 0.74220 0.70925 132.3 365.2 1.04941 0.71685 0.70787 275.6 198.1 4.04123 0.74503 0.71045 233.9 196.0 3.46503 0.74067 0.71102 257.1 154.0 4.85238 0.75098 0.70946 266.1 163.5 4.73044 0.75102 0.71054 257.4 174.8 4.27803 0.74637 0.70977 246.9 129.5 5.54782 0.76266 0.71519 273.9 136.6 5.83441 0.76230 0.71238 228.7 153.5 4.32991 0.74975 0.71271

360.9 337.8 154.5 10661.3
1680.8 1379.6
442.4 440.1 134.0 132.6 123.1 118.1 129.1 62.3 78.1 92.7 184.8 103.8 143.5 197.8 210.6 77.4 57.8 94.5 102.5 80.4 95.8 84.8 161.8 121.9 126.5

206

Pb/204Pb Error % (1s)

20.825 19.624 20.682 e e e 18.894 20.392 18.197 18.521 17.953 17.491 17.596 17.858 17.678 17.209 18.516 19.543 19.163 18.754 18.760 17.133 16.445 16.830 16.815 17.004 17.176 16.675 17.692 17.611 17.536

0.007 0.007 0.006 e e e 0.008 0.007 0.007 0.010 0.004 0.008 0.005 0.004 0.004 0.006 0.035 0.005 0.008 0.018 0.007 0.007 0.005 0.006 0.010 0.007 0.010 0.007 0.007 0.008 0.008

207

Pb/204Pb Error % (1s)

15.852 15.783 15.728 e e e 15.599 15.724 15.587 15.617 15.575 15.551 15.557 15.571 15.539 15.486 15.651 15.647 15.632 15.622 15.609 15.443 15.477 15.345 15.292 15.405 15.387 15.279 15.449 15.440 15.508

0.007 0.007 0.006 e e e 0.009 0.007 0.007 0.010 0.004 0.009 0.006 0.005 0.004 0.007 0.034 0.005 0.007 0.015 0.007 0.008 0.005 0.005 0.010 0.007 0.009 0.007 0.007 0.008 0.008

208

Pb/204Pb Error % (1s)

38.951 38.936 39.250 e e e 38.143 37.882 38.997 39.777 38.995 38.274 38.049 37.999 38.087 39.158 38.646 39.045 38.976 39.225 39.004 38.526 37.710 37.446 37.281 38.397 37.800 36.976 38.466 38.245 38.540

0.006 0.008 0.007 e e e 0.011 0.007 0.007 0.010 0.004 0.009 0.005 0.004 0.005 0.007 0.038 0.005 0.008 0.021 0.008 0.007 0.005 0.005 0.010 0.008 0.010 0.007 0.007 0.008 0.008

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~o Joa ~o Batista SJBS Sa

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Fig. 15. (a) SiO2 vs. 87Sr/86Sr (i) and (b) SiO2 vs. εNd. Data shows a distinctive crustal affinity for the GIBG. Note that the SJBS data are rather scattered, while the VS and NTS are homogeneous and continuous. Symbols as in Fig. 8.

vary from 2.08 to 2.76. On comparing the Nd evolution of the GIBG to that of regional rocks, the most similar unit is the Camboriú Complex, from which the ample variation spectrum encompasses all of the studied rocks. There is also an important overlap with the field outlined by the metapsamitic rocks from the Brusque Group, especially within the SJBS. Correlation with rocks from the metabasic portion of the Brusque Group and the Florianopolis Batholith, however, are only very limited. On a common Pb isotope evolution diagram, comparing the 206 Pb/204Pb vs. 207Pb/204Pb ratios (Fig. 18), once more a connection between the VS and NTS is suggested, in opposition to the SJBS, which defines a predominantly separate compositional field. 7. Discussion 7.1. Division of the GIBG in suites The addition of substantial new elemental and isotopic geochemical data strongly supports the three-suite classification of the GIBG. A synthesis of this division is presented in Table 3. Many diagrams define clear compositional trends or fields for each suite (e.g. Figs. 8, 9, 11, 15 and 16), reflecting its similarities. Punctual divergences and characteristics, however, deserve to be discussed. The SJBS is a rather heterogeneous suite in comparison to the other two. This is evidenced by the scattered geochemical and isotopic data and varied mafic mineralogy within a peraluminous specter. This suite, however, also concentrates the smallest intrusions within the Brusque Group, which spread throughout a wide area, being thus the most susceptible to reflect variation on its

147

Fig. 16. εSr vs. εNd diagram with a comparison between the GIBG and main regional units. All ratios calculated for 600 Ma. Data reference: Brusque Group e Yamamoto polis batholith: Chemale et al. (2010); Camboriú Complex e Lopes (2008); Floriano (2012), Florisbal et al. (2012c), Passarelli et al. (2010) and unpublished data. Note that the GIBG show more affinities to the Camboriú Complex and metapsamitic rocks polis batholith and from the Brusque Group, and little to no similarity with the Floriano the Brusque Groups' metabasic rocks. Symbols as in Fig. 8.

protolithic sources, which likely accounts for this heterogeneity. Nonetheless, its distinctive petrographic features and geochemical signatures such as the conspicuous “seagull” chondrite-normalized REE pattern and common disturbance in the isotopic systems, possibly linked to hydrothermal activity, indicate that these rocks underwent analogous geologic processes. As opposed to that, the VS, with its large batholiths, distinctive textural features and overall petrographic homogeneity, stands out as the least variable and easiest identifiable suite within the GIBG. The variation within it is restricted to minor differences between its northern and southern batholiths, especially regarding its trace elements and REE patterns, which seem to suggest more oxidizing conditions, a regional distinction also observed in the NTS. Despite comprising a large array of scattered plutons like the SJBS, the NTS shows a more consistent geochemical and isotopic signature. Two intrusions, however, the Faxinal and Gaspar Granites, stand out for its hornblende-rich mineralogy, based on which Caldasso et al. (1988, 1995) classified them into a distinct Faxinal Suite. This characteristic is reflected in the few available geochemical data, especially for the SiO2-depleted Faxinal Granite. They bear some resemblances to the close-by Northern Valsungana batholith, such as the presence of pink K-feldspars and lack of Eu anomalies in their chondrite-normalized REE patterns, inter-suite similarities first noticed by Castro et al. (1999). On the absence of detail-scale studies concerning these rocks, however, the question whether a distinct lithostratigraphic division should be determined remains open. 7.2. Regional affinities and origin of the magmatism One of the foremost characteristics of the GIBG is its distinct

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Fig. 17. εNd vs. time diagram (De Paolo, 1981) for (a) SJBS, (b) VS and (c) NTS. (d) shows a comparison between the GIBG and main regional units. Data reference: Brusque Group e polis batholith: Chemale et al. (2012), Florisbal et al. (2012c), Passarelli et al. (2010) and unpublished data. Note Yamamoto (2010); Camboriú Complex e Lopes (2008); Floriano distinguished patterns for each suite and similar regional affinities.

Fig. 18. 206Pb/204Pb vs. 207Pb/204Pb diagram. VS and NTS suggest a magmatic connection, as opposed to the SJBS. Symbols as in Fig. 8.

crustal signature, as evidenced by the geochemical results and isotopic data. Tracing its possible source rocks in comparison with other regional units, the most straightforward options for protoliths are the metasedimentary rocks of the Brusque Group and its crystalline basement, a part of which is exposed as the Camboriú Complex. Although the analyzed rocks do not overlap entirely with these entities in the εSr vs. εNd diagram (Fig. 16) they all share an evident crustal affinity which stands out from other lithotectonic

associations, such as the Brusque metabasic rocks and the Flopolis Batholith. The same can be said from the εNd vs Time riano diagram (Fig. 17), in which the three suites have more restrained intersections with the Brusque Group and its basement, whilst the latter rocks have significantly younger TDM ages. The importance of paraderived rocks to the generation of the magma is evident on the SJBS, with its peraluminous mineralogy, high initial 87Sr/86Sr ratios suggestive of K-rich sources and, in some cases, presence of rounded inherited zircon cores (Hueck and Basei in preparation). Furthermore, the majority of analyzed SJBS samples show similar TDM ages and εNd evolutionary paths to that of the Brusque Group's metasedimentary rocks. The presence of mafic enclaves virtually restricted to the VS is consistent with the slightly less negative εNd values for rocks of this association, which may indicate limited mantle-derived contribution, as postulated by Florisbal et al. (2012a). On the other hand, among the three GIBG suites, the NTS has the oldest TDM ages, suggesting a larger contribution of old crust to its source rocks. The extent to which the metasedimentary rocks may or may not have influenced the composition of the magmas that led to the generation of the VS and NTS suite is unclear, since both units seem to be most closely related to its crystalline basement and lack clear evidence of paraderived sources. The most obvious candidate for these suite's source rocks is the Camboriú Complex, which is the only outcropping basement unit to the Brusque Group. However, on a petrological study of two granites from the VS and the NTS, Florisbal et al. (2012a) suggests that this unit alone cannot be responsible for the compositional variations observed in the Neoproterozoic magmatism, implying contrasting crustal sources.

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149

Table 3 Main characteristics of the three suites of the GIBG. Suite

~o Joa ~o Batista Sa

Valsungana

Nova Trento

Macroscopic aspects

Fine- to medium-grained, equigranular, leucocratic to hololeucocratic, gray to white Elongated bodies parallel to the structural trend of host rocks; Intruded by VS; rare metasedimentary xenoliths

Porphyritic with medium- to coarsegrained matrix, leuco- to mesocratic, gray to white megacrysts Large NE-SW elongated batholiths with wide contact aureoles; Intrudes on SJBS, is intruded by NTS; common metasedimentary xenoliths and mafic enclaves Transition from magmatic flux to solidstate deformation and late lowtemperature overprint; deformation evidenced by porphyrocrysts Monzogranites, quartz-monzonites and monzodiorites; biotite is the main mafic, with rare amphibole; accessories and trace minerals include apatite, zircon, allanite, monazite and titanite.

Medium-grained equigranular to seriated inequigranular, leucocratic, gray to pink Circumscribed bodies mainly intruding on the VS; rare VS xenoliths and microgranular felsic enclaves

Meta- to peraluminous; calc-alkaline to alkaline; medium to high REEfactionation usually with negative Eu anomalies Sr(i) from 0.708 to 0.713; εNd from
16.0 to
9.1; Nd TDM ages from 1.7 to 2.2 Ga; 206Pb/204Pb from 17.1 to 18.5; 207Pb/204Pb from 15.48 to 15.62

Moderately peraluminous; calcalkaline; medium to high REEfactionation usually with negative Eu anomalies Sr(i) from 0.708 to 0.718; εNd from
24.0 to
12.5; Nd TDM ages from 2.1 to 2.7 Ga; 206Pb/204Pb from 16.4 to 19.5; 207Pb/204Pb from 15.29 to 15.65 Crust e basement rocks of the Brusque Group, differentiation from the VS

Field relationships

Deformation

Virtually isotropic, deformed only in the microscopic scale

Mineralogy

Alkali-feldspar granites, sienogranites and monzogranites; muscovite and biotite are main mafic minerals; Garnet, tourmaline, apatite, zircon, allanite and monazite are accessories and trace minerals Moderately peraluminous; calc-alkaline to alkaline; frequent “seagull” REE pattern

Geochemical signature

Isotopic signature

Sr(i) from 0.715 to 0.735; εNd from
14.7 to
8.5; Nd TDM ages from 1.5 to 2.7 Ga; 206Pb/204Pb from 18.9 to 20.8; 207Pb/204Pb from 15.60 to 15.85

Probable source rock

Upper crust e metavolcanosedimentary sequence of the Brusque Group

Medium crust e basement rocks of the Brusque Group

Thus, it is possible that different rocks with a broad compositional range, in analogous conditions as crystalline basement for the Brusque Group, were source rocks for the GIBG magmas. The new isotopic data sustains the importance of the MGSZ as a boundary between terranes, as long identified in the literature (Basei et al., 2005, 2008; Florisbal et al., 2012b). 7.3. Magma evolution and emplacement Many of the geochemical and isotopic diagrams point to a genetic connection between the VS and NTS, especially taking into account for the high silica contents, usually accompanied by welldefined trends on the variation of other elements or isotopic ratios. Naturally this effect cannot be solely attributed to crystal fractionation processes, since many of the analyzed samples were collected from intrusions that are not directly connected. On a regional scale, however, this pattern suggests that at least some magmatic interaction between both suites took place. Considering the common distribution of NTS intrusions along the borders or in center of the two VS batholiths, a hypothesis might involve an evolutionary history in which the more homogeneous VS's composition worked as a starting point to development of the individual NTS intrusions, which further assimilated local rocks. This process lead to a more heterogeneous intrasuite behavior, commonly with a more pronounced crustal signature. This would agree with most isotopic diagrams, in which the NTS data spreads to independent areas of the chart from a more regular compositional trend or field of the VS. Characteristics such as the absence of negative Eu anomalies in the REE patterns and distribution of trace elements suggest that the crystallization conditions of both suites seem to have been more oxidizing in the northern portion of the Brusque Group. This evolutionary model does not apply, however, to the SJBS. Its heterogeneity is reflected in most diagrams as a rather scattered behavior, in a dubious position to the other suites. Furthermore,

Transition from magmatic flux to solidstate deformation and late lowtemperature overprint; deformation masked by equigranular texture Sienogranites and monzogranites; biotite or amphibole are the main mafic minerals; apatite, zircon, allanite, monazite, muscovite and tourmaline are accessories and trace minerals

although the field relations determine its rocks to be the oldest within the GIBG, it has the most evolved geochemical signature, which cannot be a result of inter-suite differentiation processes. Recent geochronological data show little differences among the ages of the granitic magmatism in the Brusque Group within the 610e590 Ma interval (Hueck and Basei in preparation), and the inter-suite trend expected from the field relationships, with zircon ages from the SJBS being older than those from the VS and NTS, is not present. This indicates that the generation of each suite occurred within a same age interval, with independent melting events occurring synchronically during a period of ca. 20 Ma, as opposed to a setting in which distinct granitic pulses responsible for each suite followed one another. Therefore, it seems likely that the causes for this magmatism were of a regional scale, enabling melt to generate independently throughout the central domain of the DFB. In this scenario, in which the SJBS was generated synchronically to the VS and the NTS, a possible hypothesis to justify its conspicuous field relationships with the VS, which is intrusive in it, would be that the melts that originated it were generated in a shallower crustal environment, allowing them to be emplaced into the Brusque Group before the other two suites. This would be in accordance with the evidences that the metasedimentary rocks themselves contributed to the SJBS magmas, as discussed above, since they are expected to have been in a less deep environment than that of its basement. The voluminous magmatic intrusion occurred shortly after the main thrusting phase of the Brusque Group, generating a metamorphic aureole that overprints the main metamorphic paragenesis (Basei et al., 2011; Philipp et al., 2004). These authors point to the influence of transcurrent shear in the magmatic emplacement, also noted by Steenken et al. (2007) in the alignment of semihorizontal magnetic lineations. Plutons of all scales are broadly aligned to the Brusque Group's general structure, being elongated parallel to the megafolds that

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characterize the metasupracrustal sequence and to the main regional tectonic structure, the MGSZ. Locally the plutons have intrusive contacts to the metasedimentary rocks, and the magmatic flow structures easily observed in the rocks from the VS have mostly very similar orientations to that of the S2 foliation in the country rocks. 8. Conclusion The GIBG were generated by the melting of crustal rocks, most likely related to the Brusque Group and its crystalline basement, part of which is exposed in the Camboriú Complex. For all its amplitude, large number and diversity, these rocks can be organized into suites that are coherent not only in its mineralogical, chemical and isotopic characteristics, but also in the processes by which they were formed. The SJBS melts were extracted from a relatively shallower environment in which metasedimentary rocks acted as important sources. Each granite evolved independently, leading to this suite's heterogeneity. Synchronically, voluminous melts were produced in the crystalline basement rocks which led to the VS. They concentrated on big batholiths, causing little variety within this suite. Juvenile contribution to the GIBG was probably limited to these rocks. The NTS intrusions emplaced near the border of the main VS batholith show the more evolved terms among the three suites, and were likely the result of the assimilation of local host rocks by most differentiated terms of the VS. Variations in the oxidizing conditions lead to differences between the granites in the northern and southern portion of both suites. Although on a broad scale the GIBG can be described as the result of a coeval magmatic episode occurred between 610 and 590 Ma, contrasting crustal level sources and magmatic interactions between the VS and NTS magmas were responsible for the relative chronostratigraphy for the suites in the field. In addition, local heterogeneity within the same source rocks and variations on the crystallization conditions were responsible for the differences recognized within the three studied suites. Acknowledgements Most field activities and laboratory analyses were funded by FAPESP (Projects 2005/58688-1 and 2006/06957-1). Mathias Hueck thanks the CNPq for a past scientific initiation scholarship and for the present PhD scholarship. The authors would like to thank three unknown reviewers for their helpful comments. References Almeida, F.F.M., Hasui, Y., de Brito Neves, B.B., Fuck, R.A., 1981. Brazilian structural provinces; an introduction. Earth Sci. Rev. 17 (1/2), 1e29. Babinski, M., Chemale, F., Hartmann, L.A., Van Schmus, W.R., da Silva, L.C., 1997. UePb and SmeNd geochronology of the Neoproterozoic granitic-gneissic Dom Feliciano belt, southern Brazil. J. S. Am. Earth Sci. 10 (3e4), 263e274. Basei, M.A.S., Siga Jr., O., Masquelin, H., Harara, O.M., Reis Neto, J.M., Preciozzi, F., 2000. The Dom Feliciano Belt of Brazil and Uruguay and its Foreland Domain the Rio de la Plata Craton: framework, tectonic evolution and correlation with similar provinces of Southwestern Africa. In: Cordani, U.G., Milani, E.J., Thomaz Filho, A., Campos, D.A. (Eds.), Tectonic Evolution of South America, pp. 311e334. Basei, M.A.S., Frimmel, H.E., Nutman, A.P., Preciozzi, F., Jacob, J., 2005. The connection between the Neoproterozoic Dom Feliciano (Brazil/Uruguay) and Gariep (Namibia/South Africa) orogenic belts. Precambrian Res. 139, 139e221. Basei, M.A.S., Campos Neto, M.C., Castro, N.A., Santos, P.R., Siga Jr., O., Passarelli, C.R., gico 1:100,000 das Folhas Brusque e Vidal Ramos, SC, Con2006. Mapa Geolo ^nio USP-CPRM. In: XLII Congresso Brasileiro de Geologia, Aracaju, SE. ve Basei, M.A.S., Frimmel, H.E., Nutman, A.P., Preciozzi, F., 2008. West Gondwana amalgamation based on detrital zircon ages from Neoproterozoic Ribeira and Dom Feliciano belts of South America and comparison with coeval sequences from SW Africa. In: Pankhurst, R.J., Trouw, R.A.J., de Brito Neves, B.B., de Wit, M.J. (Eds.), West Gondwana: Pre-Cenozoic Correlations Across the South Atlantic

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