Mineralogy, petrology, and origin of the Pedra Branca Suite: a tonalitic-trondhjemitic association with high Zr, Ti and Y, Carajás Province, Amazonian Craton

The Pedra Branca suite (2.75 Ga) is located in the Canãa dos Carajás domain in the southeastern Amazonia Craton. It diverges from typical TTG in mineralogical and geochemical terms, by the presence of hornblende and clinopyroxene and because it has a high content of HFSE (Zr, Y, Ti, and Nb). It belongs to the low-K subalkaline series, which varies from metaluminous to peraluminous, and are mostly calc and ferroan granitoids. Amphibole is calcic and classified as ferroan-edenite, and hastingsite. Plagioclase is mainly oligoclase. The Fe/(Fe + Mg) ratios found in the amphiboles indicate that these granitoids were formed under high to moderate fO2 conditions. Geobarometric calculations suggest pressures between 9.3 and 71 Kbar for the origin and 4.8-53.4 Kbar for the emplacement. Geothermometric calculations suggest initial crystallization temperatures between 945 and 862°C, and the water content in the magma is estimated to be higher than 4 wt%. The magma source was defined as tholeiitic continental gabbro melted in an extensional setting (Carajás Rift) with geochemical features similar to diabase from Nova Canadá (PA). The Pedra Branca magma was originated by partial melting (~28%), leaving a residue with plagioclase (An40), hornblende, clinopyroxene, and may or may not have magnetite.


INTRODUCTION
Archean cratons are commonly composed of greenstone belts and granitoids, among which tonalite-trondhjemite-granodiorite associations stand out (TTG; Windley 1996). Studies about these rocks are essential to understand the dynamics during Archean on Earth (Condie 1994). TTG are the most abundant rock types of the early Archean, found in many cratonic terrains (Smithies 2000, Martin et al. 2005, Moyen 2011). They are intermediate to felsic (most > 65 SiO 2 wt%), with high Na 2 O/K 2 O ratios (> 1.5), low to moderate large-ion litophile elements (LILE), and no potassium enrichment with increased differentiation (Champion and Smithies 2003). These rock associations are derived from rocks with low K and basaltic composition (garnet eclogite), generated by partial melting of subduction slabs (Condie 2005, Martin et al. 2005, Martin 1986, Moyen and Martin 2012, Barker and Arth 1976, Barker 1979.
Typical Archean TTG have well-defined and consecrated petrogenetic models geochemical characteristics (Martin 1994). In the Carajás Province (CP), TTG suites have been extensively studied and characterized (Leite et al. 2004, Guimarães et al. 2010, Almeida et al. 2011, 2017, Santos et al. 2013b, Silva et al. 2014. The Pedra Branca Suite (PBS; Gomes andDall'agnol 2007, Feio et al. 2013) outcrops in Canaã dos Carajás region, southeastern Pará State, Brazil. This tonalite-trondhjemite suite shows both similarities and differences with typical Archean TTG. It is similar to TTG suites in classificatory terms such as low Sr, K content and low K/Na ratios, however, diverge from TTG since it has distinct geochemical features such as high HFSE content (Ti, Zr, Y, and Nb), low transitional elements (Cr and Ni). Another characteristic comparing to other TTG rocks from Rio Maria Domains in the CP is the presence of amphibole and relicts of clinopyroxene (Sardinha et al. 2004, Gomes and Dall'agnol 2007, Sousa 2015.
Mineralogy, petrology, and origin of the Pedra Branca Suite: a tonalitic-trondhjemitic association with high Zr, Ti and Y, Carajás Province, Amazonian Craton In this sense, this paper had integrated field data; petrography, mineral chemistry, geochemistry, and geochemical modeling to elaborate a petrogenetic model to Pedra Branca Suite and, thus, unravel the role of these rocks in the evolution of Canaã dos Carajás Domain.

GEOLOGICAL SETTING
The Carajás Province (Fig. 1) is located in the southeastern portion of the Amazonian Craton, in the geologic context of the Amazonia Central Province (Tassinari and Macambira 2004) or the Carajás Province . The CP represents the oldest portion of the Amazonian Craton (Tassinari andMacambira 2004, Santos et al. 2006). The Carajás Province is divided into four tectonic domains according to Dall'Agnol et al. (2013): Rio Maria Domain (RMD), Sapucaia Domain (SD), Canaã dos Carajás Domain (CCD), and Carajás Basin (CB).
The Rio Maria Domain was formed between 3.0 and 2.86 Ga (Machado et al. 1991, Macambira and Lafon 1995, Almeida et al. 2011). The domain is composed of greenstone belts, TTG assemblages, leucogranodiorites, high-Mg granitoids, and potassic granites (Althoff et al. 2000, Souza et al. 2001, Dall' Agnol et al. 2006, Oliveira et al. 2010a, Almeida et al. 2011. The main units of the Sapucaia domain (2.95-2.73 Ga; Oliveira et al. 2010b, Dall' Agnol et al. 2013, Gabriel and Oliveira 2014, Santos et al. 2013b, Silva et al. 2014, Santos and Oliveira 2014, Rodrigues et al. 2014) are similar in lithologic terms to the dominant rocks in the Rio Maria domain, but the former was strongly affected by Neoarchean tectonic events and intruded by plutons of the Vila Jussara Suite.
The Canaã dos Carajás domain differs from SD and RMD in terms of lithologic associations, deformation and Nd isotopic signatures (Dall'agnol et al. 2013. Previous studies performed at the CCD indicate that this domain underwent a more complex evolution and various magmatic events have been distinguished ): • at ~3 Ga, the formation of the Bacaba Tonalite (Moreto et al. 2011 (Feio et al. 2012Santos et al. 2013a).
The main assemblages of the Carajás Basin are of Neoarchean age (~2.76 Ga; Gibbs et al. 1986, Machado et al. 1991. They are composed predominantly of mafic to intermediate metavolcanic rocks and banded iron formations, both included in the Itacaiúnas Supergroup. The latter is intruded by the Neoarchean (~2.75-2.73 Ga) Estrela, Igarapé Gelado, and Serra do Rabo granites.

Field Aspects and Petrography
Previous geological mapping performed in the Canaã dos Carajás region , Gomes 2003, Gomes and Dall' Agnol 2007, Sardinha et al. 2004) were able to recognize and individualize several geologic units previously encompassed in the Xingu Complex, among which the Pedra Branca suite.
The rocks from PBS occupy a restricted area and are represented by two bodies (Fig. 2). This suite is formed by tonalites and trondhjemites. In the "south body", the rocks are very deformed, showing magmatic banding striking near E-W with alternation between tonalitic and trondhjemitic bands and sub-vertical foliation striking E-W. In the "north body", rocks are mainly isotropic, showing tonalitic and trondhjemitic domains. The PBS is admittedly intrusive in the Planalto suite and Itacaiunas Supergroup, although field relations are not entirely conclusive (Gomes and Dall' Agnol 2007).
The petrographic studies were performed on 13 thin sections at the petrography laboratory of the Instituto de Geociências e Engenharias from Universidade do Sul e Sudeste do Pará (Unifesspa). The mineral abbreviation followed the rules suggested by Whitney and Evans (2010). The rocks from PBS are tonalites and trondhjemites (Fig. 3) and have a fine-grained, equigranular allotriomorphic texture (Figs. 4A and 4D) with variation to medium-grained. They show intense deformational textures such as mylonitic texture and polygonal grain-boundary (Figs. 4B and 4E). Tonalites are mesocratic and trondhjemites hololeucocratic ( Fig. 4C). The main mineralogy in tonalites and trondhjemites is represented by plagioclase (An 16 -An 23 ) and quartz, alkali-feldspar crystals are rare. Hornblende is the main mafic mineral in tonalites, and biotite in trondhjemites. In some places clinopyroxene remnants can occur in tonalites. Accessory minerals in tonalites and trondhjemites include titanite (Fig. 4F), zircon, apatite, and muscovite; secondary minerals are tourmaline, scapolite, epidote, and sericite (Gomes and Dall'agnol 2007). Opaque minerals in both tonalites and trondhjemites are ilmenite (Fig. 4F) and magnetite.

Geochemistry
The chemical analyses for major and trace elements, including rare earth elements (REE), was performed by Inductively Coupled Plasma Emission Spectrometer (ICP-ES) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS), respectively, at the Acme Analytical Laboratories Ltda. in Canada. The representative chemical compositions of the Pedra Branca Suite are given in Table 1 and illustrated in Harker diagrams (Figs. 5 and 6).
Silica contents range from 55.74 to 79.52 wt%; these rocks show high TiO 2 content and low Al 2 O 3 . They can be classified as low aluminium (Al) TTG (15% ≥), except for sample AER-70 (Barker and Arth 1976 Normalized REE patterns are given in Figure 7. The PBS is enriched in light rare earth elements (LREE) and slightly depleted in heavy rare earth elements (HREE). Tonalites are more enriched in REE than trondhjemites, they show discrete Eu anomalies (positive and negative), except for sample AMR-121C; on the order hand, trondhjemites show high positive Eu anomalies. All samples have low (La/Yb)n ratios (0.73-1.33).

Mineralogy
Representative samples of the Pedra Branca suite were selected for mineral chemical analyses. The analyzed minerals were amphibole, plagioclase, titanite, and iron-titanium oxides. Polished thin sections of the selected samples were initially submitted to semiquantitative chemical analysis by energy dispersive spectroscopy (EDS) in the LEO 1430 SEM of the Laboratório de Microanálises da Universidade Federal do Pará, which were performed at an accelerating voltage of 20 kV. The samples were also submitted to wavelength dispersive spectroscopy (WDS) quantitative analyses at the Laboratório de Microssonda da Universidade de Brasília, using a JEOL JXA-8230 electron probe microanalyzer (EPMA), which were performed under the following operating conditions: column accelerating voltage of 15 kV; current of 10 nA; analysis time of 10 s for peak and background radiation. The matrix effects were correct within the EPMA software by the ZAF method. The standards used for instrument calibration were andradite (Ca and Fe), microcline (Si, Al, and K), olivine (Mg), albite (Na), pyrophanite (Ti and Mn), vanadinite (V and Cl), nickel oxide (Ni), chromium trioxide (Cr), and Celestine (Sr). All thin sections selected for electron microprobe analyses were previously carbon-coated.

Amphibole
Amphibole analyses (Suppl. Tabs. 1 and 2) were performed using free-H 2 O content, and the structural formula was calculated based on 23 oxygen atoms, according to the method of Leake et al. (1997). For structural formula calculation, the cations were collected into a set of 13 cations minus Ca, Na, and K. Amphiboles were classified ( Fig. 9) according to the criteria of Leake et al. (1997).
The Pedra Branca suite has a calcium amphibole classified as hastingsite and ferroan-edenite [(Ca + Na)B ≥ 1.00 and NaB < 0.50] according to Leake et al. (1997). Still according to these authors, the amphiboles from PBS fit in the first parameter [CaB ≥ 1.50; (Na + K)A ≥ 0.50]. The Si content in the amphiboles vary between 6.14 and 6.59. Mg/(Mg + Fe) ratio varies between 0.38 and 0.49. Fe/(Fe + Mg) ratio between 0.51 and 0.59. Al total between 1.63 and 2.50.

Epidote
Representative chemical analyses of epidote from the Pedra Branca suite are presented in Supplementary Table 3. The criteria indicated by Tulloch (1979) was used to evaluate the magmatic vs. subsolidus origin of the studied epidote crystals, based on the 'pistacite' component (Ps = molar [Fe 3+ /Fe 3+ + Al] / 100).

Plagioclase
Representative chemical analyses of plagioclase from the Pedra Branca suite are presented in Supplementary Table 4. The plagioclase shows an average composition of An 18 (An 20 -An 16 ) classifying oligoclase.

Titanite
Titanite has no significant compositional difference (Suppl. Tabs. 5 and 6). It shows a Fe/Al ratio varying between 0.43 and 0.84. Titanite plot mostly near the field of metamorphic titanite and subordinately near the igneous titanite (Fig. 11). Therefore, the titanite was initially formed in a magmatic state and posteriorly underwent a compositional rebalance due to a deformational or a superimposed metamorphic event.

Iron-titanium oxide minerals
Preliminary chemical compositions were obtained by EDS (Suppl. Tab. 7). Ilmenite is the main iron-titanium oxide. It was deduced that ilmenite crystals are primary and originated during Pedra Branca crystallization, based on petrographic observations. The magnetite was re-equilibrated during the suite evolution, and its composition is similar to that of pure magnetite.

Geochemical modeling
Major and trace element modeling was performed to assess the origin of the Pedra Branca suite, using the Genesis 4.0 software (Teixeira 2005). The mineral/liquid partition coefficients (KD) used in the modeling are given in the Supplementary  Table 8; most of them are from the software (Genesis 4.0) and Rollison (1993) and references therein. Geochemical modeling was focused on hornblende tonalite (AMR-124A). This rock was interpreted to represent the parental magma because it has the lowest silica and highest ferromagnesian contents. Two hypotheses were considered to explain the origin of the Pedra Branca magma: • partial melting of a mafic source; • contamination of a mafic magma by the less evolved facies from Planalto A-type granite (Feio et al. 2012).
Moreover, modeling using the least evolved (AMR-124A) and the most evolved (AMR-126A) samples from this suite were performed using mineral chemistry data, showing unsatisfactory results. Therefore, the modeling discussed throughout this work is valid to explain only the origin of tonalites from PBS.
For major elements, six models were obtained with distinct mineralogical residual assemblage; in two models, results for major and trace elements were satisfactory. In the first model,  the residual assemblage was composed of clinopyroxene, hornblende, and plagioclase (An 40 ). The second model was composed of clinopyroxene, hornblende, plagioclase (An 40 ), and magnetite. The results of both modelings are exposed in Table 2 (Fig. 12).

Geochemistry as petrogenetic indicator
The rocks from PBS belong to the Low-Al TTG group (Barker and Arth 1976), they have a lower content of Sr and Eu, less fractionated REE, and low Sr/Y ratios compared to High-Al TTG. Moreover, these suits show low values of (La/Yb) N . These characteristics imply a petrogenesis outside the garnet stability field and were controlled by plagioclase, either by being a main residual phase or by its fractionation during magmatic differentiation (Almeida et al. 2011, Moyen andStevens 2006).
The mineralogical assemblage of the liquid that generated the PBS reflects directly in the geochemical features of the rocks. As exposed in the Harker diagrams (Fig. 5), CaO, MnO, MgO, TiO 2 , and Y show a negative relation with the silica content, as opposed to K 2 O, Rb, and Ba, which show a positive one. These trends tend to  occur when the fractionation is dominated by ferromagnesian phases such as amphibole and calcic plagioclase (Janousěk et al. 2000).
Tonalite REE enrichment compared to trondhjemites implies the fractionation of mineral phases with higher KD, like amphibole, or due to amphibole accumulation during magmatic flow (Suppl. Tab. 8;Janousěk et al. 2000).

Parental magma
The most primitive rock from the PBS is the hornblende tonalite (AMR-124A) with 55.74 wt% SiO 2 . This rock has the highest compatible element content (i.e., Ca, Mg, Fe, Ti, P, and V) and the lowest incompatible element content (i.e., K, Th, and U). Therefore, the AMR-124A is assumed to represent   the parental magma of PBS, whose composition is much less siliceous than the average Archean low-Al TTG suite (~71 wt% SiO2, Almeida et al. 2011, Zhang et al. 2012. The REE pattern of the assumed parental magma of the Pedra Branca suite can be reproduced using a tholeiitic source with flat REE pattern (ADK43, Marangoanha and Oliveira 2014), moderate degrees of partial melting (~ 28%) and a residue with 21.39% Cpx + 70.74 % Hbl + 7.86 % Pl (An40) 7.86 % or 16.23% Cpx + 53.59% Hbl +27.35% Pl (An40) + 2.84% Mt.

Magmatic differentiation
Several diagrams were constructed to unravel the processes responsible for differentiation in tonalites from PBS.
Crystallization in plutonic rocks of hornblende, plagioclase, and accessory Fe-Ti oxides, zircon, and apatite are indicated by the negative correlation of silica with Ca, Fe, Mg, and Ti, as well as by trace elements such as V, Sr, and Y (Seixas et al. 2012). According to Martin (1987), crystal fractionation and partial melting can be evaluated by plots of the granitoids samples in logarithmic graphs of compatible elements versus incompatible elements in the suite, in this case, were elaborated graphs of V (compatible) versus Rb and Th (incompatible) (Fig. 13). It is also important to notice that magmas originated by fractionation crystallization or partial melting, assuming identical bulk distribution coefficient, show distinctive trends (Cocherie 1986).
The magmatic differentiation process can also be analyzed by covariant diagrams of K 2 O, Sr, Y, and Zr as a function of the CaO content and Mg# (Fig. 14), once that both CaO and Mg# are affected by hornblende and plagioclase and both are present in PBS tonalites. Geochemical variations against these proxies can be used to examine the influence of amphibole and plagioclase fractionation on tonalitic suites (Arth et al. 1978, Kalsbeek 2001. Therefore, the PBS tonalitic rocks range from 55.74 to 72.68 wt% SiO 2 , showing scattered inter-element correlation in the Harker diagrams between the low and high silica members. The other evaluated diagrams (Figs. 13 and 14) also show a scattered pattern and do not reproduce the hypothetical liquid line starting from the proposed parental magma. These features do not suggest that crystal fractionation nor partial melting were the mechanisms to explain the magmatic differentiation of the suite, so we suggest that the main process was the crystal accumulation during the magmatic flow.

Crystallization parameters
Temperature Ridolfi et al. (2010) and Ridolfi and Rezulli (2012) reviewed thermobarometric equations in the literature and have shown calibration models to estimate temperature using the content of the main oxides in the amphibole. Those equations are recommended to amphiboles crystallized in rich to poor H 2 O magma and in moderately oxidized to moderately reduced calc-alkaline to alkaline magmas (Erdmann et al. 2014). However, it was considered by Erdmann et al. (2014) that the following equation, proposed by Ridolfi et al. (2010), would be most suitable to calculate temperature: The Ridolfi et al.'s (2010) geothermometer showed that the amphibole's temperature varies between 945 and 862°C. The dataset suggests an interval between 945 and 862°C for the liquidus temperature of the Pedra Branca magma (Tab. 2), which is consistent with the proposed mafic tholeiitic source proposed by Feio et al. (2013) and in this paper.

Pressure
The Al-in-hornblende geobarometer was proposed by Hammarstron and Zen (1986) and Hollister et al. (1987) to estimate the emplacement pressure of intermediate silicate plutons. The pressure calculation may match the granitoid emplacement. The Pedra Branca suite has an ideal paragenesis to use the geobarometers proposed by Hammarstron and Zen (1986) and Hollister et al. (1987), the plagioclase present in Pedra Branca suite (An < 25) are more sodic than the plagioclase founded in calc-alkaline granitoids in which the geobarometer was initially proposed (~An 25-35 ; Anderson and Smith 1995). Therefore, the geobarometers proposed by Hammarstron and Zen (1986), Hollister et al. (1987), Johnson and Rutherford (1989), and Schmidt (1992) was used to determine the pressure (Tab. 3).
According to the data obtained in this and in previous works , the Pedra Branca magma was derived from a lower tholeiitic mafic crust, so the pressure related to the magma source can be estimated between 9.3 and 7.1 Kbar, based on the proposed lower crustal source. On the order hand, these granitoids present intense deformation, magmatic banding, sub-vertical foliation, and local lineation caused by ductile deformation (Gomes and Dall' Agnol 2007), probably generated during the emplacement. These features indicate pluton emplacement in mesozone, possibly corresponding to the lower pressures of 4.8-3.4 Kbar. Thus, it is possible to conclude that pressures around 9.3-7.1 Kbar correspond to the magma source, and pressures around 3.4-4.8 Kbar represent the emplacement of the Pedra Branca suite (Tab. 3).
Petrographic data show ilmenite as the main opaque mineral in the Pedra Branca suite, occurring mainly in tonalites. The FeOt/(FeOt + MgO) ratio of this lithology and Fe/(Fe + Mg) ratio in amphibole indicate an equilibrium between rock crystallization and these mineral phases. On the order hand, magnetite was found only in one sample (AMR-191) with a 0.96 FeOt/(FeOt+MgO) ratio.
Thus, it can be affirmed that tonalites are classified as oxidized granitoids from the Magnetite series (Ishihara 1997), and trondhjemites are lightly oxidized to reduced.

Water content
The water content necessary to stabilize amphibole varies along with pressure: 2.0-4.0 Kbar requires 4% of water, 5% of the water in pressures around 4.0 Kbar, and 7-9% in a 9.6 Kbar pressure are necessary to stabilize amphibole without pyroxene in a silicate magma (Naney 1983, Dall' Agnol et al. 1999, Klimm et al. 2003, Prouteau and Scaillet 2003, Bogaerts et al. 2006. Clinopyroxene relicts occur in the Pedra Branca suite (Gomes and Dall' Agnol 2007) and are scarce and located, which suggests that clinopyroxene was stable during initial magma state and almost totally reacted during cooling (Naney 1983, Dall' Agnol et al. 1999).
Thus, it is possible to affirm that these tonalites and trondhjemites are derived from magmas with more than 4% H 2 O, and depending on the assumed pressure crystallization, possibly around or even more than 7%. This evidence is endorsed by the absence of clinopyroxene crystals.

Petrogenesis
The tonalites from PBS were originated from the partial melting of rocks with compositional similarities with diabase from Nova Canadá (Marangoanha and Oliveira 2014). According to Marangoanha and Oliveira (2014), these diabases are post-Archean, so they are not the real source of PBS. However, we consider that the real source of PBS had similar features if compared to the Nova Canadá diabase. These data match with the geochemical modeling, which shows that the tonalites were derived from a partial melting with a residue containing hornblende, plagioclase, and clinopyroxene, and may or may not have magnetite. It is worth pointing out that according to Marangoanha and Oliveira (2014), the diabase from Nova Canadá is enriched in Y (14.9 to 63.9 ppm) and Zr (56.1 to 236.6 ppm). The sample used in the modeling was a diabase classified as hornblende-grabbronorite (ADK 43, Marangoanha and Oliveira 2014), as representative of the magma source. Therefore, it is possible to affirm that the HFSE enrichment in the granitoids of the Pedra Branca suite is derived directly from the source and not associated with the order process as hydrothermal alteration.
For the trondhjemites, it is proposed that they were originated by the same processes (partial melting) as tonalites, from similar but not identical sources, probably with lower melting degrees than tonalites, and evolved as two different liquids throughout magmatic differentiation.

Geotectonic setting
A subduction setting does not seem capable of explaining the genesis of Pedra Branca magma (2.75 Ga; Feio et al. 2013, Sardinha et al. 2004, considering the opening and closing of the Carajás rift occurred during the Neoarchean (2.76-2.68 Ga; Tavares 2015, Gibbs et al. 1986, which was responsible for generating the metavolcanic rocks of the Itacaiunas Supergroup (2.76-2.73 Ga; Machado et al. 1991). Moreover, several A-type granites were formed in the Carajás Basin, and Canaã dos Carajás Domain during Neoarchean, such as the Estrela Granitic Complex (2.76 Ga, Barros et al. 2001), Serra do Rabo granite (2.74 Ga, Sardinha et al. 2006) and Planalto granite (2.74-2.73 Ga;Feio et al. 2013). This evidence indicates that, during the Neoarchean, there was a continental intraplate setting in the CB and the CCD. Also, the hypothesis of an extensional continental setting for this region is ratified by the presence of Diopside-Norite Pium, which was dated from 3.0 Ga and metamorphosed in 2.85 Ga . However, recent research shows that this unit in the Canãa area was crystallized 2.74 Ga (Santos et al. 2013a) in an extensional setting.
The accentuated crustal thickening associated with the formation of Itacaiunas shear belt, the elevated geothermal gradient in the Archean and the high volume of magma generation during the Neoarchean in the Canaã dos Carajás Domain and Carajás basin indicate that there was an expressive thermal anomaly in the Canaã dos Carajás area (Gomes and Dall' Agnol 2007). The small  volume of Pedra Branca bodies associates its genesis to lower continental crust partial melting (continental tholeiitic gabbros composition) generated in an extensional setting (Carajás Rifte) just like Diopside-Norite Pium (Santos et al. 2013a). This granitic magmatism and associated Neoarchean mafic volcanism related to Grão-Pará group (Martins et al. 2017), and other mafic bodies in Canaã and adjacent areas , Machado et al. 1991 might have been responsible for such high temperatures (almost 1,000°C) in a rift setting. Zhang et al. (2012) studied the generation of TTG magmas associated with partial melting from the lower continental crust, in the North China Craton. According to these authors, the Neoarchean trondhjemites with high-and low-Al are contemporaneous and were formed by partial melting of the juvenile lower crust induced by magma underplating to form the high-Al group and the intraplate to low-Al.

Why the Pedra Branca Suite Diverge From Typical Archean TTGs?
The unique geochemical features can be explained by three reasons: • The magmatic source has different geochemical and mineralogical features than typical TTG, which are related to partial melting of garnet-amphibolite or eclogite under varying conditions of fluids presence (Martin 1994, Martin and Moyen 2002, Moyen et al. 2003); on the order hand, PBS rocks are associated with the partial melting of continental tholeiitic grabbros; • The PBS was originated in a distinct geotectonic setting.
TTG are associated with the partial melting of basalts from a thickened oceanic crust (Smithies 2000, Condie 2005 or to subduction of a basaltic oceanic crust (Condie 1989, Martin 1994, Rollison 1993, Martin and Moyen 2002, Moyen et al. 2003); on the order hand, PBS were originated from partial melting of continental gabbros in an extensional setting (Carajás Rift); • The high water content in Pedra Branca magma (up to 4%) diverge from TTG' s magmas. According to Moyen and Stevens (2006), based on experimental petrology studies, the partial melting that originate TTG's magma can be divided according to the fluids content. These authors emphasize mainly the fluid-absent melting; the water content in this process comes only from hornblende breakdown, which can generate less than 1.8 wt% H 2 O in these magmas.

Comparison with other Neoarchean TTGs and similar rocks
The Pedra Branca suite has unique features that differ from the Archean TTG. For this reason, similar rocks like PBS have not been previously described in the literature. Gomes and Dall' Agnol (2007) compared the suite to Paleoarchean grey gneisses (3,42 Ga) from Sete Voltas Massif, São Francisco Craton. According to Martin (1997), these rocks show positive anomalies of Zr (142-288 ppm) and Nb (6-13 ppm), similar to PBS.

CONCLUSIONS
• Tonalites are metaluminous, and trondhjemites vary from peraluminous and metaluminous. They both belong to the subalkaline low-K series, which are calc and ferroan granitoids; • The magmatic differentiation process among the suite members was possibly controlled by crystal accumulation during the magmatic flow; • Amphibole is classified as ferroan edenite and hastingsite. Plagioclase is oligoclase. Titanite is a primary igneous mineral that was reequilibrated during a deformational or metamorphic event; • A temperature interval of 862-945°C was concluded for the initial crystallization of the Pedra Branca suite. Pressures of 9.3-7.1 kbar for the origin and 4.8-3.4 kbar for the emplacement of the Pedra Branca magma. The dominance of amphibole and biotite among the mafic minerals of the Planalto Suite and the typical absence of pyroxene indicate that the water content in the magma was higher than 4 wt% and could even exceed 7 wt%; • Pedra Branca Magma originated from the partial melting of continental tholeiitic gabbros, in an extensional setting (Carajás Ritfte). This process left a residue containing plagioclase, hornblende, clinopyroxene and may or may not have magnetite. The magma source had chemical-mineralogical features similar to Nova Canadá Diabase (Marangoanha and Oliveira 2014) and not rocks similar to Serra Geral Basalts, as affirmed by Gomes and Dall' Agnol (2007); another divergence is about the fusion degree, those authors affirmed that the Pedra Branca bodies were formed by a low scale fusion, however, according to the geochemical modeling, fusion degree was ~28%; • The enrichment in HFSE in these granitoids is derived directly from the source rock and is not related to the order process as hydrothermal alteration; • Pedra Branca suite diverges from typical Archean TTG, due to the derivation from a different source, formed in a different geotectonic setting proposed to most TTG, and by the presence of elevated quantities of water in the magma if compared to typical TTG; • In geochemical and petrographic terms, it is similar to Vila União tonalites (Oliveira et al. 2018), both units have high HFSE content and hornblende and biotite as ferromagnesian minerals.

ACKNOWLEDGMENTS
The Grupo de Petrologia de Granitoides from Universidade Federal do Pará are acknowledged for their support in geological mapping and previous works in the studied area. M.J James is acknowledged for her support in writing, and P.V.F.S Alves for helping with the EPMA analysis. The reviews by Silvio RF Vlach, an anonymous reviewer, and the editorial handling of C. Ricominni were greatly appreciated and helped to improve the original manuscript. This research received financial support from CNPq (R. Dall' Agnol -Grants 0550739/2001-7, 476075/2003-3, 307469/2003-4, 484524/2007PRONEX -Proc. 66.2103/1998