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The Borborema Province is a complex neoproterozoic orogen in northeastern Brazil, made of a mosaic of fault-bounded terrains and several metassedimentary sequences. In the present work, new zircon U–Pb provenance data for metasedimentary rocks in the Western Pernambuco-Alagoas Domain, southern part of the Province, are reported. Detrital zircon ages range from Archean to Neoproterozoic. Three samples of the Cabrobo Complex were investigated: (i) sillimanite-kyanite-garnet-biotite schist, which presented mostly Ediacaran and Cryogenian detrital zircon ages (youngest zircon at ca. 554 Ma) indicating erosion of neoproterozoic sources, (ii) garnet-biotite schist, which has a dominant Tonian/Stenian population, a less abundant Cryogenian (youngest zircon age at ca. 643 Ma) as well as Paleoproterozoic and Archean zircon grains, and (iii) tourmaline-muscovite quartzite, which contains detrital zircon varying in age between ca. 2.08 Ga and 1.57 Ga, and an abundant population close to the Meso/Paleoproterozoic boundary, possibly associated with the erosion of rocks formed during the Statherian taphrogenesis, known in the central part of the Sao Francisco Craton as well as in other areas of the Borborema Province. Two samples of the Riacho Seco Metasedimentary Complex were also investigated: (i) a biotite schist with a dominant population presenting ages mostly between 2.3 and 2.7 Ga (youngest zircon age at ca. 2023 Ma) and (ii) a magnetite-biotite-muscovite quartzite, having detrital zircon grains with ages ranging between ca. 1.9 and 2.7 Ga. The sedimentary rocks of the Riacho Seco Complex may have their origin related to the erosion of sources within the Sao Francisco Craton. The data for the Riacho Seco metasedimentary rocks, however, are not conclusive with respect to the depositional age of the original sedimentary rocks. The sequence might represent exposure of an old (Paleoproterozoic) sedimentary pile or, alternatively, it comprises a neoproterozoic passive margin sequence, with the original sediments derived from the erosion of the cratonic areas to the south.

The Portalegre shear zone separates the Rio Piranhas-Serido and the Jaguaribeano geological terranes in the Northern Domain of the Borborema Province. Banded gneisses of the Caico and the Jaguaretama Complexes represent the basements of these terranes. U-Pb analyses yielded ages of 2,193 ± 16 Ma for the Jaguaretama Complex, which is similar to those obtained for the Caico Complex. T DM Sm-Nd ages for these basement complexes showed Neoarchean values (ca. 2.5 Ga), with eNd(t) values close to the CHUR composition. Elongated bodies were found intruding into the rocks of the Jaguaretama Complex. These foliated bodies with elongated phenocrysts are described as augen gneisses of the Serra do Deserto Suite. These gneisses yielded crystallization ages of 1,777 ± 8 Ma, confirming an extensional period during the Statherian, which is well represented in the Jaguaribeano Terrane by A-type plutonic rocks. Augen gneisses with similar textures, the so called Poco da Cruz Suite, are found intruding the Caico Complex in the Rio Piranhas-Serido terrane; however, the ages found throughout the domain are predominantly Rhyacian (ca. 2.2 Ga) and present calc-alkaline affinities. These findings indicate that the augen gneisses, which are widely distributed in these two terranes, have different signatures and are temporally well separated. Furthermore, in agreement with previous geophysical data suggesting a division of terranes marked by the Portalegre Shear Zone, it also demonstrates that even though the Caico and the Jaguaretama Complexes have similar ages, similar structural evolution and metamorphism under similar pressure and temperature conditions, they exhibit marked differences in composition.

The Estreito Anticline is the main structure in the northwestern sector of Passos Nappe, formed in the Late Neoproterozoic during West Gondwana amalgamation. It is characterized by folding of the thrust surface that separates the Passos Nappe from the Canastra Group. The hanging wall of the thrust includes lower units of the Passos Nappe (A, B and C units) and in the core of the fold (footwall) occur metasedimentary rocks of the Canastra Group and Metasiltite Unit. U-Pb dating of detrital zircon grains by LA-ICPMS from metasedimentary units of the Canastra Group shows contribution from a Neoarchean source (ca. 2.54–2.76 Ga) with minor contribution from Rhyacian source ( ∼ 2.10–2.30 Ga) with the youngest grain at 1.57 Ga. Results from the Passos Nappe samples show an important Rhyacian source (2.1 Ga), and a minor cluster with ages ranging from ca. 1.60 to 1.76 Ga (Statherian). Mesoarchean- Statherian terranes of the southwest margin of the Sao Francisco Craton represent the main sources of detrital sediments of the Passos Nappe and Canastra Group of a passive margin developed along the western margin of the continent. The U-Pb ages obtained for metasiltite show a broad distribution, with peaks between ∼ 0.54-0.70 Ga, and minor age groups ranging within 0.82–1.08 Ga, 1.60–1.97 Ga, 2.02–2.22 Ga and ∼ 2.60–2.85 Ga. The younger ages are compatible with the Bambui Group exposed in the Sao Francisco Craton interior. An Ediacaran age for metasiltite in the fold interior suggests termination of deformation within the Passos Nappe at least the Early Cambrian.

After it had been assembled in the very early Orosirian, the western Sao Francisco–Congo Paleocontinent experienced several rifting events since the Statherian (ca. 1750 Ma) to Cryogenian (ca. 700 Ma). Records of anorogenic magmatism and/or associated sedimentation from those events have been found in the Neoproterozoic Aracuai–West Congo orogenic system (AWCO), located between the Sao Francisco (eastern Brazil) and Congo (central Africa) cratons. Based on detailed field studies and data from lithochemistry, zircon and titanite U-Pb dating, whole-rock Nd and Hf-in-zircon isotopic analyses, we characterize a previously poorly described Early Tonian, rift-related, volcano-sedimentary succession in order to decipher the evolution of the AWCO precursor basins. That volcano-sedimentary succession, found in the Capelinha Formation type-area, now assigned to the Lower Macaubas Group, includes quartzites with lenses of ortho-amphibolite (metabasalt) covered by pelitic schists. Zircon grains from ortho-amphibolite samples yielded ages of 957 ± 14 Ma and 576 ± 13 Ma, constraining their magmatic crystallization and regional metamorphism, respectively. These mafic rock show ƐNd(t) from −3.64 to +0.21 and Nd TDM ages from ca. 1.4 to ca. 1.7 Ga. Positive covariation of FeOtot/MgO + FeOtot, TiO2, P2O5, V and Zr, enrichment in light rare earth elements, slightly positive Eu/Eu* anomaly and depletion of high field-strenght elements, suggest tholeiitic protolith related to a continental rifting setting. The metasedimentary rocks show broad spectra of detrital zircon ages from the Early Tonian (ca. 940 Ma) to Paleoarchean, with wide-ranging ƐHf values from predominantly negative (as low as −10.76) to positive (+9.94), evoking well-known sediment sources in the Sao Francisco–Congo Paleocontinent. The youngest age peak (949 ± 12 Ma) constrains a maximum sedimentation age coeval with the basaltic volcanism represented by the ortho-amphibolite. The Capelinha volcano-sedimentary succession nearly correlates in age and origin with other anorogenic units (e.g., Ilheus and Pedro Lessa dike swarms, Salto da Divisa granitic suite, Gangila basaltic and Mayumbian felsic volcanisms) found in a large region covered by the AWCO and neighbouring cratonic region. However, the Capelinha magmatism seems to preceed by some 20–30 m.y. the main peak (930–900 Ma) of this Early Tonian anorogenic magmatism, suggesting a long-lived and complex rift system.

The Paramirim aulacogen occupies the region of the northern Sao Francisco craton that extends from the northern Espinhaco range to a large plateau known as the Chapada Diamantina in the northeastern Brazilian state Bahia. Corresponding to a long-lived and partially inverted rift-sag basin, the aulacogen hosts and exposes the most complete section of the cratonic cover complex accumulated between the Statherian and Edicaran periods. The sedimentary and volcanic rocks of the basin fill successions are grouped into two major lithostratigraphic units, the Espinhaco and Sao Francisco supergroups. Exhibiting remarkable facies differentiation between their occurrences in the northern Espinhaco range, on the west, and Chapada Diamantina, on the east, these units are associated with Statherian granitic rocks, as well as Statherian, Calymmian and Tonian mafic dykes and sills. The Espinhaco Supergroup comprises five unconformity bounded sequences, which record alternating mechanical and flexural subsidence pulses that took place between 1775 and 900 Ma. Frankly dominated by quartz-rich sandstones, deposited in alluvial, aeolian and shallow marine systems, the supergroup reflects continuous recycling of sediments in the large depocenters of the aulacogen. The Neoproterozoic Sao Francisco Supergroup is composed of three distinct sequences, deposited between 900 and 500 Ma, among them the glaciogenic Bebedouro Formation and the shallow marine carbonates and pelites of the Salitre Formation. The overall geologic architecture of the aulacogen is dominated by structures generated during its contractional inversion in the Edicaran/Cambrian boundary. The regional structure of the aulacogen corresponds to a NNW-trending basement cored uplift, flanked on both sides by systems of reverse faults, thrusts, folds, and strike-slip shear zones. Structures related to the basin generation processes are preserved only in a small area of the central segment of the aulacogen. The dominant NNW-oriented fabric elements interact or are overprinted by E–W-trending structures in the northern and southern ends of the aulacogen. These structures represent the Neoproterozoic Brasiliano orogenic fronts that propagated from the marginal belts toward the craton interior.

International audience; The Buracão area, Central Brazil, comprises a group of structurally–controlled vein–type gold prospects, hosted in the metasedimentary Traíras Fm. of the Araí Group. This group records all tectonic stages of the Statherian taphrogenesis in Central Brazil and represents part of the Brasília Fold Belt (BFB) developed during the Neoproterozoic Brasiliano Orogeny. Three lithostratigraphic units were identified at the study area: two phyllitic and one composed of intercalation of quartzite and carbonaceous/sericite phyllites that hosted the Au mineralized vein systems. These units were metamorphosed to the biotite zone, greenschist facies. The high–grade mineralization (up to 31 g/t) occurs as subvertical zoned or massive veins with quartz, white mica, Fe–sulfides and Fe–oxides oriented in four main directions (i.e. N50°E; N°20E; N–S and E–W). Two deformational phases, each subdivided in two stages (D1a, D1b, D2a and D2b) were recognized in the study area. These deformational phases comprise different sets of structures, such as foliations, folds, faults, fractures and veins that represent regional deformational events on subordinated scale. The D1a and D1b stages represent the regional N–S trending thrust fronts and propagation folding developed during the evolution of W–E shortening, respectively. The D2a and D2b were correlated to the development and reactivation of regional–scale N– and NE–trending transpressive shear systems at different crustal levels, respectively. The gold–bearing quartz veins were developed during D2a stage as a complex shear fracture set according to a Riedel system, representing subordinated structures of the regional transpressive system. The structurally–controlled gold occurrences of the Buracão area is an example of orogenic vein–type gold mineralization developed during the Brasiliano–Pan African Orogeny at the BFB in Central Brazil. Our work suggests that this poorly studied part of BFB has good potential for additional high-grade orogenic gold deposits.

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

The Paleoproterozoic (Statherian) Thelon Formation consists of unmetamorphosed sandstone and conglomerate that was deposited in the Thelon Basin, a continental basin in northern Canada. This study presents the first detailed sedimentological and sequence stratigraphic analysis of the expansive and under-studied western Thelon Basin, and its relation to uranium mineralizing processes in the vicinity of the Boomerang Lake unconformity-related U prospect. Four lithofacies comprise the Thelon Formation in the western Thelon Basin, consisting of breccia, conglomerate, sandstone, and minor mudstone. These are grouped into four facies associations that represent deposition in alluvial fans and braided fluvial streams. Three stratigraphic sequences were identified based on the recognition of widespread surfaces that mark significant periods of subaerial exposure or changes in depositional environment. These unconformity-bounded sequences are composite in nature and can be subdivided into six high-frequency sequences (HFS). Low-accommodation and high-accommodation systems tracts are delineated, instead of the traditional systems tracts that are linked to changes in relative sea level, as no marine deposits are recognized in the Thelon Formation. Two significant strataform paleohydrogeological units were distinguished in the Thelon Formation, based on the relative timing of key diagenetic events such as compaction, grain dissolution, and cementation. Diagenetic aquicludes became isolated from basinal fluid flow due to stylolite-catalyzed early diagenetic quartz cementation, and occlusion of secondary intergranular macroporosity by kaolinite and muscovite, and minor dickite during later peak diagenesis. Diagenetic aquifers conducted U-bearing basinal fluids throughout diagenesis and are marked by an abundance of peak diagenetic dickite. Sequence stratigraphic correlation indicates that diagenetic aquicludes, which were not effective at conducting U-bearing basinal fluids, overlie the unconformity at the Boomerang Lake prospect and extend along the entire strike length of a related exploration trend. In contrast, thick diagenetic aquifers lie approximately 10 km to the north of the Boomerang Lake prospect along a different exploration trend. The western and eastern portions of the Thelon Basin experienced depositional environments and diagenetic conditions distinct from one another, suggesting that they were separate sub-basins. The western Thelon Basin contains fewer of the well-cemented facies that compartmentalized basinal fluid flow than the eastern Thelon Basin, and contains a kaolin-dominated diagenetic mineral assemblage rather than a muscovite-dominated assemblage that is common in the eastern Thelon Basin. In these regards, the western Thelon Basin evolved more similarly to the eastern portion of the Athabasca Basin, where thick, regional, kaolin-rich diagenetic aquifers were fluid conduits for the movement of the U-rich fluids that formed high-grade unconformity-related U deposits.

The Paleoproterozoic (Statherian) Thelon Basin is located in the Churchill Province of the Canadian Shield, formed following the Trans-Hudson Orogeny. Basin formation followed an interval of felsic volcanism and weathering of underlying bedrock. The diagenetic evolution of the Thelon lasted about one billion years and was punctuated by fluid movement influenced by tectonic events. Early quartz cements formed in well-sorted, quartz-rich facies during diagenetic stage 1; fluids in which these overgrowths formed had δ18O values near 0‰ (Vienna Standard Mean Ocean Water). Uranium-rich apatite cement (P1) also formed during diagenetic stage 1 indicating that oxygenated, uranium-bearing pore water was present in the basin early in its diagenetic history. Syntaxial quartz cement (Q1) formed in water with δ18O from −4 to −0.8‰ in diagenetic stage 2. Diagenetic stage 3 occurred when the Thelon Formation was at ca. 5 km depth, and was marked by extensive illitization, alteration of detrital grains, and uranium mineralization. Basin-wide, illite crystallized at ∼200 °C by fluids with δ18O values of 5–9‰ and δD values of −60 to −31‰, consistent with evolved basinal brines. Tectonism caused by the accretion of Nena at ca. 1600 Ma may have provided the mechanism for brine movement during deep burial. Diagenetic stage 4 is associated with fracturing and emplacement of mafic dikes at ca. 1300 Ma, quartz cement (Q3) in fractures and vugs, further illitization, and recrystallization of uraninite (U2). Q3 cements have fluid inclusions that suggest variable salinities, δ18O values of 1.5–9‰, and δD values of −97 to −83‰ for stage 4 brines. K-feldspar and Mg-chlorite formed during diagenetic stage 5 at ca. 1000 Ma in upper stratigraphic sequences, and in the west. These phases precipitated from low-temperature, isotopically distinct fluids. Their distribution indicates that the basin hydrostratigraphy remained partitioned for >600 Ma.

New data on the Fennoscandian Shield and the Baltic area suggest a need for reinterpretation of the stratigraphy of Estonian Precambrian rock complexes. The rocks of the Tallinn Zone formed in the framework of the Fennian orogeny at the margin of the Bergslagen microcontinent 1.90-1.88 Ga ago. The precise age of the Alutaguse Zone is not known. It may have formed either during the 1.93-1.91 Ga Lapland-Savo orogeny or as a rifted eastern part of the Tallinn Zone in the Fennian orogeny. The granulites of western and southern Estonia belong to the volcanic arcs inside the 1.84-1.80 Ga Svecobaltic orogenic belt and show peak metamorphic conditions of 1.78 Ga. Small shoshonitic plutons formed 1.83-1.63 Ga, the small granitic plutons of the Wiborg Rapakivi Subprovince 1.67-1.62 Ga, and the Riga pluton 1.59-1.54 Ga ago.

A biostratigraphic model of the temporal distribution of distinctive Proterozoic microfossil assemblages is suggested, based on studies of upper Precambrian chert-embedded and compression-preserved organic-walled microfossils from the reference sections of Eurasia, North America and Australia. Microfossils from 2.0 to 0.542 Ga can be divided into seven successive informal global units which can be compared to standard units of the International and Russian time scales. Each unit is characterized by a particular association of taxa, typified by the fossil assemblage that gives it its name. These form broad biostratigraphic units comparable to assemblage zones of Phanerozoic successions; in general (but with minor differences) they correspond to chronostratigraphic units accepted by the Internal Commission on Stratigraphy. The units are: (1) Labradorian, the upper part of the Paleoproterozoic (Orosirian and Statherian), 2.0–1.65 Ga; (2) Anabarian, lower Mesoproterozoic (Calymmian–Ectasian)/Lower Riphean–lower Middle Riphean, 1.65–1.2 Ga; (3) Turukhanian, upper Mesoproterozoic (Stenian)/upper Middle Riphean, 1.2–1.03 Ga; (4) Uchuromayan, lower Neoproterozoic (late Stenian–Tonian)/lower Upper Riphean, 1.03–0.85 Ga; (5) Yuzhnouralian, upper Neoproterozoic (Cryogenian)/upper Upper Riphean, 0.85–0.63 Ga; (6) Amadeusian, lower Ediacaran/lower Vendian, 0.63–0.55 Ga; (7) Belomorian, upper Ediacaran/upper Vendian, 0.55–0.542 Ga.

The São Francisco Craton, in the central-eastern region of Brazil, is a cratonic fragment stabilized after the Rhyacian tectono-metamorphic event (2.25–2.05 Ga). Volcanic and sedimentary rocks of the Espinhac¸ o (Paleo- to Mesoproterozoic) and São Francisco (Neoproterozoic) basins crop out on this craton. In the northern sector of the craton, the Espinhac¸ o basin crops out in two domains: the Northern Espinhac¸ o Range and the Chapada Diamantina, that are separated by the Paramirim Corridor, a Brasiliano/Pan African (650–500 Ma) deformation zone, which crosses the craton in NNW–SSE direction. The stratigraphic framework of the Northern Espinhac¸ o is characterized by eight synthems that comprise units bound by unconformities, or stratigraphic discontinuities with regional extent over the Espinhac¸ o basin. These synthems are: Algodão, São Simão, Sapiranga, Pajeú and Bom Retiro (lower interval), São Marcos and Sítio Novo (intermediate interval) and Santo Onofre (upper interval). For each interval the sedimentary processes, the depositional systems, the filling style of the basin and the tectonic settings were evaluated, based mainly on the facies association characteristics and their lateral/vertical changes. Zircon U–Pb SHRIMP and basin analysis studies carried out along the eastern border of the Northern Espinhac¸ o Range provide a few new or improved anchors upon which the tectonic evolution of the Espinhaco basin can be pinned. We identified Statherian rifting in the São Simão Synthem, by dating volcanic rocks at 1.73 Ga. This is followed by a previously unknown, minor intracratonic rift phase within the São Francisco Craton, dated at circa 1.57 Ga through a volcanic unit within the Pajeú Synthem. The entire lower interval is cut by mafic intrusive dykes of which we dated one at 850 Ma, which we correlate with a Tonian rifting phase affecting the eastern part of the São Francisco craton, and related to the break-up of the Rodinia Supercontinent. Our data showthat the development of the Northern Espinhac¸ o Range spans a large time interval, and comprises a discontinuous series of tectonic events that gave rise to the formation of the various synthems and are punctuated by the extrusion of minor volcanic units and emplacement of dykes within the eastern part of the São Francisco Craton.

Deposition of Palaeo- Mesoproterozoic sedimentary rocks on the Sao Francisco- Congo craton started during Statherian taphrogenesis (1.8- 1.75 Ga), as verified by ages of c. 1.7 Ga determined for volcanic rocks of the lower part of the Espinhaco Supergroup in the states of Minas Gerais and Bahia (Brazil). These basins contain volcanic rocks and conglomerates alternating with sandstones, argillites and dolomites, deposited in continental, transitional and marine environments. The rocks in the westernmost sector of the Congo Craton (Central Africa) compose the Chela Group, comprising sandstones, argillites and dolomites. In the eastern- most region of the Congo Craton the Kibaran, Akanyaru, Kagera and Muva supergroups occur: the first three in the Kibaran Belt and the last in the Irumide Belt and on the Bangweulu Block. They consist predominantly of pelites and schists, sandstones and, in lesser proportion, conglomerates, deposited in shallow marine, fluvial and lacustrine environments. Their sedimentation ages are constrained through ages on felsic tuff layers as follows: Chela Group 1790+ 17 Ma, Kagera Supergroup 1780 + 9 Ma, and Muva Supergroup 1879+ 13 Ma. These data show that broadly coeval and sedimentologically similar epi-continental sedimentary basins occurred on the Sao Francisco and Congo cratons, suggesting the possible existence of a long-lived wide epi-continental sea covering large areas of these cratons during Statherian times.

Statherian siliciclastic sedimentary rocks in the southern Lake Superior region are key to understanding the evolution and stabilization of Paleoproterozoic crust in the midcontinent. Deposited during an important period of significant crustal growth, controversy exists regarding the conditions of sandstone deposition and the relations between magmatism and sedimentation. In central Wisconsin, the Hamilton Mounds inlier, although restricted in areal extent, is significant in that it reveals the existence of two separate Statherian units: an 1800–1760 Ma immature meta-arkose and a post-1760 Ma Baraboo Interval supermature quartzite. The meta-arkose is crosscut by 1762 Ma granite and contains abundant Penokean age detrital monazite grains. The younger quartzite contains detrital monazite as young as 1750 Ma and was deposited unconformably upon these older units. All units experienced 1630 Ma low-grade recrystallization and isotopic disturbance associated with the Mazatzal Orogeny. In addition, the supermature quartzite experienced K-metasomatism and brecciation at 1470 Ma, ascribed to regional-scale hydrothermal alteration related to the influence of the nearby 1470 Ma Wolf River batholith. Collectively, these data suggest an early Statherian episode of arkosic deposition and magmatism during Yavapai orogenesis, followed by a longer interval of deposition of supermature quartz arenite associated with crustal stabilization. The existence of two separate Statherian units reconciles apparent conflicts in depositional models and provides a greater understanding of the Paleoproterozoic evolution of the midcontinent.

Recent geological, geochronological and isotopic studies allow the identification of four important crustal segments in the basement of the Sao Francisco Craton in Bahia. The oldest is the Gaviao block in the WSW part of the studied area, and comprises granitic, granodioritic and migmatitic continental crust including remnants of 3.4 Ga TTGs which are amongst the oldest rocks in South America, and are associated with Archean greenstone belts. The youngest segment is exposed in the Itabuna–Salvador–Curaca belt which extends from SE Bahia along the Atlantic coast to Salvador, then northwards into NE Bahia. It is mainly composed of a low-K calc-alkaline plutonic suite, and also contains strips of intercalated metasediments and ocean floor/back-arc basin gabbro and basalt. In the SSW part of the area the Jequie block comprises granulitic migmatites with inclusions of supracrustal rocks, intruded by many charnockite plutons. In the NE, the Serrinha block is composed of orthogneisses and migmatites which form the basement for Paleoproterozoic greenstone belts. During the Paleoproterozoic Transamazonian Cycle, these four crustal segments collided, resulting in the formation of an important mountain belt. The regional metamorphism, resulting from the crustal thickening associated with the collision, occurred at around 2.0 Ga. Major mineralizations were formed during the evolution of the four Archean blocks, and also during and after the Paleoproterozoic collision.

Four events have been identified in the Tagragra d’Akka and Tafeltast–Kerdous inliers: (i) a middle Palaeoproterozoic (Orosirian, ca. 2.047 Ga) event corresponding to the emplacement of calc-alkaline and peraluminous granites containing older inherited zircon (2.07–2.15 Ga), (ii) an upper Palaeoproterozoic (Statherian) event corresponding to the emplacement of pegmatites and porphyritic microgranites (ca. 1.76 Ga), intimately associated with numerous mafic dikes assumed to be, at least partly, of the same age, (iii) an upper Neoproterozoic event corresponding to dacite dikes (600 ± 5 Ma), (iv) a Variscan (301 ± 7 Ma) hydrothermal event corresponding to the crystallization of muscovites related to Au-quartz veins. A polycyclic magmatism (Eburnian-Birimian, Pan-African and Variscan) is now evidenced in these two inliers of the western Anti-Atlas. The Pan-African orogeny is very homogeneous all along the Anti-Atlas during Neoproterozoic time. No inherited Archaean component has been found in zircons from granites or dikes. It appears that the northern border of the West African craton is an important juvenile cratonic limit submitted to periodical continental growth since 2.05 Ga at least.

The Late Paleoproterozoic–Neoproterozoic (1800–541 Ma) sedimentation, volcanism and igneous events, and rifting in the North China Craton can be categorized into different stages: (1) Stage 1 (1800–1730 Ma, Early Statherian): It is represented by the Taihang (1780–1770 Ma) and Miyun (~1730 Ma) dyke swarms, the Xiong’er volcanic province (~1780 Ma), and a little clastic sedimentation related to the evolution of the Xiong’er rift. (2) Stage 2 (1730–1600 Ma, Late Statherian): It is represented by the Damiao–Shachang anorthosite–rapakivi granite–dyke complexes (1710–1680 Ma), the Laiwu (~1680 Ma) and Taishan (~1620 Ma) dyke swarms, the Dahongyu lavas (~1620 Ma), and some clastic rocks and a little limestone related to the Yan-Liao rift, the Xiong’er rift, and probably the Bayan Obo rift. (3) Stage 3 (1600–1400 Ma, Calymmian/Jixian): It is represented by the dolomite-dominated strata in the Yan-Liao rift, the Xiong’er rift, and probably the Bayan Obo rift, with little volcanism and magmatism. (4) Stage 4 (1400–1200 Ma, Ectasian): It is represented by the ~1320 Ma dykes–sills–granites and ~1230 Ma Licheng dyke swarm, and the sedimentation dominated by clastic rocks with a little marlstone and limestone possibly limited in the Yan-Liao rift. (5) Stage 5 (1200–1000 Ma, Stenian): It is unclear whether there were any magmatism and deposition during this period. (6) Stage 6 (1000–800 Ma, Tonian): It is represented by the Dashigou (~925 Ma) and Qianlishan (~810 Ma) dyke swarms, the Sariwon (Dalian–Chulan–Zenghekou) sills (925–890 Ma), and clastic rocks/carbonate-dominated sediments within the Xuhuai rift. (7) Stage 7 (800–541 Ma, Cryogenian–Ediacaran): It is uncertain yet if there were any igneous events or sedimentation during this period, although some strata in Henan province are candidates. Multiple stages of rifting indicate a prolonged and stepwise rifting lasting for 1000 Ma, with the center of the rifts shifted from the south (the Xiong’er rift, 1780–1730 Ma) to the north (the Yan-Liao rift, 1730–1200 Ma) and to the southeast (the Xuhuai rift, 1000–800 Ma) of the North China Craton.

The itabirite-bearing metasedimentary sequence from Morro Escuro Ridge comprises the basal units of the Espinhaco Supergroup and makes up a small tectonic inlier developed during one of the Brasiliano orogenic events (800-500 Ma), amongst horses of the Archean TTG gneisses, including sheared granites of the anorogenic Borrachudos Suite (∼1700 Ma). The metasedimentary rocks are comprised of low-to intermediate-amphibolite facies schists, quartzites, conglomerates and banded iron formation (itabirite) correlatable with the sequences of the Serro Group, which underlies the metasedimentary rocks of the Espinhaco Supergroup in the Serra da Serpentina Ridge. A maximum Statherian deposition age (1668 Ma) was established using SHRIMP U–Pb isotopic constraints on zircon grains from conglomerate and quartzite units overlying the itabirite. The itabirite is predominantly hematitic and its geochemical characteristics are typical of a Lake Superior-type BIF deposited in a platformal, suboxic to anoxic environment distant from Fe-bearing hydrothermal vents. Close to the contact zone with amphibolites of the Early Neoproterozoic Pedro Lessa mafic suite, an increase of the magnetite content and crystallization of metasomatic Mg-hornblende and Ce-allanite can be observed. These mineralogical changes developed preferentially along the igneous contact zone but are probably co-genetic with the formation of alteration haloes in zircon grains during the Neoproterozoic Brasiliano orogeny (506 ± 6 Ma).

O presente trabalho tem como principal objetivo o estudo geocronológico de rochas granitóides alcalinas deformadas que ocorrem nos núcleos de embasamento Betara e Tigre, localizados em meio às seqüências metavulcanossedimentares da Faixa Apiaí. Apresentam-se em formas elipsoidais, orientadas NE-SW e seu contexto regional é caracterizado pela grande complexidade geológica, resultante da sobreposição de eventos tectônicos ocorridos durante sua história. Predominam sienogranitos protomiloníticos, miloníticos e ultramiloníticos, com características litogeoquímicas de granitos tipo 'A' (anorogênicos). Os resultados obtidos pelo método U-Pb (zircão) indicam idades Paleoproterozóicas de 1748 ± 5.4 Ma no Núcleo Betara, e 1772 ± 9.5 Ma no Núcleo do Tigre. Representam um importante marco na região, relacionado à Tafrogênese Estateriana. Idades entre 1600 - 1800 Ma, associadas a processos predominantemente extensionais, são reconhecidas principalmente na porção centro - oriental do continente Sul-Americano e devem representar importantes cicatrizes associadas à ruptura do Supercontinente Atlântica do Paleoproterozóico.

A reassessment of the recent palaeomagnetic data on Proterozoic mafic dykes in the Bundelkhand and Bastar cratons permits a robust estimate of 1.466 Ga (Calymmian) pole (λ = 49.4°N; Φ; = 132.9°E; A 95 = 6.6°; N = 11) for the Indian shield. The pole corresponds to a mean direction of D = 40.5°; I = 56.4° (α 95 = 5.5°; K = 70). The Indian pole at c. 1.65 Ga (Statherian) is suggested to have been situated at λ = 59.6°N and Φ = 47.9°E (A 95 = 8.1°; N = 6); it is estimated from a mean direction of D = 336.4°; I = 66.0°N (α 95 = 5.3°; K = 159). The 1.466-Ga-old dykes are confined to the Eastern Ghats orogenic front in the easternmost part of the Bastar craton. Geochemically, the shoshonitic/high-K calc-alkaline affinity of these dykes is uniquely distinct from the tholeiitic composition found in Mesoor Palaeoproterozoic dykes in other parts of the Indian shield. Testing the existing pre-Rodinia Mesoproterozoic tectonic reconstructions negates the Columbia reconstructions in which the Indian shield is shown in juxtaposition with North China/Laurentia. On the other hand, palaeomagnetic and geological data suggest that the linkages between the Indian shield and Western Australia proposed earlier for the Palaeoproterozoic appear to persist during the Mesoproterozoic as well. The linkages may be further extended into Baltica.

As rochas metassedimentares, aflorantes no entorno da cidade de Santa Maria de Itabira (MG), compreendem quartzitos orosirianos, informalmente denominados de Unidade Quartzítica Serra da Pedra Branca, além da sequência estateriana portadora de formação ferrífera bandada típica da Borda Leste da Serra do Espinhaço Meridional. Esse conjunto constitui um bloco alóctone delimitado por zonas de cisalhamento, entre fatias de rochas granito-gnáissicas arqueanas do Complexo Dona Rita e do Granito da Suíte Borrachudos, com idade de 1729 ± 12 Ma. Rochas intrusivas da Suíte neoproterozoica Pedro Lessa e diques de diabásio mesozoicos cortam todo o conjunto. Em todas as unidades foram reconhecidas três famílias de dobras geradas durante a edificação do Orógeno Aracuaí: D1, D2 e D3, que, em conjunto com as zonas de cisalhamento observadas na área, permitiram um esboço de um modelo da evolução tectônica da região, compreendendo três fases, F1, F2 e F2'. A sequência evolutiva aliada ao arcabouço cinemático e geométrico da região leva à interpretação de que a região está inserida num sistema regional transpressivo. O esforço tectônico principal do cinturão de dobramento é transferido na forma de falhas transcorrentes de direção oblíqua à tensão principal.

An integrated approach of stratigraphic analysis and U–Pb age dating reveals some information on the tectono-sedimentary evolution of the Statherian cover of the Sao Francisco craton in the so-called Espinhaco basin (Atlantic shield in eastern Brazil). Here, continental sedimentation patterns, such as alluvial fan, braided-plain and lacustrine facies associations, with associated volcanic rocks are documented in two superposed basin fill-successions, which are defined as the Algodao and Sapiranga Synthems and grouped in the Botupora Supersynthem. Both studied units consist mainly of conglomerates and cross-bedded sandstones and minor amounts of mudstones, sedimentary breccias, volcanic lava beds and volcaniclastic rocks, which were deposited in a rift basin – the Botupora rift – during two syn-rifting phases. The Algodao Synthem represents the first rifting phase. The basal synsedimentary conglomerates of this unit were deposited mainly by subaerial debris flows, most likely along and near a rift border fault. The framework of this rock consists of only crystalline rock clasts from the basement and no fragments of volcanic rocks. Detrital zircon grains that were extracted from this facies show ages older than 2.05 Ga. The remainder of the section is dominated by fluvial sandy lithofacies with minor conglomerate lenses and sandstone–mudstone heterolithic lithofacies, which represent distal, waning-flood deposits in a lacustrine environment. The upper section also contains hummocky cross-stratified sandstone lithofacies, which are related to a storm-influenced deposition. On top of the Algodao succession, the volcanic rocks were dated at 1775 ± 7 Ma, which was interpreted as the near final age of the first rift-phase. Representing the second rift-phase, the Sapiranga Synthem shows similar sedimentation patterns to the Algodao Synthem. The Sapiranga Synthem rests directly on the volcanic rocks of the Algodao Synthem, and its basal conglomerates (which are most likely also related to a master fault) contain voluminous clasts of volcanic rocks, sandstones and crystalline rocks. The detrital zircon grains that were extracted from this facies show ages of 1741 ± 14 and 1766 Ma as well older than 2.05 Ga. The volcanic rocks on the upper succession of the Sapiranga Synthem record ages of 1740 ± 10 Ma, which finalized the Botupora rift evolution. A preliminary geochemical study of volcanic rocks from the Botupora Supersynthem showed that these rocks are alkaline rocks with high K 2 O/Na 2 O ratios, which belong to an ultrapotassic suite. The low concentrations of MgO wt.% suggest a felsic ultrapotassic character. The Botupora Supersynthem is unconformably covered by a volcano-sedimentary rift-succession of EoCalymmian age — the Pajeu Synthem, which represents the second rifting stage of the Espinhaco basin. Several Statherian-related volcano-sedimentary sequences and anorogenic granitoids occur dispersed in the Sao Francisco block, which requires a regional geologic model to explain the extensional and magmatism process during this time. We used the last Columbia paleocontinental reconstruction to constrain these processes by relating them to far-field continental extensional and magmatic record as part of a silicic LIP, which was triggered by the convection-driven tectonic-plate motion on the western border of the Atlantica block inside of the Columbia supercontinent.

Consoante os mais recentes dados geológicos e geocronológicos do embasamento da Plataforma Sul-Americana, a colagem orogênica Brasiliana se deu em quatro pulsos distintos: a) eocriogeniana (ca. 800 - 70Ma); b) tardicriogeniana-eoediacarana (ca. 660 - 610 Ma); c) eo-médio ediacarana (ca. 590 - 560 Ma) e d) tardicambriana (520 - 500 Ma). Os três primeiros pulsos da colagem apresentam boa representatividade na maioria das províncias estruturais do Neoproterozóico, em todo Gondwana Ocidental. O último e mais jovem pulso orogênico constitui casos específicos locais registrados na Argentina (Orogenia Pampeana) e no Brasil, no leste do Rio de Janeiro (Orogenia Búzios). No cômputo geral, o intervalo de tempo (ca. 750 - 500 Ma) é comparável com o que é conhecido sobre o conjunto mais oriental (Árabe-Nubiano, Moçambique, Kuunga) e norte de Gondwana (Cadomiano), nos vários segmentos derivados deste supercontinente. No detalhe são encontradas diferenças importantes de eventos e idades entre os vários segmentos de Gondwana, o que é esperável diante da magnitude territorial da aglutinação do supercontinente e da natural diversidade dos cenários paleogeográficos e tectônicos. Em Gondwana Ocidental observa-se peculiaridade interessante: sotoposta aos edifícios orogênicos do Brasiliano e retrabalhada fortemente nos quatro pulsos principais, é encontrada série muito diversificada de terrenos do Toniano, em termos de rochas e proveniência tectônica. Estes terrenos (1000 - 900 Ma) e sua relação tanto com os processos da fusão de Rodinia como com os de aglutinação de Gondwana constituem um problema em aberto. Há algumas outras indicações, ainda muito pouco documentadas, da presença de tais terrenos em Gondwana Oriental. Analysis of recent geological and geochronological data from the basement of the South American platform indicates that the Brasiliano orogenic collage took place in four distinct pulses: a) Early Cryogenian (ca. 800 - 740Ma); b) Late Cryogenian-Early Ediacaran (ca. 660 - 610 Ma); c) Early-Middle Ediacaran (c. 590 - 560 Ma); and d) Late Cambrian (520 - 500 Ma). The first three pulses are well represented in most Neoproterozoic structural provinces in West Gondwana. The youngest orogenic phase/pulse, however, is only seen in Argentina (Pampean Orogeny) and Brazil, in eastern Rio de Janeiro State (Búzios Orogeny). The period between ca. 750 and 500 Ma is comparable to that reported for the amalgamation of various continental fragments in East (Arabian-Nubian, Mozambique, Kuunga) and North Gondwana (Cadomian). However, important differences in the nature and ages of events are recognized, which can be expected in view of the magnitude of Gondwana agglutination and the diversity of paleogeographic and tectonic scenarios. West Gondwana shows an interesting peculiarity: lithologically and tectonically diversified Tonian terranes underlie Brasiliano orogenic buildups. They were strongly reworked during most of the orogenic pulses. The Tonian terranes (1000 - 900 Ma) and their relation with Rodinia or with the processes of Gondwana fusion remains an open question. Indications of their presence in East Gondwana are still poorly documented.

The basement of the South American platform consists of two large distinct geologic domains: the Amazonian or pre-Tonian (N-NW portions) and the “Brasiliano” (or “Extra-Amazonian”, the central and eastern portions). These domains are separated by a set of two long linear fault zones, the Transbrasiliano lineament (NNE-SSW) to the south and the Araguaia lineament (NS) to the north. The Amazonian domain consists of large Archaean nuclei surrounded by Paleoproterozoic and Mesoproterozoic mobile belts of all of the systems of these eras. These mobile belts strike NNW-SSE, with indications of crustal growth from NNE to SSW, as recorded by the belts themselves as well as by subsequent anorogenic plutonism and cratonic covers. The western portion of the Amazonian domain and the basement inliers of the Andean orogenic belt present important affinities in terms of composition and crustal evolution. Most of the general framework and most of the Amazonian domain are akin to those recorded to the north in the Laurentian continent. The Brasiliano domain records a complex orogenic collage, representing branching systems of orogens, dated from tectonic cycles of the Tonian up to the Early Ordovician. This domain includes several minor cratonic nuclei formed of Archaean and Paleoproterozoic rock units, amalgamated by fold belts generated during (at least) five Wilsonian orogenic cycles. Crustal growth follows different centripetal processes because the vergences of the belts are towards the small cratonic nuclei. Aside from the cratons, several other pre-Neoproterozoic terranes were also amalgamated, and submitted to strong tectonic-thermal reactivations. Mesoproterozoic mobile belts have not been detected yet. The few geological records known from the Statherian and from the Mesoproterozoic were reset during the Neoproterozoic tectonism. At the end of the Neoproterozic orogenic cycles, a striking post-collisional scenario led by extrusional tectonics was in place. These processes reshaped the final structural framework of the Brasiliano provinces, distinguishing them from the Amazonian domain. The Brasiliano domain displays many compositional, structural and crustal evolution affinities with those of the westernmost part of the African continent. The more than 4500 km long NNE-SSW Transbrasiliano lineament is the main record of the extrusional processes (from ca. 540 Ma onwards) and displays evidence of seismic and faulting activities along the Phanerozoic. The Araguaia lineament is the final record of orogeny and collision, as the result of interactions between the Amazonian craton/plate and the backlands situated to the east in Neoproterozoic times (Colmeia-Xambioa, Paranaiba and Granja terranes are good candidates).

The Espinhaço Supergroup cropping out between the cities of Macaúbas and Canatiba, in the northernEspinhaço range, Bahia, is composed by the Pajeú Group (metarhythmites and intermediate to acidmetavolcanics), the Bom Retiro Formation (mature quartzites with metric to decametric cross-bedding), theSão Marcos Group (quartzites with wavy stratification and wave-related cross-bedding, intercalated with micaschists)and the Sítio Novo Group (cross-bedded, conglomeratic and massive quartzites, metarhythmites andmetapelites). The bedrock (gneisses and schists) is tectonically emplaced over the Espinhaço Supergroup inthe eastern portion of the area, and the Espinhaço Supergroup is unconformably covered by the Santo OnofreGroup (graphite-phyllites and metarhythmites) in the western portion of the area. This whole stratigraphicpackage is inverted, allowing, together with relations between bedding and schistosity, to define a largeinverted limb of an assymmetric fold with axis NNW-SSE.In the Veredas Formation, intermediate portion of the Sítio Novo Group, occurs a bed of approximately10 m of deep blue dumortierite-quartzites, used as ornamental rocks. Samples of these rocks have beenanalysed using optic, cathodoluminescence and electronic microscopic techniques, revealing its mineralogicand micromorphologic features.Comparing the stratigraphic and sedimentologic features of the studied area with other outcropping areas ofthe Espinhaço Supergroup, it can be concluded that it has evolved through three sedimentary megacycles,represented on each of the portions of the Espinhaço Range and Diamantina Plateau in the eastern regionof Brazil. The first megacycle involves syn-rift sedimentation, starting at about 1,75 Ga (Statherian Period).The second megacycle involves fundamentally eolian sedimentation. The third megacycle involves mainlyshallow marine to transitional sedimentation, with important tectonic reativation in the northern sector ofthe basin. All megacycles evolded in intracratonic environment..

QUANTOS EVENTOS DE RIFTEAMENTO PRECEDERAM O DESENVOLVIMENTO DO ORÓGENO ARAÇUAÍ-CONGO OCIDENTAL? A edificação do Orógeno Araçuaí-Congo Ocidental teve início por volta de 630 Ma, como indicam as idades U-Pb mais antigas até agora obtidas de rochas do seu arco magmático. Esta orogenia foi precedida de, pelo menos, seis eventos de rifteamento e/ou magmatismo anorogênico que afetaram a região ocupada pelo Orógeno Araçuaí-Congo Ocidental, bem como o domínio cratônico São Francisco-Congo a ele adjacente. São eles os eventos E1 (Estateriano, 1,77-1,7 Ga), E2 (Calimiano, 1,57-1,5 Ga), E3 (Esteniano, 1,18 - ? Ga), E4 (no limite Esteaniano-Toniano, ca. 1 Ga), E5 (Toniano, 930-850 Ma) e E6 (Criogeniano, 750-670 Ma). O evento E1, chamado de Tafrogênese Estateriana, teve lugar entre 1,77 e 1,70 Ga e tem como registros mais importantes a deposição rifte das unidades sedimentares e vulcânicas da base do Supergrupo Espinhaço, bem como o alojamento dos plutons anorogênicos das suítes Borrachudos e Lagoa Real. O evento E1 é sucedido por uma nova fase de distensão durante o período Calimiano, em torno de 1,57 Ga, que é representada no Espinhaço Setentrional e Chapada Diamantina por rochas sedimentares e vulcânicas da porção média do Supergrupo Espinhaço. Manifestações do evento E3 (Esteniano) tiveram início em torno de 1,18 Ga com a deposição da Formação Sopa-Brumadinho (Supergrupo Espinhaço), exposta na Faixa Araçuaí. Os três primeiros eventos (E1, E2 e E3) parecem não ter ocorrido na Faixa Congo Ocidental. Nesta faixa, os granitos Noqui (999 ± 7 Ma) e rochas vulcânicas associadas representam um magmatismo anorogênico do limite Esteniano-Toniano, registrando um evento provavelmente local (E4), mas que pode ser correlacionável aos diques máficos de idade similar que ocorrem no sul da Bahia, no extremo oriental do Cráton São Francisco. As espessas sucessões de rochas vulcânicas bimodais dos grupos Zadiniano e Mayumbiano (930-910 Ma) constituem os principais registros do evento E5 na Faixa Congo-Ocidental. O magmatismo anorogênico representado pela Suíte Salto da Divisa e enxames de diques máficos tonianos (e.g., Pedro Lessa e Espinhaço Setentrional), assim como, muito provavelmente, os depósitos pré-glaciais da bacia Macaúbas são manifestações de E5, em terrenos do Orógeno Araçuaí e Cráton do São Francisco. O evento criogeniano, E6, é evidenciado pela Província Alcalina do Sul da Bahia entre 735 e 675 Ma, e, muito provavelmente, pelas formações diamictíticas do Grupo Macaúbas e unidades correlativas na Faixa Congo Ocidental, e pelo vulcanismo félsico La Louila (≤ 713 Ma) do sudoeste do Gabão. O evento E6 evoluiu para espalhamento oceânico no setor centro-sul da Bacia Macaúbas, mas este processo não afetou a parte norte desta bacia e, por isto, deixou íntegra a ligação continental (a ponte Bahia-Gabão) entre a Península São Francisco e o Continente Congo. De fato, nenhum dos eventos distensionais mencionados logrou levar à ruptura a placa São Francisco-Congo que, aglutinada na transição Riaciano-Orosiriano (ca. 2,05 Ga), permaneceu íntegra até o Cretáceo Inferior quando, então, o rifte Atlântico finalmente conseguiu desmembrá-la.Palavras-chave: rifte, magmatismo anorogênico, Orógeno Araçuaí-Congo Ocidental, Cráton São Francisco-Congo ABSTRACT: The development of the Araçuaí-West Congo orogen (AWCO) started around 630 Ma, as suggested by U-Pb ages from the oldest rocks yet found in its pre-collisional magmatic arc. This orogeny was preceded by at least six events of rifting and/or anorogenic magmatism, which affected the area occupied by the AWCO and the adjacent São Francisco-Congo craton, namely: the Statherian E1 (1.77-1.7 Ga), Calymmian E2 (1.57-1.5 Ga), Early Stenian E3 (1.18 - ? Ga), Stenian-Tonian E4 (ca. 1 Ga), Tonian E5 (930-850 Ma) and Cryogenian E6 (750-670 Ga) events. The E1 event, currently referred to as the Statherian taphrogenesis, took place between ca. 1.77 Ga and 1.7 Ga. It is recorded by the rift-related sedimentary and volcanic rocks of the basal section of the Espinhaço Supergroup, as well as the anorogenic plutons of the Borrachudos and Lagoa Real suites. The E1 event was followed by a Calymmian episode, the E2 (ca. 1.57 Ga), recorded in the northern Espinhaço range and Chapada Diamantina by sediments and volcanics of the middle portion of the Espinhaço Supergroup. The manifestations of the Stenian E3 event started around 1.18 Ga with the syn-rift deposition of the Sopa-Brumadinho Formation (Espinhaço Supergroup), exposed in the Araçuaí belt. The first three events (E1, E2 and E3) are so far not found in the West Congo belt. In this belt, a magmatism took place at the Stenian-Tonian time boundary, the anorogenic Noqui granites (ca. 999 ± 7 Ma) and related volcanic rocks, recording a probably local extensional event, E4, which can be correlated to mafic dykes of similar age found in southern Bahia (eastern tip of the São Francisco craton). The thick bimodal volcanic pile of the Zadinian and Mayumbian groups and related intrusions are the main records of the Tonian E5 event in the West Congo belt. The A-type Salto da Divisa Suite and Tonian mafic dykes (e.g., Pedro Lessa and Northern Espinhaço range), as well as the deposition of the pre-glacial formations of the Macaúbas basin are manifestations of the E5 event in the Araçuaí orogen and São Francisco craton. Records of the Cryogenian E6 event include the Southern Bahia alkaline province (ca. 735-675 Ma) and, probably, the La Louila felsic volcanism in SW Gabon (≤ 713 Ma), as well as the deposition of the diamictitic formations of the Macaúbas Group and correlatives. The E6 event evolved to oceanic spreading in the central-southern Macaúbas basin, but this process died out toward north keeping unbroken the continental link between the São Francisco peninsula and Congo continent (the Bahia-Gabon bridge). In fact, all those extensional events were unsuccessful in splitting the São Francisco-Congo plate, which amalgamated in the Rhyacian-Orosirian time boundary (ca. 2.05 Ma) and remained as such until the Lower Cretaceous, as the Atlantic rifting then successfully broke through the old continental mass.Keywords: rift, anorogenic magmatism, Araçuaí-West Congo orogen, São Francisco-Congo craton

Two new stromatolites, Ephyaltes edingunnensis and Eucapsiphora leakensis, are described from the Palaeoproterozic Earaheedy Group, in the Earaheedy Basin (formerly the eastern part of the Nabberu Basin), Western Australia. In addition, new localities are reported for Asperia digitata comb. nov. (= Yelma digitata Grey 1984), Pilbaria deverella Grey 1984, and Yandilla meekatharrensis Grey 1984 from problematic successions in the adjacent Glengarry Basin (formerly the western part of the Nabberu Basin), confirming correlation of these rocks with the base of the Earaheedy Group. Four of the five groups recorded, Asperia, Eucapsiphora, Ephyaltes and Pilbaria, are known from outside the Earaheedy Basin and their stratigraphic age is consistent with the probable minimum 1.65 Ga age of the Earaheedy Group. However, none of the forms has yet been recorded from outside the Earaheedy Group.

Five tectonic periods can be distinguished in the tectonic evolution of Chinese continent during the Meso-Neoproterozoic and Early Cambrian: (1) the Changcheng Tectonic Period (Latest Paleoproterozoic-Early Mesoproterozoic, equal to the Statherian and Calymmian periods, 1, 800–1, 400 Ma); (2) the Jixian Tectonic Period (Middle-Late Mesoproterozoic, equal to the Ectasian and Stenian periods, 1, 400–1, 000 Ma); (3) the Qingbaikou Tectonic Period (or Jinning Period as it is called in South China, equal to the global Tonian Period, 1, 000–800 Ma); (4) the Nanhua Tectonic Period (Cryogenian Period, 800–680 Ma); (5) the Sinian Tectonic Period (Latest Neoproterozoic-Early Cambrian Epoch, 680–513 Ma) (National Commission on Stratigraphy of China, 2001; International Commission on Stratigraphy, 2004).

International audience; More than 15 years of field and laboratory investigations on samples from Terre Adélie to the western part of George Vth Land (135 to 146°E) during the GEOLETA program allow a reassessment of the Terre Adélie Craton (TAC) geology. The TAC represents the largest exposed fragment of the East Antarctic Shield preserved from both Grenville and Ross tectono-metamorphic events. Therefore it corresponds to a well-preserved continental segment that developed from the Neoarchean to the Paleoproterozoic. Together with the Gawler Craton in South Australia, the TAC is considered as part of the Mawson continent, i.e. a striking piece of the Rodinia Supercontinent. However, this craton represents one of the less studied parts of the East Antarctic Shield. The three maps presented here clearly point out the extent of two distinct domains within the Terre Adélie Craton and suggest that the TAC was built up through a polyphased evolution during the Neoarchean-Siderian (c.a. 2.5Ga) and the Statherian (c.a. 1.7Ga) periods. These data support a complete re-assessment of the TAC geology and represent a valuable base for the understanding of global geodynamics changes during Paleoproterozoic times.

International audience; New geochronological analyses (U–Pb SIMS zircon ages) have yielded ages of 552 ± 5 Ma for the Bou Madine rhyolitic dome (Ougnat, eastern Anti-Atlas), 543 ± 9 Ma for the Tachkakacht rhyolitic dyke (Saghro–Imiter, eastern Anti-Atlas), and 531 ± 5 Ma for the Aghbar trachytic sill (Bou Azzer, central Anti-Atlas). Inherited zircon cores from the Aghbar trachytic sill and from the Bou Madine rhyolitic dome have been shown to be of Statherian age (ca. 1600–1800 Ma) and Palæoproterozoic (>2100 Ma) age, respectively, suggesting that a significantly older protolith underlies the Pan-African rocks in the Central and Eastern Anti-Atlas. Granodiorites and rhyolites from the Saghro–Imiter area have similar low 87Sr/86Sr (0.702–0.706) and 143Nd/144Nd (0.5116–0.5119) initial ratios, suggesting a mixture of mantle and lower crust sources. This can also be inferred from the low 187Os/188Os ratios obtained on pyrite crystals from the rhyolites. A recently published lithostratigraphic framework has been combined with these new geochemical and geochronological data, and those from the literature to produce a new reconstruction of the complex orogenic front that developed at the northern edge of the Eburnian West African craton during Pan-African times. Three Neoproterozoic magmatic series can be distinguished in the Anti-Atlas belt, i.e., high-K calc-alkaline granites, high-K calc-alkaline to shoshonitic rhyolites and andesites, and alkaline-shoshonitic trachytes and syenites, which have been dated at 595–570, 570–545 and 530 Ma, respectively. The accretion of the Pan-African Anti-Atlas belt to the West African super continent (WAC) was a four-stage event, involving extension, subduction, moderate collision and extension. The calc-alkaline magmatism of the subduction stage was associated with large-scale base metal and gold mineralisation. Metallogenic activity was greatest during the final extensional stage, at the Precambrian–Cambrian boundary. It is characterised by world-class precious metal deposits, base–metal porphyry and SEDEX-type occurrences.

The geological correlation between Northwest Africa and Northeast Brazil faces a series of problems of both virtual and real natures. The lack of an IGCP (International Geological Correlation Program) on this subject is a crucial aspect. The first group of problems encompasses the heterogeneity backgrounds of geological knowledge (much of which is in papers of restricted circulation) as well as the diversity of scientific thought in the schools involved with this problem. Recent improvements in pre-drift (Aptian) paleogeographic maps, and a series of new PhD theses on the Precambrian shield in Brazil and Africa have stimulated the authors to review this theme. The correlation between the large cratonic blocks that confine the Brasiliano-Pan-African System - Sao Luis- and West African cratons in the north and the Sao Francisco and Congo-Kasai-Angola cratons in the south - is relatively well assigned and reasonably constrained from the litho-stratigraphic and tectonic points of view. These cratons/blocks seem to have been major fragments of the same Mesoproterozoic supercontinent, in which Paleoproterozoic orogenic collage was very important. Similarly, the set of Neoproterozoic orogenic belts that delimitate external outlines of these cratonic nuclei presents only minor correlation problems for discussion, such as those to the north, as in the case of the Medio Coreau/Dahomeyides-Pharusian belts, or those to the south, as in the case of Sergipano/Oubanguides-Lindian belts. The main problems concern the branching systems of orogens of the internal Brasiliano/Pan-African domains, distal to cratonic nuclei. North of the Patos (Patos-Garoua) shear zone in the northern part of the Borborema Province, a large basement block has been identified that contains several vestigial supracrustal belts ("schist belts"). It is considered a tectonic-stratigraphic terrane, former part of Rodinia (like the cratonic nuclei) and considerably reworked during Brasiliano - Pan African events. This reworked landmass mostly composed of high-grade rocks Paleoproterozoic (2.35, 2.15, 2.0 Ga), orthogneisses of varied compositions, with minor insertions of calc-silicatic and aluminous gneisses, extends castward from NW Ceara to the Brazilian continental margin and, in Africa, from the coast far into the interior of Niger. This terrane displays a complex structural framework (Transamazonian/Eburnian) involving some small Archean nuclei (3.45; 2.8 / 2.6 Ga). Several scattered schist belts overlying this basement block are composed of volcano-sedimentary sequences of Late Paleoproterozoic (Statherian) and Neoproterozoic (ca. 820 Ma, 730, 640-600 Ma) ages, all of them reworked during the last phases of the Brasiliano collage. Although the radiometric data for the schist belts of Nigeria are controversial, the recent set of Neoproterozoic data from Ceara and Rio Grande do Norte (Brazil) may be extended to Africa. In the central part of the Borborema Province, between the Patos (Patos- Garoua) and Pernambuco/Ngaoundere shear zone systems ("Median Shear Corridor") correlation is still a difficult. In the Brazilian territory an Early-Neoproterozoic (1000-960 Ma"Cariris Velhos") fold belt has been identified, which seems to be part of the worldwide framework of the Grenvillian collage. There is little evidence for this event on the African side, however. Additionally, correlation of Neoproterozoic fold belts well-exposed in Brazil is rather difficult due to the scattered record and deeper crustal nature of these supposed African equivalents.

The Paleoproterozoic orogenic collages were very important for the origin of the older cratonic nuclei of the South American continent, with coalescence of various Archean blocks. Such fusion processes have been designated as the Transmazoninan Orogeny or Cycle, which is an oversimplification, because there were different (both in time and space) orogenetic events from 2.2 to 1.9 Ga (from the Rhyacian to the Orosirian period). Subsequent global process of taphrogenesis took place on the newly formed Paleoproterozoic landmasses- from Amazonia to Uruguay – with a striking synchronization, in the 1.8-1.7 Ga time interval (Statherian Period). These widespread extensional regimes were responsible for the evolution of different types of tectonic setting (including both magmatism and basinal sedimentation), starting from the preliminary branching systems of rifts within the post-Orosirian landmasses. Lithological assemblages for these periods/events, as well as they present records are variable within each occurrence. Felsic to intermediate volcanics (rhyolites, rhyodacites, dacites) and anorogenic A-type granites (and rare gabbro-anorthosite bodies) are the most commom, together with minor mafic dike swarms and mafic-ultramafic layered igneous intrusions. Some initial rift systems evolved to very large cratogenic basins, during an interval of hundreds of million years, with very typical quartzite-pelite-carbonate assemblages, of epicontinental seas and other continental environments. The age control for the upper sequences (Upper Mesoproterozoic) is still poor. There are several knows systems, in different cratonic blocks, from northern South America (Amazonia) to Uruguay and Argentina (Rio de La Plata craton) which will be mentioned. In all mentioned occurrences, there are a series of variables (geological and tectonophysical characteristics) still unknown. Relationships among time, heat flux and average factors of extension (β) cannot yet be estimated due to the scarcity of geochronological data. The only possibility for estimating the magnitude of those processes is through comparison of the intensity of the preserved geological records, keeping in mind their different crustal levels at present. Only small parts of these Proterozoic basins have remained as cratonic covers up to the present time. Some segments of them were first involved in collisional orogenic processes in Late Mesoproterozoic times (± 1.3 Ga), although geological records for this orogeny (so-called Uruacuano) are still deficient. Additionally, most of these basins were involves in the fission of the Rodinia supercontinent, during the initial steps of the Brasiliano/Panafricano Cycle (around 1000 Ma) and many of their structural trends have been reactivated during the Neoproterozoic orogenic collage resulting in the agglutination of Western Gondwana. In such conditions, there are somes cases where the time interval is about 1.1 Ga from the basin-forming tectonics (Statherian Period) to the last period of orogenesis (c a 600 Ma, Neoproterozoic III). Sometimes, it is possible to observe along the same structural trends, or even side-by-side, both fold belts (Brasiliano domains0 and weakly deformed covers (on the Brasiliano cratonic blocks), with coeval volcano-sedimentary piles.

The granites orthogneisses, hydrothermal albitities and rocks which have suffered uranium mineralization from the Lagoa Real District (South State of Bahia, Brazil) have been investigated by U-Pb, Rb-Sr and Sm-Nd techniques. U-Pb values on zircons from the granitic protolith give an age of 1725 Ma; U-Pb on U-mineralization dates the primary mineralization at 1395 Ma and indicates a reworking at 480 Ma, which may represent the age of the thrusting of the Lagoa Real complex over Espinhaco metasediments during the Brazilian orogeny. These two dates are given by Rb-Sr on albitites, but from sparse information and are not supported by unequivocal arguments. The uranium deposition and sodium metasomatism, however, cannot be linked either with the thermal history of the granite or with Brazilian thrusting. Sm-Nd gives scattered results which are suggestive of autochtonous reworkings of REEs. These results lead to the following suggestions (1) magmatic activity of subalkaline affinity existed within the Sao Francisco craton at about 1.7 Ga (2) such subalkaline plutons are likely sources for U-mineralization (3) at about 1.4 Ga an unknown event caused hydrothermal activity leading to U-deposition at Lagoa Real (4) Brazilian overthrusting at about 480 Ma did not play any genetic role in the hydrothermal activity.

This paper presents and discursses some of the last geochronological determinations carried out on rocks of the Espinhaco Mountain Belt; by different radiometric methods. For the most part, the basement is composed of Archaean rocks, with formation of magmatites and granites during the Transamazonian cycle (2,0 b.y.). The geologic evolution of the Chapada Diamantina Group is proposed as follows: 1- At 1,7 b.y. formed the first sedimentary basins, associated with continental acid voleanism. 2 - The main stage of folding and epizonal metamorphism occured at approximately 1,2 b.y, with post-tectonic events until 1,0 b.y. These last ones include basicfissure volcanism and tectonic uplift. 3 - During the Brazilian cycle (650-400 m.a.) the tectonothermal phenomena have affected in several ways and with different intensity the age determinations of all geological units.