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The multiscale structural analysis carried out in the NNW sector of the Juruena Terrane, SE of the State of Amazonas combines structural mapping, microtectonic analysis and aeromagnetic data analysis. It shows a complex structural and metamorphic history composed of successive deformation events, responsible by the formation of its tectonic framework. Event D2 (1520-1460 Ma) is responsible for the main structure of the NNW sector of the Juruena Terrane, and it generates a dextral transpressive shear zone NW-SE, called Roosevelt-Guariba Transpressive Belt (RGTB). This is an intracontinental high-temperature, medium-pressure tectonothermal event, compatible with the conditions of the upper amphibolite to granulite facies. The RGTB controls the tectonic compartmentation of the region, particularly affecting the Granitic Gneiss Domain (1760-1750 Ma). Other sectors, such as the Supracrustal Rock Domain (1800-1730 Ma) and the Pre-Juruena geological-structural association (>1830 Ma), are subordinately affected. Event D2 overlaps the regional structure E-W (ENE-WSW) attributed to Event D1 (1690-1630 Ma), which is restricted to the deep basement in the NNW sector, but dominant in the south central sector of the Juruena Terrane. There are also two late brittle-ductile to brittle deformation events (events D3 and D4). Event D3 (1320-1300 Ma) is represented by NE-SW cataclastic and shear zones, commonly serving as conduits for hydrothermal fluids relative to gold mineralizations. Event D4 is constituted by normal faults and fractures that reactivate RGTB shear zones, limiting Neoproterozoic and Paleozoic-Mesozoic sedimentary exposures. The tectonic structural model proposed in this study reinforces the interpretation that the Juruena Terrane evolved from a foreland basin, which was formed during the Juruena Orogen and whose basement is the Tapajos Crust. This basin was preserved from the tectono-thermal effects of the end of the Statherian (D1), and it was only during event D2, after emplacement of the RGTB, that it underwent high-grade deformation and metamorphism, whose driving force is attributed to the propagation of stresses in pericratonic regions, associated with Calymmian orogens. The successive events are related to the cratonization of the Juruena Terrane, represented by late crust reactivation (D3) and neotectonic events (D4).

This study presents LA-ICP-MS U-Pb detrital zircon ages on a migmatitic paragneiss of the Jaguaretama Complex, northern Borborema Province, NE-Brazil. This metasedimentary rock comprises a stromatic migmatite with alternating layers of metapelite, metapsammite, and garnet-tourmaline-bearing leucosome. The paleosome displays a well-developed schistosity, with fine to medium-grained textures, and locally garnet porphyroblasts. Backscattered electron images show that many of the zircon grains display metamorphic overgrowths (recrystallization) and cores with igneous oscillatory zoning. The detrital zircon grains show 207Pb/206Pb ages clustering from 2.51 to 2.12 Ga (with 90% conc.), evidencing that the igneous sources were generated mostly during the Transamazonian/Eburnean orogeny. The age of 2137±9 Ma of the youngest and most concordant detrital zircon (core) is interpreted as the maximum depositional age of the protolith. The youngest and most concordant (conc. 99%) 207Pb/206Pb apparent age obtained in a metamorphic zircon overgrowth was 2046±6 Ma, which is interpreted as the age of high-grade metamorphism. This age of metamorphism is similar to other records of Paleoproterozoic high-grade metamorphic events in the Borborema Province and other cratonic domains (e.g. São Francisco and West Africa cratons). This age also represents the minimum depositional age of the protolith. Therefore, the depositional age of the studied supracrustal rock may be bracketed between ca. 2.14 and 2.05 Ga.

The Mana district, located in the northern part of the Birimian Hounde greenstone belt in western Burkina Faso, is a world-class Paleoproterozoic orogenic gold district (∼8 Moz) including five gold deposits (Fofina, Nyafe, Siou, Wona-Kona and Yaho). These deposits are located in specific lithostratigraphic domains, and gold is controlled by various structural features. Deposit- and regional-scale mapping, intrusion age and geochemistry, as well as airborne aeromagnetic and electrical resistivity geophysical data, were used to decipher the tectonic evolution of each gold deposit and the district. Five deformational and four gold mineralizing events were recognized. The first deformation event (D1MD: E-W oriented shortening) affected the metamorphosed volcanic and sedimentary rocks of the Lower Birimian group. This early deformation episode was correlated with the formation of gently N-plunging folds (F1MD) and N-S-striking thrusts faults coeval with emplacement of the pre- to synkinematic Wona-Kona and Siou plutons dated at ∼2172 Ma, under greenschist facies metamorphism. The quartz-carbonate veins (V1MD) at Fofina and Siou formed during D1MD at Eoeburnean time, manifesting the first gold event at approximately ∼2172 Ma. The following deformation event (D2MD: E-W oriented extension) is associated with the deposition of the Upper Birimian group (Mana basin) overlying the Lower Birimian group. The geometry of the Mana basin is controlled by the Mana and Maoula shear zones. The Tarkwaian-type rock formation overlying the Upper Birimian group, controlled by the Wona-Kona and Siou shear zones, is constrained at the end of D2MD or at the beginning of the D3MD event with a maximum deposition age at ∼2113 Ma. The third deformation event (D3MD: E-W to WNW-ESE transpression) affected the entire supracrustal rock. Such event is correlated with the formation of map-scale F3MD folds and dextral shear zones during the Eburnean orogeny (∼2113–2090 Ma). A second gold mineralizing event occurred during D3MD and is manifested by quartz-carbonate veins (V3MD) and disseminated sulfides at the Yaho, Fofina and Nyafe and possibly Wona-Kona deposits. The fourth deformation event (D4MD: NNW-SSE transpression) is correlated with sinistral shearing along the major transcurrent faults and the development of asymmetric NNE-striking folds (F4MD) associated with vertical fold axes. Syn-D4MD mineralization is characterized mainly by a strong silicification (Si4MD) with disseminated pyrite and arsenopyrite along the Wona-Kona shear zone and by tiny quartz-carbonate veinlets (V4MD). This event is considered the main gold-bearing event in the western margin of the Mana district. The fifth and last deformation event (D5MD) is brittle in character and was responsible for the formation of E-W subvertical crenulation cleavages and reverse faults under overall N-S shortening. This late deformation event is tentatively associated with a last gold event recorded as free gold associated with muscovite in brittle fractures developed in competent orebodies at the Wona-Kona and Siou deposits. This event could be as young as ∼2022 Ma, the age obtained from Ar-Ar datation of muscovite-schists at the Wona-Kona deposit. Our main contribution is that we decipher multiple gold mineralizing events at the district scale based on deposit- and regional-scale mapping. It is interpreted that gold was introduced as early as ∼2172 Ma and possibly as late as ∼2022 Ma during at least 3 or even 4 shortening tectonic events in a timeframe not yet recognized at the district scale for all the Birimian belts.

Recent advances in high-precision in-situ analysis of zircon U-Pb-Hf-O isotopes have significantly improved our approach to studying the origin and evolution of Archean crust. This study presents high-precision in-situ zircon U-Pb-Hf-O isotopes for the Southern Jilin Complex (SJC) on the northeastern margin of the North China Craton (NCC) and explores the potential of such an integrated approach in understanding the Archean crust evolution and its tectonic implications. The SJC consists mainly of Archean granitoid gneisses hosting minor supracrustal rock xenoliths. Zircon U-Pb data from representative lithologies reveal three episodes of magmatism at ~2.78, ~2.69 and ~2.55 Ga, respectively. The former two granitoid magmatic events are recognized for the first time in NE NCC, while the latest one is widespread over the NCC. All metamorphic zircon domains document similar metamorphic ages of 2.51–2.48 Ga, consistent with the widespread metamorphism of ~2.50 Ga in the NCC. Most concordant magmatic zircons preserve “mantle-like” O isotopic signatures, indicating the magma sources were not contaminated by large amounts of high δ18O supracrustal sediments. Hf depleted mantle model ages of magmatic zircons display one predominant peak at 2.9–2.8 Ga and two subordinate peaks at 3.3–3.2 Ga and 2.7–2.6 Ga, indicating possible episodic crust-mantle differentiation in Southern Jilin. Integrated zircon U-Pb-O-Hf data from the SJC suggest that magma sources were mainly derived from multiple episodes of reworking of juvenile or ancient crust with mantle component addition, while recycling of sediments was trivial during the Neoarchean in this region. The spatial–temporal relations of magmatism, lack of supracrustal addition to magma sources, and other geological evidence from the NCC are in favor of a bottom-up geodynamic regime possibly related to plume activities, arguing against a widespread top-down mechanism involving modern-style subduction in the NCC during the Neoarchean.

As one of the major Neoarchean granite-greenstone belts in China, the Helong terrane is located at the northeastern margin (Southern Jilin Province) of the North China Craton (NCC). It is dominated by metamorphic supracrustal rock assemblage and granitoid gneiss. The former contains amphibolite, hornblende plagioclase gneiss, biotite plagioclase gneiss and banded iron formation (BIF), whereas the latter is dominated by the Tonalite–Trondhjemite–Granodiorite (TTG) gneisses. Zircon LA–ICP–MS U–Pb isotopic analyses indicate that the supracrustal rock assemblage was formed at 2683–2654 Ma and underwent regional metamorphism (lower amphibolite facies) at 2614–2553 Ma before the widespread emplacement of plutonic granitoids at 2551–2532 Ma. Both greenstone sequence and plutonic granitoid rocks experienced the subsequent regional metamorphism (greenschist to lower amphibolite facies) at 2508–2400 Ma. The supracrustal rocks can be divided into three groups based on their lithological and geochemical characteristics. Detailed petrogenetic and geochemical studies suggest that the Group #1 amphibolite samples were derived from partial melting of depleted upper mantle that had been metasomatized by slab-derived fluids; Group #2 amphibolite samples were derived by partial melting of a depleted mantle wedge that was strongly metasomatized by subduction-derived fluids or melts; and Group #3 hornblende/biotite plagioclase gneiss samples were derived from partial melting of juvenile basalt and minor amounts of older sediments in the lower crust level. The granitoid gneisses in the Helong granite-greenstone belt can be divided into relatively high magnesium group (HMG) and low magnesium group (LMG). The HMG samples were derived from parental magmas generated by partial melting of juvenile basalt and minor amounts of older sediments within the lower crust level, whereas magmatic precursors of the LMG samples were generated by partial melting of a metapelite-dominated source under lower temperature melting conditions. U–Pb dating of inherited or captured zircons, combined with zircon Lu–Hf isotope data, indicates a significant ∼2.9–2.7 Ga crustal growth episode, whereas the ∼2.55–2.53 Ga magmatism involved crustal recycling in the Helong terrane. Consequently, the Helong terrane preserves a record of Neoarchean tectonic environment of Andean-type active continental margin.

The Crixas Greenstone Belt is a supracrustal rock sequence of the allochthonous Archean-Paleoproterozoic Crixas-Goias Terrane of the Neoproterozoic Tocantins Province of Central Brazil. The belt occurs between Mesoarchean (2.9-2.8 Ga) primitive orthogneiss complexes intruded by Siderian intracratonic mafic dikes and stocks. The rock succession of the greenstone belt consists of metakomatiites followed by metabasalts, both of greenschist to low amphibolite facies, underlying metasedimentary rocks of low greenschist facies. The greenstone belt is divided into the southern, central, and northwestern sectors, with different rock associations. The northwestern sector tectonically underlies a small exotic block known as the Mina Inglesa Sequence. The sequence consists of a low greenschist facies volcano-sedimentary package similar to a greenstone belt, but of unknown origin. The latest stratigraphic nomenclature for the belt labels its rock package as the Crixas Group. From base to top, the Group comprises the Corrego Alagadinho, Rio Vermelho, and Ribeirao das Antas Formations, made up of metakomatiites, metabasalts, and metasedimentary rock, respectively. The Mina Inglesa Sequence is an independent unit of the Crixas Group, in spite of the similar rock assemblage of both units. Protoliths of the Ribeirao das Antas Formation comprise shallow water black shales with dolomite lenses, laterally wedge-shaped with impure turbiditic sandstones (wakes). Published U/Pb and Sm/Nd whole-rock isotopic data indicate that the metakomatiites and metabasalts erupted during the Mesoarchean (3.0 Ga). Detrital zircon grains from the sedimentary protoliths suggest a mixed Mesoarchean and Rhyacian source-area (3.2 and 2.2 Ga). The U/Pb age from hydrothermal zircon grains of a gold-bearing quartz vein indicates that the sedimentation ended just before 2.1 Ga. Field, drilling, and the isotopic data led the authors to review the stratigraphic content of the Crixas Group by subdividing it into an Upper and Lower Subgroups. The Lower Subgroup comprises the Mesoarchean volcanic section subdivided, from base to top, into the currently adopted Corrego Alagadinho and Rio Vermelho Formations. The Upper Subgroup rests ubnconformable on the Lower Subgroup, and comprisess the Rhyacian metasedimentary section. The Upper Subgroup contains two rock units deposited in different environments. The currently used Ribeirao das Antas Formation is the lower unit, which is redefined as composed of carbonaceous phyllites with dolomite lenses. The upper unit comprises the new proposed Corrego Geral Formation, composed of metagraywackes. The wedge-shaped contact between both sedimentary units indicates that they were coevally deposited. The Paleoproterozoic sedimentary basin consisted of a small depression formed during the sagduction of the volcanic pile, triggered by the diapiric rise of the adjacent orthogneiss protoliths. The sediment deposition started with black shales in response to a slow rise of the seawater and paleoclimatic conditions. An increasing input of siliciclastic turbidites occurred in response to the uplift of a Rhyacian/Mesoarchean source-area that provided a mixed clastic load. Anomalous positive δ13C data from the dolomite lenses indicate that they deposited during the 2.2-2.1 Ga Lomagundi Event, which is compatible with the dominant Rhyacian zircon grains of the graywackes. The Crixas-Goias Terrane lacks geologic evidence for the existence of an internal Rhyacian crustal block to justify the youngest detrital zircon grains of the graywackes. These observations render uncertainty about the geographic position of the rising crust. Paleoproterozoic crustal shortening of the belt resulted in stacked thin-skinned thrust-faults that host gold orebodies. An eastward age decrease of the crustal shortening from Crixas to an easterly belt leads the authors to propose that the clastic load source could occur to the West of the Terrane. The Mina Inglesa Sequence is an allochthonous block with lithologic and isotopic features that distinguish it from the greenstone belt. The authors also describe that there is no isotopic evidence for Meso- to Neoproterozoic source-areas, neither for the Corrego Geral Formation nor for the Mina Inglesa Sequence. These findings raise a suggestion that the granite-greenstone belt association of the Terrane may represent a craton border that remained stable before its amalgamation to the province during the Neoproterozoic.

The Earth is a unique planet, which has been highly evolved, diversified and complicated through geologic time, and underwent many key events, including giant impact, magma ocean, core formation, large-scale mantle differentiation and late heavy bombardment, especially in its dawn. But, our knowledge of early Earth is limited due to the lack of the Hadean supracrustal rocks. The supracrustal rocks with the Eoarchean ages provide key evidence for the Earth's early evolution, but few supracrustal rocks have been comprehensively investigated. Therefore, we mapped in seven areas of the Saglek Block, northern Labrador, where ancient supracrustal sequences are interleaved with a diverse assemblage of orthogneisses. Early studies suggested that some of them have the Mesoarchean ages because of the lack of the Mesoarchean Saglek dyke, but we found the Saglek dykes in the areas to recognize the Eoarchean Nulliak supracrustal rocks and Uivak Gneiss in all the areas. Recent reassessment of U–Pb dating and cathodoluminescence observation of zircons from the oldest suites of the Uivak Gneiss showed that the Uivak Gneiss has the Eoarchean age, > 3.95 Ga, and forms the Iqaluk–Uivak Gneiss series. Because our geological survey clearly showed that the Iqaluk–Uivak Gneisses were intruded into the Nulliak supracrustal belts, the Nulliak supracrustal rocks are the oldest supracrustal rock in the world. The supracrustal belts consist of piles of fault-bounded blocks, which are composed of the ultramafic rocks, mafic rocks and sedimentary rocks in ascending order, similar to modern ocean plate stratigraphy (OPS). In addition, small-scale duplex structures are found over the areas. The presence of duplex structure and OPS indicates that the > 3.95 Ga Nulliak supracrustal belts originate from an accretionary complex. The presence of the accretionary complex, ophiolite and granitic continental crust provides the oldest evidence for the plate tectonics on the early Earth.

We report on volcanic rocks of the Qinglong-Zhuzhangzi area in northeastern Eastern Hebei Province, North China Craton. The supracrustal rock associations in the study area consist of amphibole/biotite plagioclase gneiss, mica (plagioclase) gneiss/schist, biotite K-feldspar gneiss, (pyroxene) plagioclase amphibolite and amphibolite. Twenty-five new mafic, intermediate to felsic samples can be geochemically classified into four groups. Group 1 is similar to fore arc low Ti tholeiite and is characterized by low SiO 2 (49.7 wt%) and TiO 2 (0.43 wt%), slightly depleted LREE and MREE pattern with (La/Yb) N ratio of 0.74, (Gd/Yb) N ratio of 0.82. It most likely derived from depleted mantle in a subduction initiation environment. Group 2 is akin to primitive arc tholeiites with low SiO 2 (49.7–51.8 wt%), slight enrichments of LREE ((La/Sm) N : 1.06–1.53) and negative Nb anomalies ((Nb/La) PM : 0.50–0.76). Group 3 resembles evolved arc tholeiites and displays pronounced enrichments of LREE ((La/Yb) N of 2.38–11.3, (La/Sm) N of 1.70–2.86) and negative Nb, Ta anomalies ((Nb/La) PM : 0.14–0.34, except sample 11JD28-4 with that ratio of 1.00). Group 2 and 3 formed by partial melting of sub-arc depleted mantle wedge modified by differing quantities of slab flux addition. Group 4 comprises K-rich andesite-dacites, which are distinguished by the highest SiO 2 (54.0–71.8 wt%), K contents (up to 5.03 wt%), strong enrichments of LREE ((La/Yb) N ratios of 4.83–19) and negative Nb–Ta anomalies, analogous to shoshonitic rocks marking late stage of subduction. LA-ICPMS zircon U–Pb and Lu–Hf analyses of evolved arc basalts and K-rich andesite-dacites display crystallization ages of 2511–2604 Ma and single stage Hf model ages of 2534–2927 Ma (most focus on 2650–2800 Ma). In contrast to ∼2510–2560 Ma arc associations, ∼2604 Ma shoshonitic dacites most plausibly represent an older orogenic event. Collectively, supracrustal rocks in the Qinglong-Zhuzhangzi area constitute a series of volcanic arc associations that correspond to an entire subduction cycle ranging from orogen to primitive arc–evolved arc and back to an orogenic setting, which further demonstrate that, by the late Archean, plate tectonic and subduction processes already closely resembled modern counterparts.

The presence of old residual continental crustal rocks in cratons is crucial for investigation of their early evolution. Due to the poor exposure of Archean rocks, the early evolution of the Yangtze Craton has not been well constrained yet. In this study, a combined study of zircon U–Pb and Hf–O isotopes, as well as whole rock major and trace elements and Nd isotopes have been conducted for a granite pluton at Huji town, in the northern part of the Yangtze Craton. U–Pb dating for magmatic zircons yielded a weighted mean age of 2656 ± 6 Ma, revealing another Archean outcrop in the Yangtze Craton besides the Kongling terrane. The granite samples show relatively evaluated (K 2 O + Na 2 O)/CaO, TFeO/MgO ratios, and Zr, Nb, Ce, Ga and Y contents, sharing the same features as the A-type granite. They have pronounced Eu, Sr and Ba negative anomalies on the primitive mantle-normalized trace element spidergram, implying the residual of plagioclase in the magma sources. Their high Zr contents of 440–529 ppm correspond to initial magma temperatures of 930–962 °C. The zircons have negative ɛ Hf ( t ) values of −2.7 to 0.1, and Hf model ages of ca. 3.2 Ga, respectively. The δ 18 O values of the zircons range between 4.94 and 5.72‰ and give an average of 5.26 ± 0.14‰, suggesting no contribution of supracrustal rock into the host magma. Therefore, the Hf model ages indicate the generation of the Huji granite by reworking of ca. 3.2 Ga juvenile crustal rocks. Combined with previous studies, the finding of the Neoarchean Huji granites with ca. 3.2 Ga Hf model ages suggests the widespread of Archean basement in the Yangtze Craton. The occurrence of the ca. 2.65 Ga Huji granites likely records the thermally stable lithosphere and thus heralds the craton stabilization of the eastern part of the Yangtze Block.

Based upon 1:200,000 regional gravity and aeromagnetic data, gravity and aeromagnetic slice maps were obtained through fast Fourier transformation (FFT) upward continuation. A comparison between gravity and aeromagnetic slice maps at different depths combined with regional geological data and Magneto-Telluric sounding reveals the deep geological structure of Benxi-Huanren area and provides important information for study of the deep geological evolution process of Benxi-Huanren area. Yanshanian granitic pluton is widely distributed in this area and tends to be continuous toward depth. Significant metallogenic areas, such as Dataigou and Nanfen areas, lie above the buried granitic pluton. The Paleoproterozoic strata distribution area and the Archean strata distribution area have similar characteristics in terms of gravity anomaly. The iron-bearing formation in Anshan area is Archean supracrustal rock which was not engulfed by Archean granite. The thickness of Liaoji paleo-rift can be up to 10 km, whose lower part was intruded by Yanshanian granites. The basement of the Liaoji rift was remelted during granite intrusion in Yanshanian period.

Chemical sedimentary rocks such as banded iron formation (BIF) and pillow basalts are persistent features of the oldest volcanic and sedimentary record by 3.8–3.7 Ga, and are direct evidence for oceans by the start of the Archean. However, their presence does not dictate an equitable 3.8–3.7 Ga terrestrial climate. This is because they could have formed in oceans below global pack ice on a frigid Earth. The oldest known depositional structures occur as locally preserved features in ca 3.7 Ga deformed, amphibolite facies rocks of the Isua supracrustal belt (Greenland). These include units up to ∼1 m thick, in which there are stacked or jumbled clasts of chert. Detailed structural analysis shows that these rocks are not tectonic breccias. Also, their reported location in chemical sedimentary units capping slightly older volcanic rocks shows they are unlikely to be mass-flow deposits in a deep basin. In both composition and structure, these units resemble edgewise breccias observed on later Precambrian and P...

New geochronological and geochemical constraints on Precambrian sedimentary and volcanic successions exposed in the western part of the Central Domain of the Borborema Province, NE Brazil, indicate the presence of two distinct tectono-stratigraphic complexes: Riacho Gravata and Sao Caetano. Both complexes and associated orthogneisses are referred in the literature as the Cariris Velhos belt, having depositional, extrusive, or intrusive ages within the interval 985–913 Ma. The Riacho Gravata complex consists of bimodal (but mostly felsic) volcanic and volcanoclastic rocks, muscovite ± graphite schists, quartzites, and marble with local occurrences of banded-iron-formation. The Sao Caetano complex mainly consists of metagreywackes, marbles, calc-silicate rocks, and rare meta-mafic rocks. Meta-mafic rocks from both complexes have geochemical signatures similar to those of continental flood basalts, with ɛNd (1.0 Ga) values ranging from −1.0 to −2.8. Felsic volcanic rocks from the Riacho Gravata complex show ɛNd (1.0 Ga) values ranging from −1.0 to −7.4 and geochemical signatures similar to A 2 -type granitoids. New SHRIMP U–Pb zircon data from felsic volcanic rocks within the Riacho Gravata complex yielded ages of 1091 ± 13 Ma and 996 ± 13 Ma. In contrast, meta-graywackes from the Sao Caetano complex show a maximum deposition age of ca. 806 Ma in the northern part and ca. 862 Ma in the southern part of the outcrop area. The orthogneisses show ɛNd (1.0 Ga) values ranging from 1.0 to −4.2 with U/Pb TIMS and SHRIMP ages ranging from 960 to 926 Ma and geochemical signatures of A 2 -type granitoids. The data reported in this paper suggest at least two periods of extension within the Central Domain of the Borborema Province, the first starts ca. 1091 Ma with magmatism and deposition, creating the Riacho Gravata basin and continued intrusion of A-type granites to 920 Ma. A second rift event, which reactivated old faults, generated a basin with a maximum deposition age of ca. 806 Ma. Furthermore, the oldest granitoids cutting these metasedimentary rocks have crystallization ages of ca. 600 Ma. This suggests that the second rift event could be early Brasiliano in age. The resulting Sao Caetano basin received detritus from a variety of sources, although detritus from the Riacho Gravata complex dominated. Deposition ages of the Riacho Gravata and the Sao Caetano complexes are coeval with deposits in other basins of the Borborema Province (Riacho do Tigre in the Central Domain; Macurure and Maranco in the Sergipano Belt of the Southern domain). The Macaubas Group from SE Brazil and its counterparts in Africa, the Zadanian and Mayumbian Groups, in the western edge of the Congo Craton are also coeval. Closure of the Riacho Gravata and Sao Caetano basins occurred during the Brasiliano convergence (705–600 Ma). During the last stage of convergence, ca. 612 Ma, pull-apart basins were created and filled; final basin closure took place 605–592 Ma, after deposition ceased.

Widely distributed on the southern margin of the North China Craton, the Taihua complex extends roughly in an east-west direction and the relatively complete successions are found in Lushan County, Henan Province. Like many other Archean terranes, the Taihua Complex can be divided into two major lithological units along the Dangze River, namely gneisses series and supracrustal rocks. The former is located on the north side of the river and chiefly composed of TTG gneisses and amphibolites; the latter on the south side of the river is mainly supracrustal rock. Coupled with the previous studies, the results obtained by this study show that the Taihua complex was formed in a large time span from Neoarchean to Palaeoproterozoic. The TTG gneisses and amphibolites are dated at Neoarchean (2794–2752 Ma). The 2.9 Ga and 3.1 Ga zircons in amphibolites could be xenocrysts. In the North China Craton, the 2.8–2.7 Ga old rocks crop out in several areas e.g. western Shandong Province, Jiaodong Peninsula and Lushan area of Henan Province. In addition, 2.8–2.7 Ga detrital zircons or xenocryst zircons have been recognized in Huai’an, Fuping, Wutai areas of North China Craton and also reported in the Early Paleozoic diamondiferous kimberlites in Mengyin and Fuxian. All these age results indicate that the 2.8–2.7 Ga rocks may have been developed much broader region than today’s outcrops. Zircon Hf and whole rock Nd isotopes show that the 2.8–2.7 Ga tectono-thermal event represents an important period of crustal growth with minor ancient crust reworked in the North China Craton. However the formation of supracrustal rocks is limited to 2.2–2.0 Ga in the Palaeoproterozoic time, not the Archaean, as previously believed. Combined with the chronological data of aluminium-rich metamorphic rocks (Khondalite series) on the southern margin of the North China Craton and adjacent areas, it is suggested that the above areas have widely developed Paleoproterozoic passive continental margin environment.

This paper reports a study of the metamorphic evolution of pelitic, semi-pelitic migmatites and mafic granulites of the Chafalote Metamorphic Suite (CMS), Uruguay, which represents the southernmost exposures of high-grade metamorphic rocks in the Dom Feliciano Belt, Uruguain—Sul-Rio-Grandense shield, South America. This belt is one of the Brasiliano orogens that crop out along the Brazilian and Uruguayan Atlantic margin, and the CMS is one of several disconnected segments of supracrustal rock in a dominantly granitic terrain. Petrological evidence from CMS mafic granulites and semi-pelitic migmatites indicates four distinct metamorphic assemblages. The early prograde assemblage (M 1 ) is preserved only as inclusions in porphyroblasts of the peak-metamorphic (M 2 ) assemblage. Peak-metamorphism was followed by near-isothermal decompression (M 3 ), which resulted in symplectites and coronitic textures in the mafic granulites and compositional zoning of Ca in garnet (decreasing rimwards) and plagioclase (increasing rimwards) in the semi-pelitic migmatites. The retrograde metamorphic assemblage (M 4 ) is represented by hydration reaction textures replacing minerals of the M 2 and M 3 assemblages. Average P – T calculations using the program THERMOCALC and conventional thermobarometric methods yield peak-metamorphic (M 2 ) P – T conditions of 7–10 kbar and 830–950 °C, near-decompressional (M 3 ) P – T conditions of 4.8–5.5 kbar and 788–830 °C and M 4 retrograde P – T conditions of 3–6 kbar and 600–750 °C. The calculated P – T path for the CMS rocks is ‘clockwise’ and incorporates a near-isothermal decompression segment followed by minor cooling, consistent with a history of crustal thickening followed by extensional collapse at ca. 650–600 Ma. The metamorphism recorded by rocks of this crustal segment may be correlated with ∼650 Ma metamorphism in the Coastal Terrane of the Kaoko Belt in Namibia, being the first unequivocal match between South America and Africa provided by crystalline rocks south of the Congo Craton.

Meta-supracrustal migmatitic packages in the Sierras Valle Fertil–La Huerta of northwestern Argentina occur as wedge- or strip-shaped septa interlayered among mafic to intermediate igneous plutonic rocks. Meta-supracrustal rocks were metamorphosed under granulite-facies conditions during the development of the Famatinian magmatic arc, and are among the structurally deepest rocks exposed within the belt dominated by Ordovician plutonism. Petrographic analysis, mineral chemistry and whole rock geochemistry of granulite-facies migmatites are used to argue that the meta-supracrustal packages comprise a sequence of pelitic to quartzo-feldspathic sedimentary rocks that achieved peak metamorphic P–T conditions of 5.2–7.1 kbar and 770–840 °C. There are no resolvable differences in peak P–T conditions for migmatites separated 70 km along strike of the Sierras Valle Fertil and La Huerta, suggesting that similar levels of the Famatinian paleo-arc crust are currently exposed in these ranges. Idioblastic poikilitic garnets displaying weak to absent chemical zoning profiles developed at or close to the peak metamorphic stage are used in conjunction with petrogenetic grid constraints to interpret the prograde evolution. At the time the supracrustal rocks experienced maximum thermal conditions, they underwent dehydration partial melting. Microtextural features show that felsic melt (leucosome) back reacted with the adjacent coexisting mineral assemblage (mesosome). These observations are interpreted as evidence that the migmatites evolved through a continuous heating–cooling cycle with minor pressure change. This is consistent with the general lack of reaction textures denoting decompression at high temperatures, and with the possibility that in some migmatites retrograde reactions formed staurolite. Collectively, these features indicate that when the migmatites attained peak thermal conditions, the deepest exposed arc crust was about 20–25 km beneath the Ordovician surface. Comparing these results with metamorphic studies elsewhere in the Famatinian arc between 31° and 32°S. indicates that much of the main-arc records primarily prograde P–T trajectories associated with a regional contact metamorphism, but that specific locations in the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.

We report the first U–Th–Pb ion microprobe depth profiles of four Hadean zircons from the Jack Hills and Mount Narryer supracrustal belts of the Narryer Gneiss Complex (NGC), Western Australia. This ultra-high spatial resolution technique probes the age and origin of sub-micron features in individual crystals that can record episodes of zircon growth. Near-surface grain dates of 2700 Ma or older are coincident with post-depositional growth/modification. Some ages may coincide with documented pre-deposition metamorphic events for the NGC and igneous emplacement at ca. 3700 Ma. Separate events that do not correlate in time with known geologic episodes prior to the preserved rock record are also present on pre-4000 Ma zircons. We find evidence for a ∼3.9 Ga event, which is coterminous within age uncertainty with one or several large basin-forming impacts (e.g. Nectaris) on the Moon attributed to the late heavy bombardment of the inner solar system.

A relict oceanic island arc complex in the eastern Akia terrane, Godthabsfjord, southern West Greenland, constitutes a magmatic and geotectonic link between c . 3.05–3.0 Ga tonalitic orthogneiss and enclaves of older supracrustal amphibolite. The relict arc forms isoclinally folded panels of volcaniclastic meta-andesite with major and trace element island arc signatures, intercalated with volcano-sedimentary schist, tholeiitic amphibolite and opx-rich cumulate rocks. A zircon U–Pb age of 3071 ± 1 Ma obtained from a volcano-sedimentary schist is marginally older than the main orthogneisses and is the first depositional age reported from a supracrustal rock within Akia terrane. Granite sheets were emplaced at c . 3005–2980 Ma synkinematically with the isoclinal folding, and were followed by peak metamorphism at 2990–2970 Ma with substantial recrystallization of volcanic zircon and mobility of large-ion lithophile elements. The identification of the arc complex provides new insight into mid-Archaean continental crustal accretion in West Greenland, and substantiates previous ideas that the orthogneisses are products of slab melting in convergent plate-tectonic settings. The presence of the arc complex also implies that Archaean high-grade orthogneiss–amphibolite associations may not represent plate-tectonic environments distinct from granite–greenstone associations, but expose deeper sections of the same convergent systems.

The central portion of the structurally complex and poly-metamorphosed Namaqua Province of western South Africa is underlain by a series of pelitic and psammitic metasediments, termed the Bushmanland Group, which is host to world class Broken Hill-type Pb-Zn-Cu-Ag deposits at Aggeneys. Geochemical, U-Pb SHRIMP zircon geochronology and Sm-Nd isotopic determinations of the metasediments at Aggeneys were undertaken to determine the age and nature of the provenance, as well as to confine the age of deposition of the Bushmanland Group in this area. The metasediments were derived from moderately-weathered granodiorites to granites, or their volcanic equivalents, with ~2.65 to ~2.25 Ga Sm-Nd T DM model ages. Mixed sources are likely from the geochemical signatures of the metasediments as well as the varied detrital zircon ages, with two main age groupings present of ~2.12 to ~1.97 Ga and ~1.88 Ga to ~1.64 Ga. The upper part of the succession has a narrower compositional range and was derived from a more mafic provenance than the basal portion. The provenance is likely to have been a combination of ~1.8 Ga Gladkop Suite granitic gneisses found to the west and the ~2.1 to ~1.9 Ga intrusive and volcanosedimentary rocks of the Richtersveld Subprovince to the northwest. The metasediments were deposited in a passive margin setting and underwent extensive reworking in addition to recycling. The time of deposition of the Bushmanland Group is constrained between the age of the youngest detrital zircon (~1.64 Ga) and the onset of the regionally extensive Kibaran Orogeny at ~1.2 Ga. Metamorphic overgrowths and rims on detrital zircons record two distinct events, the ~1.21 to ~1.18 Ga Kibaran Orogeny, characterised by extensive granitic magmatism, peak D 2 deformation and peak upper amphibolite facies grade M 2 metamorphism, and the more ubiquitous ~1.04 to ~1.01 Ga Namaquan Orogeny characterised by weaker M 3 metamorphism.

Chronological studies show that the Late Archean petrographic formation of the Tarim craton includes Tuogelakbulak complex in the northern margin and the Milan Group in the northern slope of the eastern Altun Mountains. The Tuogelakbulak complex is mainly plagioclase amphibolite, hornblende schist, gray gneiss, garnet biotite schist, actinolite mica quartz schist, biotite quartz schist, and migmatite, mixed with minor amount of marble lenticular bodies, and intruded by gneissic muscovite biotite granite. The Milan Group is composed of various types of felsic gneiss, granulite, marble, and plagioclase amphibolite, and belongs to hypometamorphic supracrustal rock series. The Neoarchean is an important episode of continental crust growth and basement cratonization of the Tarim craton, and a continental crust with the age of about 3.6 Ga might have existed in the Tarim craton basement. The Lower Proterozoic of the Tarim craton is extensively distributed and outcropped at Quruqtagh in the northern margin, Altun Mountains in the eastern margin and Yecheng area in the southwestern margin. Protoliths of the Paleoproterozoic Xingditag Group and Altun Mountains Group are mainly clastic sedimentary rock, carbonate rock, and volcanic formations, indicating a relatively stable and extensive littoral-neritic sedimentary environment. They are mainly composed of a suite of intermediate and high grade metamorphic rocks, including biotite plagioclase gneiss, muscovite biotite plagioclase gneiss, quartz schist, marble, and garnet sillimanite plagioclase quartz gneiss, resembling khondalite series. Magmatism was not significant during this episode, though the Paleoproterozoic magmatic rocks are observed in Altun Dunhuang, Tiekelike and Korla areas. During the Mesoproterozoic episode, the Tarim craton was relatively stable. The Jixianian Aierjigan Group is characterized by carbonate and clastic rock series formed in epicontinental sea. Magmatic formation consists of the Changchengian Sailajiazitage Group and the Jixianian Ailiankate Group formed in intracontinental extension setting.

The main hole (MH) of the Chinese Continental Scientific Drilling Project (CCSD) in southern Sulu has penetrated into an ultrahigh-pressure (UHP) metamorphic rock slice which consists of orthogneiss, paragneiss, eclogite, ultramafic rock and minor schist. Recovered eclogites have a UHP metamorphic mineral assemblage of garnet + omphacite + rutile ± phengite ± kyanite ± coesite ± epidote. Ultramafic rocks contain garnet + olivine + clinopyroxene + orthopyroxene ± Ti-clinohumite ± phlogopite. Gneisses and schists contain an amphibolite-facies paragenesis, but their zircons have coesite, garnet, omphacite (or jadeite) and phengite inclusions, indicating that eclogites and gneisses have been subjected to in situ UHP metamorphism. Using available geothermobarometers, P–T estimates of 3.1–4.4 GPa and 678–816°C for eclogites were obtained. If surface outcrops and neighboring shallow drill holes are considered together, we suggest that a huge supracrustal rock slab (> 50 km long × 100 km wide × 5 km deep) was subducted to a depth > 100 km and then exhumed to the surface. The depth interval (0–2,050 m) of the CCSD-MH can be divided into six lithological units. Unit 1 consists of alternating layers of quartz-rich and rutile-rich eclogites, with thin interlayers of gneiss and schist. Eclogites of unit 1 are characterized by Nb, Ta, Sr and Ti depletions, low Mg number and general LREE enrichment. Unit 2 comprises rutile- and ilmenite-rich eclogite and minor “normal” eclogite and is characterized by high TiO2, total Fe, V, Co and Sr, and very low SiO2, alkali, Zr, Ba, Nb, Ta and total REE contents, and LREE-depleted REE patterns with slightly positive Eu anomalies. Unit 3 contains ultramafic rock and minor MgO-rich eclogite. Protoliths of UHP rocks from units 1, 2 and 3 represent a layered mafic to ultramafic intrusion at crustal depth. Units 4 and 6 consist of interlayered eclogite and paragneiss; the eclogites are characterized by Th, U, Nb, Ta and Ti depletion and K enrichment and LREE-enriched REE patterns. Paragneisses show Nb, Ta, Sr and Ti depletions and LREE-enriched REE patterns occasionally with slightly negative Eu anomalies, indicating that their protoliths represent metamorphic supracrustal series. Unit 5 consists mainly of orthogneisses, showing distinct Nb, Ta, Sr and Ti depletions, and LREE-enriched REE patterns with pronounced negative Eu anomalies, suggesting granitic protoliths. In conclusion it is proposed that the southern Sulu UHP belt consists of a series of meta-supracrustal rocks, a layered mafic–ultramafic complex and granites.

Using the reported new U-Pb age with the Sensitive High-Resolution Ion Microprobe (SHRIMP II), zircon U-Pb ages were obtained from two samples of K-feldspar felsic paragneiss and K-feldspar gneissoid trondhjemite on the southern margin of the Taihang Mountains in the North China Craton. The protolith of the K-feldspar felsic paragneiss is argillaceous-sandy clastic sedimentary rock, probably deposited in the Neoarchean. Most of the detritus zircons show heavy loss of Pb. Five spots of zircons near the upper point, yield a weighted mean 207Pb/206Pb age of 3399±8 Ma, representing an age of the sedimentary source. Two groups of zircons from the K-feldspar gneissoid trondhjemite give weighted mean 207Pb/206Pb ages of 2511±13 Ma and 2735±16 Ma respectively. The former represents the emplacement time of the pluton, while the latter is interpreted as the age of the inherited zircons. The new data support that the Archean geological body in the central zone has an affinity with those from the eastern block of the North China Craton.

Best known for its Neoarchean greenstone-granite terranes in the east and west, the Wabigoon subprovince of the Superior Province features a central transverse corridor of Meso- and Neoarchean gneissic, granitoid, and minor supracrustal rocks resembling an eroded intermontane plateau. Structural analysis and U–Pb geochronology in the north-central Wabigoon subprovince reveal a complex history of plutonism, supracrustal rock deposition, polyphase deformation and amphibolite-facies metamorphism between 3075 and 2670 Ma. The geometric and kinematic character of D 1 and D 2 deformational events recorded in 2890–2718 Ma tonalitic gneisses remain cryptic as a result of magmatic and structural (D 3–5 ) overprinting, but the early structures are bracketed in age between 2725 and 2713 Ma by a polydeformed gneiss and tonalite dyke. These events occurred deep within an active continental magmatic arc and correspond in age to a collision between the juvenile Wabigoon and continental Winnipeg River subprovinces recognized to the west. Clastic sediments deposited after 2701 Ma are the youngest rocks involved in subsequent regional deformation. A D 3 event is responsible for rapid burial of supracrustal units to 15 km within warm arc crust, and imposition of a regional, penetrative, S 3 foliation that accommodated some relative uplift prior to 2697 Ma, the age of a discordant granodiorite dyke. This event corresponds to variably preserved, steep, north-trending D 1 structures recognized in adjacent greenstone belts. Subsequent (D 4 ) ductile deformation defines the map pattern in the deep crustal rocks of the central Wabigoon subprovince. Upright, east-trending F 4 folds developed synchronously with D 2 dextral transpressive structures that formed throughout the Wabigoon subprovince prior to 2698 Ma. The final (D 5 ) sinistral shearing event occurred during emplacement of mantle-derived granodiorites of sanukitoid affinity (2688 Ma) and crust-derived granites (2685 Ma). This event appears to have triggered rapid cooling, reflected in 2680–2670 Ma titanite dates and late brittle increments of displacement.

The southwestern Sulu terrane, eastern China is divided into four fault-bounded lithologic units. From northwest to southeast, they are: (1) orthogneiss unit (Unit I); (2) supracrustal rock unit (Unit II); (3) kyanite-bearing quartzite—marble unit (Unit III); and (4) paragneiss—schist unit (Unit IV). Inclusions of index minerals in zircon separates from more than 90 samples from these units were identified using laser Raman spectroscopy and electron microprobe analysis. Coesite and coesitebearing ultrahigh-pressure (UHP) mineral assemblages occur in zircon separates from various amphibolite-facies metamorphic rocks in Units I and II. In contrast, aragonite- and phengite-bearing high-pressure (HP) mineral assemblages are preserved in zircons from many amphibolite-to greenschist-facies metamorphic rocks in Units III and IV. These together with previous studies yield P-T estimates of peak metamorphic recrystallization at 723°-852°C, and P > 2.8 GPa for UHP rocks, and 500°-600°C, and P = 1.2-2.5 GPa for HP ro...

Geology and tectonics of the Korean Peninsula have been considered to be closely associated with those of the adjacent Chinese continent. Although Phanerozoic connections between the two areas have been reasonably well worked out, Precambrian ones are less well established. We obtained Sm–Nd and U–Pb garnet ages of 12 metamorphic rocks from widely separated parts of the Gyeonggi and Yeongnam massifs in South Korea to better understand their Precambrian history. The two massifs consist of late Archean to Paleoproterozoic basement rocks and Meso- to Neoproterozoic supracrustal rocks. Previous studies have shown that the two massifs experienced upper amphibolite to granulite facies metamorphism of medium pressure type with clockwise P – T -time paths, suggesting that the two massifs may represent remnants of a collisional orogen. Pb–Pb and U–Pb garnet ages give two distinct age groups: ten Paleoproterozoic (1989±34 to 1835±56 Ma) ages of basement rocks from the two massifs, and one late Permian (265±8 Ma) age of a supracrustal rock from the Gyeonggi massif that corroborates previous estimates of Permo-Triassic (298–245 Ma) metamorphic age for the supracrustal rocks. On the other hand, Sm–Nd garnet ages are less precise and display a wide range of ages from 2257 to 413 Ma for the basement rocks. When we compare the Sm–Nd and Pb–Pb ages from the same sample, the Sm–Nd age is similar to or younger than the Pb–Pb age, suggesting that the blocking temperature of the Sm–Nd garnet system may be lower than that of the U–Pb system (>800 °C). We interpret the Pb–Pb and U–Pb ages as representing the timing of metamorphic garnet growth, since the blocking temperature of the U–Pb garnet system is similar to or higher than the metamorphic temperature of the analyzed samples. Apparently, the younger metamorphism, possibly associated with the Permo-Triassic collision between the North and South China cratons, was not strong enough to reset the older metamorphic age. Similar Paleoproterozoic metamorphic ages for basement rocks of the two massifs suggest that they may have come from the same Precambrian terrane. The metamorphic ages of the basement rocks of South Korea agree very well with those of the Central Zone (orogenic belt) in the North China craton, suggesting a possible correlation between the two terranes.

The Jiaodong Terrane of the Eastern Shandong Complex in the Eastern Block of the North China Craton (NCC) consists predominantly of Archean granitoid gneisses with minor supracrustal rock enclaves or lenses. This study presents new zircon LA-ICP-MS U–Pb and Lu–Hf isotopic data for these lithologies, which help to better understand the Archean crustal evolution of the Eastern Block of the NCC. Magmatic zircon U–Pb data reveal that zircons in the supracrustal rocks and granitoid gneisses were generated by multistage events at ~2.9, ~2.7 and ~2.5 Ga. Metamorphic zircon U–Pb data obtained for these rocks show distinct metamorphic ages at ~2.50 and ~1.9–1.8 Ga, suggesting that the Jiaodong Terrane experienced a regional metamorphic event at the end of the Neoarchean and encountered reworking by a tectonothermal event that was associated with the formation of the Paleoproterozoic Jiao-Liao-Ji Belt. Magmatic zircons have variable eHf(t) values from −5.5 to +7.7 with model ages of 3.92–2.57 Ga, of which most eHf(t) values are positive with a predominant peak of model ages at 3.4–3.1 Ga and a subordinate peak at 2.8–2.7 Ga. These Hf features reveal major juvenile crustal growth stages with significant additions of older crustal materials at 3.4–3.1 and 2.8–2.7 Ga, and a crustal reworking event with minor juvenile additions at ~2.5 Ga in the Jiaodong Terrane.