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The Punta del Este Terrane, located in southeastern Brazil and eastern Uruguay, is a tectonostratigraphic terrane recognized in the Dom Feliciano Belt, the southern segment of Mantiqueira Province (Brasiliano Orogen). The northern sector of the terrane, called here by the Jaguarão Domain, is constituted by Arroio Telho, Arroio Grande, Matarazzo metamorphic complexes, and the Arroio Pedrado Gneisses. The first is composed of low to medium-grade metasedimentary rocks. Metasiliciclastic schists and marbles constitute the second, with serpentinites, magnesian schists, amphibolites, and metagabbros. The Matarazzo Complex comprises pure and siliceous dolomitic marble, metadolerite, and metagabbro. Arroio Pedrado unit comprises granodioritic to monzogranitic augen-gneisses. The rocks of the complexes were poly-deformed and intruded by high-K calc-alkaline peraluminous and metaluminous granitoids. The Pedro Osório, Arroio Grande, and Cerro Amaro dextral shear zones delimited the domain to the north. To the south and east, the units of the Jaguarão Domain were covered by coastal plain sediments. In gravimetric maps, the domain shows a high-density relief in contrast with the rocks of the granite belt (Pelotas Batholith). U-Pb zircon data from garnet-muscovite granites present crystallization ages of 587–568 Ma, which point to a widespread Ediacaran magmatism in the northern Punta del Este Terrane. U-Pb zircon provenance data of the metasedimentary sequences indicate main Meso- to Paleoproterozoic contribution, with subordinate Tonian to Cryogenian age populations. The geochronological results of the supracrustal rocks indicate a sedimentary deposition in an extensional setting, in which posterior deformation and metamorphism/magmatism compatible with a syn-orogenic setting in the context of the Dom Feliciano Belt framework. [ABSTRACT FROM AUTHOR]

Abstract The origin and significance of the metavolcanic rocks of the Vila Nova Greenstone Belt (VNGB) is an important issue in order to understand the evolution of the Guyana Shield in Paleoproterozoic times. This work presents new LA-MC-ICPMS U-Pb zircon data and geochemical analyses carried out on metavolcanic rocks of the VNGB. This information was supplemented by petrography, stratigraphic and structural data acquired through geologic mapping and boreholes descriptions. In the Vila Nova region, the VNGB units rest on the Archean basement composed of orthogneisses of the Tumucumaque Complex. The lower portion of the VNGB consists of metabasalts and andesitic metabasalts, covered by an upper metasedimentary domain with subordinate metavolcanic and exhalative chemical rocks. The metavolcanic rocks include metabasalts, meta-andesites, amphibolites and amphibole schists, deformed and elongated according to the regional NW-SE structure. U-Pb zircon data yielded an age of 2154 ± 6 Ma for a meta-andesite of the lower portion of VNGB. One orogenic metamorphism followed by three deformational events were recognized. The D 1 and D 2 events formed the schistosity (S 1), preserved as intrafolial folds (F 2) and the crenulation cleavage (S 2) associated with the development of the oblique shear zones. Two distinct assemblages: 1) garnet, hornblende and biotite, and 2) hornblende, plagioclase and diopside define two distinct metamorphic peaks: M 1 and M 2 with temperatures of 450 and 650 °C, and lithostatic pressure between 4 and 6 kbar. The metabasites comprise geochemical compositions of Fe- and Mg-tholeiites with komatiitic affinity. The first group is enriched in LREE and HFSE. The second group shows MORB-like REE patterns in association with negative Nb, Ti and P anomalies. The observed features indicate that the metavolcanic rocks of the VNGB represent the evolution of back-arc basins and island arcs associated with the Trans-Amazonian Orogeny. These rocks characterize the Rhyacian evolution of the Maroni-Itacaiunas Province in the eastern portion of the Guyana Shield. Graphical abstract Image 1 Highlights • La-ICP-MS U-Pb zircon geochronology data on meta-andesite established a Rhyacian age (2,154 ± 6 Ma) for the magmatism. • The protoliths are tholeiitic basalts and andesites with geochemistry associated with an island arc-back-arc system. • E-MORB, N-MORB and plume type sources were involved in the formation of the volcanic rocks. • The volcanic rocks were affected by metamorphic events under greenschist-amphibolite and hb-px hornfels facies conditions. [ABSTRACT FROM AUTHOR]

A provenance and stratigraphic study of the Neoproterozoic Pontas do Salso Complex (PSC), western portion of the Dom Feliciano Belt (DFB), was conducted with U–Pb zircon geochronological analysis of the metasediments and the host rocks. The U–Pb isotopic data from detrital zircon of the metasediments indicate the source from the latest Middle Tonian to Late Cryogenian (between 897 and 684 Ma) and maximum depositional age of 685 ± 18 Ma in an arc-related basin setting adjacent in the Sao Gabriel Arc. The metasediments of the PSC form an elongated body in the N35°E direction and occur in the central portion of the São Gabriel Terrane (SGT), which is constituted by ophiolitic complexes and arc-related rocks, generated probably during the final consolidation of Rodinia supercontinent, although this question is still open. Low- to medium-K calc-alkaline, metaluminous affinity, and trace-element geochemistry suggest that the chemical composition of the protoliths was generated from metasomatized mantle sources in subduction zones. The PSC is composed of meta-arkoses, with subordinate metaconglomerates and metapelites. The meta-arkoses are disposed in plane-parallel layers, which also internally feature small-scale cross-bedding structures. The matrix has a blastopsammitic, poorly selected, fine to coarse texture, and hexagonal quartz and plagioclase porphyroclasts with superimposed thermal metamorphism. The polymict metaconglomerates are matrix-supported, with 15–55% of clasts of metavolcanic rocks, metasediments, undeformed granites, and quartz veins. The metapelites comprise mainly muscovite phyllites with syn-tectonic garnet and chloritoid porphyroblasts. The PSC represents a sedimentary succession deposited on an arc-related basin formed during the collapse and uplift of the SGT. [ABSTRACT FROM AUTHOR]

U Pb LA-ICPMS geochronological analyses were carried out on zircon grains from metavolcanic rocks of the Bossoroca Complex and for one ash tuff of the Acampamento Velho Formation of the Camaquã Basin, in order to understand the evolution of the Neoproterozoic São Gabriel magmatic arc. A total of 42 analyses of igneous zircon grains were performed in three samples. The results yielded U Pb ages of 767.2 ± 2.9 Ma for the metavolcanic agglomerate (BOS-02); 765 ± 10 Ma for the metacrystal tuff (BOS-03) and 565.8 ± 4.8 Ma for the ash tuff (BOS-04). The Orogenic Cycle in Brazil is characterized by a set of orogenic belts consisting of petrotectonic associations juxtaposed by two collisional events that occurred at the end of the Neoproterozoic. In southern Brazil this orogeny formed the Dom Feliciano Belt, a unit composed of associations of rocks developed during two major orogenic events called São Gabriel (900–680 Ma) and Dom Feliciano (650–540 Ma). The main São Gabriel associations are tectonically juxtaposed as elongated strips according to the N20–30°E direction, bounded by ductile shear zones. The Bossoroca Complex comprises predominantly metavolcano-sedimentary rocks, characterized by medium-K calc-alkaline association generated in a cordillera-type magmatic arc. The volcanism occurred in sub-aerial environment, developing deposits generated by flow, resurgence and fall, sporadically interrupted by subaqueous epiclastic deposits, suggesting an arc related basin. The São Gabriel Terrane contains the petrotectonic units that represent the closure of the Charrua Ocean associated to the subduction period of the Brasiliano Orogenic Cycle in the Sul-rio-grandense Shield. [ABSTRACT FROM AUTHOR]

Abstract: The Cordilheira Suite is comprised of peraluminous granites that constitute, together with the Quitéria granite, the beginning of the formation of the Pelotas Batholith in the central portion of the Dom Feliciano Belt. The batholith is composed of seven granitic suites with minor occurrences of gabbro, diorite and subvolcanic rocks. Its evolution between 650 and 550 million years ago is characterised by a ranging from metaluminous to peraluminous rocks and from calc-alkaline to alkaline and peralkaline series. The Cordilheira Suite is composed of the Cordilheira, Arroio Francisquinho, Butiá and Três Figueiras granites, which contain muscovite and/or biotite, with the following accessory minerals: tourmaline, garnet, sillimanite, apatite, zircon, monazite and ilmenite. The granitic bodies are elongate; their ascent and emplacement were controlled by high-angle shear zones oriented at N45-70°E. They have mylonitic structures with magmatic foliation accompanied by a low-angle stretching lineation, indicating that these bodies were emplaced under syn-kinematic conditions during a transcurrent event. The granites have high-K calc-alkaline affinity and are peraluminous. The LILE and REE contents are low. The K2O/Na2O and CaO/Na2O ratios are approximately 1 and less than 0.3, respectively. Pseudosections calculated using the Perple X program suggests that the granites were formed at partial melting temperatures between 740 and 820 °C and pressure between 8.5 and 9 kbar. Petrographic and chemical data suggest that the magmas were generated by the partial melting of the migmatitic pelitic gneisses of the Várzea do Capivarita Complex and, to a lesser degree, orthogneisses of the Arroio dos Ratos Complex, which left a granulitic residue. UHT conditions of granulite facies metamorphism were recorded in the Várzea do Capivarita paragneisses by mineral paragenesis and indicate that temperatures between 900 and 1000 °C and pressures between 4 and 8 kbar were required for the partial melting. It is likely that these medium-pressure conditions resulted from the thickening of the continental crust when the Rio de La Plata Craton collided with the Kalahari Craton to form southwestern Gondwana at the end of the Neoproterozoic. [Copyright &y& Elsevier]

Abstract: The post-collisional magmatism related to Brasiliano orogeny represented the final stage of the Dom Feliciano Belt in Rio Grande do Sul and Santa Catarina states, southern Brazil, presenting high-K calc-alkaline to shoshonitic and alkaline chemical signatures. Magmatic episodes related to this early period were found in Botuverá region, Santa Catarina state, represented by diabase and lamprophyre (spessartite-type) dikes intrusive in metavolcano–sedimentary rocks of the Brusque Metamorphic Complex (CMB). These dikes have massive structure and igneous textures ranging from very fine equigranular to porphyritic, and the latter is characterized by the presence of phenocrysts of plagioclase and hornblende. The dikes have northeast direction and sharp contacts with the metamorphic rocks, indicating that its position was after the main orogenic regional metamorphism that affected the CMB, interpreted as of collisional nature. The diabase has a basic composition, whereas spessartite lamprophyres are intermediate, with geochemical affinities to the tholeiitic series, with a significant enrichment in light rare-earth elements (LREE) and large ion lithophile elements (LILE) such as Cs, Rb, Ba, K and Sr, and negative anomalies for high-field-strength elements (HFS) such as Nb, Ta, U and T. The concentration of standard trace elements and the Th/Yb and Ta/Yb ratios indicate that these magmas were derived from an enriched mantle source and were strongly contaminated by crust. Except for higher values of K, these features are similar to those found in basaltic volcanic rocks associated with the post-collisional period in south Brazil. The widely dispersed values of ɛND (618), ranging between −13.74 and +5.52, highlights the heterogeneity of the source and reinforces the importance of a crustal component in the generation of these rocks. The extremely low value of εNd (618), of −21.67 obtained for spessartite lamprophyres supports the importance of the involvement of crust in the genesis of this rock. Using the U–Pb and LA–ICP–MS method, a concordant age of 618 ± 8.7 Ma was obtained in zircon crystals of a diabase dike of the region of Barra do Areia, in Botuverá, SC. The existence of inherited zircon grains older than 1800 Ma in this sample supports the involvement of Paleoproterozoic continental crust. The data analysis characterizes the first magmatic age related to the post-collisional period of the Brasiliano orogeny in this region of the Santa Catarina Shield. [Copyright &y& Elsevier]

The Brusque Metamorphic Complex (BMC) is one of the main units of the Tijucas Terrain within the Dom Feliciano Belt, located in the state of Santa Catarina in southern Brazil. In the Itapema region, the BMC is composed chiefly of metasediments, including subordinate metabasalts, meta-ultramafic rocks, and clinoamphibole schists. The metavolcanic rocks form 4 m-thick lenses interlayered with metapelites and calc-silicate schists. Based on the observed textures and the associated structural, bulk-rock geochemical, and mineral chemical data, these metamafites and ultramafites were ancient lava flows of tholeiitic basalts and ultramafic cumulates. The mineral parageneses of the metabasalts are albite + actinolite + chlorite + epidote + titanite + magnetite and oligoclase + hornblende + epidote + titanite + magnetite, indicating progressive transformations produced under greenschist to amphibolite facies conditions. Volcanogenic metasediments show the same geochemical patterns as the metabasalts, whereas the metamorphosed ultramafic rocks consist of cumulates generated by crystal fractionation and flow segregation. The studied rocks show similar rare-earth element (REE) patterns, characterized by clearly higher normalized contents of light REEs compared with heavy REEs, without Eu anomalies in the metabasalts and positive Eu anomalies in meta-ultramafic rocks and volcanogenic metasediments. In accordance with the trace element contents that indicate a within-plate nature, the corresponding mafic melts apparently formed in the mantle by partial fusion and were subsequently enriched with crustal components during ascent into the sialic crust. The analysed 143Nd/144Nd and 87Sr/86Sr ratios lie between 0.5123 and 0.5126 and 0.7067 and 0.7086, respectively, and are thus typical of tholeiitic basalts of the continental plateau type. Initial ϵNd(936) values and derived model ages (T DM) between 1028 and 1762 million years support a mantle source or sources, with extraction and emplacement in the Neoproterozoic. Field relations and geochemical data (including isotopic data) indicate the generation of the studied mafic and ultramafic rocks in a continental rift. In the regional geologic context, the formation of the BMC volcanic and metasedimentary units marks a period of fragmentation of the Palaeoproterozoic continental crust. This extensional event is preserved regionally in gneisses from the Santa Catarina Granulitic Complex and the Camboriú Complex. [ABSTRACT FROM AUTHOR]

Abstract: The Capivarita Anorthosite, formed in an intraplate environment and later metamorphosed under amphibolites facies conditions, is exposed in the Dom Feliciano Belt as part of the Brasiliano magmatic arc and occurs as a roof-pedant in, or is even intruded by, 0.6Ga post-collisional granites. In this work, magmatic and metamorphic minerals were dated using the LA-MC-ICP-MS in situ method. U–Pb magmatic and metamorphic zircon dating yielded an age of 1573±21Ma and of 606±6Ma, respectively, whereas the igneous titanite dating yielded an age of 1530±33Ma and the metamorphic ages were 651±9Ma and 601±5Ma. The Lu–Hf model ages showed two clusters from 1.81 to 2.03Ga (ɛɛHf from +2.21 to +6.42) and 2.55–2.62Ga (ɛɛHf from −4.59 to −5.64). This intraplate magmatism can be connected to a very important episode of continental accretion in an extensional setting from the fragmentation of the supercontinent during the Early Mesoproterozoic. [Copyright &y& Elsevier]

Hartmann and Cerva-Alves (2021) describe a field of silicified Cretaceous Paleodunes of the Botucatu Formation present in southernmost Brazil. In this comment, we explore pressing problems of their study and demonstrate that the authors inadequately use their data to support their conclusions. We evidence that: (1) the methodology misses basic information about the used datasets, as well as petrography and geochemistry data of the Botucatu sandstones; (2) the proposed silicification model is not supported by any petrographic or geochemical data; (3) the interpretations about dune morphology, wind pattern and direction are incorrect and differ from the available eolian record for the study region; and (4) the 'explosive' hydrothermal hypothesis for Cerro do Jarau site is based upon a not sustainable hydrothermal model that neglects substantial evidence for an impact origin for Cerro do Jarau and is broadly inconsistent with physical constraints. • Data and methods do not support the main conclusions • Unsupported silicification model for the Botucatu Sandstones • Inaccurate interpretation of dune morphology and wind direction • 'Explosive' hydrothermal model broadly inconsistent with physical constraints • Unsupported claim for a geomorphological origin for the Cerro do Jarau impact crater [ABSTRACT FROM AUTHOR]

The genesis of Precambrian granitic batholiths related to supercontinent assembly is controversial, especially regarding their generating processes and tectonic settings. The present study focused on the Pelotas Batholith (Magmatic-arc domain) of the Dom Feliciano Belt, which comprises the southern segment of the Mantiqueira Province in southeastern South America. New U–Pb and Lu–Hf zircon data from plutonic rocks with evidence of magma mixing and mingling, as well as assimilation of wall rocks, suggest multi-stage magmatism related to flare-up episodes of intense magmatism, potentially triggered by changes in the tectonic setting. U–Pb zircon analyses yielded crystallization ages of granodioritic gneiss xenolith at 691.5 ± 7 Ma, microgranodiorite xenolith at 645.9 ± 3.7 Ma, host monzogranite at 634.4 ± 4.4 Ma, and intrusive syenogranite at 620.1 ± 4.7 Ma, all intruded by syenogranitic pegmatite at 606.9 ± 1.7 Ma. Other analyses were performed on calc-alkaline granite (633 ± 4 Ma) and peraluminous granite (609.6 ± 2.2 Ma). The Lu–Hf data highlights a model age interval ranging from 1.7 to 1.3 Ga with εNd values between −4 and 1, except for the pegmatite sample which also includes Paleoproterozoic and Archean model ages (3.3-1.6 Ga) and εNd values between −33 and −1. Furthermore, the acquired data, together with the gathered dataset Dom Feliciano Belt granites, emphasizes a contribution from slightly juvenile to crustal sources, with model ages ranging primarily from Statherian-Orosirian to Mesoproterozoic. Signature patterns are consistent with sources from African basement rocks. • The studied magma mixing outcrop represents the Granite belt's fractal evolution. • The magmatic suites are primarily classified as I-Type and S-Type granites. • The Hf isotopes present mainly Meso-to Paleoproterozoic model ages (1.7-1.3 Ga). • The εHf values are primarily slightly negative to positive. • The U–Pb dataset shows well-defined intervals of magmatic pulses. [ABSTRACT FROM AUTHOR]

Thick quartzites record significant information on cratonic environments during long geological periods. The capacity to resist weathering and deformation turn the quartzite covers especially useful in the provenance studies of Precambrian basins. Provenance of 194 detrital zircon grains from two samples of thick quartzite cover on the Paleoproterozoic Encantadas Complex displays mostly Paleoproterozoic (95%) and minor Archean (5%) sources. The results indicate that sediments were derived from the La Plata Craton with the maximum depositional age at 2.03 Ga possibly up to 1.7 Ga. In comparison, the adjacent Porongos Group has provenance data of 61 detrital zircon grains indicating mostly Mesoproterozoic (69%), subordinately Paleoproterozoic (26%) and minor Archean ages (5%). Considering previous published data, the Porongos Group is Ediacaran in age and probably chronocorrelated with sedimentary basins from the Tandilia Belt (Argentina). Therefore, the quartzite cover and the Porongos Group require distinct evolution in time and in tectonic environment. [ABSTRACT FROM AUTHOR]

Two ash fall beds (tonstein) sampled from the post-glacial Permian deposits of the Paraná Basin have provided new U–Pb radiometric age constraints for this stratigraphic interval. The zircon grains were recovered from tonstein layers interbedded with fine-grained and carbonaceous lithologies in the middle portion of the Rio Bonito Formation. In both samples, the dominant population is interpreted as generated by explosive volcanism, as having formed immediately before the eruption. Based on 238 U/ 206 Pb, the selected zircon grains from the dominant population have weighted mean ages of 290.6 ± 2.8 Ma and 281.7 ± 3.2 Ma, corresponding to the Sakmarian and Kungurian ages in the Cisuralian epoch, respectively. These ages constrain the time of the deposition of the tonstein horizons and have important stratigraphic implications for the Late Paleozoic evolution of both the Paraná Basin and the southwestern region of Gondwana. The results presented here and the radiometric data already published suggest that deposition of the post-glacial coal-bearing deposits of the Rio Bonito Formation was probably initiated before the Early Permian. Thus, we infer that the climate had already ameliorated by this period in order to allow for the formation and accumulation of peat in this region of Gondwana. [ABSTRACT FROM AUTHOR]

Abstract: The Lower Permian sedimentary succession of the Paraná Basin in southernmost Brazil has an overall transgressive sedimentation regime, recorded by a clear retrogradation of the facies belt. However, important depositional strike-orientated variations and regional inversions occur in the sedimentation regime along the paleo-shoreline (i.e., along-strike) of the basin. At the regional scale, a huge source area was uplifted by the end of the Artinskian in the north and caused regression; the southern part of the study area increasingly was transgressed by the epicontinental sea (= regional inversion). This important tectonic overprint on the stratigraphic signature of the basin’s infill has a tectonic origin. The variable sedimentation regime along the paleo-shoreline is controlled by the structural framework of the basement, which is formed by several crustal blocks with different responses to tectonic strain induced by terrain accretion on the occidental margin of Gondwana during the Permian. Stratigraphic data indicate that during the Early Permian, there were at least two differential subsidence and uplift events, one by the end of the Sakmarian–Artinskian and another during the Late Artinskian–Kungurian. [Copyright &y& Elsevier]

Ediacaran volcanic sequences in southernmost Brazil are related to intense post-collisional magmatism of the Brasiliano Orogeny. A portion of this volcanism occurs in the oriental Ramada Plateau located in the center part of the Rio Grande Sul State and is correlated with Hilário and Acampamento Velho formations. The first one is represented dominantly by lava flows and dikes of shoshonitic andesitic composition, besides of volcanogenic sedimentary deposits. The acid rocks of the Acampamento Velho Formation are expressive in the area, comprising high-silica ignimbrites, usually densely welded. Dikes and domes are common too and rhyolitic lava flows occur at the top and intercalated to ignimbrites in the middle of the sequence. The acid rock association has a sodic alkaline affinity. In this unit we mapped a subvolcanic sill of trachyte showing evidence for magma mixing with the rhyolitic magma. It has sodic alkaline affinity, and FeOt/FeO + MgO ratios and agpaitic index lower than those recorded in the rhyolites/ignimbrites. The Acampamento Velho Formation includes in this area, subordinately, basalts as àà flows and dikes intercalated with acid rocks. They have sodic alkaline nature and characteristics of intraplate basic rocks. New zircon U-Pb dating indicates crystallization age of 560 ± 2 Ma in a densely welded ignimbrite, 560 ± 14 Ma for a mafic trachyte and 562 ± 2 Ma for a subvolcanic rhyolite. The sodic alkaline rocks in this region evolved by fractional crystallization processes and magma mixing with major crustal contribution at approximately 560 Ma. The chemical characteristics are similar to those of A-type granites associated with Neoproterozoic post-collision magmatism in the Sul-rio-grandense Shield. [ABSTRACT FROM AUTHOR]

Highlights: [•] We combined U-Pb and Lu-Hf analyses of detrital zircon grains. [•] We analysed paleocurrent data for information about the sedimentary provenance. [•] The U–Pb zircon data present predominantly Paleoproterozoic and Neoproterozoic ages. [•] Lu–Hf model ages exhibit a predominantly Archean and Paleoproterozoic inheritance. [•] The zircon grains display a predominantly negative ɛHf values. [Copyright &y& Elsevier]