Search

• The 2.2 Ga monzogranite identified in the western part of the North Qinling Orogen (NQO) was originally formed in the southwestern North China Craton (NCC). • The monzogranite was involved into the NQO by continental collision between the NQO and the NCC during the early Paleozoic. • The early Precambrian rocks at the southwestern margin of the Ordos Blocks recorded similar tectono-thermal events of 2.5–1.75 Ga with the basement of the central-southern Ordos Block. Precambrian continent remnants in Phanerozoic orogenic belts contain vital information about not only the Precambrian evolution history of continent remnants but also the relationship between orogenic belts and adjacent blocks. This paper presents an integrated study of petrology, geochemistry and accessory mineral chronology on a monzogranite, its wall rocks biotite-quartz schist and an amphibolite interlayer in the schist in the Kuanping Group, from the western part of the North Qinling Orogen (NQO), adjacent to the southwestern margin of the Ordos Block (OB). The results reveal that the crystallization age of the monzogranite is 2200 ± 12 Ma and the protolith of the biotite-quartz schist deposited during 526–447 Ma, and they experienced similar multistage metamorphism during 450–400 Ma. The 2.2 Ga formation age of the monzogranite is significantly older than the protolith deposition age of the biotite-quartz schist, and there is almost no ca. 2.2 Ga detrital zircon age in the schist, indicating that the monzogranite is neither an intrusive body in the Kuanping Group, nor its provenance. Considering the ca. 2.2 Ga magmatism is widely distributed in North China Craton but never found in the NQO, and the monzogranite and host schist recorded similar metamorphic ages, we proposed that the monzogranite initially formed at the southwestern margin of the North China Craton and involved into the NQO during the closure of the Kuanping sedimentary basin at early Paleozoic. Combined with existing studies, three Paleoproterozoic magmatic events of ca. 2.5 Ga, 2.2–2.0 Ga and 1.8–1.75 Ga, and one ca. 1.9–1.85 Ga metamorphic event occurred at the southwestern margin of OB. These tectono-thermal events as well as their geological setting are very similar to the basement rocks of the central-southern part of the OB. Therefore, the early Precambrian rocks at the southwestern margin of the OB should belong to the basement of the central-southern part of OB, and the late tectonic events placed them at their present position. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Structural signatures for 2.45 Ga rifting were preserved. • Rifting utilized pre-existing structures of the Archaean basement. • Pull-apart structures controlled deposition and structural evolution of supracrustal belts. • Segmentation of the Archaean crust explained. • Active mode of rifting favoured. Abstract Constraints from restoration of minor rift-related faults preserved from subsequent Palaeoproterozoic overprint along the southern margin of the Peräpohja Belt, northern Fennoscandia indicate local NE-SW extension directions prevailed at the time of 2.44 Ga rifting of the Archaean continent. This palaeostress field is attributed to pull-apart setting of the Peräpohja Belt at a left overstepping zone of major sinistral N-S trending deformation zones. Consequently, the variably overprinted NW-SE trending structures of the Peräpohja Belt, including the NW-SE central graben were originally generated as normal faults. The proposed setting is compatible with a conducted reconnaissance sandbox analogue model where the orientation of the major normal faults was controlled by the ambient stress field within the step-over zone between strike-slip faults. By contrast, the faults bounding E-W to ENE-WSW trending basement horsts are the result of reactivation of older basement structures underlying the pull-apart basin. Based on the results, we infer that the final break-up of the Archaean continent in northern Fennoscandia utilized the 2.44 Ga rift-related NW-SE trending crustal anisotropy (parallel with dyke swarms), with pre-existing Archaean N-S trending structures reactivated as second-order shear zones in-between. The voluminous syn-rift 2.5–2.4 Ga and later pulses of mafic magmatism (2.32–1.98 Ga) are considered indicative of active-type rifting which onset was controlled by a mantle plume centred within a supercraton formed by the Superior, Hearne and Karelian (-Kola) cratons. The presented model supports the continuity of the Archaean craton beyond the Caledonian Orogen towards north-west and explains its segmentation, suggesting a model for the localization of the Palaeoproterozoic supracrustal belts of Northern Fennoscandia. Moreover, this paper provides an approach to understand the basement-cover relationships and the structural signatures within these relatively shallow supracrustal belts which are highly prospective for mineral deposits. [ABSTRACT FROM AUTHOR]

[Display omitted] • Zircon xenocrysts have low-δ18O and high-εHf(t) values. • Zircon xenocrysts were generated from high temperature altered gabbroic rocks of subducted oceanic slab. • This paper provides new evidence for Paleoproterozoic oceanic slab subduction in the Trans-North China Orogen. The Trans-North China Orogen (TNCO) is suggested to form under a transition from subduction to collision from 2500 Ma to ∼ 1850 Ma, and the Taihua TTG gneiss in the Xiong'ershan district is thought to have formed in an Andean-type continental arc setting or island arc setting during this geological event. However, to date, the geochemical record of the subducted oceanic slab is still lacking. This study focuses on Hf-O isotopic analyses of zircon xenocrysts from the Qi189 hornblende monzogranite, Qiyugou Au orefield, TNCO. The results reveal that zircon xenocrysts with ages from 2304 Ma to 1934 Ma generally have low-δ18O values from 2.66‰ to 3.83‰ and high-εHf(t) values from 2.7 to 7.8. These zircon grains were generated from remelting of high-temperature altered gabbroic rocks of the subducted oceanic slab during the transition from compression to extension. In this paper, we present new evidence for Paleoproterozoic oceanic slab subduction in the TNCO. [ABSTRACT FROM AUTHOR]

[Display omitted] • Distinct P-T -t paths of basement and cover units within an Ediacaran-Cambrian orogen. • The highest-P gneisses in Brasiliano-Pan African belts at the South Atlantic continental margins. • Paleosuture zone in the Central Ribeira belt records low-angle NW-subduction. • Zircon and monazite crystallization from melt at late-collisional stage. Deeply eroded collisional orogens show complex structural and inverted stratigraphic relations with juxtaposition of rock stacks from distinct crustal levels, origins and ages, hence with contrasting P-T -t paths during convergent tectonics. This paper presents petrochronological data on Paleoproterozoic (basement) and Ediacaran (cover) gneisses tectonically interleaved during the Ediacaran-Cambrian Búzios Orogeny, in southeastern Brazil. U-Pb in zircon and EPMA U-Th-Pb in monazite data, coupled with geothermobarometric data, plus Zr-in-rutile, reveal that at a first orogenic stage (ca. 530–520 Ma), these units were at distinct crustal levels. Samples within the Paleoproterozoic basement show metamorphic near-peak conditions of ∼800 °C and 10 kbar, at a depth of c.37 km. Contrastingly, Ediacaran kyanite-orthoclase-garnet-biotite granulite with retrometamorphic sillimanite (cover) reached near-peak conditions of 15 kbar and 818 °C–785 °C at depths of c. 55 km, in high-pressure granulite facies. This deep burial of Ediacaran sediments in less than 20 m.y. would be compatible with a low angle subduction zone active from ca. 550 to 530 Ma. Intrusion of ca. 550 Ma tholeiitic dykes in the Paleoproterozoic gneiss indicates a high geothermal gradient for this subduction setting, which is consistent with a low subduction rate. In a second orogenic stage (ca. 520–500 Ma), these distinct stratigraphic units were placed tectonically side by side during a fast exhumation, preserving an inverted metamorphic stack. The cover underwent retrometamorphic conditions of 800 °C and 10 kbar on a clockwise return path due to decompression. It is proposed here that the contact between reworked units within a Paleoproterozoic continental crust and Ediacaran magmatic and sedimentary units represent the suture of an Ediacaran NW-subduction of the Angola continental paleomargin below the Oriental Terrane of the Ribeira belt. This paper reports the highest pressure recorded in Ediacaran-Cambrian metamorphic rocks from the Brasiliano belts along the actual South Atlantic continental margins. The suture we propose here is aligned along strike, with a medium to high-pressure Ediacaran metamorphic occurrence 700 km to the SW, in the Curitiba Terrane. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Araçuaí-Ribeira orogenic system (AROS). • Rhyacian-Orosirian orogenic systems (ROOS). • First isotopic Hf signatures for ROOS in AROS. • Brazil-Africa links in Palaeoproterozoic time. Abstract Assembled during the Rhyacian-Orosirian boundary, the Congo-São Francisco palaeocontinent remained linked by a continental bridge from ca. 2 Ga to the Atlantic Ocean opening in the Cretaceous. To the south of that bridge, precursor basins and orogenic outcomes encompassed by the Neoproterozoic-Cambrian Araçuaí-Ribeira orogenic system (AROS) and its African counterparts, developed. The AROS discloses reworked basement units, like the Juiz de Fora, Pocrane and Quirino complexes, which are key units to retrieve the Palaeoproterozoic history of the Congo-São Francisco palaeocontinent. This paper presents new U-Pb ages, and the first Lu-Hf in zircon signatures from those complexes. All magmatic zircon grains show Rhyacian and Orosirian ages, ranging from c. 2250 Ma to c. 1850 Ma. The best Concordia ages range from 2184 ± 9 Ma to 2080 ± 19 Ma. Hf in zircon and whole-rock Sm-Nd data disclose mantle-related signatures for both, the Pocrane and Juiz de Fora complexes, suggesting igneous protoliths with no or very few involvement of continental crust, similarly to juvenile magmatic arcs. Conversely, Hf in zircon data for the Quirino complex show an evolved signature compatible with a magmatic arc developed on a continental older crust with Archaean components. Together with a thorough compilation on Rhyacian-Orosirian orogenic systems (ROOS), our data allow us to envisage links within the Congo-São Francisco palaeocontinent, comprising orogens characterised by mostly evolved isotopic signatures and zircon inheritance. They are grouped into the: (i) W-ROOS, including the Mantiqueira complex, the west segment of the Eastern Bahia belt, intrusions in the south Gavião and Porteirinha blocks, and parts of the Mineiro belt; and (ii) E-ROOS, comprising the Quirino complex, basement rocks of the Cabo Frio tectonic domain, the coastal Eastern Bahia belt, and, in Africa, Eburnean and Kimezian complexes, as well as the western Angola shield. Assembled between the W-ROOS and E-ROOS, an orogenic system with prominent juvenile to moderately juvenile isotopic signature (JU-ROOS) includes the Juiz de Fora and Pocrane complexes, and the Buerarema complex at the central segment of the Eastern Bahia belt. [ABSTRACT FROM AUTHOR]

• Metabasic dykes in this study correspond to the ∼1.85 Ga metamorphic zircon age. • Metabasic dykes show clockwise P–T paths with peak conditions were constrained to be 0.6–0.9 GPa/580–650 °C (JN1929), ∼0.95 GPa/757 °C (JN1918) and ∼1.15 GPa/820 °C (JN1932), respectively. • Longgang Block has magmatism of ∼2.2 Ga indicated by protolith crystallization zircons. • A collisional orogeny started at ∼1.85 Ga along the northern margin of the NCC. The distribution and tectonic evolution of the Paleoproterozoic orogenic belts in the North China Craton (NCC) remain controversial. Especially, the extent of the Paleoproterozoic magmatic and metamorphic influences on the Archean Longgang Block needs further demonstration. This paper presents detailed petrographic and mineralogical analyses, phase equilibria modeling and zircon dating for three metabasic dyke samples in the Jiapigou area, South Jilin Province, in order to discuss their metamorphic evolution and tectonic implications. Petrographic observation and phase modeling using THERMOCALC suggest that these metabasic dykes have experienced the metamorphism with clockwise P-T paths under low-amphibolite facies, high-amphibolite facies and high-pressure granulite facies. Their peak P-T conditions were constrained to be 0.6–0.9 GPa/580–650 °C (JN1929), ∼0.95 GPa/757 °C (JN1918) and ∼1.15 GPa / 820 °C (JN1932), according to the stability fields of mineral assemblage and isopleths of Ti content in amphibole, anorthite component (X An) in plagioclase, pyrope content (X Py) and grossular content (X Grs) in garnet. The peak conditions correspond to apparent geothermal gradients of 19–22℃/km, being medium-pressure type. Zircon U-Pb dating shows that the metabasic dykes have a protolith crystallization age of 2199 ± 5 Ma (MSWD = 0.43), and a metamorphic age of 1855 ± 41 Ma (MSWD = 0.21). The protolith ages, metamorphic characteristics and ages of the metabasic dykes in South Jilin can be well compared with those for metabasic dykes in East Hebei and North Liaoning, indicating that the northern part of the Longgang Block was extensively affected by the mid Paleoproterozoic magmatism, and was involved in an orogen to be metamorphically reworked during the late Paleoproterozoic (1.82–1.85 Ga). In addition, this orogeny mainly occurred along the northern margin of the craton, which is different from the ∼1.95 Ga orogeny in the NCC. [ABSTRACT FROM AUTHOR]

The Yinshan Block located in the northern margin of the North China Craton (NCC) has been regarded as a typical Archean cratonic block, but it is argued whether the block had been affected by Paleoproterozoic tectonic and metamorphic events. This paper reports the late Paleoproterozoic high-pressure (HP) granulites for the first time from the Xiwulanbulang area in the Yinshan Block, and presents a systematic study on their petrography, mineral chemistry, phase equilibria modelling and zircon dating to confirm their metamorphic evolution and tectonic implications. Two representative samples contain the typical HP basic granulite assemblages involving garnet, clinopyroxene, plagioclase, amphibole and quartz, with garnet commonly occurring as coronae around clinopyroxene and plagioclase. Both samples show clockwise P–T paths with their peak conditions of ∼930 °C/∼15kbar (20NM01) and 970–980 °C/∼13.5 kbar (21NM05) respectively, constrained using the maximum Ti contents in amphibole and minimum anorthite (X An) in the mantle of plagioclase on P–T pseudosections. Zircon dating yields a magmatic age of ∼ 2.3 Ga and metamorphic ages of ∼2.5 Ga and ∼1.8 Ga. The ∼2.3 Ga magmatic age represents the time of protolith gabbro crystallization, which can be comparative to the extension-related bimodal magmatism in the Khondalite Belt. The ∼ 1.8 Ga age was determined from metamorphic zircons that have flat HREE patterns with the presence of garnet, interpreted as the time of the post-peak cooling and uplifting of the HP granulite facies metamorphism. The ∼2.5 Ga is defined from the captured zircon grains by gabbroic intrusions from the country Neoarchean rocks. The HP granulite facies metamorphism registers a geothermal gradient of 19–20 °C/km, indicating a collision-related orogenic event that may have occurred at ∼1.85 Ga along the northern margin of the NCC. Therefore, the Yinshan Block may represent a weak deformation domain in the orogenic belt on the northern margin of the NCC. [ABSTRACT FROM AUTHOR]

The Goiás Massif is a collage of Archean-Paleoproterozoic terranes that crop out in the central Brazil Northern Brasília Belt and acted as the continental margin onto which Neoproterozoic Brasiliano orogenic events took place. Most belts in the massif formed from 2.2 to 2.0 Ga, a widespread age bracket in the São Francisco-Congo Craton, pericratonic areas and other terranes associated with the formation of the “Atlantica Supercontinent”. However, the genesis of the Goiás Massif has always been a matter of debate due to a sharp crustal thickness contrast marked on surface by the trace of the Rio Maranhão Thrust and widely hypothesized as a suture zone. The hypothesis that this suture would have been formed when a microcontinent was accreted to the rest of the massif during the Neoproterozoic Brasiliano Orogeny is tested in this paper through mapping and zircon geochronology of rocks along the Rio Maranhão Thrust. Our study indicates that units contain Paleoproterozoic ages, have similar geological features to other Goiás Massif 2.2–2.0 Ga terranes and show no evidence of syn-collisional Neoproterozoic magmatism. We therefore reinterpret the available data to propose instead, that the amalgamation of the massif occurred fully in the Paleoproterozoic. First, the gravimetric contrast marked by the Rio Maranhão Thrust represents in fact a Neoproterozoic lower crust delamination event that affected both the Brasiliano Orogen and the terrane it was accreted against, the Campinorte Arc. Second, Serra da Mesa Suite Mesoproterozoic granites intruded both sides of the Rio Maranhão Thrust and thus, indicate the two domains were amalgamated prior to the Mesoproterozoic. Finally, Mesoproterozoic volcanic and plutonic rocks follow the trace of the Rio Maranhão Thrust, suggesting a reactivated intracontinental structure rather than an original product of Brasiliano collision. The Goiás Massif also show important similarities to the São Francisco Craton: a) orogen building and magmatism from 2.2 to 2.0 Ga; b) metamorphic peaks from 2.11 to 2.08 Ga; c) zircon age peaks at ∼1.76 Ga, ∼1.58 Ga and ∼1.2 Ga largely attributed to crustal extension events and d) contiguous seismic signature from massif to craton. These common features allied to our reassessment of central Brazil geochronology and the nature of central Brazil sharp crustal thickness contrast indicate that the Goiás Massif was fully assembled during a 2.2–2.0 Ga Orogeny as part of the western border of the São Francisco(-Congo) paleocontinent. A comprehensive understanding of this orogeny is vital to test the validity of Atlantica and to infer the landmasses later involved in the assembly of Columbia. [ABSTRACT FROM AUTHOR]

The Precambrian evolution of the Central Asian Orogenic Belt (CAOB) in NE China remains enigmatic. In this paper, we report petrography, zircon U–Pb ages, and major and trace element data of the Precambrian gneissic granites from the Xilinhot Complex in the Xilinhot terrane of the eastern CAOB. Zircons in four gneissic granite samples yielded weighted mean 207 Pb/ 206 Pb ages of 1397–1360 Ma, suggesting that the Xilinhot terrane is a microcontinental fragment with Precambrian basement rather not a Paleozoic accretionary complex as previously thought. The gneissic granites contain high SiO 2 (73.7–78.6 wt%) and K 2 O (4.1–4.9 wt%) but low Al 2 O 3 (9.5–12.1 wt%), with depleted Sr, Ba, Ti, P, fractionated REE patterns, and strong negative Eu anomaly. These features are comparable to those of A-type granites related to extensional environments. This first discovery for the occurrence of ∼1.4 Ga A-type granites suggests that the Xilinhot terrane in the CAOB was likely originated from part of the Columbia supercontinent, and re-assembled after the breakup of Columbia during the Mesoproterozoic, probably at ca. 1.4 Ga. [ABSTRACT FROM AUTHOR]

Plate tectonics revolutionized the Earth Sciences during the 1960s and led to a fundamentally new view of tectonic processes inside mountain belts. Application of the new theory to pre-Permian and especially Precambrian orogenic belts developed somewhat reluctantly during the 1970s and 1980s. The present article presents and discusses the ideas of Boris Choubert (1906–1983), a French colonial geologist of Russian origin, which he first developed in 1935. He tried to test Wegener’s theory of continental displacement (a forerunner of plate tectonics) by applying it to Paleozoic and Precambrian orogenic belts around the Atlantic (a topic altogether neglected by Wegener). To achieve this, he produced a fit of the continents across the Atlantic which is almost identical to the famous 1965 fit of Bullard et al. Starting from this Paleozoic continental configuration, he presented an inter-continental synthesis of Precambrian geology and discussed problems from a wide array of topics, ranging from regional tectonics of the West African Craton, questionable Precambrian fossils, tillites (and cap carbonates) to the supposed origin of detrital diamonds in Gabon and Brazil. He also provided probably the first Precambrian plate reconstruction avant la lettre . After his 1935 paper, Choubert worked for decades in Africa and South America and had opportunity to test and refine his synthesis. His example is a call, addressed to present-day geologists working on Precambrian geology in Africa and other regions, to consult the old colonial literature which contains a wealth of factual information and theoretical inspiration which is still of interest today. [ABSTRACT FROM AUTHOR]

It is widely accepted that the North China Craton (NCC) was finally formed by collision of the Eastern and the Western Blocks along the Trans-North China Orogen (TNCO) at approximately 1.85 Ga. The continent–continent collision along the TNCO was partly defined by metamorphism of high pressure mafic granulites with clockwise P – T paths. However, the continental subduction process has not been well recorded by previously reported HP granulites due to lack of prograde metamorphism and their plutonic protoliths. In this paper, we report HP mafic granulites among a metamorphic volcanic-sedimentary sequence south to Chicheng, northern part of the TNCO, in which the prograde metamorphism was well preserved. The prograde metamorphic stage (M1) has been revealed by a distinct growth zone of garnet (Grt) porphyroblasts with an inclusion-rich core and inclusion-free mantle. The peak metamorphic mineral assemblage (M2) consists of Grt and clinopyroxene (Cpx) predominantly with minor plagioclase (Pl), Rutile (Ru), hornblende (Hb) and quartz (Q). The Pl + Hb symplectite or corona surrounding garnet and Cpx + Ilm (ilmenite) symplectite surrounding sphene provide evidence for the post-peak decompression (M3) stage. Ubiquitous Hb especially along cracks represents further retrogression (M4) within amphibolite facies. Phase equilibria modeling by the THERMOCALC program combined with thermobarometric calculations yielded a consecutive hairpin shaped clockwise P – T path, which indicate that the HP granulites experienced remarkable prograde metamorphism, during which the temperatures increased from 630 °C to 740 °C while the pressures increased from 8 kbar to the barometric peak of 16 kbar. After the barometric peak, the HP granulites subjected to decompression from 16 kbar to 13 kbar while the temperature continued to increased from 750 °C to 790 °C, suggesting a thermal relaxation. After the thermal peak, the HP granulites began their consecutive decompression with cooling from 790 °C and 13 kbar to 700 °C and 7 kbar through 740 °C and 9 kbar, avoiding access to the orthopyroxene (Opx) stability field as experienced by many other HP granulites in the TNCO. The hairpin-shaped P – T path of the Chicheng HP granulites suggests a continuous continental subduction and tectonic uplift, providing a better metamorphic constraint on the final assembly of the NCC along the TNCO. [ABSTRACT FROM AUTHOR]

This paper presents the results of U–Pb dating of detrital zircons from six metasedimentary rocks in the Taowan and Kuanping groups in the northern margin of the North Qinling Orogenic Belt (NQB), Central China, for constraining the tectonic affinity of the NQB, the existence time and tectonic features of the Kuanping Ocean and the accurate northern boundary of the NQB. Zircon U–Pb dating indicates that the protoliths of the two metasedimentary rocks from the upper and lower parts of the Taowan Group were deposited later than ∼1111 and ∼871 Ma respectively. However, the protoliths of the four metasedimentary rocks from different layers of the Kuanping Group were deposited later than ∼781, ∼668, ∼515 and ∼477 Ma, respectively, suggesting that the Taowan Group and the Kuanping Group both have an abnormal or non-Smithian stratigraphic sequence. The age populations and predominant peak ages of detrital zircon grains from the Mesoproterozoic–middle Neoproterozoic metasedimentary rocks in the Taowan and Kuanping groups indicate that their provenances were mainly attributed to the NQB and subordinately from the Yangtze Craton (YZC), suggesting that the two groups both belong to the NQB and the northern boundary of the NQB should be placed to the north of the Taowan Group, which can be called the Paleo-Luonan–Luanchuan Fault. However, the Nd–Pb whole-rock isotopes, zircon Hf isotopes and trace element compositions of the Precambrian basement rocks and the Neoproterozoic granitic magmatic events in the NQB are significantly different from those in the YZC, suggesting that the NQB was more likely to be an independent microcontinent adjacent to the YZC from the Mesoproterozoic to the Neoproterozoic, and experienced a unique geological history. On the other hand, together with the record of the oldest MORB-type basalt with an age of 1445 Ma in the Kuanping Group, the first late Mesoproterozoic sedimentary record (∼1111 Ma) in the Taowan Group, to be reported using precise geochronological data in this study, it indicates that the Kuanping Ocean separated the NQB from the NCC that had already existed to the north of the NQB before the Mesoproterozoic, and was a major ocean basin which had lasted for a long time, rather than as a back-arc basin. [ABSTRACT FROM AUTHOR]

The Jiangnan Orogen is traditionally considered the suture zone, along which the Yangtze and Cathaysia blocks collided to form the united South China Block. There are still major controversies surrounding the pre-collisional tectonic pattern and amalgamation process along the Orogen and the relationship of the united South China Block (SCB) with the Rodinia. Our recent field investigations identified the presence of the volcano-sedimentary unit of the Lengjiaxi Group at Jianxichong, with the thickness of over 1700 m. A set of new zircon U–Pb geochronological, whole-rock elemental and Sr–Nd isotopic data for the metabasites have been obtained and presented in this paper. The layered diabase and tuffaceous samples from the Jianxichong volcano-sedimentary unit yielded the weighted mean ages of 837 ± 5 Ma and 835 ± 6 Ma, respectively. The U–Pb ages of detrital zircons from the phyllite interlayer form a main age-cluster at the peak age of 870 Ma with the youngest apparent age of 845 ± 23 Ma. This indicates that the metabasites in the Jianxichong volcano-sedimentary unit formed at ∼845–835 Ma rather than in the previously-thought Neoarchean in the Central Jiangnan Orogen. The metabasitic samples have SiO 2 ranging from 48.78 wt.% to 53.72 wt.% and MgO from 7.71 wt.% to 12.74 wt.% with mg-number of 63–71, and hence can be classified as tholeiitic basalt and basaltic andesite. They demonstrate a sub-parallel and right-sloping chondrite-normalized REE pattern with slightly negative Eu anomalies and sub-parallel spiky PM-normalized patterns with enrichment in LILEs, depletion in HFSEs and P–Ti negative anomalies, similar to those of arc volcanic rocks. Their ɛ Nd ( t ) values range from −1.64 to −0.37 and initial 87 Sr/ 86 Sr values from 0.7046 to 0.7081, respectively. Such crust-like geochemical characteristics might have been inherited from a sub-arc source modified by fluid/melt released from the subduction sedimentary component. In conjunction with available data and geological observations, we herein propose the development of the early Neoproterozoic (∼840 Ma) continental arc-basin system along the Central Jiangnan Orogen in response to an arc-continent accretionary assembly along the Rodinia exterior. [ABSTRACT FROM AUTHOR]

V. Ngako and E. Njonfang addressed in their comment an interesting and debated issue about the collision geodynamics of the Pan-African Central African Orogenic Belt (CAOB) in Cameroon. However, the reason for this comment is still not clear to us since it mainly deals with issues far away from the scope of our study, namely, the pre-collisional set up of the belt. The comment raises two main points – the reworking process during plate collision and the Pan-African strain pattern – not discussed in our paper for the simple reason that it was not our goal and because our data set does not even allow such discussion. Having said that, the comment gives us the opportunity to clarify our view on the nature of the Adamawa-Yade domain (Central Cameroon) and the early evolution of the CAOB. We will successively discuss two other points raised in the comment: (1) our Fig. 12 depicting a possible pre-collisional configuration at the northern and southern margin of the Congo craton in the Early Neoproterozoic, and (2) the nature and extent of the Adamawa-Yade domain. [ABSTRACT FROM AUTHOR]

Geodynamic models offer insight into deformation styles of syn- and post-collisional extensional processes. Such models often ignore the effect of lateral viscosity contrast between accreted terranes and inherited tectonic boundaries. This paper presents a set of crustal-scale analog experiments of one-way post-collisional gravitational spreading testing the effect of crustal heterogeneity by using two mechanically contrasting blocks, pre-existing cuts with varying dips, and three layers with contrasting rheologies. Two blocks represent strong, mature, and weak, juvenile crustal parts. Both blocks have three horizontal crustal layers: brittle upper, weak partially molten middle and dry strong lower layer. Cuts represent pre-existing crustal-scale shear zones and tectonic boundaries. The experiments indicated that tectonic boundaries may facilitate exhumation and increase extensional strain, when the boundaries dip opposite to the flow direction. The tectonic boundaries may also split and divide the crust into separate blocks with independent deformation signatures: shortening, elongation or rotation. The tectonic boundaries rotated along vertical axes toward the flow direction. The modeling results suggest that in areas with inherited tectonic boundaries and compositional differences the amount of extension is unevenly distributed between the different parts during the widespread unilateral gravitational spreading and that the flow has different effects on the contrasting crustal units, in both lateral and vertical directions. To validate the modeling, the results are compared to geophysical and geological data from the Paleoproterozoic Svecofennian orogen in the Fennoscandian Shield. The comparison suggests that the orogen underwent 50% extension and was thinned by maximum of 20% via westward gravitational spreading. This spreading rotated the crustal-scale blocks, shear zones and tectonic contacts. It also brought exhumed, high grade middle crustal blocks into contact with subsided, low grade, upper crustal blocks. We suggest that results of the analog models can be used as proxies in both ancient and modern hot accreted orogens, which have undergone post-convergence continental mid-crustal weakening and have comprised of juxtaposed terranes with varying rheological compositions. [ABSTRACT FROM AUTHOR]

• Three episodes of Neoproterozoic magmatisms are identified in the Songnen Massif. • These Neoproterozoic granitoids formed by reworking of Paleo-Mesoproterozoic crust. • The ca. 790 Ma monzonites were formed via a magma mixing process. • Precambrian basement composition of the Songnen Massif is laterally heterogeneous. This paper reports new zircon U–Pb geochronological, whole-rock geochemical, and zircon Hf isotopic data for Neoproterozoic intrusive rocks in the Songnen Massif in the eastern Central Asian Orogenic Belt (CAOB), with the aim of revealing the petrogenesis of the Neoproterozoic intrusive rocks, and constraining the basement composition and crustal growth process of the Songnen Massif. Dating results identify three episodes of Neoproterozoic magmatism at ca. 950, ca. 856, and ca. 790 Ma in the eastern Songnen Massif. The ca. 950 Ma magmatic rocks consist of syenogranites, the ca. 856 Ma magmatic rocks comprise mainly gneissic monzogranites, and the ca. 790 Ma magmatic rocks consist of gneissic monzonites and monzogranites. The Neoproterozoic granitoids have high contents of SiO 2 and K 2 O, low contents of total Fe 2 O 3 and MgO, and show characteristics of enrichment in large-ion lithophile elements (e.g., K and Rb), and depletion in high-field-strength elements, implying that their primary magmas could have been derived from partial melting of the lower crust. However, compared with the ca. 790 Ma monzogranites [ε Hf (t) = +7.3 to +9.5] in the south of the Songnen Massif, the ca. 950 and ca. 856 Ma granitoids in the north have much lower zircon ε Hf (t) values (−2.0 to −0.2 and −10.6 to −8.9, respectively), suggesting that the ca. 950 and ca. 856 Ma magmas were generated by the reworking of ancient mafic lower crust, whereas the ca. 790 Ma granitic magma was generated by the reworking of juvenile mafic lower crust. In contrast, the ca. 790 Ma gneissic monzonites were formed by mixing of the mantle-derived and crust-derived melts. Considering the Precambrian magmatism, detrital and captured zircons, and zircon Hf model ages together, the Precambrian basement of the Songnen Massif includes not only the Neoproterozoic crustal materials, but also the Neoarchean–Mesoproterozoic components. Zircon ε Hf (t) values of the Neoproterozoic granitoids in the Songnen Massif appear to progressively decrease from south to north, reflecting a lateral heterogeneity of basement composition of the eastern Songnen Massif, and indicating that crustal growth occurred mainly during the late Mesoproterozoic and Neoproterozoic in the south, while during the late Paleoproterozoic in the north. [ABSTRACT FROM AUTHOR]

The Central Asian Orogenic Belt (CAOB) is one of the largest accretionary orogens in the world. It was formed mainly by amalgamation of island arcs, accretionary wedges and microcontinents. Revealing the origins of the Precambrian continental blocks is essential for the understanding of the tectonic framework and geodynamic evolution of the CAOB. In this paper we present detrital zircon U–Pb ages of Precambrian meta-sedimentary rocks and late Paleozoic undeformed sandstone from the northern Yili Block, Chinese North Tianshan, in order to better understand the regional tectonic evolution. Two mica-schist samples from the Wenquan Metamorphic Complex (WMC) show similar zircon age distribution patterns with peaks at ∼0.43 Ga, ∼0.54 Ga, ∼0.65–0.68 Ga, ∼0.74–0.79 Ga, ∼0.89–0.92 Ga, ∼1.3–1.55 Ga and ∼1.69–1.70 Ga, respectively. Minor age peaks of ∼1.1 and ∼2.2 Ga are also separately recognized in individual samples. A phyllite from the Mesoproterozoic Changcheng System yielded detrital zircon ages mainly ranging from 855 to ∼1500 Ma with a single peak at ∼906 Ma. According to the analysis of age data and corresponding CL images of the dated zircon grains, protoliths of the mica-schists and phyllite should have deposited later than 645 Ma and 850 Ma, respectively, and were subjected to medium- to low-grade metamorphism during mid-late Silurian time. The good agreement between the age patterns of the meta-sediments and those of the nearby granitic and high-grade metamorphic rocks of the WMC indicates that the detrital zircon grains were mainly derived from the local metamorphic/crystalline basement. Occurrence of much older zircons (∼1.0–2.2 Ga) in the mica-schists and absence of such zircon populations in the phyllite suggest that (1) the protoliths of the mica-schists and phyllite had distinct sources and were deposited at different time, and (2) Mesoproterozoic to Paleoproterozoic rocks probably existed in the northern Yili Block. Three undeformed sandstone samples yielded consistent single age peak at ∼368–376 Ma and contain only a few Proterozoic detrital zircon grains. The peak age is in agreement with ages of neighboring late Paleozoic arc magmatic rocks in the Chinese North Tianshan. Thus, the sandstone was probably deposited during latest Devonian to earliest Carboniferous time in a forearc or interarc basin, around which Proterozoic basement was not exposed or completely isolated. A comparison between the zircon age patterns of the northern Yili Block and the surrounding cratons and microcontinents leads us to conclude that (1) the northern Yili Block had a Proterozoic basement similar to that of the Chinese Central Tianshan and Kyrgyz North Tianshan, and (2) these microcontinental blocks share the same origin as the Tarim Craton, but are distinguished from the Siberian Craton. [ABSTRACT FROM AUTHOR]

Precise age determination and source tracing of the granitic and pegmatitic gneisses of the Taihua Complex in the Xiaoqinling area are important to address the debates on the timing and processes of the amalgamation of the Western and Eastern Blocks along the Trans-North China Orogen. This paper conducted zircon dating of metamorphic rocks from the Xiaoqinling area. The results demonstrate that the collision between the Western and Eastern Blocks occurred in the Paleoproterozoic. Laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) zircon uranium–lead (U–Pb) analyses yielded consistent results. The Early Paleoproterozoic (the first period) age of 2346±28Ma was determined for granitic gneiss in the Taihua Complex and 2328±14Ma for the Xiaohe granite pluton that intruded into the granitic gneiss. The gneissose pegmatitic granite and granitic veins that intruded into the granitic gneiss yielded LA-ICP-MS zircon ages of 1881±24 and 1866±19Ma, respectively. These Paleoproterozoic ages strongly indicate that the ocean between the Eastern and Western Blocks were completely subducted at ∼1.85Ga. The ɛ Hf(t) values of the zircons from the granitic gneiss can be divided into a positive group (0.44 to 3.77) and a negative group (−3.11 to −1.27). The two-stage hafnium (Hf) model ages (T DM2(Hf)) corresponding to the positive values are between 2672 and 2887Ma. The ɛ Hf(t) values of the zircons from the Xiaohe granite range from −2.49 to 2.58, with the Hf isotope model ages ranging from 2742 to 3022Ma. Thus, the Xiaohe granite could have resulted from the partial melting of the Late Archean lower crust caused by subduction and the presence of juvenile mantle material. The primary magma of the granitic gneiss of the Paleoproterozoic Taihua Complex was derived from the differentiation of the depleted Late Archean mantle source with a small portion derived from the remelting of the subducted lower crust. [ABSTRACT FROM AUTHOR]

Abstract: Eclogites in an orogen, serving as a credible marker for deep subduction of oceanic or continental crust, are a key to decipher the process and fate of plate subduction. The nature of eclogite precursors bears important information on orogenic mechanism and pre-subducted geological history. Despite their importance, the nature of ultra-high pressure (UHP) eclogites in the North Qinling (NQ) terrane is still poorly constrained, which leads to conflicting tectonic scenarios for the evolution of the Qinling orogenic belt. In this paper, we provide a combined study of zircon U–Pb ages, major and trace element data, and Sr–Nd–Pb–Hf isotope compositions for eclogites from the NQ terrane. U–Pb age determinations on magmatic zircon cores of two eclogite samples yield similar ages of ca. 800 Ma, indicating that the protoliths of the NQ UHP eclogites formed in the Neoproterozoic. The NQ eclogites have tholeiitic compositions and are characterized by high TiO2 (1.40–2.40%), and low P2O5 (0.09–0.22%), Na2O (1.10–2.49%) and K2O (0.17–1.04%) contents. They are moderate fractionation in REEs (LaN/YbN =2.31–4.20) and show negligible Nb, Ta, Ti, and Eu anomalies (Eu/Eu*=0.82–1.10). The eclogites have high positive whole-rock ɛ Nd(t) (2.81–5.53) and zircon ɛ Hf(t) (10.5–11.9) values, indicating their derivation from a relatively depleted mantle source. On geochemical discriminant diagrams based on immobile element ratios, the NQ eclogites fall in the field of continental basalts. Moreover, both the geochronological and geochemical features of the eclogite protoliths are quite different from those of the Erlanpging basaltic rocks, but comparable to those of the coeval continental basalts in South Qinling (SQ) orogen and the northern margin of the South China Block (SCB). As the mid-Neoproterozoic basaltic rocks in the SQ orogen and the northern margin of the SCB were well documented to form in a continental rift setting in response to the global-scale breakup of the Rodinia supercontinent, it is inferred that the NQ eclogite precursors might also form in a continental rift setting at ca. 800Ma, which resulted in the splitting of the NQ terrane from the SCB. As the protoliths of the NQ eclogites have a continental property, we suggest that the ca. 490Ma UHP metamorphism of the NQ unit might result from its northward subduction beneath the Erlangping arc and thus manifested an arc-continent collision process. [Copyright &y& Elsevier]

Abstract: This paper discusses the exhumation history of Palaeoproterozoic high-grade units from the Lapland Granulite Belt (northern Finland) through a reappraisal of previous structural and metamorphic data and a new structural analysis. The Lapland Granulite Belt is located between two cratons (Inari Craton and South Lapland Craton). It is marked by a major thrusting event associated with the development of an inverse metamorphic gradient within the underlying Tanaelv and Karasjok Belts. The review of published metamorphic data combined with our new structural analysis suggests that the exhumation history of the Lapland Granulite Belt was accommodated by the development of coeval basal thrusting and early normal-sense shear-zones, and later by distributed erosion. We propose also that the early exhumation stages of the Lapland granulite unit were associated with heating of both the overlying Inari Craton and the underlying South Lapland Craton. The occurrence of coeval thrusts and normal-sense shear-zones combined with the important role of distributed erosion during the final exhumation stages suggest that this Palaeoproterozoic collisional belt may represent an intermediate stage between ultra-hot accretionary orogens involving weak lithospheres and modern orogens involving stiff lithospheres (mixed-hot orogen of ). Our analysis emphasizes that the transition between ancient-type orogens and modern-type ones was gradual in space and time, being firstly dependent on the thermal and rheological state of the sub-continental lithospheric mantle of the lithospheres involved in compression. [Copyright &y& Elsevier]

Abstract: This paper presents the results of a detailed and fully integrated pressure–temperature–time-deformation (P–T–t-D) study of the country rocks around Venetia Mine in the Central Zone of the Limpopo Belt, South Africa. Detailed structural mapping around Venetia Mine delineates four deformation events (D1–D4). Relict S1 comprises quartzofeldspathic bands in biotite gneiss and amphibolite. S2, defined by biotite in biotite schist, gneissic banding in biotite gneiss, long axes of quartzofeldspathic augen, and the long axes of amphibolite lenses/boudins, is axial planar to F2. F3 occurs predominantly at the contacts between biotite gneiss and biotite schist, forming open to closed, upright to inclined, E-W- to ENE-trending, shallowly plunging folds. D4, which was constrictional-prolate in nature, refolded S1, S2, F2 and F3. F4 folds and an L4 mineral lineation, defined predominantly by sillimanite in metapelitic schist, plunge moderately NE to NNE and overprint all previous fabrics. Poles to refolded S2 foliations show a characteristic great circle distribution. In turn, the pole to this great circle coincides with the orientation of L4. Such patterns are also found in the Avoca, Bellevue and Ha-Tshansi sheath folds in the Central Zone, albeit that the plunge of the lineations at Venetia are predominantly NE-wards, rather than SW-wards. The moderately NE- to NNE-plunging F4 sheath folds and L4 lineations accord with the NE-SW trend of sheath folds and associated mineral elongation lineations observed elsewhere in the Central Zone. However, PbSL dating of syntectonic garnets constrain the minimum and maximum age of D2 and D4 structures respectively to c. 2037–2040 +/− 22Ma. The metamorphism developed in metapelitic lithologies is characterized by peak amphibolite facies conditions of ∼6.5kbar and 680°C. Pseudosection modelling of growth zoning in garnet provides evidence of a prograde pressure and temperature increase from ∼5kbar at 600°C to ∼6–6.5kbar at 650–680°C, which is interpreted to be a consequence of tectonic thickening. Collectively, the integrated P–T–t-D data unequivocally demonstrates that the country rocks around Venetia experienced a structural–metamorphic event in the palaeoproterozoic. Coupled with published data we suggest a simple two-fold tectonic model, which involves the Central Zone as separate terrane docking with the Kaapvaal during the Neoarchean and later, during the Palaeoproterozoic this Central Zone-Kaapvaal amalgam collides with the Zimbabwe Craton. [Copyright &y& Elsevier]

Abstract: Gavilgarh-Tan Shear Zone (GTSZ) – a map-scale ductile shear zone occurring in the southern part of the Central Indian Tectonic Zone (CITZ), contains many important clues to the tectonics of this important Proterozoic mobile belt of central India, which is yet controversial and hotly debated. Data from structural mapping, microstructural study and kinematic analyses of the GTSZ have been presented in this paper which clearly implies that GTSZ is mainly represented by a wrench-dominated transpressional shear zone with sinistral shear sense. Analysis of lineation patterns shows that, while horizontal stretching dominated within the ductile shear zone, rocks on either side (north and south) of it stretched vertically, with a transition zone of simultaneous horizontal and vertical stretching in between these two domains. A general transpressional strain has thus been partitioned into wrench- and pure shear-dominated domains at large scale. Further strain partitioning also took place at the outcrop scale. Geochemistry of the granitoids occupying the shear zone and its surrounding area indicates continental collision set-up, which supports the structural model. On the basis of earlier proposed tectonic models, and limited geochronological data available, of the southern part of CITZ, it is suggested here that an oblique collision, and final suturing, between the northern (Bundelkhand Craton) and southern (Bastar Craton) terrains within the CITZ around ∼1100Ma, have been partly accommodated by partitioned transpression along GTSZ and its surrounding gneiss–granitoid terrain. More intensive geochronological constraint of the collision event from both northern and southern side are however lacking at present. [Copyright &y& Elsevier]

Abstract: The NNW-trending tectonic grain of the eastern Yilgarn Craton (EYC) was established as a result of predominantly ENE–WSW directed extension (D1 and D3) and E(ENE)–W(WSW) (D2, D4) to NE–SW directed (D5) contraction. The result has been a succession of NNW-striking temporally discrete fabric elements, which can be difficult to interpret reliably at any single location. Despite this, many past workers interpreted the NNW-striking fabric as the result of only one regional contractional event, and used it as a marker for correlating structural events across the region. In order to unravel the complexity, this paper presents a new sixfold (D1–D6) deformation nomenclature based on >10,000 new mesoscale structural observations, including their kinematic analysis and cross-cutting relationships. These mesoscale data were referenced with regional 3D map patterns, stratigraphic-magmatic-metallogenic considerations, and deep seismic reflection images. This integrated geodynamic-architectural approach is applicable to solving structural-event histories in other polydeformed terrains. Gold mineralisation occurred during the first five events, but was particularly concentrated from D3 onwards. The D3 event marked the most profound change in the tectonic evolution of the EYC, with changes in greenstones, granites and tectonic mode (lithospheric extension and core complexes), with the first significant gold deposited within extensional shear zones that dissect the crust. Later contraction (D4) was imposed at a high angle to the previously established anisotropic architecture. The outcome was the creation of a new dynamic permeability framework, which resulted in gold mineralisation during NNW-striking sinistral strike-slip faulting and associated thrusting. A further stress switch (D5) further modified the architecture resulting in N- to NNE-striking dextral strike-slip faulting, and the final period of gold mineralisation, before late-stage extension (D6). [Copyright &y& Elsevier]

Abstract: This paper presents a reappraisal of the tectonic evolution of the Zanhuang Massif that lies at the eastern margin of the Trans-North China Orogen, a continent–continent collision belt that marked the amalgamation of the North China Craton in Late Paleoproterozoic. Detailed field work with focus on geometries of structures and kinematics was performed. This was completed with LA-ICP-MS U–Pb analyses on zircon, EPMA U–Th/Pb dating on monazite and 40Ar/39Ar dating on amphibole. These studies led us to propose a new three-fold litho-tectonic subdivision of the massif: The Western Zanhuang Domain (WZD) made of TTG, migmatite and pink anatectic granite is correlated to the Fuping Massif that crops out to the north-west. Both areas represent a continental block, called the Fuping Block, which acquired most of its architecture around 2100Ma ago. The Eastern Zanhuang Domain (EZD) made of TTG and migmatite represents the western edge of an Eastern Neoarchean Block. In between, the Central Zanhuang Domain (CZD) is a NE–SW trending stack of supracrustal, gneiss and mafic magmatic rocks thrust sheets displaced toward the ESE upon the Eastern Block. The lithological features suggest that the CZD represents the remnant of an oceanic basin, called the Taihang Ocean that closed during the amalgamation of the Eastern Block and the Fuping Block around 1880–1850Ma. In agreement with recent work done along the western margin of the belt, in the Lüliang Massif, this study documents the amalgamation of the North China Craton in response to the closure of two oceanic basins, namely the Lüliang Ocean and the Taihang Ocean. West-dipping subductions and collisions involving three distinct continental blocks, called the Western, the Fuping and the Eastern Blocks, took place around 1880–1850Ma. [Copyright &y& Elsevier]

The Khondalite Belt is widely regarded as a Paleoproterozoic collisional orogen between the Yinshan and Ordos Blocks in the Western Block of the North China Craton. However, the deformation history of the Khondalite Belt is poorly understood, and many aspects of the tectonic processes involved in the collision remain enigmatic. In this paper, we carried out detailed field-based structural analyses integrated with geochronological studies in the Helanshan Complex, one of the multiply deformed high-grade gneiss terrains in the Khondalite Belt. Three major phases of deformation (D 1 -D 3) were identified in the Helanshan Complex. D 1 mainly produced S(SW)-verging recumbent to overturned intrafolial isoclinal folds F 1 , originally sub-horizontal penetrative transposition foliations S 1 and SSW-plunging mineral lineations L 1. D 1 deformational fabrics occurred coevally with the granulite-facies peak metamorphism. D 2 dominantly generated steeply SE(E)-plunging asymmetrical upright open folds F 2 that successively refolded the previous D 1 structures. D 3 gave rise to a series of NE- to E-trending ductile shear zones, featured by top-to-the-(N)NW oblique thrusting with a component of sinistral strike-slip movement. LA-ICP-MS U-Pb zircon dating results of seven deformation-related samples reveal that D 1 occurred at some time from 1954 Ma to 1911 Ma, most likely at 1954–1949 Ma. D 2 successively happened in the period of 1911–1870 Ma, and D 3 had broadly taken place at ∼ 1870 Ma. The D 1 -D 3 deformation sequences recorded tectonic processes including the initial top-to-the-SSW thrusting and crustal thickening, subsequently followed by exhumation of the khondalites in the Paleoproterozoic. Combined with previous studies, these new structural and geochronological data indicate that the Khondalite Belt underwent a long-term (>100 Myr) orogenic history and developed polyphase deformation, high-grade metamorphism as well as magmatism in response to the NNE-SSW-directed oblique collision between the Yinshan and Ordos Blocks at ∼ 1.95 Ga. [ABSTRACT FROM AUTHOR]

Abstract: At Forsmark, ca. 120km north of Stockholm in central Sweden, ductile high-strain belts with WNW to NW trend anastomose around tectonic lenses with an inferred lower degree of ductile strain. Previous studies of ductile deformation zones with WNW to NW trend, elsewhere in the western part of the Svecofennian orogen in central Sweden, have yielded estimates for the timing of at least one phase of discrete ductile deformation that fall in the time interval 1.82–1.78Ga. Most of these ages were determined by the U/Pb dating of titanite and, for this reason, provide no information on the thermal evolution. In this paper, we make use of 40Ar/39Ar hornblende geochronology to address late Svecofennian cooling, ductile deformation and exhumation. The data demonstrate the presence of three 40Ar/39Ar hornblende age generations. All ages have been adjusted to take account of ca. 1% systematic bias between 40Ar/39Ar and U/Pb ages recently reported in the literature. The oldest age, ca. 1.87Ga, and the intermediate age generation, 1.85–1.84Ga, are spatially restricted to the tectonic lenses. By contrast, the youngest age generation, 1.83–1.81Ga, occurs both within the tectonic lenses and the enveloping high-strain belts. One explanation for the structurally controlled age distribution involves regional cooling beneath the closure temperature for argon isotopic mobility around or above 500°C by 1.84Ga, as represented in the oldest and intermediate age generations, followed by resetting of the argon isotope system in hornblende between 1.83 and 1.81Ga, as represented in the youngest age generation. This resetting occurred in response to retrograde, lower amphibolite- to upper greenschist-facies deformation along discrete high-strain zones within the broader high-strain belts and was associated with regional exhumation. An alternative explanation involves no resetting of the ages. Instead, it is suggested that a period of slow cooling of hornblendes with slightly different closure temperatures, from ca. 1.87 to 1.82Ga, may have caused the age variation observed within the tectonic lenses, whereas locally maintained higher temperatures, due to activity along the discrete high-strain zones, can explain the consistently younger ages in the broad, enveloping high-strain belts. In this explanation, an increase in cooling rate, in response to regional exhumation, finally closed the argon isotope system in hornblende throughout the area at 1.83–1.81Ga. It is suggested that the regional exhumation at 1.83–1.81Ga, which is included in both explanations, is related to far-field effects of the deformation that ended an accretionary tectonic cycle in adjacent tectonic domains. [Copyright &y& Elsevier]

[Display omitted] • Superposed fabrics in a syntectonic pluton record assembly of the Superior Province. • Early frontal terrane convergence occurred at around 2712 Ma in a 'hot' mode. • Subsequent dextral shearing was localized to terrane boundaries. • The two-stage evolution resembles modern accretionary orogens. The Canadian Superior Province has become one of the key test pieces to discuss tectonic processes and mechanisms of crustal growth in the Late Archean. The Province consists of a >2.8 Ga proto-cratonic core intruded by voluminous arc-like plutons and surrounded by a series of narrow, elongate ca. 2.8–2.7 Ga juvenile belts, also referred to as terranes or domains. The terranes seem to wrap around the proto-cratonic core and generally young outward, but the kinematics and geodynamic causes of their assembly remain debated. In this paper, we examine the Radisson pluton in northeastern Québec, which intruded the southern, outer edge of the presumed magmatic arc (Bienville domain) along its ~WNW–ESE-trending tectonic boundary with the proto-cratonic crust (La Grande domain). The pluton, dominated by porphyritic monzogranite to quartz monzonite, was emplaced at around 2712 Ma and exhibits complex internal structure resulting from superposed magmatic to solid-state deformations. An early margin-parallel ~WNW–ESE magmatic foliation containing a steep lineation, recognized by the anisotropy of magnetic susceptibility (AMS), is interpreted as recording vertical stretching and horizontal flattening of highly crystallized magma, either due to emplacement and/or pure shear dominated transpression. More widespread, however, is a horizontal lineation within the same foliation that is interpreted as recording post-emplacement, but still syn-magmatic, tectonic strain (~NNE–SSW shortening and boundary-parallel stretching). Upon cooling, localized dextral S–C mylonite zones accommodated further shortening within the pluton whereas undeformed late-stage felsic dikes cross-cut the solid-state fabric at an angle to the pluton margins. We suggest that this structural succession, also reproduced by numerical fabric modeling, is a local-scale signal of a two-stage assembly of the northeastern Superior Province: the frontal, NNE-directed terrane convergence and attachment to the cratonic nucleus, operating in a 'hot' regime with voluminous arc-like plutonism, was followed by more localized dextral shearing parallel to terrane boundaries. The latter phase is recorded at the proto-craton margin but also in the outboard Abitibi greenstone belt virtually at the same time (ca. 2700–2690 Ma). In combination, the two-stage evolution and similar deformation distributed over a broad region resemble modern large hot orogens formed in a plate-tectonic regime. [ABSTRACT FROM AUTHOR]

• Metasedimentary rocks in the Qinling block represent a sedimentary series with depositional ages between 1262 and 840 Ma. • The 1754–1266 Ma detritus was sourced from the Indian craton and the younger detritus was sourced from the Qinling block during assembly of Rodinia. • A sequence of oceanic subduction (1262–981 Ma), arc-continent collision (981–911 Ma), continuous subduction of oceanic crust (929–833 Ma), and continental rifting (833–774 Ma) during the formation of the Qinling block were identified. • The Qinling block, as part of the circum-Rodinia subduction zone, represents the outer margin of Rodinia. The Meso-Neoproterozoic Rodinia supercontinent formed a coherent large landmass, which was later dispersed over all current major continents and a number of microcontinents. The Qinling block is a Precambrian continental mass, located in the Qinling orogenic belt, which marks the junction of the North China and South China cratons. In this paper, we present a systematic study of the petrology, whole-rock geochemistry and geochronology of metasedimentary rocks from the Xiahe Group, which is a key unit of the Precambrian basement in the Qinling block, to constrain the paleogeographic reconstruction of Rodinia. The studied metasedimentary rocks have detrital zircon ages of 3054–1082 Ma that peak at 1172 Ma and 1582 Ma. The protoliths of the metasedimentary rocks are mainly shales and wackes with maximum depositional ages from 1147 to 1082 Ma, representing a part of a continental arc-related sedimentary sequence. Combining our results with existing data, we propose that their protoliths constituted a sedimentary series including an older sequence of basement and a younger sequence with depositional ages between 1262 and 840 Ma. The detritus that is older than 1266 Ma was sourced from the continental margin of the Indian craton, which was part of the Columbia supercontinent. There was a Paleo-Mesoproterozoic continental nucleus in the Qinling block that split from the margin of the Indian craton during the breakup of Columbia. The source rocks for the younger detritus were arc magmatic rocks in the Qinling block, which formed in a continental arc by oceanic lithosphere subduction during the assembly of Rodinia. A sequence of oceanic subduction beneath the continental nucleus of the Qinling block (1262–981 Ma), arc-continent collision between the continental nucleus and the Indian craton (981–911 Ma), continuous subduction of oceanic crust beneath the block with formation of a mature volcanic arc (929–833 Ma), and continental rifting (833–774 Ma) during the formation of the Qinling block was identified. The block faced the Neoproterozoic ocean during the assembly of Rodinia, and finally rifted off the supercontinent during its breakup to form an isolated arc terrane [ABSTRACT FROM AUTHOR]

• S-type granites in the southern Dabie terrane were dated at ~2.5 Ga. • Xenocrystic magmatic zircons record other phases of magmatism at 3.56, 3.34, and 3.18 Ga. • The Archean Yangtze Craton was composed of several independent microcontinents. It is unclear whether most Archean continents have always existed in their present-day size, or were initially microcontinents or supercratons. The Archean evolution of the Yangtze Craton in South China provides an ideal opportunity to reveal Archean continental architecture. Archean rocks in the Yangtze Craton have been documented in seven separate areas prior to this study. In this paper, we report the first discovery of Archean rocks in a new area in the southern Dabie orogenic belt, which we term the Xishui gneiss. The protolith of the granitic gneiss is strongly peraluminous with high A/CNK ratios of 1.10–1.23 and K 2 O/Na 2 O ratios of 0.70–1.72, belonging to the high-K calc-alkaline series. Three samples of the gneiss from different localities yielded protolith ages of 2.51, 2.47, and 2.47 Ga (zircon U–Pb weighted mean ages). Xenocrystic zircons with magmatic texture from the gneiss yielded U–Pb ages of 3.57–2.41 Ga, and records four phases of magmatism and crustal reworking at 3.56, 3.34, 3.18, and 2.51–2.47 Ga. The history of crustal growth recorded by the gneiss can be traced back to ~3.80 Ga, with peaks at 3.8–3.7 and 3.5–3.4 Ga. A comparison of the crustal evolution in the eight exposed Archean terranes of the Yangtze Craton suggests they were independent microcontinents during the Archean and that the present-day Yangtze Craton was amalgamated at 2.0–1.9 Ga during assembly of the Columbia supercontinent. [ABSTRACT FROM AUTHOR]

We report a complicated magnetic fidelity through time in Singhbhum Craton, India, with new, geographically wide-spread and spatially detailed, paleomagnetic results. The Singhbhum Craton in eastern India is cross-cut by multiple generations of the so-called "Newer Dolerite" dykes. A previously published 1765 Ma paleomagnetic pole represents a useful constraint on the Singhbhum Craton during the amalgamation of the Columbia supercontinent whereas an older ~2763 Ma paleomagnetic pole is problematic. We present additional data from the 1765 Ma dykes that results in a grand mean paleomagnetic pole at 43°N, 320°E (A95 = 10°, K = 17; N = 13). The 1765 Ma pole is supported by a positive baked contact test. Our additional data shows that paleomagnetic results from the 1765 Ma dykes are more complicated by magnetic overprints than originally reported. We also argue that the steep inclination paleomagnetic data from the Singhbhum Craton, previously assumed to represent a Neoarchean signal, are part of a complicated group whose magnetic age is uncertain. We establish a minimum age of 2250 Ma for connecting the Singhbhum and Dharwar cratons on the basis of published geochronology and our interpretation of paleomagnetic data in this paper. Paleomagnetic data from both cratons can be juxtaposed using a simple Euler pole rotation of the Singhbhum Craton relative to Dharwar. [ABSTRACT FROM AUTHOR]

• Two-phased late Paleoproterozoic A- and S-type granitoids were identified in the Wuyishan Domain. • These late Paleoproterozoic granitoids were derived in a continental arc/back-arc setting. • Two-phased late Paleoproterozoic arc/back-arc magmatism was related to the assembly of the Paleoproterozoic Nuna supercontinent. The Cathaysia Block amalgamated with the Yangtze Block along the Jiangnan orogenic belt to form the South China Craton during early Neoproterozoic time. However, the origin of the Cathaysia Block and its position in the Nuna supercontinent remain controversial. This paper synthesizes geochronological, geochemical and isotopic data from late Paleoproterozoic igneous rocks in the Wuyishan Domain of the Cathaysia Block (SE China). Two-phases of late Paleoproterozoic A- and S-type granitoids were identified and dated at 1925–1848 Ma and 1816–1750 Ma. The A-type granites in the Wuyishan Domain were likely derived from partial melting of mafic lower crust with a tonalitic to granodioritic geochemical composition, and the S-type granites were derived from partial melting of a meta-sedimentary source. These late Paleoproterozoic granitoids were emplaced in a continental arc/back-arc setting and the two-phased arc/back-arc magmatism was related to the assembly of the Paleoproterozoic Nuna supercontinent. Combining our results with previous late Paleoproterozoic geochemical and age data, we suggest that the Cathaysia Block was located close to northern India Shield during Proterozoic time until the breakup of the Rodinia Supercontinent in the late Neoproterozoic. [ABSTRACT FROM AUTHOR]

• 40Ar/39Ar age of hornblende of the Aketashitage orogenic belt was dated to be 1.88–1.85 Ga. • Cooling rate of this orogen was quite heterogeneous in the Paleoproterozoic. • The Aketashitage orogenic belt did no involved in the Paleozoic subduction. The Paleoproterozoic Aketashitage orogenic belt lies in between the two large accretionary orogenic systems, i.e., Paleo-Asian ocean and Paleo-Tethys ocean systems, in northwest China. Previous geochronologic studies reveal widespread Paleoproterozoic orogeny-related magmatism and high-grade metamorphism in this area, determined by the U-Pb dating of zircon and monazite. In this paper, 40Ar/39Ar dating of hornblende of three representative amphibolite samples yielded cooling ages of ∼1.88–1.85 Ga. Comparison of the zircon/monazite U-Pb and hornblende 40Ar/39Ar ages suggests that these amphibolite samples record different exhumation and cooling processes. These new geochronologic data further confirm that the Aketashitage orogenic belt only records Paleoproterozoic metamorphism but no overprint of Paleozoic thermal event. It is thus inferred that the Aketashitage area might act as a continental fragment/terrane which was passively collaged onto the ambilateral Paleozoic orogens but was not involved in the Paleozoic subduction. [ABSTRACT FROM AUTHOR]

• The ~3.67 Ga TTGs from Aketashitage area derived from the melting of a thickened oceanic plateau crust or island-arc crust. • Two Paleoproterozoic orogenic belts along the southern and northern margins of the Dunhuang Block. • The Southern Orogen is ~150 m.y. earlier than the Northern Orogen. • In the Paleoproterozoic, Dunhuang Block was assembled into the Columbia supercontinent. The evolution of the Dunhuang Block associated with the assembly of the Columbia supercontinent is poorly constrained. The geochemical composition and temporal evolution of magmatic and metamorphic rocks may hold key information regarding critical geodynamic processes that occurred during the evolution of the Dunhuang Block. In this paper, we present a systematic petrographic, geochemical, and zircon U-Pb and Hf isotopic investigation on tonalitic gneiss, carbonatite, granitic dyke, mafic granulite and A-type granite in the Dunhuang Block. The results suggest that tonalitic gneiss was derived from partial melting of a thickened oceanic plateau crust or island-arc crust at ~3.67 Ga and then it recorded an important subduction-collision orogenesis in the Paleoproterozoic (~2.02 Ga to ~1.96 Ga). The ~1.94 Ga carbonatite and ~1.85 Ga granitic dyke were formed by partial melting of marble and Meso- to Neoarchean basement rocks, respectively. Both of them were formed in post-collisional setting. The ~1.82 Ga mafic granulite recorded high-pressure granulite facies metamorphism followed by a medium–low pressure granulite facies metamorphic overprint, suggesting a clockwise P-T path and implying an environment of collisional orogenesis. The ~1.76 Ga A-type granite resulted from the reworked Neoarchean crust and was most likely related to a post-collisional episode. Combined with previous studies, we identify two Paleoproterozoic orogenic belts of the Dunhuang Block: the ~2.00–1.96 Ga South Orogen and ~1.85–1.80 Ga North Orogen. According to the coupling of these two orogenies with the Columbia orogeny, we conclude that the Dunhuang Block was associated with the assembly of the Columbia supercontinent. [ABSTRACT FROM AUTHOR]

• Crustal-scale study of partially molten orogenic crust. • Competent, not weak, overall deformation style within middle crust during compression. • Overall deformation style folding, with shear zones not melt fraction-related. Granitic partial melts are generally thought to significantly weaken the orogenic crust and, ultimately, lead to the collapse of an orogen. Studies from different orogens have shown that the syn -melt deformation behaviour at the orogenic scale is, however, more complex. In addition, once fully crystalline, granitic material strengthens the crust. Linking the evolution from melt-present to melt-absent deformation at the scale of the orogen is a challenging but necessary task if one wishes to investigate the overall behaviour of the middle crust. In this paper, we make observations of orogen-scale deformation, developed over a period of 30–40 Ma during crustal partial melting of the middle and lower crust of a Palaeoproterozoic orogen. The crust shows a globally common pattern where coeval partial melting, compressional deformation, and transtensional structures co-exist. We demonstrate this complex interaction through an integrated approach using multiple datasets. The key observation is that of widespread, regular, orogen-scale shortening by folding of sub-horizontal anatectic granitic sheets and highly migmatized lithologies; this shortening interacted with modest orogen-parallel lateral stretch expressed as local extensional/transtensional structures. The pervasive and dominant deformation style is that of folding of the syn -kinematic granite sheets and voluminous migmatites: this demonstrates that the principal deformation style of deformation within the partially molten mid-crust is competent rather than weak. The observed evidence of weak behaviour such as strike-slip or transtensional shear zones accommodating lateral escape are localized in comparison and not necessarily associated directly with the granite sheets or the highly migmatized volumes of the crust. Moreover, the strain intensity (fold wavelengths and amplitudes) seems independent of the overall melt fraction. The implications are that, while widespread volumes of partial melt will weaken the crust overall (compared to the brittle upper crust) and while individual melt bodies can possibly persist for up to some millions of years in the middle crust, i) the relative strength between (partially) molten volumes is not primarily controlled by melt fraction; and ii) individual melt volumes may be too short-lived at the time-scale of orogenic deformation (i.e. orogenic strain rates) to significantly influence the overall deformation style. [ABSTRACT FROM AUTHOR]

• The structural configuration of the Hadabei area is a granitic-gneiss dome. • Rocks experienced three stages of Paleoproterozoic deformation. • The peak deformation occurred from >1860 Ma to 1822 Ma. • Doming was accompanied by intensive lower to middle crustal flow deformation. • JLJOB experienced early E-W rifting and contraction, and late N-S contraction. A group of Paleoproterozoic gneiss domes are well preserved in the southern Liaodong segment of the Jiao-Liao-Ji Orogenic Belt (JLJOB), eastern North China Craton. Similar to the domes in many other orogenic belts, they may provide important clues to our understanding of the orogenic processes and related middle-lower crustal mass flow during the tectonic evolution of the orogenic belt. This paper conducted detailed structural analysis of the Hadabei dome, a typical example in the dome group to unravel the Paleoproterozoic structural styles and deformation history of the southern Liaodong orogenic belt. Three stages of deformation (D 1 -D 3) are reconstructed for the structural evolution of the dome. The D 1 deformation is characterized by meso- to micro-scale intrafolia folds (F 1), penetrative foliations (S 1) and mineral lineations (L 1) in the metamorphosed volcanic-sedimentary rocks. The D 2 deformation intensively transformed S 1 foliations to form asymmetrical folds (F 2) and crenulation cleavages (S 2). The D 3 deformation is mainly evidenced by occurrence of open folds (F 3) at various scales. U-Pb zircon geochronological dating of syn-tectonic leucogranitic dykes shows that the D 2 deformation occurred from >1860 Ma to 1822 Ma. It is also shown that the D 2 deformation is the peak stage of deformation that contributed to the formation of the overall tectonic framework of the Hadabei dome, and therefore, the orogenic belt. At this stage, subhorizontal mass flow contributed to the widely developed shear structures. The formation of the Hadabei dome was ascribed to early diapirism (D 1), subhorizontal shearing and doming (D 2) and fold superposition (D 3). The multi-stage structural evolution was resulted from successive E-W oriented rifting, extension and contraction, and subsequent superimposition by N-S shortening in the southern Liaodong Paleoproterozoic orogenic belt. These conclusions provide a better understanding of the mechanisms of doming, regional structural deformation, and tectonic evolution of the JLJOB. [ABSTRACT FROM AUTHOR]

• Rocks of North and South Liaohe Groups show similar detrital zircon age patterns. • Rocks of North and South Liaohe Groups have similar Hf isotope compositions. • Liaoji Grantiods and adjacent Archean basement serve as source for the Liaohe Groups. • Back-arc basin deposition occurred for corresponding formations of the Liaohe Groups. The Jiao-Liao-Ji Belt (JLJB) is one of the most important Paleoproterozoic orogenic belts, which is intervening between the Longgang and Nangrim-Liaonan blocks. The Liaohe Group is an important research subject for understanding the Paleoproterozoic tectonic setting and evolution of the JLJB. However, the relationship of depositional spatial and chronological distributions between the North and South Liaohe groups are still under debates. In this paper, we present geochronological and zircon Lu-Hf isotopic results of meta-sedimentary rocks from the Liaohe Group to decipher their provenance depositional ages and environment, as well as their tectonic significance on the JLJB. The detrital zircons from the corresponding formations, including the Li'eryu, Gaojiayu and Dashiqiao formations of the North and South Liaohe groups, show similarities in age patterns and Hf isotopic compositions. The detrital zircons from the Li'eryu Formation of the two groups display unimodal 207Pb/206Pb age peaks at ca. 2.2–2.1 Ga. On the other hand, detrital zircons from the Gaojiayu and Dashiqiao formations of the two groups, yield two dominating age peaks at ca. 2.2–2.1 and ~2.5 Ga. In summary, all detrital zircons with age peaks at ca. 2.2–2.1 Ga, have ε Hf (t) value of −6.99 to +9.41 and two-stage Hf depleted mantle ages (T DM2 model ages) of 3143 to 2137 Ma. The ~2.5 Ga detrital zircons however, have ε Hf (t) value and T DM2 model ages which widely range from −9.37 to +10.13 and from 349 to 2367 Ma, respectively. Geochronological results indicate that ca. 2.2–2.1 Ga zircons were derived from the Liaoji granitoids. The adjacent basement rocks of the Longgang and Liaonan-Nangrim blocks provide the major sources to detrital zircons that yield an age peak at ~2.5 Ga. Combined with previous studies, the new geochronological data suggest that the protoliths of the corresponding formations of the North and South Liaohe groups deposited their detritus progressively in a back-arc basin. The Liaoji granitoids are the main sources providing detritus for the Li'eryu Formation. Subsequently, clastic sediments transported from the Longgang and Liaonan blocks, as well as from the Liaoji granitoids, were successively deposited and provided sources to the Gaojiayu and Dashiqiao formations. [ABSTRACT FROM AUTHOR]

• First report of late Tonian within-plate mafic magmatism in the Costeiro Domain. • Crustal thickening and extensional partial melting in the Costeiro complex. • Embu and Costeiro Domains have a shared geological history since 800 Ma. The tectonic evolution of the Ribeira Belt comprises a protracted history involving several magmatic, deformational and metamorphic events mainly associated with the Neoproterozoic Brasiliano Orogenic Cycle. Most tectonic models relate the evolution of the Ribeira Belt to a protracted orogenic history with diachronous accretion of different terranes against larger cratonic blocks. However, recent proposals challenge models of multi-stage terrane accretions. In this paper we revisit the current tectonic models proposed for the Central Ribeira Belt, based essentially on a large data compilation and new geochemical and geochronological data from samples of the Costeiro Complex. The critical evaluation of these data indicates a long-lasting shared evolution for two geological domains in the Central Ribeira Belt (Embu and Costeiro Domains), usually thought to be different terranes accreted during the late Ediacaran. The first report of late Tonian within-plate tholeiitic to alkaline mafic magmatism and the late Cryogenian-early Ediacaran metamorphism in the Costeiro Complex support the interpretation of shared evolution on both Embu and Costeiro Domains, challenging the current models of diachronous accretion of terranes during the late Ediacaran in the Central Ribeira Belt. [ABSTRACT FROM AUTHOR]

• Quebecia terrane (Grenville Province) consists of over 95% juvenile 1.5 Ga oceanic arcs. • Slivers of crust with 1.8 Ga Nd ages divide Quebecia into a composite arc belt of terranes. • 1.5 Ga oceanic arcs were accreted to Laurentia after the 1.5 Ga Pinwarian orogenic event. • Some Quebecia terranes were rifted from the active margin and re-accreted further east. • Oblique tectonics may explain Pinwarian arc accretion without a major collisional orogen. There continues to be confusion in the geological community concerning the ages of crustal formation and crustal accretion within the central Grenville Province of Quebec. To clarify the geological history of crustal growth in the eastern part of the Quebecia terrane, sixty new Nd isotope analyses are presented from a 60,000 km2 area northwest of Baie Comeau. Most samples yield Pinwarian Nd model ages that suggest them to be derived from juvenile oceanic arc terranes. However, two large slivers with Paleoproterozoic TDM ages attest to the existence of hidden blocks of old crust, which divide the area of juvenile Pinwarian crust into a composite arc belt of smaller accreted terranes. The old crustal blocks probably do not reach the present surface, but represent an igneous crustal protolith of younger I-type magmatism. By comparison with a Mesozoic tectonic analogue, it is proposed that accreted juvenile arc crust with attached slivers of older crust were rifted away from an active margin to the west, and translated eastwards until blocked by the previously accreted Labradoria terrane. Although the Quebecia composite arc belt consists of over 95% of Pinwarian juvenile arc crust, the age of arc accretion was post-Pinwarian. The proposed oblique nature of the accretion process may explain the lack of a major collisional orogen at that time. This paper shows the usefulness of large-scale Nd isotope mapping of Precambrian crustal terranes to clarify complex processes of crustal formation and arc accretion. [ABSTRACT FROM AUTHOR]

• Westward compressive belt evolved to a sinistral transpresional belt at the Archean Paleoleoplate margin. • Through gravimetric analysis the Pindobaçu Lienament marked the transcrustal boundary. • Archean and Paleoproterozoic rocks were interleaved during the Paleoproterozoic Orogeny. • 3-D structural modelling were generated to reconstruction of the Archean Jacobina Basin during the Paleoproterozoic. • Different crustal segments suggest a complex structural arrangement. Defintion of the geometry and tectonic style of Paleoproterozoic mobile belts at the Paleoarchean cratonic margin of the Gavião Block brings new insights into the early evolution of the São Francisco Craton. This paper presents the regional structural framework and tectonic stratigraphic 3D models made from geological mapping and gravimetric modeling of the Jacobina Range. The Jacobina Range is composed of an Archean greenstone belt, Au-U detrital pyrite-bearing sedimentary rocks and Paleoproterozoic granite-gneissic terranes deformed between 2.1 and 1.9 Ga as the result of collision of the Archean Gavião, Serrinha, and Jequié blocks. Two deformational phases and three subdomains were described in the field area. The deformational phases include (i) a compressional phase with a westward tectonic convergence that built an imbricated fault system and (ii) a sinistral transpressional phase with a northwestward tectonic convergence, which forms a subvertical fault system with sinistral-oblique to lateral displacement. The southern subdomain is characterized by an imbricated tectonic system overprinted by transpressional faults. The central subdomain contains western-verging meso- to megascopic, slightly asymmetric folds, preserved as evidence of high strain. The northern subdomain is characterized as a fold and thrust system that was tilted by the intrusion of late granitic bodies. The modeling of two gravimetric sections identified deep structures that suggest sutures between the Gavião and Serrinha crustal blocks. Here, we propose a model for the Archean evolution of the Mundo Novo Greenstone Belt and the subsequent deposition of sediments in the Jacobina Basin, followed by intrusion of mafic-ultramafic sills and dikes and Paleoproterozoic deformation. [ABSTRACT FROM AUTHOR]