Addition Of Juvenile Material Research Articles

Zircon Hf isotopic compositions of the basement gneiss in Bayan Obo: Constraints on crustal evolution of the Yinshan Block in the North China Craton

Bayan Obo, located in the north margin of the Yinshan Block, North China Craton (NCC), contains the Archean to Paleoproterozoic basement rocks which may shed light on the early crustal evolution of the NCC. In this paper, to reveal the formation and modification of the basements, we report Hf isotope of zircons from the biotite plagiogneisses in Bayan Obo. Combined with the published U–Pb ages and Hf isotope compositions of the zircons from the Bayan Obo basement rocks, a comprehensive review was employed to provide new insights into the formation and modification of the basement in this area. The oldest formation age of the basement rocks was found to be approximately 2.6 Ga, with positive εHf(t) values indicating the contribution from the depleted mantle to the rocks. The age of ∼2.0 Ga marks the major formation period of the basement rocks. The varied εHf(t) values (−17.2 to +8.9) of the magmatic zircons suggest a mixture origin between the depleted mantle and crustal rocks for the gneiss. The basement went through extensive metamorphism during 1.95–1.9 Ga. In addition, zircon U–Pb–Hf isotope data of the Precambrian units in Guyang and Wuchuan, which are adjacent to Bayan Obo, were compiled for comparison. The comprehensive review on the data of the concordant magmatic zircons indicates the existence of 3.5 Ga crustal fragments in the Yinshan Block. The melting of the depleted mantle and the addition of juvenile materials into the crust at 2.6–2.9 Ga and 2.45–2.55 Ga were confirmed by the high positive εHf(t) values of the magmatic and inherited zircons. An increase in remelting of the crust at 2.0 Ga is deduced from the extremely unradiogenic Hf isotope of the magmatic zircons.

Silurian to Early Devonian tectonic evolution of the southeastern Qilian Orogen inferred from zircon U–Pb dating and geochemistry of intrusive rocks

Early to mid-Paleozoic tectonothermal events in the Qilian Orogen developed during the closure of the Proto-Tethys Ocean and the convergence of microcontinents in the periphery of East Gondwana. In this paper, we present geochronological, geochemical and Sr–Nd-Hf isotopic data for the granitoid rocks and mafic dykes in southeastern Qilian Orogen. The Liwan (440 Ma), Shixia (434 Ma) and Huchuan (429 Ma) granitoid rocks have metaluminous to weakly peraluminous features, with whole-rockεNd(t) values of 1.1 to 1.6, −4.2 to −4.4 and −2.6 to 1.1, and zirconεHf(t) values of 0 to 8.9, −6.6 to 1.6 and −4.6 to 2.2, respectively. Geochemical data suggest that the Liwan, Shixia and Huchuan granitoids are derived from partial melting of the Proterozoic basement with addition of juvenile material, felsic crustal basement and mafic crustal material, respectively. The Zhangjiayuan mafic dykes (403 Ma) are high-K to shoshonitic with whole-rockεNd(t) (−1.1 to −0.9) and zirconεHf(t) values (−0.9 to 13.3), derived from an enriched lithospheric mantle. We suggest that these Silurian–Early Devonian intrusive rocks were formed via complex events involving arc-related subduction followed by slab-tearing to post-collisional processes during the Silurian and subsequent lithospheric extension in the Early Devonian.Supplementary material:Tables giving zircon U–Pb isotopic data, whole-rock major and trace element results, whole-rock Sr–Nd isotopic data and zirconin situLu–Hf isotopic data are available athttps://doi.org/10.6084/m9.figshare.c.6693575

The Carboniferous-Permian tectonic setting for the southernmost Central Asian Orogenic Belt: Constraint from magmatic and sedimentary records in the Alxa area, NW China

The northern Alxa orogenic belt, a junction between the western and eastern Central Asian Orogenic Belt (CAOB), is not well understood, especially in its Carboniferous to Permian tectonic history. In this paper, an integrated study incorporating the geochronology, geochemistry, and isotopes of magmatic rocks and provenance analysis of clastic rocks is conducted to address the above issue. The zircon UPb age data, both in this study and in previous studies, indicates that the Permian magmatic activities in the Alxa Block were intensive and peaked at ca. 276 Ma. The magmatic zircons yield negative εHf(t) values with a wide range, indicating their dominant derivation from the crustal reworking of the Alxa Block with the addition of juvenile materials. The Permian high-K to shoshonitic, I-type granitoids combined with the A-type granitoids/rhyolites were most likely formed in extensional settings. The late Carboniferous sandstones collected along the Badain Jaran fault yield a high proportion of early Paleozoic zircons peaked at ca. 429 Ma with both positive to negative Hf(t) values and a low proportion of Precambrian zircons with positive to negative Hf(t) values. Thus, their provenance were likely the Precambrian to Paleozoic rocks in the Alxa Block and in the terranes in the CAOB. The zircon age spectra with no indicators of Carboniferous zircons approximating their depositional age supports an extensional setting. The Permian A-type granites and volcanic rocks in the Alxa area have some geochemical affinity with the Permian alkaline granitoids in the eastern Tianshan–Beishan and central-north Inner Mongolia regions. These findings support the extension of the Gobi–Tianshan belt in the Alxa area.

Decratonization by rifting enables orogenic reworking and transcurrent dispersal of old terranes in NE Brazil

Dispersion and deformation of cratonic fragments within orogens require weakening of the craton margins in a process of decratonization. The orogenic Borborema Province, in NE Brazil, is one of several Brasiliano/Pan-African late Neoproterozoic orogens that led to the amalgamation of Gondwana. A common feature of these orogens is that a period of extension and opening of narrow oceans preceded inversion and collision. For the case of the Borborema Province, the São Francisco Craton was pulled away from its other half, the Benino-Nigerian Shield, during an intermittent extension event between 1.0–0.92 and 0.9–0.82 Ga. This was followed by inversion of an embryonic and confined oceanic basin at ca. 0.60 Ga and transpressional orogeny from ca. 0.59 Ga onwards. Here we investigate the boundary region between the north São Francisco Craton and the Borborema Province and demonstrate how cratonic blocks became physically involved in the orogeny. We combine these results with a wide compilation of U–Pb and Nd-isotopic model ages to show that the Borborema Province consists of up to 65% of strongly sheared ancient rocks affiliated with the São Francisco/Benino-Nigerian Craton, separated by major transcurrent shear zones, with only ≈ 15% addition of juvenile material during the Neoproterozoic orogeny. This evolution is repeated across a number of Brasiliano/Pan-African orogens, with significant local variations, and indicate that extension weakened cratonic regions in a process of decratonization that prepared them for involvement in the orogenies, that led to the amalgamation of Gondwana.

The crust-mantle evolution of the Anabar tectonic province in the Siberian Craton: Coupled or decoupled?

To clarify the tectonic-thermal evolution of the Anabar tectonic province in the central Siberian Craton, we performed an isotope-geochemical study of 20 xenoliths from the Udachnaya, Zarnitsa, and Komsomolskaya kimberlite pipes to represent different crustal levels. Most mafic granulites have Proterozoic Nd model ages and geochemical characteristics close to those of intraplate basalts, whereas some mafic and intermediate granulites with Archean model ages exhibit geochemical features of supra-subduction ophiolitic basalts. Analysis of U-Pb ages and hafnium isotopic composition of zircon indicates that the main tectonic-thermal events modified the crust at 2.7 and 1.9–1.8 Ga, which is consistent with ages of mantle depletion events from previous studies. All zircons have Archean Hf model ages (TDMC3.6-3.2 Ga). Overall, thermal events with ages of 2.9–2.8, 2.7, 2.4, 1.97 and 1.8 Ga have remarkable influence on the studied zircons. Tectono-thermal events at 2.4 1.97, 1.9 and 1.8 Ga with no addition of juvenile material are recorded by zircons from xenoliths of mafic and intermediate granulites and metadiorites. A compilation of isotope-geochemical data demonstrates that instead of age-stratified, the crust of the Anabar tectonic province consists of variably reworked Paleoarchean rocks and juvenile Proterozoic rocks at all crustal levels. Hence the crust and mantle of the Siberian Craton has been coupled since the Paleoarchean.

Geochronology of Metamorphic Events in the Lower Crust beneath NW Russia: a Xenolith Hf Isotope Study

Hf isotope data for zircons and whole-rocks from lower crustal mafic granulite and pyroxenite xenoliths from NW Russia are presented together with the results of U–Pb zircon dating, Sm–Nd and Rb–Sr isotopic compositions of bulk-rocks and minerals, and trace element compositions of minerals. Most zircons preserve a record of only the youngest metamorphic events, but a few Grt-granulite xenoliths retain Archean magmatic zircons from their protolith. Metamorphic zircons have highly variable ɛHf(t) values from –25 to –4. The least radiogenic zircons were formed by recrystallization of primary magmatic Archean zircons. Zircons with the most radiogenic ɛHf grew before garnet or were contemporaneous with its formation. Zircons with ɛHf(t) from –15 to –9 formed by various mechanisms, including recrystallization of pre-existing metamorphic zircons, subsolidus growth in the presence of garnet and exsolution from rutile. They inherited their Hf isotopic composition from clinopyroxene, pargasite, rutile and earlier-formed zircon that had equilibrated with garnet. Subsolidus zircons were formed in response to a major change in mineral association (i.e. garnet- and zircon-producing reactions including partial melting). Recrystallized zircons date the onset of high-temperature conditions without a major change in mineral association. Age data for metamorphic zircons fall into five groups: >1·91 Ga, 1·81–1·86 Ga, 1·74–1·77 Ga, 1·64–1·67 Ga and <1·6 Ga. Most ages correlate with metamorphic events in the regional upper crust superimposed onto rocks of the Belomorian belt during formation of the Lapland Granulite Belt. Zircon formation and resetting at 1·64–1·67 Ga significantly postdates Lapland–Kola orogenic events and may relate to the onset of Mesoproterozoic rifting. The youngest ages (1·6–1·3 Ga) correspond to an event that affected only a few grains in some samples and can be explained by interaction with a localized fluid. The observed garnet-granulite associations were formed at 1·83 Ga in Arkhangelsk xenoliths and 1·74–1·76 Ga in most Kola xenoliths. By the end of the Lapland–Kola orogeny, the rocks were already assembled in the lower crust. However, no addition of juvenile material has been detected and preservation of pre-Lapland–Kola metamorphic zircon indicates that some xenoliths represent an older lower crust. Granulites, pyroxenites and Phl-rich rocks have a common metamorphic history since at least c. 1·75 Ga. At about 1·64 Ga metasomatic introduction of phlogopite took place; however, this was only one of several phlogopite-forming events in the lower crust.

Petrogenesis and tectonic implications of Late Devonian arc volcanic rocks in southern Beishan orogen, NW China: Geochemical and Nd–Sr–Hf isotopic constraints

Late Devonian (ca. 370Ma) volcanic rocks provide important information about the nature of magmatism during the tectonic transition between the Early and Late Paleozoic in the Beishan orogen, southern Central Asian Orogenic Belt. They are predominantly an andesitic–dacitic–rhyolitic assemblage, characterized by alkali contents ranging from slightly calcic to slightly alkaline. The rhyolitic rocks are generally ferroan, whereas the andesitic rocks are magnesian. These volcanic rocks exhibit similar trace element characteristics to those of continental arcs. Strongly negative εNd(t) values (−2.8 to −3.6) and high Sr isotopic compositions (initial 87Sr/86Sr=0.7036–0.7108) suggest that they are mainly derived from an ancient crust. However, the positive zircon εHf(t) values (+1.4 to +16.4) support the role of juvenile components in their genesis, indicating the significant input of new mantle-derived magmas. These characteristics imply a hybrid derivation, from an ancient crustal source with the addition of juvenile materials during magma genesis, or perhaps heterogeneous contamination or hybridization during magma emplacement. Combined with the regional geology, our results indicate that the Late Devonian magmatism resulted from a southward retreat of the subduction zone, which records significant continental crustal growth in a transitional arc or an accretionary arc setting. The distinct geochemical compositions, especially the Nd–Hf isotope decoupling of the Dundunshan volcanic rocks, imply a significant change in the geodynamic setting in the Late Paleozoic.

Episodic widespread magma underplating beneath the North China Craton in the Phanerozoic: Implications for craton destruction

A comprehensive synthesis of U–Pb geochronology and Hf isotopes of zircons from granulite/pyroxenite xenoliths entrained in Phanerozoic magmatic rocks and inherited xenocrysts from the associated lower crust rocks from various domains of the North China Craton (NCC) provides new insights into understanding the Phanerozoic evolution of the lower crust in this craton. Episodic widespread magma underplating into the ancient lower crust during Phanerozoic has been identified throughout the NCC from early Paleozoic to Cenozoic, broadly corresponding to the Caledonian, Hercynian, Indosinian, Yanshanian, and Himalayan orogenies on the circum-craton mobile belts. The early Paleozoic (410–490Ma) ages come from xenoliths in the northern and southern margins as well as the central domain of the Eastern Block of the craton which mark the first phase of Phanerozoic magma underplating since the final cratonization of the NCC in the Paleoproterozoic. The magmatism coincided with the northward subduction of the Paleotethysian Ocean in the south and the southward subduction of the Paleoasian Ocean in the north. The subduction not only triggered magma underplating but also led to the emplacement of the diamondiferous kimberlites on the craton, marking the initiation of decratonization. The late Paleozoic event as represented by the 315Ma garnet pyroxenite and/or lherzolite xenoliths in Hannuoba was restricted to the northern and southern margins of the craton, correlating with the arc magmatism continuous associated with the subduction of the Paleotethysian and Paleoasian Oceans and resulting in the interaction between the melts from subducted slabs and the lithospheric mantle/lower crust. The early Mesozoic event also dominantly occurred in the northern and southern margins and was related with the final closure of the Paleotethysian and Paleoasian Oceans as well as the collisional orogeny between the NCC and the Yangtze Craton. The late Mesozoic (ca. 120Ma) was a major and widespread magmatic event which manifested throughout the NCC, associated with the geothermal overturn due to the giant south Pacific mantle plume. The Cenozoic magmatism, identified only in the dark clinopyroxenite xenoliths in the Hannuoba, was probably induced by the Himalayan movement in eastern Asia and might also have been influenced by the subduction of the Pacific Ocean to some extent. These widespread and episodic magma underplating or rejuvenation of the ancient lower crust beneath the NCC revealed by U–Pb and Hf isotope data resulted from the corresponding addition of juvenile materials from mantle to lower crust, with a mixing of the old crust with melts. The process inevitably resulted in the compositional modification of the ancient lower crust, similar to the compositional transformation from the refractory lithospheric mantle to a fertile one through the refractory peridotite — infiltrated melt reaction as revealed in the lithospheric mantle beneath the craton.

Episodic growth of Precambrian lower crust beneath the North China Craton: A synthesis

A comprehensive review of U–Pb geochronology and Hf isotopes of zircons separated from granulite xenoliths entrained in Phanerozoic magmatic rocks and inherited xenocrysts from the associated lower crust rocks from various domains of the North China Craton (NCC) provides new insights into understanding the evolution of the lower crust in this part of the Precambrian nucleus of Asia. The oldest zircons recorded in granulite xenoliths show ages up to 3.6Ga, slightly younger than the oldest zircons (3.8Ga) from samples of the exposed Archean upper crust. However, the Hf isotope features indicate that the oldest lower crust might have been derived from a 4.0 to 4.1Ga primordial crust as indicated by the data from an inherited zircon in the North Qinling Orogenic Belt at the southern part of the NCC. Our synthesis also suggests that ca. 2.5Ga mark an important period for the evolution of the lower crust of the NCC and the cratonization of the Archean blocks in the NCC, at least for the Eastern Block, with a possible link to mantle plume activity. The occasional presence of zircons with 2.6–3.1Ga ages in the lower crustal granulite xenoliths suggests a continuous reworking of the Paleoarchean lower crust during the Archean. The comprehensive data also show that 1.8–2.0Ga period was the first significant event for the evolution of the lower crust after the cratonization of the Archean blocks of the NCC, which affected the whole lower crust of the Eastern NCC. Episodic growth or rejuvenation of the Precambrian lower crust beneath the NCC is also revealed by U–Pb and Hf isotope data, resulting from the corresponding addition of juvenile materials from mantle to lower crust, with a mixing of the old crust with juvenile magma. This compositional modification of the lower crust resembles the compositional transformation from the refractory lithospheric mantle to a fertile one through the refractory peridotite – infiltrated melt reaction as revealed in the lithospheric mantle beneath the NCC.

Neoarchean (2.7–2.8 Ga) accretion beneath the North China Craton: U–Pb age, trace elements and Hf isotopes of zircons in diamondiferous kimberlites

Zircon xenocrysts from the Early Paleozoic Mengyin and Fuxian diamondiferous kimberlites, on opposite sides of the translithospheric Tanlu fault in the North China Craton, have been used to probe the deep crust. Based on detailed studies of external forms and internal structures, the zircons can be roughly divided into magmatic and metamorphic zircons. There are no consistent differences in U, Th or Th/U between the two zircon populations. The trace-element affinities of the igneous zircons vary widely from mafic, through intermediate, to felsic rocks with minor populations similar to zircons from carbonatite and syenite. In situ isotopic analysis for U–Pb and Lu–Hf reveals that all zircons both from Mengyin and Fuxian kimberlites, regardless of their chemical affinities, have similar formation ages (2.5–2.7 Ga) and depleted mantle model ages ( T DM, 2.7–2.8 Ga). These ages are also similar within error to those of zircons in mafic granulite xenoliths from the Fuxian kimberlites, implying that the lower crust was similar (Neoarchean cratonic basement) beneath the Mengyin and Fuxian areas, but the latter experienced stronger thermal modification in Proterozoic time. The magmatic zircons may be derived from late differentiates of underplated mafic magmas with some contamination by crustal components, and the metamorphic populations developed during heating events linked to the ongoing underplating. The addition of juvenile material (up to + 9.5 ε Hf) at this time (2.7–2.8 Ga) corresponds to a known major episode of global crustal formation.

U‐Pb Age and Hf Isotope Study of Detrital Zircons from the Wanzi Supracrustals: Constraints on the Tectonic Setting and Evolution of the Fuping Complex, Trans‐North China Orogen

Abstract: Located in the middle segment of the Trans‐North China Orogen, the Fuping Complex is considered as a critical area in understanding the evolution history of the North China Craton (NCC). The complex is composed of various high‐grade and multiply deformed rocks, including gray gneiss, basic granulite, amphibolite, fine‐grained gneiss and marble, metamorphosed to upper amphibolite or granulite facies. It can be divided into four rock units: the Fuping TTG gneisses, Longquanguan augen gneisses, Wanzi supracrustals, and Nanying granitic gneisses. U‐Pb age and Hf isotope compositions of about 200 detrital zircons from the Wanzi supracrustals of the Fuping Complex have been analyzed. The data on metamorphic zircon rims give ages of 1.82‐1.84 Ga, corresponding to the final amalgamation event of the NCC, whereas the data for igneous zircon cores yield two age populations at ∼2.10 and ∼2.51 Ga, with some inherited ages scattering between 2.5 and 2.9 Ga. These results suggest that the Wanzi supracrustals were derived from the Fuping TTG gneisses (∼2.5 Ga) and the Nanying granitic gneisses (2.0–2.1 Ga) and deposited between 2.10 and 1.84 Ga. All zircons with ∼2.51 Ga age have positive initial ∍Hf values from +1.4 to +10.9, suggesting an important crustal growth event at ∼2.5 Ga through the addition of juvenile materials from the mantle. The Hf isotope data for the detrital zircons further imply that the 2.8 Ga rocks are important components in the lower crust, which is consistent with a suggestion from Nd isotope data for the Eastern Block. The zircons of 2.10 Ga population have initial ∍Hf values of −4.9 to +6.1, interpreted as mixing of crustal re‐melt with minor juvenile material contribution at 2.1 Ga. These results are distinct from that for the Western Block, supporting that the Fuping Complex was emplaced in a tectonic active environment at the western margin of the Eastern Block.

Integrated Nd isotopic and U–Pb detrital zircon systematics of clastic sedimentary rocks from the Slave Province, Canada: evidence for extensive crustal reworking in the early- to mid-Archean

A combined U–Pb geochronology and Nd isotopic analysis of clastic metasedimentary rocks from the Archean Slave Province, Northwest Territories, Canada is presented. A series of clastic sedimentary rocks with deposition age of ∼3.13 Ga to ∼2.58 Ga was collected from the west-central Slave Province. These samples include conglomerates as well as finer sedimentary rocks such as greywacke, arkose and quartzite. Although it is generally agreed that the Nd model age ( T DM) of clastic sedimentary rocks represents the average sedimentary provenance age, T DM of samples studied here is generally older than the average U–Pb age of detrital zircons extracted from the same sample. Rather, there seems to be a better ∼1:1 relationship between the T DM and U–Pb age of the oldest zircon from each sample. A simple model relationship between U–Pb geochronology and T DM suggests that such correlation is a result of Archean crustal evolution of the Slave Province being dominated by crustal reworking (i.e. intracrustal processes) rather than addition of juvenile materials from the mantle. One exception is the period between ∼3.1 and ∼3.2 Ga, during which period a significant portion of detrital zircons have U–Pb ages exceeding the T DM, indicating a large input of juvenile material and/or decreasing level of crustal reworking. An alternative explanation for the U–Pb vs. T DM trend may be a mixing of older mafic juvenile crust (containing no zircon) and younger felsic juvenile crust. However, the general lack of extensive pre-2.8 Ga mafic crust in the Slave Province makes this scenario unlikely. The results of this study cannot constrain the change in the volume of continental crust at any given period of time, since the addition of juvenile crust may always be counterbalanced by recycling of crustal material back into the mantle. However, a dominance of crustal reworking during the early- to mid-Archean strongly implies that a large part of ancient crust was lost during the younger tectonomagmatic events. Since the majority of zircon may be lost during crustal reworking processes (unless they are preserved as an inherited core), absence of a large quantity of ancient detrital zircon cannot be used as evidence for the lack of large sialic crust existing on the early Earth.

The West Central African belt: a model of 2.5–2.0 Ga accretion and two-phase orogenic evolution

A mapping, tectonic (deformation, kinematics), petrologic ( P– T paths) and geochronological approach has enabled us to define the Paleoproterozoic West Central African Belt (WCAB), to reconstruct its organization and its evolution, and to determine its position within the Congo–São Francisco craton. The belt extends from southwestern Cameroon to the Congo and evolved between 2500 and 2000 Ma. The initial tectonic stage had a continental character. It corresponds to the break up of an Archean craton (no ocean opening, no addition of juvenile material) with the appearance of a zone of tectonic instability comprising blocks whose boundaries are partly marked by sedimentary basins (Ogooué, Nyong, Ikobé–Waka) and plutonic rocks emplaced between 2515 and 2435 Ma. A first crustal shortening event (E1) occurred between ca 2235 and 2300 Ma. This event led to thickening, at first homogeneous and then heterogeneous (nappe tectonism of unknown vergence). The sediments deposited during the previous stage were thus buried to depths of 20–35 km (7–12 kbar at peak metamorphism) and underwent a prograde–retrograde type metamorphic evolution characterized by an anticlockwise P– T path. The retrograde metamorphic evolution was due to crustal thinning arising from isostatic uplift and erosion of the thickened zones. The crustal thinning was also accompanied by a new break up of nearby Archean continental blocks. This break up was associated with the opening, before 2145 Ma, of the pre-oceanic Francevillian extensional basins [deposition of formation A (FA) of the Francevillian sediments]. A second crustal thickening (event E2) took place after 2145 Ma through thrust tectonism that accreted the Archean block, and the sediments buried during the E1 event, onto the edge of the Congo craton. E2 was accompanied by further prograde–retrograde metamorphism characterized by a clockwise P– T path in the inner zone of the belt and an anticlockwise P– T path in the outer zone. The tectonic activity of this second event began in the inner zone, where the rocks underwent high-grade metamorphism (9 kb and 810°C) that peaked ca 2120 Ma. At the same time the foreland was subjected to brittle tectonism with accelerated subsidence of the Francevillian basins and the deposition of marine sediments (flysch; formations FB and FC) from 2100 Ma onwards. The thickened inner zone was then transported onto the outer zones of the belt, which were thus buried and locally reached anatectic conditions at peak metamorphism (600°C and 8 kb). The lithotectonic pile was finally transported onto the autochthonous Archean Chaillu Block (=Congo craton), this transport being completed ca 2050–2040 Ma in a transitional ductile/brittle context with rapid erosion of the mountain belt giving rise to the deposition of terrigenous molasse (formations FD and FE) in the Francevillian basins. A third tectonic event (E3) saw the return, ca 2040 Ma, of the thickened domain to isostatic equilibrium. This was accompanied by the emplacement of late-orogenic granite (2040–1920 Ma) and the development of folds and strike-slip faults. Comparing the Congo–São Francisco craton with the Ubendian, Luiza and Transamazonian orogenic belts shows similarities in the successions and distributions (with time) of the sedimentary, tectonic, metamorphic and magmatic events, revealing a period (2500–2000 Ma) of major displacement (break up, extension, convergence) of the Archean continental blocks (São Francisco, Congo, Tanzanian) and leading one to consider a vast orogenic domain comprising the West Central African and Transamazonian belts. This period of continental displacement includes an early stage (2500–2400 Ma) corresponding to the Archean–Proterozoic transition which is characterized by dislocation of the margins of the Congo (WCAB, Luiza belt) and São Francisco (Transamazonian belt) cratons and development of oceanic crust in an intercontinental setting (Atlantic Coast Complex, Salvador–Curaça belt and early basic magmatism of the Luiza basin). A second stage of extension occurred between 2300 and 2145 Ma, with the opening of new pre-oceanic basins: the early Booué; Franceville; and Sembé-Ouesso (Francevillian A) and Luiza basins (Archean Congo block); Rio Itapicuru and Rio Jacare greenstone belts (Archean São Francisco block). At the scale of the WCAB, and probably also of the Transamazonian belt, this second extension occurred between two stages of crustal thickening (E1 and E2) each characterized by metamorphism with complete P– T cycles (i.e. a prograde stage followed by a retrograde stage). This alternation of extensional and compressive tectonic phases leads us to propose a two-phase (if not a two-cycle) orogenic model.