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This work reports on the first identification of sapphirine‐bearing ultrahigh‐temperature (UHT) metamorphic rocks within the Borborema Province, in NE Brazil. The investigated UHT diatexites outcrop in the Arapiraca Complex, a high‐grade Palaeoproterozoic block embedded within the Neoproterozoic metavolcano‐sedimentary sequence of the Sergipano fold‐and‐thrust belt. A sapphirine‐bearing diatexite sample preserves two distinct residual mineral associations as inclusions in cordierite poikiloblasts: a volumetrically dominant silica‐saturated, garnet–sillimanite–orthopyroxene–quartz domain, and a restricted silica‐undersaturated, sapphirine–magnetite–spinel–corundum domain. Phase equilibrium modelling for the whole‐rock bulk composition constrains the reactions preserved in the silica‐saturated domain, which, coupled with reintegrated ternary feldspar thermometry and Al‐in‐orthopyroxene thermobarometry, indicates peak UHT metamorphism occurring at ~970°C/8.5 kbar followed by a clockwise near isobaric cooling stage crossing the H2O‐undersaturated solidus at ~910°C/7.7 kbar. The T–MSiO2 and P–T phase equilibrium models reveal that the stabilization of magnetite‐spinel in the silica‐undersaturated domain can be a product of domanial SiO2‐depletion ascribed to inherited compositional banding and progressive melt‐loss episodes. The appearance of sapphirine as thin coronae around previously formed magnetite‐spinel cores requires an increase in the bulk silica content during retrograde metamorphism. This was driven by variable degrees of chemical interaction between the silica‐undersaturated domain and trapped silica‐rich leucosomes. U–Pb dating of zircon coupled with trace element behaviour records the timing of melt crystallization between ca. 2.03 and 1.96 Ga, after peak UHT metamorphism and supporting a protracted, ca. 70 My period of melt presence in the crust. The UHT metamorphism in the Arapiraca Complex is related to a contemporaneous UHT event recorded within the São Francisco Craton and more broadly coincides with high geothermal gradients at ca. 2.0 Ga linked to the formation of the Columbia supercontinent. The integration of new petrological and geochronological data indicates that the Arapiraca Complex is a continental ribbon pulled away from the São Francisco–Congo palaeocontinent possibly during the early Neoproterozoic intermittent rifting events and opening of the Sergipano oceanic basin between ca. 0.98–0.74 Ga. During the late Neoproterozoic at ca. 0.63–0.57 Ga, the Arapiraca Complex continental ribbon was thrusted back onto the northern margin of the São Francisco Craton as an inlier of the Sergipano fold‐and‐thrust belt. [ABSTRACT FROM AUTHOR]

The Cr-rich Jacurici Complex is located at the limit between the Serrinha Block and the Salvador-Curaçá Belt, Northeastern São Francisco Craton. In order to better understand the age span of magmatism and tectonism, we have studied a basement high-grade charnockite orthogneiss, a metanorite of the Complex and a crosscuting undeformed quartz-feldspar pegmatite. For the orthogneiss, SHRIMP U-Pb ages of zircon cores and overgrowth rims yielded, 2966 ± 9 Ma for crystallization and 2091 ± 10 Ma for metamorphism, respectively. Zircons from the metanorite show internal textures consistent with high grade metamorphism. The U-Pb LA-ICP-MS age determination provided a 2099 ± 6 Ma metamorphic age for the Jacurici Complex, indicating it was already emplaced during amalgamation around 2.1 Ga. Zircons from the undeformed quartz-feldspar pegmatite provided a LA-ICP-MS U-Pb age of 2083 ± 11Ma, marking the end of the N-S transcurrence. The magmatic Jacurici Complex age remains undefined, but is equal to, or older than, 2.1 Ga. Therefore, possible correlations with other mafic-ultramafic intrusions, such as the Cu-rich Caraíba Complex, should be reassessed. Our results indicate that the N-S transcurrence ended earlier in the Jacurici Complex region than in the northwestern area of the Salvador-Curaçá belt. [ABSTRACT FROM AUTHOR]

The Gentio metagranitoid presents equigranular and porphyritic facies, modal composition ranging from tonalite to monzogranite with calculated TZr<800 °C for most samples. Its mineralogy is dominated by quartz and feldspar (77% to 95%), biotite is the only mafic mineral present (2% to 18%) and, titanite, zircon, apatite, allanite are important accessory phases. These rocks range from metaluminous to weakly peraluminous, and have large variation in major and trace elements, and high alkali contents (>6 wt.%). Zircon analyses by LA-ICP-MS and SHRIMP yielded a concordia age of 2 119±10 Ma for the porphyritic facies and an upper intercept age of 2 111±15 Ma for the equigranular facies. The whole-rock Sm-Nd TDM ages vary from 2.4 to 2.8 Ga with εNd(2.1) values between −0.7 and −5.3, indicating crustal derivation from distinct and/or heterogeneous protoliths. Field observations indicate that the Gentio metagranitoid was formed through different pulses of magma. Individual batches were subject to little or even no fractionation process after its emplacement. Although the Gentio metagranitoid crosscuts metamafic and metaultramafic rocks akin to an oceanic arc setting, this pluton is likely originated by partial melting of a more evolved quartz-feldspathic crustal igneous rock in a post-collisional environment, after the accretion of the arcs from the Mineiro belt and rocks of the Mantiqueira Complex. [ABSTRACT FROM AUTHOR]

In Brazil, Paleoproterozoic khondalites were recognized in Ceará, Bahia, Goiás, Tocantins, and Minas Gerais. The Itapecerica supracrustal succession in the Southern São Francisco Craton (Minas Gerais) contains sillimanite-cordierite-garnet-biotite gneiss (khondalite) with an anatectic record. The high-grade khondalite preserve representative mineral assemblages of peak and orogen collapse after post-peak decompressional stage. Based on petrographic observations and P–T pseudosections of bulk rock compositions, a clockwise pressure-temperature-time (P–T-t) path was inferred. The metamorphic peak assemblage is liquid + plagioclase ± K-feldspar + garnet + biotite + ilmenite + sillimanite + quartz at 715–772ºC and 5.5–7.5 kbar. In addition, the precursor sediments had mixed pelitic-wacke compositions resulting from erosion of different sources. Sediment deposition would have occurred at active continental marginal setting. Surrounding the khondalite occurs a peraluminous metagranite named here as Água Rasa, formed in syn- to post-collisional setting, whose εNd(t) (−0.5 to −2.7) and 87Sr/86Sr(t) (1.04 to 1.08) and the data set indicate that the precursor magma of the Água Rasa metagranite originated from anatexis of the khondalitic rocks (crustal source) and associated amphibolites (mantle source) during the crustal thickening followed by tectonic exhumation at peak metamorphism and at decompressional stage during the orogenic collapse. The khondalite yielded ages from monazite U-Th-PbT dating of 2090 ± 26 Ma and 1937 ± 32 Ma, while the Água Rasa metagranite yielded ages of 2077 ± 24 Ma and 1941 ± 23 from monazite and 1934 ± 74 Ma from zircon U-Pb. The ages of >2.0 Ga are related to the metamorphic peak, while the younger ones (~1940 Ma) are related to the orogen collapse after post-peak decompressional stage. Similarities between the khondalite rocks of this study and of the North China Craton suggest that the São Francisco-Congo Craton was near the North China Craton in the supercontinent Columbia for the 2.1–1.9 Ga period. [ABSTRACT FROM AUTHOR]

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We present the first data on the geochemistry and isotopic age of zircons from rocks of the Roseta (lherzolite and olivine orthopyroxenite) and Córrego da Areia (olivine orthopyroxenite) ultramafic massifs localized among Archean-Proterozoic metamorphic strata in the southern folded framing of the São Francisco Craton. The examined zircons differ in crystal morphology, the intensity and type of cathodoluminescence, oscillatory zoning, the distribution of trace elements, and U-Pb isotopic age. Zircon crystals from the Roseta lherzolite have an age of 800-728 Ma and show negligible cathodoluminescence. Some of them have reaction rims with an age of 663-619 Ma. The crystal cores are enriched in rare earth elements (REE) but are often depleted in U as compared with the reaction rims. The age of zircons from the Roseta olivine orthopyroxenite showing moderate cathodoluminescence is within 622.6-596.9 Ma. Zircons from the Córrego da Areia olivine orthopyroxenite show moderate to intense cathodoluminescence and often have a rhythmic oscillatory zoning. They are characterized by an uneven distribution of REE and other trace elements and have high contents of U and Th. Most of these zircons have an ancient isotopic age (2558-2100 Ma). The examined zircons are of several types: relict, xenogenic, syngenetic, and epigenetic. The Roseta and Córrego da Areia massifs are considered to be protrusive outliers of a deep-seated Precambrian mafic-ultramafic complex, which were tectonically transferred along faults into the intensely metamorphosed Archean-Proterozoic strata in the southern folded framing of the São Francisco Craton. [ABSTRACT FROM AUTHOR]

More than three hundred mafic-ultramafic bodies of different sizes, containing copper sulfide mineralization, are present in the Curaçá River Valley Copper Province, northeastern São Francisco Craton, Bahia State, Brazil, covering an area of about 1700 km 2 . The basement, supracrustal sequence, and mafic-ultramafic intrusive rocks underwent granulite facies metamorphism and were reworked during the evolution of the Itabuna-Salvador-Curaçá Orogeny, resulting in retrograde metamorphism to the amphibolite facies, partial migmatization, and intrusion of granitic and syenitic rocks. During the slow and progressive rise of the terrain, hydrothermal reactions mainly along shear zones retrogressed part of these rocks to assemblages characteristic of the greenschist metamorphic facies. The main orebodies with copper sulfide minerals are associated with pyroxenite, mica-rich (glimmerite) and noritoid rocks. The present investigation focuses on the major Caraíba, Sussuarana, Surubim, and Vermelhos deposits. Chalcopyrite and bornite compose the ore, in a ratio of 70–30%, with copper grade varying between 0.69% and 1.4%, and associated gold and silver. The sulfide minerals are invariably accompanied by magnetite. Two mineralization styles are distinguished: (i) disseminated in non-altered mafic-ultramafic rocks; and (ii) tectonic controlled related to hydrothermal alteration zones. New geochronological data show that quartz-microcline metasomatites of the Caraíba Mine contain Neoarchean inherited zircons (upper intercept at 2723 ± 51 Ma), related to the early stages of magmatism, whereas Orosirian ages (2047 ± 12 and 2042 ± 15 Ma) are related to the main hydrothermal mineralization activity. Norite from the Surubim Mine has a Paleoproterozoic age (2047 ± 11 Ma), and the dated gabbro shows Pb loss in the Neoproterozoic, probably related to the Brasiliano Orogeny (670–490 Ma). Previous studies have demonstrated that the main hydrothermal event is Paleoproterozoic. Phlogopite Ar-Ar dating from the Caraíba Mine yields plateau-ages around 2000–2100 Ma. A cluster of δ 34 S values approaching zero is related to interstitial sulfide minerals in the least-altered ultramafic rocks, while values above and below zero are related to remobilized sulfides. These data support the hypothesis of the existence of a primary (magmatic) mineralizing event, alleged to have precipitated disseminated, interstitial sulfide minerals, and a second (hydrothermal) event, responsible for the economically more important mineralization, which is structurally controlled and related to significant potassic alteration. The sulfide minerals are associated with different generations of magmatic and hydrothermal magnetite, as well as distal plagioclase and microcline alteration halos. The combination of these features reaffirms the concept that the Curaçá Valley deposits may be part of the same alteration system, as described in IOCG deposits, with the deepest deposits being located further south. Based on the data obtained during the present study, it is possible to establish a tectono-metallogenic evolutionary model to explain the genesis of the copper mineralization in the Curaçá Valley. The mafic-ultramafic bodies were emplaced as multiple intrusions in Neoarchean arc-related gneisses and chemical sediments, along with bornite and chalcopyrite mineralization. The sulfide minerals that preserve the characteristics of this stage are chalcopyrite or bornite, both with δ 34 S values around 0‰ V-CDT . A continental collision affected the Caraíba arc and the related sequences between 2100 and 2080 Ma. During this Rhyacian-Orosirian orogeny, deformation and amphibolite-granulite facies metamorphism, the rocks underwent partial melting, and sapphirine formation developed. Between 2050 and 2020 Ma, the main mineralization stage took place at Caraíba, Vermelhos, and Surubim, which corresponds to an earlier stage in the Sussuarana deposits. The southern deposits were formed deeper than those to the north, resulting in less extensive potassic alteration and related hydrothermal mineralization. The sulfide minerals of the deeper deposits have negative δ 34 S (between 0‰ and −6.81‰), to slightly positive values, where the igneous protoliths are best preserved. This alteration took place near the brittle-ductile boundary, mainly associated with ductile structures. The latest stage of mineralization took place between 1950 and 1920 Ma, in the Caraíba, Vermelhos and Surubim deposits, along with major sulfide remobilization in Sussuarana. This stage was characterized by the participation of oxidizing fluids, possibly meteoric waters, which raised the δ 34 S values up to +11.77‰. [ABSTRACT FROM AUTHOR]

Cratons, as well as the basement of their marginal orogens, may represent important sites of research regarding the formation and evolution of Archean continental crusts. The Gavião Block is one of the oldest terranes in South America with rocks aged up to 3.6 Ga. Among the Archean units that outcrop in the southern sector of this block is the Santa Izabel Complex, which for the most part is located in the São Francisco Craton, close to its limit with the Araçuaí-West Congo Orogen. This complex has generally been described as comprising ortho- and paraderived rocks that were metamorphosed in high amphibolite facies. Studies in the southern region of this complex have shown the main components: (i) orthogneisses, whose protoliths are the Mesoarchean rocks of the Santa Izabel Magmatic Suite; and (iii) migmatites. and (iv) amphibolitic and metaultramafic enclaves. U-Pb studies (LA-ICPMS and SHRIMP) performed on zircons of the paleosome in metatexites and inherited zircons in migmatites indicate crystallization ages between 3091 ± 24 and 3136 ± 8 Ma for the rocks of the Santa Izabel Magmatic Suite. Inherited zircons aged ca. 3.4 Ga in paleosomes demonstrate the influence of older continental crust in the formation of these rocks. For the Caraguatai Magmatic Suite, the alignment of zircons and monazites suggests a crystallization age around 2.6 Ga. The Rhyacian migmatites were divided into metatexites and diatexites. Diatexites were divided into: (i) discontinuous boudinated early diatexites, which are parallel to stromatic metatexites, composing the gneissic banding. These rocks have diffuse metamorphic banding and features that suggest the action of mylonitization processes; and (ii) late diatexites, forming more continuous bodies, which truncate the gneissic banding. The migmatization occurred in two stages, with time interval between ca. 2.1 Ga and 2.07 Ga. The structural framework reveal the existence of four progressive Rhyacian deformation phases (D n to D n+3 ), and one deformation phase assumed to be Ediacaran (D n+4 ). Gneissic banding is the dominant structure and lithofacies of the Santa Izabel and Caraguatai Magmatic suites, in which metatexites and late diatexites alternate between themselves. This progressive deformation occurred in conditions of high amphibolite facies, with stress fields varying between NW-SE and WSW-ENE. The youngest phase, D n+4 , was associated with distal deformations related to the evolution of the intracontinental Araçuaí-West Congo Orogen with a WSW-ENE stress field. The combined data suggest a complex evolution for the Gavião Block, involving juvenile accretion, crustal reworking, deformation and metamorphism/migmatization from the Paleoarchean to the early Rhyacian. Almost all elements of the evolutionary stages of the Gavião Block can be recognized in the study area, setting it as a natural laboratory to unravel the evolutionary history of this sector of the South American continental crust. [ABSTRACT FROM AUTHOR]

Abstarct The Archean and Paleoproterozoic terrane of the northeastern part of the São Francisco Craton shows evidence of a prolonged accretionary history. A major boundary within this portion of the craton is the Contendas-Jacobina lineament, a 600 km-long north-trending left-lateral thrust fault that separates major Archean blocks amalgamated during the Paleoproterozoic orogeny. Different supracrustal sequences occur along this lineament, but the tectonic imbrication erased the original stratigraphy, precluding the reconstruction of the sedimentary and tectonic evolution of the different groups. We investigated the sediment provenance and tectonic setting of the Saúde Complex, located in the northern part of the Contendas-Jacobina lineament and previously taken as part of the Bahia Gold Belt. We found that the Saúde Complex is part of a Paleoproterozoic foreland basin and correlates with the Contendas-Mirante Basin in the south. The correlation with the western Au-bearing Jacobina Basin as a single Paleoproterozoic basin is no longer favorable. The Saúde Complex contains abundant 2.06–2.20 Ga and 2.50–2.68 Ga detrital zircons mainly derived from the eastern Itabuna-Salvador-Curaçá Orogen and reworked Neoarchean rocks within the orogen, mainly the Caraíba magmatic arc. [ABSTRACT FROM AUTHOR]

The low-grade Contendas-Mirante meta-volcano-sedimentary belt (CMB) was previously interpreted as an Archean greenstone belt with the uppermost formation deposited in the Paleoproterozoic. New zircon U-Pb LA-ICP-MS ages on sedimentary groups and granite sheets intrusive in the belt constrain the timing of basin development. Phyllites of the Lower Group and meta-arenites of the Upper Group yielded similar young zircon populations at ca. 2080 Ma, which are interpreted as the maximum deposition age for the entire sequence. The unique exception is the 3273–3338 Ma zircon-bearing quartzite that occurs in spatial association with the 3300 Ma rhyolite. A granite sheet intrusive into metagraywacke of the Lower Group constrains the minimum deposition age of 2045 ± 26 Ma for the CMB. Altogether four main age clusters of detrital zircon grains were recognized, namely 2075–2200 Ma, 2200–2440 Ma, 2500–2770 Ma, 3270–3380 Ma. These age intervals match the ages of igneous and metamorphic rocks in the different terranes that comprise the São Francisco craton. Maximum deposition age for both groups indicates that sedimentation occurred immediately prior the high-grade metamorphism in the adjacent Archean-Paleoproterozoic Jequié Block and Itabuna-Salvador-Curaçá Orogen. These observations, along with coarsening upwards in the sediments, indicate that the CMB represents a foreland basin developed along the eastern margin of the Gavião Block during plate convergence. Paleoarchean basement rocks were reactivated and emplaced into the CMB during basin inversion and is timely correlated with the granitic intrusion. Recognition of older supracrustal fragments is ambiguous, one main example is the 3273–3338 Ma zircon-bearing quartzite, which correlates with the northern Jacobina basin along the Contendas-Mirante lineament (e.g., Bahia gold belt) and may represent part of an Archean intracontinental rift sequence. [ABSTRACT FROM AUTHOR]

In this study we present U–Pb and Hf isotope data combined with O isotopes in zircon from Neoarchean granitoids and gneisses of the southern São Francisco craton in Brazil. The basement rocks record three distinct magmatic events: Rio das Velhas I (2920–2850 Ma), Rio das Velhas II (2800–2760 Ma) and Mamona (2750–2680 Ma). The three sampled metamorphic complexes (Bação, Bonfim and Belo Horizonte) have distinct ε Hf vs. time arrays, indicating that they grew as separate terranes. Paleoarchean crust is identified as a source which has been incorporated into younger magmatic rocks via melting and mixing with younger juvenile material, assimilation and/or source contamination processes. The continental crust in the southern São Francisco craton underwent a change in magmatic composition from medium- to high-K granitoids in the latest stages, indicating a progressive HFSE enrichment of the sources that underwent anatexis in the different stages and possibly shallowing of the melting depth. Oxygen isotope data shows a secular trend towards high δ 18 O (up to 7.79‰) indicating the involvement of metasediments in the petrogenesis of the high potassium granitoids during the Mamona event. In addition, low δ 18 O values (down to 2.50‰) throughout the Meso- and Neoarchean emphasize the importance of meteoritic fluids in intra-crustal magmatism. We used hafnium isotope modelling from a compilation of detrital zircon compositions to constrain crustal growth rates and geodynamics from 3.50 to 2.65 Ga. The modelling points to a change in geodynamic process in the southern São Francisco craton at 2.9 Ga, from a regime dominated by net crustal growth in the Paleoarchean to a Neoarchean regime marked by crustal reworking. The reworking processes account for the wide variety of granitoid magmatism and are attributed to the onset of continental collision. [ABSTRACT FROM AUTHOR]

Detrital zircon ages are an important tool to study the provenance and evolution of sedimentary rocks, and currently there is a general lack of such studies in greenstone belt basins. In this paper, we combine field observations and in situ U–Pb/Lu–Hf detrital zircon analyses to constrain the evolution of a large, ancient convergent basin in SE Brazil. The Maquiné Group (the uppermost clastic sequence of the Rio das Velhas Greenstone Belt) was deposited during a fundamental shift in the evolution of the southern São Francisco Craton that ended with closure of the greenstone belt basin and the stabilization of the continental crust at ca. 2730–2700 Ma. We show that detritus accumulated in the Maquiné basin derived from uplifted nearby source rocks and that sedimentation was marked by drastic upward lithological changes (from flysch to molasse-type sedimentation). The restricted distributary provenance (marked by a strong uni-modal age spectra at 2770–2780 Ma) requires that sedimentation was concomitant with exhumation of a proximal 2770–2780 Ma TTG magmatic arc. The entire detrital zircon spectra show that maximum deposition ages are very close to the timing of deposition, and confirm that deposition occurred during or immediately after tectonic convergence. Variations in ɛHf (t) values support the idea that the Archaean crystalline crust of the craton was built by crust–mantle mixing processes with a successive decrease of values in zircons crystallized after 3100 Ma. In a regional context, our dataset supports previous interpretations of a long-lived evolution of the southern São Francisco Craton comprising a succession of magmatic arcs and Archaean convergent basins. [ABSTRACT FROM AUTHOR]

Paleoproterozoic to Mesoproterozoic cratonic basins in the São Francisco Craton are classified into three megasequences: Statherian, Calymmian–early Ectasian, and Stenian–early Tonian sequences. The location, depositional age, and provenance of these sequences are reflected in their detrital zircon U–Pb age distributions. A minimum of five detrital zircon age distributions are distinguishable: i) the Archean and Rhyacian distribution, which is restricted to the Calymmian interval at Chapada Diamantina; ii) the Rhyacian distribution, which occurs in the Statherian, Calymmian, and Stenian intervals and generally precedes the Proterozoic distribution; iii) the Proterozoic distribution, which always succeeds the Rhyacian distribution and appears in the Brasília Belt and Southern Espinhaço; iv) the mixed Archean and Proterozoic distribution, restricted to the Stenian interval at the Southern Brasília Belt; and v) the Statherian distribution, which is present in the Statherian interval at Espinhaço Basin and is recycled into the Calymmian and Stenian intervals at Chapada Diamantina. Based on the Hf isotope compositions of the detrital zircons, most of the sequences are predominantly sourced from Archean juvenile terrains and from Archean and Paleoproterozoic evolved terrains. The exception is the Paranoá Group, western São Francisco Craton, whose positive ɛHf(t) values suggest juvenile Paleoproterozoic sources such as the Goiás Massif. The Archean zircons from Chapada Diamantina have Hf depleted mantle model ages ranging from Paleoarchean to Neoarchean and are mainly derived from the Gavião Block within northeastern São Francisco Craton. The model unify a dataset spanning hundreds of millions of years of the depositional record over a large area of central and eastern Brazil. The records will assist researchers in unraveling the sedimentary and tectonic history of the Archean and Paleoproterozoic continents from new data collected regionally and in other continents. [ABSTRACT FROM AUTHOR]

Zircon U–Pb–Hf and geochemical data provide new clues for a juvenile TTG segment in the Mineiro belt, outlined by published information about the nearby 2.35 Ga Lagoa Dourada suite. The Resende Costa Orthogneiss and coeval rocks yield U–Pb crystallization ages from 2351 ± 48 to 2317 ± 16 Ma and coherent Sm–Nd T DM ages between 2.3 and 2.5 Ga. These rocks show ɛ Nd(2.35Ga) and ɛ Sr(2.35Ga) values that suggest derivation from a short-lived, slightly depleted source akin to products of island arcs, whereas the geochemistry is consistent with a tholeiitic source with minor crustal assimilation. The positive to negative zircon ɛ Hf(2.35Ga) suggests the subordinate involvement of crustal components during the hypothesized c. 2.35 Ga slab subduction event. In a similar manner, metabasalts (lower unit) of the adjoining Congonhas-Itaverava belt show Nd–Sr isotopic and chemical constraints indicating derivation from an early Paleoproterozoic tholeiitic source subjected to crustal assimilation. A coeval metagraywacke from the upper unit yields U–Pb zircon detrital ages as young as 2349 + 14 Ma suggesting the maximum depositional age for the precursor basin (foreland setting?) whilst most of the grains indicate contribution from nearby Archean sources. The Resende Costa-Lagoa Dourada rocks characterize the precocious arc magmatism of the Minas accretionary orogeny . This composite orogeny created the Mineiro belt and the adjoining Mantiqueira and Juiz de Fora belts in the 2.35–2.00 Ga interval. Due to such a polycyclic framework the Resende Costa Orthogneiss and coeval rocks show multiple metamorphic overprints dated at 2140 and 2050 Ma. The new and compiled data and regional geologic correlations provide evidence for a growing Paleoproterozoic landmass in the South America continent. [ABSTRACT FROM AUTHOR]

The N-S running Espinhaço fold belt, situated in the São Francisco craton in central-eastern Brazil, separates this craton in a western and an eastern part along the Paramirim Corridor, a Brasiliano-Panafrican (~650-500Ma) deformation zone. The (meta)sediments of the Espinhaço basin consist of several synthems with dominantly siliciclastic deposits. Among them, Al- and P-rich, lazulite-bearing blue quartzite, the amphibolite-facies equivalent of a phosphatic sandstone, of the Veredas Formation in the Northern Espinhaço form a conspicuous horizon. Zircon crystals from these quartzites have been dated using laser ablation inductively coupled plasma mass spectrometry. The zircon crystals are both detrital and metamorphic in origin, the latter exhibiting highly unusual textures produced by dissolution-reprecipitation reaction and concomitant replacement of metamict areas: (REE, Y, Th, U) zircon+fluid=zircon+xenotime. Detrital zircons reveal relict age groups of 3.1-3.3Ga, 2.6-2.7Ga, 2.0-2.3Ga, and 1.5Ga. The end of sedimentation and erosion of the magmatic and metamorphic rocks of the Sao Francisco craton can be estimated therefore as ≤1.5Ga. The major metamorphic event recorded by reprecipitated zircon is Neoproterozoic and documented by a lower-intercept age of 634±19Ma, which was calculated from analyses of individual spots on19 grains with a common relict Orosirian-Rhyacian age of 2032±31Ma, temporal equivalent to Transamazonian. The Neoproterozoic age of the metamorphosed zircons of the Vereda formation corresponds to the Brasiliano-Panafrican remobilization of the São Francisco-West Congo craton along the eastern side of the Espinhaço fold belt in the Paramirim Corridor. [ABSTRACT FROM AUTHOR]

Abstract: New U–Pb in situ zircon dating provides a new approach for the study of the Espinhaço Supergroup units exposed in the São Francisco Craton and Araçuaí Orogen. Located in Southern Espinhaço, Minas Gerais, the following two basins were formed in intraplate conditions: (i) the Lower Espinhaço Basin is marked by a volcano-sedimentary sequence with alluvial, fluvial and eolian deposits that were formed from 1.68Ga to 1.80Ga; (ii) the overlying sequence, called the Upper Espinhaço Basin, is a rift-sag basin that presents basal diamond-bearing continental deposits (the Sopa–Brumadinho Formation) with a younger zircon peak at 1192Ma, which is the maximum age for deposition of the upper units. The obtained U–Pb detrital zircon data of the studied units show age groupings related to the orogenic cycles of Jequié (Neoarchean) and Transamazonian (Paleoproterozoic), which are associated with the stability period from 1.8Ga to 0.91Ga in the São Franscico Craton, and record deposition during at least the three basinal cycles. The Stenian–Tonian ages of the Upper Espinhaço Basin units (906Ma to 1192Ma) suggest a direct link with the evolution of the Rodinia Supercontinent and represent a marker for Mesoproterozoic to Early Neoproterozoic evolution in the São Franscico Craton and adjacent areas. [Copyright &y& Elsevier]

Abstract: The eastern portion of the Brasilia belt, part of the Neoproterozoic Tocantins Province in central Brazil, is mainly constituted by metasedimentary rocks that partially represent the evolution of a passive margin developed during the Meso-Neoproterozoic in the western margin of the São Francisco paleocontinent. New in situ U–Pb and Lu–Hf isotope analyses on detrital zircons by LA-MC-ICP-MS were obtained for clastic sedimentary rocks of the Paranoá Group, considered to be the oldest unit of the this sedimentary sequence. The U–Pb data define a maximum depositional age of 1.54Ga and a minimum depositional age of ∼1.04Ga, the latter obtained on diagenetic xenotime overgrowth on zircon grains. Combined U–Pb and Lu–Hf data permitted to reconstruct the tectonomagmatic evolution of the potential source areas identified in the São Francisco craton. Two zircon populations at 1.54 and 1.78Ga, with ɛ Hf(t) values from +5.1 to −5.5, are possibly related with the Mesoproterozoic extensional magmatism registered in the Arai and Espinhaço rifts, located in the Brasilia belt and in the São Francisco craton respectively. The most important Paleoproterozoic zircon population, at 2.0–2.25Ga, shows positive ɛ Hf(t) (0 to +8) and Paleoproterozoic T DM values indicating a continuous long-period of magmatism with generation of juvenile crust during the Paleoproterozoic. Two minor zircon populations, at 2.1 and 2.15Ga, showing negative ɛ Hf(t) values, 0 to −10.1, and T DM values between 2.65 and 3.22Ga may represent arc related magmatism, with reworking of Archean crust, during the evolution of an active margin of the São Francisco craton. A third minor zircons population, at 2.05Ga, with strongly negative ɛ Hf(t) values, between −8.6 and −17.7, and T DM values between 2.93 and 3.46Ga, may represent a collisional magmatism that characterized the final stage of an active margin evolution with reworking of Early Archean crust. Several minor zircon populations of Archean ages (2.7, 2.85, 3.1 and 3.42Ga), derived from the Archean nuclei in the interior of the São Francisco craton, suggest the presence of different magmatic pulses that repeatedly reworked a juvenile Paleoarchean crust. The oldest event of generation of juvenile crust is registered by zircons with U–Pb age of 3.42Ga, positive ɛ Hf(t) values of 3.0 and T DM of 3.54Ga. [Copyright &y& Elsevier]

Abstract: U–Pb single zircon crystallization ages were determined using TIMS and sensitive high resolution ion microprobe (SHRIMP) on samples of granitoid rocks exposed in the Serrinha nucleus granite–greenstone terrane, in NE Brazil. Our data show that the granitoid plutons can be divided into three distinct groups. Group 1 consists of Mesoarchaean (3.2–2.9Ga) gneisses and N-S elongated TTG (Tonalite-Trondhjemite-Granodiorite) plutons with gneissic borders. Group 2 is represented by ca. 2.15Ga pretectonic calc-alkaline plutons that are less deformed than group 1. Group 3 is ca. 2.11–2.07Ga, late to post-tectonic plutons (shoshonite, syenite, K-rich granite and lamprophyre). Groups 2 and 3 are associated with the Transamazonian orogeny. Xenocryst ages of 3.6Ga, the oldest zircon yet recorded within the São Francisco craton, are found in the group 3 Euclides shoshonite within the Uauá complex and in the group 2 Quijingue trondhjemite, indicating the presence of Paleoarchaean sialic basement. Group 1 gneiss-migmatitic rocks (ca. 3200Ma) of the Uauá complex constitute the oldest known unit. Shortly afterwards, partial melting of mafic material produced a medium-K calc-alkaline melt, the younger Santa Luz complex (ca. 3100Ma) to the south. Subsequent TTG melts intruded in different phases now exposed as N-S elongated plutons such as Ambrósio (3162±26Ma), Araci (3072±2Ma), Requeijão (2989±11Ma) and others, which together form a major part of the Archaean nucleus. Some of these plutons have what appear to be intrusive, but are probably remobilized, contacts with the Transamazonian Itapicuru greenstone belt. The older gneissic rocks occur as enclaves within younger Archaean plutons. Thus, serial additions of juvenile material over a period of several hundred m.y. led to the formation of a stable micro-continent by 2.9Ga. Evidence for Neoarchaean activity is found in the inheritance pattern of only one sample, the group 2 Euclides pluton. Group 2 granitoid plutons were emplaced at 2.16–2.13Ga in a continental arc environment floored by Mesoarchaean crust. These plutons were subsequently deformed and intruded by late to post-tectonic group 3 alkaline plutons. This period of Transamazonian orogeny can be explained as a consequence of ocean closure followed by collision and slab break-off. The only subsequent magmatism was kimberlitic, probably emplaced during the Neoproterozoic Braziliano event, which sampled older zircon from the basement. [Copyright &y& Elsevier]

• New U-Pb and Hf isotope data of 3.51–3.4 Ga tonalites and diorites from GB. • Crustal source chance at 3.51 Ga evidenced by the input of juvenile material. • Evidence of input from a strongly depleted mantle at 3.4 Ga. • Change in the geodynamic regime of continental crust formation at ca. 3.51 Ga. The continental crust growth/evolution processes and the tectonic regime through Eo- and Paleoarchean times are enigmatic due to the scarcity of preserved crust. The Gavião Block, São Francisco Craton (Brazil), contains exposed and well-preserved Eo-Paleoarchean crust remnants, providing a rare opportunity to investigate these issues. Here, we describe new U-Pb ages and Hf isotope data of 3.51–3.4 Ga tonalites and diorites from the Gavião Block and compare these with previously published Lu-Hf data from Hadean/Eo-Paleoarquean zircons from the Gavião Block and other primitive cratons. The Eo- to Paleoarchean evolution of the Gavião Block is registered by ca. 360 Myr of continuous magmatic events from ca. 3.66 Ga to 3.30 Ga. From the available Hf data, we interpret that each of the events younger than 3.6 Ga registers a new juvenile addition that assimilated older crust, whereas the rocks older than 3.6 Ga are exclusively formed through the reworking of a Hadean, and to a less extent early Eoarchean crust. The shift in the crust generation process with the input of juvenile material into the Gavião Block has been documented within the ∼ 3.8–3.5 Ga time in other primitive cratonic complexes including the Wyoming, Pilbara, Kaapvaal, Slave, Singhbhum, and Yilgarn. As documented in these other cratons, our data suggest that a shift in the Hf isotope record to rocks younger than 3.6 Ga reflects a transition from stagnant-lid to mobile-lid tectonics in the crust formation process of the São Francisco Craton. This change in the geodynamic regime appears to have been global at ca. ∼ 3.8–3.5 Ga and facilitated the extraction of juvenile melts, crustal reworking, evolved magmatism, and the production of stabilizing melt-depleted lithospheric mantle. [ABSTRACT FROM AUTHOR]

Abstract: The Serrinha nucleus is one of the Archaean granite-gneiss terrains of São Francisco craton, Brazil. In this area, many granitic rocks formed during the Trans-Amazonian orogeny, and intruded during and following a greenschist metamorphic event. Zircon geochronology and Nd isotopes record a history of extensive crustal reworking that began at 3.6Ga and culminated in the emplacement and deformation of a continental arc during the Trans-Amazonian accretionary orogeny at 2.1Ga. The basement to the arc is represented by migmatitic gneiss of the Uauá Complex, which records a period of zircon growth at 3195±11Ma but contains cores as old as 3314±20Ma, as well as metamorphic zircon as young as 3090Ma. The Meso to Paleoarchean ages, as well as the absence of evidence for widespread Neoarchean magmatism are similar to what is observed in the Kaapvaal craton in South Africa. The Quijingue trondhjemite was emplaced into Uauá Complex migmatitic gneiss at 2155±3Ma probably during a period of TTG magmatism associated with arc construction on the edge of a Mesoarchean continent. Although older cores appear to be absent from the Quijingue trondhjemite, its depleted mantle Nd age of 3.3Ga suggests that it was derived from partial melting of the basement. Xenocrystic zircon grains with ages as old as 3.62Ga are present in this pluton and indicate that Eoarchean crust was present and may still be preserved in the area. Ocean convergence was probably followed by a Trans-amazonian collisional event that resulted in widespread syn to post-tectonic alkaline magmatism such as the shoshonitic Euclides pluton. Primary zircon from this pluton records an emplacement age of 2097±8Ma but the depleted mantle Nd age of 2.87Ga indicates derivation of these magmas from Archean sources. The inherited zircon population from Euclides preserves a complex record of growth. One possible xenocryst gives a discordant and relatively imprecise age of 3654±125Ma. SHRIMP dating of other zircon grains gives concordant ages that range from 2350Ma to 2500Ma as well as a 2.14-Ga Trans-Amazonian component. The provenance of the very early Proterozoic ages is unknown but may indicate zircon growth or resetting events at deep crustal levels. These data combined with other results suggest that mid to early Archean continental crust could underlie much of the São Francisco craton. [Copyright &y& Elsevier]

The São Francisco craton and its surrounding orogens are some of the most important tectonic elements of South America, and key regions to understanding the assembly of Western Gondwana in the Proterozoic-Palaeozoic transition. During this major tectonic event, diachronic collisions between small continents developed an intricated orogenic system, where several orogens evolved in unique paths through time and space. In such collisional settings, there are some tectonic processes that promote subsidence, thus controlling the formation of orogenic-related sedimentary basins. Furthermore, the tectonic activity in collisional orogens generates dynamic landscapes that usually favor increased erosion and sediment generation to feed these basins, making them key places to seek for clues about the tectonic evolution of their surroundings. On the São Francisco craton, the Bambuí Group records a complex foreland system, which evolved in response to the lithospheric overload exerted by the uplift of both Brasília belt and Araçuaí orogen. In turn, both Salinas Formation and Ibiá Group comprise orogenic deposits resting within the Araçuaí orogen and Brasília belt, respectively, whose tectonic significance is still under debate. Here we present new U–Pb (LA-ICP-MS and SHRIMP) and Lu–Hf isotopic analyses on a great amount of detrital zircon grains extracted from the rocks of the Bambuí Group and Salinas Formation, together with a thorough data compilation from the literature. The two units present similar provenance patterns, sharing the major detrital zircon age peaks (550–650 Ma, 950–1050 Ma, 1750–2000 Ma, 2600–2800 Ma) and maximum depositional age in c. 550 Ma. The Ediacaran zircons recovered from the Bambuí Group show a wide range of the εHf(t), ranging from c. −17 to +15, which suggest the existence of multiple late Neoproterozoic sources, some of them juvenile and some with a long crustal residence. The variation in detrital zircon age patterns and εHf(t) values from different units within the Bambuí Group provided additional clues of provenance changes occurred during the evolution of the basin. The new data obtained for the Salinas Formation constrain its deposition between 548 and 500 Ma, which have an important implication on its tectonic significance. We propose that in both Brasília belt and Araçuaí orogen sides, the early foredeep deposits of the Bambuí basin should have been incorporated to the orogenic domains, which could explain the apparent lack of deposits recording the climax of the Brasilia belt uplift (c. 630 Ma) within the cratonic area. In this same direction, we consider that both Salinas Formation and Ibiá Group could represent remnants of these early foreland deposits related to the uplift of Brasília belt and Araçuaí orogen, respectively, incorporated to the orogenic wedges due to the advance of the deformational fronts. Therefore, what we know as Bambuí Group is in fact the remaining record of an advanced stage of the foreland system, when subsidence was already influenced by the two evolving orogens. Altogether, the analyses of the stratigraphic, structural and geochronological data converge towards an integrated tectonic model for the interaction between the Bambuí basin and the surrounding orogens during West Gondwana amalgamation. • We present new U-Pb and Lu-Hf data from detrital zircon grains of the Bambuí Group and the Salinas Formation. • Our results are interpreted together with a complete dataset compiled from the literature. • The results demonstrate the remarkable cyclicity in sedimentary reworking during foreland dynamics. • Our data converge toward an integrated tectonic model for the interaction between the Bambuí basin and borderer orogens. • The Bambuí Group is the late stage of the foreland system, and Salinas Fm. and Ibiá Gr. are the early foreland deposits. [ABSTRACT FROM AUTHOR]

Isotopic Lu–Hf and geochronological studies on the zircon grains of the Paleoproterozoic Borrachudos Suite provide constrains of the evolution of the tectonomagmatic events that affected the southern border of the São Francisco Craton and leaded to the formation of the associated iron and emerald deposits. The granite records magmatic crystallization in the 1740-1688 Ma time range, and A2-type geochemical signature. Zircon grains present hydrothermal and anatectic areas with Cambrian age that are related to the gravitational collapse of the final stages of the Brasiliano orogen. During this event the granite was deformed and metamorphosed in the amphibolite facies, leading to anatexis and the formation of large amount of pegmatite bodies. The Hf isotope data on the hydrothermal/anatectic areas indicate partial melting were accompanied by hydrothermal fluids enriched in radiogenic Hf. These fluids contributed to the formation of large volume of hydrous melts (pegmatites), the formation of the emerald deposits and the high-grade iron orebodies. • New Hf isotope data for the Borrachudos Suite and associated deposits. • Evidences on the hydrothermal and anatectic zircon growth. • Isotopic signatures imply a mixture of juvenile material and old crust. • Isotopic constraints on the evolution and genesis of iron and emerald mineralization. [ABSTRACT FROM AUTHOR]

Isotopic Lu-Hf and U-Pb systematics can provide important insights into the tectono-metamorphic processes that occurred in the source regions of sedimentary/metasedimentary units, helping to further clarify regional crustal evolution. The studied metasedimentary sequence is located in the southern Brasília Orogen, SE Brazil, a fold-and-thrust belt composed of a thick nappe stack transported towards the southern São Francisco Craton (SFC) during the Neoproterozoic. Adjacent to the Cratonic border is a reworked Neoproterozoic metasedimentary passive margin sequence, that includes the Carrancas succession, for which we present new U-Pb and Lu-Hf detrital zircon analyses (ca. 700 grains in total). Results yielded a maximum depositional age of 0.988 ± 0.013 Ga and an extensional tectonic setting for the precursor basin. Major source areas, constrained by comparing our data to isotopic analyses compiled from the existing literature, are probably located in the adjacent southern SFC. Lu-Hf analyses of Paleoproterozoic and Archean zircon grains, presented in this study, yielded similar results to those obtained for the basement of the SFC. However, important U-Pb age peaks found in this study do not have strong correlatives in the southern SFC (e.g. 1.84,1.87 and 1.88 Ga), with the exception of a few localized examples (e.g. Espinhaço I magmatism). These ages are abundant in the southwestern Congo Craton (CC), which was potentially relatively close to the studied area during sedimentation, since the SFC and CC probably constituted a single continental mass after the Paleoproterozoic until the opening of the south Atlantic in the Mesozoic. • U-Pb and Lu-Hf detrital zircon analysis. • Neoproterozoic (ca. 980 Ma) passive margin succession of the São Francisco Craton. • Lithostratigraphic repetition of formations due to folding corroborated by isotopic analyses. • Provenance assessment: the São Francisco and Congo cratons as likely sources. [ABSTRACT FROM AUTHOR]

The Três Marias Formation, a siliciclastic succession that occurs at the top of the Bambuí Group, has recorded the filling of the Brasiliano foreland basin that developed on the São Francisco craton. At the eastern portion of this craton, the Três Marias Formation outcrops in Gorutuba ridge, north of Minas Gerais, which area was investigated by using field work, stratigraphic analysis, and isotopic U–Pb and Lu–Hf analysis. In this area, the Três Marias Formation includes molasse deposits composed mainly of arkoses and hybrid conglomerates. The arkose sediments came into the basin through a fluvio–deltaic system located to the northeast and were reworked in a siliciclastic shelf under the influence of waves, tides and storm currents. The paleocurrents indicate a coastline around the NW and NE directions, with current flows reworking sediments parallel and transversal to the coast. The detrital zircon grains indicate a 555 ± 17 Ma maximum age of the deposition for this unit, and its main sources are related to granitoids from the pre-orogenic and pre-to syn-collisional stages of the Araçuaí orogen (ca. 630–560 Ma). The filling of the foreland basin system created in response to the Araçuaí fold–thrust belt is younger than the one existing in the occidental portion of Bambuí basin, which is related to the Brasília fold and thrust belt. Therefore, the final filling of the Bambuí basin would have been controlled by the development of these two-fold–thrust belts throughout the margins of the São Francisco craton during the assembly of West Gondwana. Image 1 • The Três Marias Formation deposition is constrained at ca. 555 Ma. • Foreland basin controlled by two diachronic contractional orogenic belts. • New eastern Bambuí Group detrital zircon U–Pb and Hf–Lu provenance data. • The new data indicate a superposed pro-foreland basin at eastern São Francisco Craton. [ABSTRACT FROM AUTHOR]