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Volcaniclastic deposits are cynosures for reconstructing volcanic archives and evaluating the tectonic imprints of the study area. This paper presents an elaborate geological field litholog, petrography and geochemistry of ~1.2 km thick sequence of the quartz-feldspar porphyry (QFP) and rhyolites in the Kadiri–Hindupur section of the Kadiri Greenstone belt from Eastern Dharwar Craton (EDC). The QFP exhibits primary stratification; the thickness of the beds varies from very thin to thick (3–8 cm) and shows large-scale tabular cross-bedding in the lower half of the section. The bedding surfaces of QFPs are marked by current crescent-shaped marks (long axis: 5–25 cm, short axis: 2–8 cm), speculated as possible remnants of volcanic bombs and pyroclastic debris during the explosive volcanism. Petrographically, these QFPs are characterised by spectacular blue opalescent quartz grains with embayed grain boundaries, anhedral feldspar with sieved texture, fractured plagioclase and polycrystalline groundmass suggesting a volcaniclastic origin. They are also endowed with significant post-depositional textures such as domino-listric faulting and sigma-shaped porphyroblasts. Geochemically, QFPs are unaltered with trachyte-trachy dacite compositions showing high-potash, calc-alkaline nature displaying shoschonitic affinity. The primitive mantle normalised trace and rare earth elements are marked by an enriched LREE-LILE pattern coupled by negative zircon–hafnium, niobium–tantalum and titanium anomalies affirming their common genetic link to a prominent island arc–back-arc system where explosive volcanism produced the felsic crystal tuffs that were deposited and preserved as volcaniclastic QFP. The associated blocks and bombs produced the current crescent-shaped marks preserved on the bedding surfaces of QFPs. Research highlights: Research Highlights Quartz-feldspar porphyry (~1.2 km thick) occurs in the Kadiri Greenstone Belt, Eastern Dharwar Craton. Blue opalescent quartz and deformed plagioclase porphyry indicate volcaniclastic origin. Enigmatic current crescent-shaped marks represent remnants of volcanic bombs and pyroclastic debris. The primitive mantle normalised REE diagram is characterised by LREE-LILE enrichment. They represent Neoarchean pyroclastic volcanism and sedimentation in an island arc–back-arc setup. [ABSTRACT FROM AUTHOR]

In order to enhance the understanding of Archean continental crust formation and evolution history of Liaonan block in North China Craton, the Neoarchean TTG(tonalite-trondhjemite-granodiorite)gneisses in Shijianfang area of Liaonan block were focused on, and the detailed field investigation, zircon U-Pb dating and Lu-Hf isotope analysis, and whole-rock geochemical analysis were intergrated. The results show that TTG gneiss in Shijianfang area crystallizes at(2 499.7±5.4)Ma. The TTG gneiss samples have high contents of SiO2(66.1%-69.1%)and Al2O3(14.6%-15.6%), are enriched in Na and depleted in K(K2O/Na2O is 0.41-0.51)with weakly positive Eu anomalies(1.06-1.59); the samples are relatively enriched in large ion lithophile elements(Ba, Rb, K, etc.)and high field strength elements(Zr, Hf, etc.), featured by high Sr/Y(44.3-69.5)and(La/Yb)N(11.8-24.0), and depleted zircon Hf isotopic composition with two-stage model ages of 2 903-2 687 Ma. Compared with TTG rocks derived from partial melting of the thickened lower crust, TTG gneisses in Shijianfang area have relatively higher contents of MgO, Cr and Ni. The above geochemical characteristics reveal TTG gneisses in Shijianfang area are typical medium-pressure TTG rocks, which is the product of partial melting of Meso-Neoarchean basaltic crust. The source area is rich in garnet and amphibolite, but short of rutile and plagioclase. Combined with previous studies, TTG gneisses in Shijianfang area are likely formed by the partial melting of subduction slabs, indicating the warm subduction tectonic system of the ancient continental margin. The North China Craton might be controlled by both plate tectonics and mantle plume tectonics during Late Neoarchean. [ABSTRACT FROM AUTHOR]

U–Th–Pb LA-ICP-MS was used for dating detrital zircon extracted from the cement of Neoarchean and Paleoproterozoic polymict conglomerates of the Karelian Province, Fennoscandian Shield. The chemical composition of terrigenous and volcanogenic rocks of the Gimolskaya Formation is presented for the first time. The data obtained showed that the detrital zircon from the cement of conglomerates of different ages yields similar results of about 2750 Ma. The clasts of the gneiss tonalite and plagioporphyry dominate in the Neoarchean conglomerates of the Sukkosero area. They are identical in chemical composition with the Neoarchean (2.78–2.73 Ga) TTG, granodiorite, and metadacite of the Central Karelian domain. These rocks are distinguished by an increased content of Ba (900–1200 ppm) and Sr (600–700 ppm), and the ratios Sr/Y = 34–90 and (La/Yb)n = 17–30. The chemical composition of the cement (values of CIA < 55 and negative values of the function DF(x)) from –1.0 to –0.4 is similar to the composition of clasts, which means the cement is composed of finer clasts of the same rocks. The Paleoproterozoic conglomerates of the Vottomuks area contain zircon from felsic rocks of the Neoarchean basement. The chemical composition of the cement of the Paleoproterozoic conglomerates and the predominance of basaltic andesites of Sumian are evidence of the post-Sumian(<2.45 Ga) age of these rocks. The absence of the Paleoproterozoic zircon in cement could have resulted from its absence in the Paleoproterozoic source rocks. The age of Neoarchean conglomerates from the Gimolskaya Formation is less than 2.75 Ga. [ABSTRACT FROM AUTHOR]

A whole-rock geochemical and zircon U–Pb and Lu–Hf isotope study of the Dengfeng complex in the Jishan area was performed to constrain the Neoarchean continental crust evolution in the southern margin of the North China Craton (NCC). The Dengfeng complex can be divided into supracrustal assemblage and plutonic intrusion. In the supracrustal assemblage, the detrital zircon of quartz schist from the Guojiayao Formation display oscillatory growth zones and streaky absorption with relatively high Th/U ratios (0.36–2.10), suggesting a magmatic origin. The 207Pb/206Pb ages range from 2963 to 2531 Ma, with a peak age of 2555 Ma, and the εHf(t) values are between + 2.3 and + 12.1. Combined with previous studies, the depositional age of the Guojiayao Formation can be constrained between 2542 and 2522 Ma, indicating that it mainly originated from the Neoarchean accretive basement material of the southern NCC. The Ruzhou gneissic syenogranites yield U–Pb ages from 2515 ± 13 Ma to 2504 ± 20 Ma, show that the plutonic intrusions also formed in the Late Neoarchean. They have high SiO2 (64.03–73.99 wt%) and Na2O + K2O (8.79–14.58 wt%) contents but low MgO (0.19–0.36 wt%) and CaO (0.02–0.27 wt%) contents, and belong to slightly peraluminous I-type granites with shoshonitic affinity. Magmatic zircon grains have positive εHf(t) values (+ 0.2 to + 6.7) with average crustal Hf model ages ranging from 2911 to 2671 Ma (average of 2765 Ma), indicating that the Ruzhou gneissic syenogranites were likely produced by partial melting of the accretive lower crust. The positive εHf(t) values and similarly ancient model ages suggest that a large-scale continental crust growth occurred in the southern margin of NCC at ca. 2.7 Ga. The Dengfeng complex was mainly derived from an arc-related setting associated with subduction in the Late Neoarchean. [ABSTRACT FROM AUTHOR]

The Alxa Block is the westernmost part of the North China Craton (NCC), and is regarded as one of the basement components of the NCC. Its geological evolution is of great significance for the understanding of the NCC. However, the Precambrian basement of the Alxa Block is still poorly studied. In this study, we present new in situ LA‐ICP‐MS zircon U‐Pb and Lu‐Hf isotope data from the Diebusige Metamorphic Complex (DMC) which located in the eastern Alxa Block. Field and petrological studies show that the DMC consists mainly of metamorphic supracrustal rocks and minor metamorphic plutonic rocks and has experienced amphibolite‐granulite facies metamorphism. Zircon U‐Pb dating results suggested that the amphibolite sample yields a crystallization age of 2636 ± 14 Ma and metamorphic ages of 2517–2454 Ma and 1988–1952 Ma, proving the existence of exposed Archean rocks in the Langshan area and indicating that late Neoarchean to Paleoproterozoic metamorphic events existed in the Alxa Block. Two paragneiss samples show that the magmatic detrital zircons from the DMC yield 207Pb/206Pb ages ranging from 2.48 Ga to 2.10 Ga with two youngest peaks at 2.13 Ga and 2.16 Ga, respectively, and they were also overprinted by metamorphic events at 1.97–1.90 Ga and 1.89–1.79 Ga. Compilation of U‐Pb ages of magmatic detrital and metamorphic zircons suggested that the main part of the DMC may have been formed at 2.1–2.0 Ga. Zircon Lu‐Hf isotope data show that the source materials of the main part of the DMC were originated from the reworking of ancient Archean crust (3.45–2.78 Ga). The Hf isotope characteristics and the tectonothermal event records exhibit different evolution history with the Khondalite Belt and the Yinshan Block and the other basements of the Alxa Block, indicating that the Langshan was likely an independent terrain before the middle Paleoproterozoic and was subjected to the middle to late Paleoproterozoic tectonothermal events with the Khondalite Belt as a whole. [ABSTRACT FROM AUTHOR]

The cratonization history of the North China Craton (NCC) and the nature of tectonothermal events are still highly controversial. Tonalite-trondhjemite-granodiorite (TTG) gneisses, as the dominant lithological assemblages in Archean metamorphic terranes, can provide significant clues to the magmatic and metamorphic evolution of Precambrian crust. This study presents zircon laser-ablation inductively-coupled-plasma mass spectrometry U–Pb ages, trace-element, and in-situ LA-MC-ICP-MS zircon Hf isotope data for the TTG gneisses from the Bengbu-Wuhe area on the southeastern margin of the NCC. Cathodoluminescence images and trace elements indicated that magmatic zircons display the characteristics of euhedral-subhedral crystals with oscillatory growth zoning structures, high ΣREE contents, marked Ce positive anomalies, and Pr–Eu negative anomalies. The metamorphic zircons display the spherical-oval crystals with distinct core-rim structures, high and homogeneous luminescent intensity, lower ΣREE, Nb, Ta, Hf contents, relative flat REE patterns, weak Ce positive anomalies, and Pr-Eu negative anomalies. The Ti–in–zircon geothermometer data indicate that the crystallization temperature of the TTG gneiss ranged from 754 to 868 °C. Zircon U–Pb ages indicate that the TTG gneisses formed at 2.79–2.77 Ga and 2.50 Ga and underwent metamorphism at 2.57–2.52 Ga. The Hf isotopic data indicate that the magmatic zircons exhibit high, positive εHf(t) values close to those of the coeval depleted mantle, whereas the metamorphic zircons exhibit negative or nil εHf(t) values. This implies that the TTG gneisses were derived from the partial melting of the ~ 2.9–2.6 Ga juvenile crustal sources mixed with ~ 3.0–2.8 Ga ancient crustal materials. Combined with the regional tectonic evolution, we propose that the metamorphic basement at the southeastern margin of the NCC underwent episodic crustal growth at ~ 2.7 and ~ 2.5 Ga and subsequently underwent crustal reworking or re-melting of the ancient crust during the Neoarchean. The Neoarchean TTG gneisses might have been derived from the partial melting of lower crustal materials related to plate subduction. [ABSTRACT FROM AUTHOR]

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Komatiites are presented as direct evidence for higher mantle temperatures during the Archean. In the North China Craton, komatiites with spinifex structure have been identified only at one locality, i.e. the Sujiagou area, western Shandong. They were considered as formed during the early Neoarchean mainly based on their association with supracrustal rocks considered to be that age. This study carried out SHRIMP U‐Pb zircon dating on metamorphosed trondhjemitic and monzogranitic dykes intruding the Sujiagou komatiites, and they have magmatic zircon ages of 2592 ± 12 Ma and 2586 ± 13 Ma respectively. This provides direct evidence that the komatiites formed during the early Neoarchean. [ABSTRACT FROM AUTHOR]

Abstract—Alkaline and subalkaline granites of the Keivy megablock belong to the potassic alkali-calcic ferroan rocks enriched in large-ion lithophile, high-field strength and rare-earth elements. Based on these criteria, they correspond to A2-type granites (Eby, 1992). The granites have elevated Y/Nb (1.9–2.5) and Yb/Ta (3.4–3.7) ratios typical of crustally derived granites. The initial 176Hf/177Hf ratios in the central parts of zircon crystals vary within 0.281004–0.281175 at εHf(T) ranging from –2.89 to 3.79. It is supposed that the underplating of high-temperature mafic melts caused melting of metasomatically altered lower-crustal rocks and formation of palingenetic lower-crustal melts, which during subsequent ascent in the upper crust experienced fractional crystallization to more siliceous subalkaline and alkaline melts. [ABSTRACT FROM AUTHOR]

The Aberdeen Lake supracrustal belt is one of several Neoarchean greenstone belts preserved within the Rae domain of the Western Churchill Province. We divide the belt into: (1) a Lower Sequence of ca. 2750 Ma komatiite, TTG (tonalite-trondhjemite-granodiorite) intrusions, and TTG-contaminated Fe-tholeiitic mafic gneiss; (2) a Middle Sequence of ca. <2687 Ma psammopelite gneiss, iron formation and ca. 2680 Ma intermediate to felsic intrusive rock; and (3) a ca. <2650 Ma Upper Sequence of pelite to psammopelite gneiss with minor iron formation and arkosic gneiss. The common association of komatiite with quartzite units and bimodal metavolcanic rocks, has previously been interpreted to indicate a continental rift setting for the formation of Neoarchean greenstone belts across the Rae domain. However, the lack of clastic metasedimentary rocks and felsic metavolcanic rocks in the Lower Sequence of the Aberdeen Lake supracrustal belt, the presence of uncontaminated komatiite, and the general absence of inherited zircons older than ca. 2750 Ma in the TTG and mafic gneiss units, suggest that the Lower Sequence formed as an oceanic plateau or oceanic crust between older, Paleoarchean to Mesoarchean, proto-Rae microcratons. Erosion of the cratons and the emergence of the oceanic plateaux due to their accretion/subcretion to these cratons shed ca. 2687–2870 Ma detritus that were deposited as the Middle Sequence into adjacent oceanic basins. Renewed uplift of the Lower and Middle sequences led to the emplacement of ca. 2680 Ma felsic intrusions, and the later deposition of the ca. <2650 Ma Upper Sequence. The involvement of oceanic plateaux is a new tectonic interpretation for the formation of Neoarchean greenstone belts in the Rae domain. [ABSTRACT FROM AUTHOR]

[Display omitted] • First report of Mesoarchean (<3.1 Ga) deposition in the Sukma Group, Bastar craton. • Terrestrial detritus of Sukma Group most likely from Western Dharwar and Singhbhum cratons. • Paleoarchean nucleus of Bastar, Western Dharwar and Singhbhum cratons were proximal by ∼ 3 Ga. • Neoarchean (<2.4 Ga) Bengpal Group was therefore deposited after a significant hiatus. Records of terrestrial detritus deposited since the Mesoarchean, preserved in sedimentary basins on cratons, are useful in continental reconstruction. The southern segment of the Bastar craton comprises Paleoarchean cratonic fragments extensively reworked, and intruded by granite batholiths, during the Neoarchean and expose two major groups of supracrustal successions. The Sukma Group, occurring as amphibolite-facies remnants within Neoarchean granitoids are mostly chemogenic supracrustal rocks in contrast to the low-to unmetamorphosed Neoarchean volcano-sedimentary Bengpal Group. In order to resolve their uncertain stratigraphic relationship, detrital zircon U-Pb analyses were carried out to obtain detrital age spectra. The youngest concordant detrital zircon 207Pb/206Pb ages from the Sukma Group metapelite (CB11C) and micaceous quartzite (CH5B) samples places its maximum depositional age at < 3.10 Ga (3128 ± 6 Ma, cumulative maximum depositional age of both samples). In contrast, the micaceous quartzite (samples CB14 and CB18) from the Bengpal Group were deposited after 2.4 Ga (2350 ± 16 Ma, cumulative maximum depositional age of both samples), indicating a considerable hiatus in depositional history of these two supracrustal successions. Comparison with globally compiled age spectra from cratonic Archean-aged metasedimentary successions indicate that a most likely clastic sediment provenance to the dominantly chemogenic Sukma Group was from the Western Dharwar and Singhbhum cratons. The inferred provenance cratons are based on the presence of extensive Mesoarchean granitoid batholiths and, therefore, indicates their proximity at least till 3.0 Ga. In contrast, clastic detritus to the possibly riftogenic volcano-sedimentary Bengpal Group was largely sourced from the voluminous Neoarchean magmatism probably from within the Bastar craton. [ABSTRACT FROM AUTHOR]

We present new isotopic data (U-Pb and Sm-Nd) from the Neoarchean granitoids of the Lentua complex, which is a part of the Western Karelia subprovince of the Fennoscandian Shield. Compositionally, the samples are granitoids belonging to the sanukitoid suite and K-rich granitoids. Certain samples interpreted as partial melts of pre-existing crust in this study display more mafic compositions than previously described from the surrounding areas. This indicates, at least locally, a source poorer in SiO2 than the TTG (Tonalite-Trondhjemite-Granodiorite) suite granitoids, which are the likely sources for the majority of the anatectic granitoids within the Lentua complex. Based on new geochronological data (LA-MC-ICPMS U-Pb on zircon), the sanukitoids and anatectic granitoids are at least partly coeval (2.69 Ga) in the area, but interaction between the two felsic magmas was limited. The dated sanukitoid sample is distinctly younger (2687±8 Ma) than the average age of the sanukitoids of the Western Karelia subprovince (2718±3 Ma) indicating, together with one previously published sanukitoid age, the existence of a younger sanukitoid phase. This study gives new important constraints to understanding the formation of the Western Karelia subprovince by expanding the observed compositional heterogeneity and the temporal overlap of the different Neoarchean granitoid suites.

The Miyun area of Beijing is located in the northern part of the North China Craton (NCC) and includes a variety of Archean granitoids and metamorphic rocks. Magmatic domains in zircon from a tonalite reveal Early Neoarchean (2752±7 Ma) ages show a small range in ∊Hf( t) from 3.1 to 7.4 and tDM1(Hf) from 2742 to 2823 Ma, similar to their U-Pb ages, indicating derivation from a depleted mantle source only a short time prior to crystallization. SHRIMP zircon ages of granite, gneiss, amphibolite and hornblendite in the Miyun area reveal restricted emplacement ages from 2594 to 2496 Ma. They also record metamorphic events at ca. 2.50 Ga, 2.44 Ga and 1.82 Ga, showing a similar evolutionary history to the widely distributed Late Neoarchean rocks in the NCC. Positive ∊Hf( t) values of 1.5 to 5.9, with model ages younger than 3.0 Ga for magmatic zircon domains from these Late Neoarchean intrusive rocks indicate that they are predominantly derived from juvenile crustal sources and suggest that significant crustal growth occurred in the northern NCC during the Neoarchean. Late Paleoproterozoic metamorphism developed widely in the NCC, not only in the Trans-North China Orogen, but also in areas of Eastern and Western Blocks, which suggest that the late Paleoproterozoic was the assembly of different micro-continents, which resulted in the final consolidation to form the NCC, and related to the development of the Paleo-Mesoproterozoic Columbia or Nuna supercontinent. [ABSTRACT FROM AUTHOR]

[Display omitted] • Yudongzi BIFs were formed at ca. 2.8 Ga, and suffered two-stage metamorphism. • Yudongzi BIFs were formed on the back–arc basin setting. • Yudongzi complex combined to Yangtze Block later than Paleoproterozoic. The Yudongzi banded iron formations (BIFs) are widely spread in the Neoarchean Yudongzi Group of the Bikou Terrane, Central China. Their sedimentary and metamorphic ages, however, remain controversial, either their forming or reworking processes. In this contribution, we conducted an integrated study of zircon U-Pb-Hf isotope geochemistry, as well as mineral and bulk-rock geochemistry on the Heishan'gou iron deposit, the largest iron deposit of the Yudongzi BIFs, to constrain their formation and metamorphism ages, source of ore-forming material and tectonic setting. Mineral chemistry analysis indicates that the amphibolite, host-rock of the Heishan'gou deposit suffered amphibolite facies metamorphism. LA-ICP-MS U-Pb dating of zircon grains from orthometamorphic host-rocks suggests that the Heishan'gou deposit was formed at the early Neoarchean (2781 ± 43 Ma for amphibolite and 2776 ± 43 Ma for plagioclase-hornblende schist), and metamorphosed at ca. 2480 ± 26 Ma and 1818 ± 44 Ma, respectively. The low contents of aluminum, titanium and high field strength elements in BIFs suggest that they are detritus-free marine chemical precipitates. The rare earth elements (REE) and Y patterns of BIFs display seawater-like signatures with light REE depletion, and positive La and Y anomalies. Meanwhile, their positive Eu anomalies suggest that submarine hydrothermal fluid might also be involved in the precipitation of BIFs. Combined with zircon Hf isotope data and geochemical compositions of amphibolites, it is proposed that the Yudongzi BIFs should be formed at back-arc basin setting. Compared with the representative Archean continent nucleus of the Yangtze Block (Kongling Complex), the Yudongzi Complex experienced distinct crustal evolutionary history. It indicates that the Yudongzi Complex might represent the accretionary block combined to the Yangtze continental nucleus later than the Paleoproterozoic. [ABSTRACT FROM AUTHOR]

The Lützow–Holm Complex (LHC) of East Antarctica forms part of the Neoproterozoic–Cambrian high-grade metamorphic segment of the East African–Antarctic Orogen. Here we present new petrological, geochemical, and zircon U–Pb and Lu–Hf isotopic data for meta-igneous rocks including charnockite, felsic gneiss, metagabbro, and mafic granulite from the LHC and evaluate the Neoarchean to Early Paleoproterozoic (ca. 2.5 Ga) and Early Neoproterozoic (ca. 1.0 Ga) arc magmatic events. The trace element geochemical signatures reveal a volcanic arc affinity for the charnockites from Sudare Rocks and Vesleknausen and felsic gneiss from Rundvågshetta, suggesting that the protoliths of these rocks were derived from felsic arc magmas. In contrast, metagabbros from Skallevikshalsen and Austhovde, occurring as boudins in metasediments, show non-arc signatures (within-plate basalt or mid-oceanic ridge basalt). The upper intercept ages of magmatic zircons in charnockite plotted on concordia diagrams yielded 2508 ± 14 Ma (Sudare Rocks) and 2490 ± 18 Ma (Vesleknausen), clearly suggesting a Neoarchean to Early Paleoproterozoic arc magmatic event. A subsequent thermal event during Early Neoproterozoic traced by 206 Pb/ 238 U age of oscillatory-zoned core of zircon in mafic granulite from Langhovde (973 ± 10 Ma) is consistent with a similar Early Neoproterozoic magmatic event reported from the LHC, suggesting a second stage of arc magmatism. The timing of peak metamorphism has been inferred from 206 Pb/ 238 U mean ages of structureless zircons in metagabbros from Skallevikshalsen and Austhovde, mafic granulite from Langhovde, and felsic gneiss from Rundvågshetta in the range of 551 ± 5.4 to 584 ± 5.0 Ma. Zircon Lu–Hf data of Neoarchean charnockites from Sudare Rocks and Vesleknausen indicate that the protolith magma was sourced from Paleo- to Neoarchean juvenile components mixed with reworked ancient crustal materials. Protolith magmatic rock of the felsic gneiss from Rundvågshetta might have been sourced from reworked Paleoarchean crust. In contrast, metagabbros from Skallevikshalsen and Austhovde were derived from the Paleoproterozoic reworked crust. The results of this study suggest the occurrence of several discrete crustal fragments of ca. 2.5 Ga and ca. 1.0 Ga juvenile magmatic arcs in the southwestern part of the LHC, which amalgamated during the latest Neoproterozoic collisional event related to the final stage of assembly of the Gondwana supercontinent. [ABSTRACT FROM AUTHOR]

In the eastern North China Craton, basement gneisses are covered by poorly dated Late Paleoproterozoic to Early Neoproterozoic sediments. This study reports new zircon data from the Jixian area to constrain the protolith age of basement orthogneisses, the detrital ages of cover clastic sediments, and the age of a post-tectonic intrusive granite. Most zircons in orthogneisses have dark cores and bright rims in cathodoluminescence images. The dark cores have 207 Pb/ 206 Pb peak ages at 2520 Ma that constrain the minimum protolith age of the orthogneiss. In contrast, the bright rims have a wide 207 Pb/ 206 Pb age range from ca. 2500 Ma to 1800 Ma that is distributed along the Concordia curve, which reflect a Paleoproterozoic overprint on the basement of the North China Craton. Overlying clastic sediments mainly contain 2.5–2.7 Ga zircons derived from the basement rocks. 2200 Ma detrital oscillatory-zoned zircons, especially in a basal conglomerate of the Xiamaling Fm., were no doubt derived from 2200 Ma igneous rocks, probably from the southern North China Craton. The intrusive granite contains euhedral zircon grains with clear oscillatory zones that yield a Concordia age of 205.6 ± 1.1 Ma, and was likely generated during early Mesozoic delamination of the eastern North China Craton. [ABSTRACT FROM AUTHOR]

Voluminous Neoarchean plutonic and supracrustal rocks are well developed in the Western Shandong Province of the North China Craton, which has been divided into a late Neoarchean crustally-derived granite belt, a middle to early Neoarchean ancient rock belt and a late Neoarchean juvenile rock belt. Earlier studies provided reconnaissance evidence for ∼2.60 Ga metamorphism in some areas. This study presents SHRIMP zircon U–Pb dating and O isotope analysis on nine metamorphosed igneous rock samples (gneissic tonalite, gneissic trondhjemite, gneissic quartz diorite and meta-gabbro) from the ancient rock belt. Magmatic zircons vary in age from 2.74 Ga to 2.60 Ga, whereas metamorphic and anatectic zircons vary in age from 2.63 Ga to 2.59 Ga, with an age peak of 2.61 Ga. In this study, we identified 2.69–2.67 Ga metamorphic zircons for the first time. Most of zircons, whether magmatic or metamorphic, have δ 18 O values of +4.5‰ to +6.5‰ (V-SMOW). However, the oldest tonalite sample with a protolith age of 2735 Ma has zircons showing low δ 18 O (V-SMOW) values, particularly in recrystallized domains and overgrowths. This suggests at least in local crustal extension and influx of meteoric water during the evolution of the rocks. Combined with data from earlier studies, we draw the conclusion that the Western Shandong Province experienced a regional tectono-thermal event at ∼2.60 Ga, as a result of high heat flow and crustal extension, perhaps caused by a mantle plume or mantle overturn activity. Therefore we conclude that 2.60 Ga can be regarded the break between early and late Neoarchean crustal accretion. The O isotope study indicates that in some cases, trondhjemitic leucosome was not derived from nearby gneissic tonalite, although they show a close relationship in outcrop. [ABSTRACT FROM AUTHOR]

The Northern Liaoning Complex in northeastern China constitutes an important component of the Eastern Block in the North China Craton. The major lithologies consist of Archean granitoid gneisses with minor supracrustal rocks occurring as tectonic lenses. This study presents zircon Lu–Hf isotopic data for the first time as well as new SHRIMP zircon U–Pb data of the major lithologies from the Northern Liaoning Complex, in order to elucidate the crustal evolution of the complex and provide new constraints on the Neoarchean crustal evolution of the Eastern Block in the North China Craton. Magmatic zircon U–Pb data from this study show that the protolith magmas of the supracrustal rocks and granitoid gneisses were generated during ∼2.55–2.50 Ga. Metamorphic zircons document consistent metamorphic ages at 2.49–2.48 Ga, suggesting a regional metamorphic event immediately after the magmatism at the end of the Neoarchean in the Northern Liaoning Complex. Inherited/detrital zircons of 2.79–2.60 Ga suggest possible existence of ancient crust in this region. Zircon Lu–Hf isotopic compositions show that the magmatic zircons have variable ɛ Hf ( t ) values from −4.0 to +9.0 with depleted mantle model ages of 3.6–2.5 Ga, of which most ɛ Hf ( t ) values are positive with a model age peak at 2.9–2.7 Ga. These zircon Hf signatures reveal major juvenile crustal growth with additions of older crustal materials during 2.9–2.7 Ga, and a crustal reworking event with minor juvenile additions at 2.6–2.5 Ga in the studied area. Integrated with previous data from other Neoarchean complexes in the Eastern Block, both the major juvenile crustal growth during 2.9–2.7 Ga and the strong crustal reworking at 2.6–2.5 Ga contribute to the extensive Neoarchean crust formation of the Eastern Block in the North China Craton. The North China Craton share similar Neoarchean continental crustal evolution to other cratons in the world, though it is distinctively featured by intensive tectonothermal overprinting at the end of the Neoarchean. [ABSTRACT FROM AUTHOR]

• Meso -Neoarchean eclogitized rocks underwent anatexis during the Neoarchean time ∼ 2.7 Ga. • The anatexis occurred at boundaries between felsic gneisses and mafic rocks. • Two potassic granitic leucosomes with contrasting geochemical signatures formed. • U-rich zircon domains affected by radiation damage between 2.7 and 1.9 Ga. Eclogites exposed along the northeastern boundary of the Belomorian orogen in the eastern Fennoscandian Shield formed as a result of Mesoarchean–Neoarchean subduction. Highly-deformed banded TTG gneisses with eclogitized mafic pods, lenses and dykes in the Gridino association of metamorphic rocks have been modified locally to have typical migmatite structures that formed as HP rocks decompressed through HP granulite-facies metamorphic conditions (16–12 kbar, 800–850 °C) to amphibolite-facies conditions (10–9 kbar, 600–700 °C). The migmatites are located with the boundaries between felsic and mafic lithologies, which are the most suitable place for partial melting, fluid migration, and component diffusion. Symplectic intergrowths of hydrous minerals (mica, epidote) together with quartz in the leucosome are important markers of arrested reaction textures that formed by reversed hydration crystallization of residual melts or by fluids where their infiltrated through migmatite areas. There are two potassic granitic leucosomes with contrasting geochemical signatures. Garnet and phengite-bearing leucosome replaces the host TTG gneiss and percolates mafic rocks. This leucosome is distinguished by a high Ba content, striking positive Eu and Sr anomalies and corresponding low concentrations of all other trace elements. The compositions of the leucosome record initial segregation and migration of melt away from the residual source and subsequent crystal fractionation, dominated by feldspars, of the escaped melt. Migration of anatectic melts led to the formation of small bodies of leucogranite that are characterized by high contents of trace elements and negative Eu and Sr anomalies. Leucogranites formed from portions of fractionated melt that percolated the migmatites and solidified. Anatexis occurred during the Neoarchean time (∼2.7 Ga). U-rich zircon domains were partly or completely affected by radiation damage that yield discordant scattered dates between 2.7 and 1.9 Ga, which are interpreted as reflecting a thermal and fluid overprint during evolution of Belomorian province that produced recrystallization and Pb loss in Neoarchean zircons. [ABSTRACT FROM AUTHOR]

• Oldest crust in the Devon–Ellesmere region is late Neoarchean (ca. 2.55–2.47 Ga). • 1.91 Ga metamorphism obtained peak P–T conditions of ca. 9 kbar and >850 °C. • First discovery of a sapphirine–quartz assemblage in the Canadian Arctic. • Evidence of UHT conditions associated with the Thelon–Inglefield orogen. • Late Neoarchean terranes may be linked between Devon Island, Boothia Peninsula, and northern Greenland. The northernmost exposures of the Laurentian shield in Canada outcrop on Devon and Ellesmere islands, near the tectonic domains of the ≥2.6 Ga Rae Province and ca. 2.0–1.9 Ga Thelon–Inglefield orogenic arc. We report (Th)–U–Pb zircon and monazite ages along with phase equilibrium modelling pressure–temperature estimates for southern Devon Island, the only area on Devon or Ellesmere islands with previously known Archean rocks. Our results demonstrate that southern Devon Island is a late Neoarchean (ca. 2.55–2.47 Ga) terrane composed of lower to middle crustal, granulite facies rocks with evidence of anatexis and pervasive solid-state ductile deformation. Protoliths of clinopyroxene–garnet quartzofeldspathic gneiss, orthopyroxene quartzofeldspathic gneiss, two-pyroxene metabasite and biotite granite gneiss were emplaced between ca. 2.55–2.51 Ga, and a clastic sedimentary protolith for rutile–garnet metasedimentary rocks was deposited at ca. ≥2.47 Ga. Earlier, poorly constrained metamorphic events are recorded at ca. 2.54, 2.47 and 2.30 Ga, possibly associated with pulses of the Arrowsmith orogen (ca. 2.5–2.3 Ga). Most recently, this terrane was reworked by high temperature (HT) to ultrahigh temperature (UHT) metamorphism at ca. 1.91 Ga during with the Thelon–Inglefield orogen; obtaining peak P–T conditions of ca. 9 kbar and >850 °C. The discovery of a sapphirine–quartz metapelite assemblage is a first for the Canadian Arctic and is diagnostic evidence of UHT conditions within the Thelon-Inglefield orogenic zone. [ABSTRACT FROM AUTHOR]

Western Shandong Province is a typical area of the North China Craton (NCC) where Neoarchean plutonic and supracrustal rocks are widely distributed. Early studies documented that ∼2.7 Ga and ∼2.5 Ga magmato-tectono-thermal events are well developed in the area. Here we report SHRIMP U–Pb ages and Hf-in-zircon isotopic data from ten samples of different magmatic rock types including hornblendite, gneissic tonalite, gneissic trondhjemite and gneissic granite. Magmatic zircon grains have 207 Pb/ 206 Pb ages ranging from 2667 to 2598 Ma. Some rocks contain ∼2.5 Ga metamorphic rims and ∼2.7 Ga zircon cores. The magmatic zircon grains have ɛ Hf ( t ) values and Hf crustal model ages of −1.1 to +11.3 and 3.02–2.4 Ga, respectively. Combined with an earlier study, our main conclusions are that the middle Neoarchean rocks mainly occur together with early Neoarchean rocks in the northeastern portion of the central belt. Juvenile additions to continental crust and crustal recycling played important roles in the middle Neoarchean of western Shandong Province, and the entire Neoarchean tectonic evolution can be divided into middle to early Neoarchean (2.75–2.6 Ga) and late Neoarchean (2.6–2.5 Ga) events. [ABSTRACT FROM AUTHOR]

The Mulgathing Complex within the Gawler Craton, South Australia, preserves evidence for magmatism, sedimentation and metamorphism spanning the transition between the Neoarchean and Paleoproterozoic (ca. 2555-2410Ma). Prior to this study, limited data were available to constrain the timing of these tectonothermal events. We report SHRIMP zircon U-Pb dating of metamorphosed sedimentary and magmatic rocks from the Mulgathing Complex that shows metasedimentary gneisses (Christie Gneiss) have maximum depositional ages ca. 2480Ma, in contrast to previous studies that have suggested deposition had occurred ca. 2510Ma. The oldest metamorphic zircons in our data are ca. 2465Ma, thus indicating there was a time interval of less than 15Myr between the cessation of sedimentation and the occurrence of high-grade metamorphism. Metamorphic zircons have a range of ages, from ca. 2465 to 2415Ma, consistent with a period of ~50Myr during which high-grade metamorphism occurred. Mafic and felsic intrusions have ages that range from ca. 2520Ma to 2460Ma, indicating magmatism occurred during sedimentation and continued during the early stages of metamorphism and deformation of these rocks. The presence of bimodal magmatism with continental arc affinity (Devils Playground Volcanics) together with mafic intrusions showing temporal overlap with sedimentation within the Mulgathing Complex suggests that the overall tectonic regime prior to deformation likely involved lithospheric extension, possibly related to a continental magmatic arc. The Mulgathing Complex shows similarities in the nature and timing of these tectonothermal processes with several other Neoarchean-Paleoproterozoic terranes, in particular the Terra Adelie Craton in Antarctica, the Sask Craton, Canada, and regions within the North China Craton and the North Australian Craton. It is possible that similarities in process could imply along-strike relationships between these terranes, for example as laterally continuous terranes at the margin of a former continental domain (or domains). Basement rocks with ages of ca. 3250-3150Ma, ca. 2950-2800Ma and 2600-2550Ma within the Gawler Craton, as inferred from magmatic and inherited zircons, are temporally equivalent to some of the main basement units within the Pilbara Craton, and basement rocks in both the Gawler and Pilbara cratons are overlain by sedimentary rocks at ca. 2480Ma that include banded iron formations. It is possible to envisage the Gawler Craton as representing an extended continental margin adjacent to a larger, more intact continental domain, such as the Pilbara. [ABSTRACT FROM AUTHOR]

We present new isotopic data (U-Pb and Sm-Nd) from the Neoarchean granitoids of the Lentua complex, which is a part of the Western Karelia subprovince of the Fennoscandian Shield. Compositionally, the samples are granitoids belonging to the sanukitoid suite and K-rich granitoids. Certain samples interpreted as partial melts of pre-existing crust in this study display more mafic compositions than previously described from the surrounding areas. This indicates, at least locally, a source poorer in SiO2 than the TTG (Tonalite-Trondhjemite-Granodiorite) suite granitoids, which are the likely sources for the majority of the anatectic granitoids within the Lentua complex. Based on new geochronological data (LA-MC-ICPMS U-Pb on zircon), the sanukitoids and anatectic granitoids are at least partly coeval (2.69 Ga) in the area, but interaction between the two felsic magmas was limited. The dated sanukitoid sample is distinctly younger (2687±8 Ma) than the average age of the sanukitoids of the Western Karelia subprovince (2718±3 Ma) indicating, together with one previously published sanukitoid age, the existence of a younger sanukitoid phase. This study gives new important constraints to understanding the formation of the Western Karelia subprovince by expanding the observed compositional heterogeneity and the temporal overlap of the different Neoarchean granitoid suites. [ABSTRACT FROM AUTHOR]

Abstract: As an important component of the Western Shandong Complex in the Eastern Block of the North China Craton, the Yishui Terrane consists of Neoarchean high-grade supracrustal rocks, granitoid gneisses and charnockites. LA-ICP-MS zircon U Pb dating and Hf isotopic analyses on these lithologies have been carried out and the results provide new insights into the Neoarchean crustal evolution of the Eastern Block of the North China Craton. New zircon dating results reveal that the magmatic precursors of the supracrustal metapelites and granitoid gneisses were generated at 2.54–2.53Ga and 2.57–2.55Ga, respectively, and the charnockites were emplaced contemporaneously around 2.56–2.53Ga. Single metamorphic zircon grains and overgrowth rims from these rocks document consistent metamorphic ages at ~2.50Ga, suggesting that the Yishui Terrane experienced a high-grade metamorphic event at the end of the Neoarchean. Detrital zircons from pelitic gneisses yield 207Pb/206Pb ages of 2.89–2.65Ga, with a major age peak at ~2.53Ga and a subordinate age peak at ~2.70Ga, implying that the sedimentary protoliths of the pelitic gneisses may have been sourced from ~2.53Ga rocks in the Yishui Terrane and ~2.70Ga rocks in the adjacent Luxi Granite-Greenstone Terrane. Hf isotopic compositions show that the Neoarchean magmatic zircons have positive εHf(t) values ranging from +1.4 to +7.8 and depleted mantle model ages of 2.92–2.60Ga with a prominent peak at 2.8–2.7Ga, suggesting that the Neoarchean crust was derived mainly from juvenile sources and partly from the recycling of old continental crust in the Yishui area. Combined with previous data from the adjacent Luxi Granite–Greenstone Terrane and other complexes in the Eastern Block, it is concluded that the Neoarchean was an important period of crust accretion in the Eastern Block of the North China Craton. [Copyright &y& Elsevier]

Abstract: The growing knowledge of the geological record reveals evidence of crustal recycling in the Archean eon. In order to assess the role of recycling of crust into the mantle we have analyzed radiogenic Hf-in-zircon as well as whole-rock Nd and Pb isotope compositions of mantle-derived granitoids of the sanukitoid series in the Neoarchean Karelian province, Fennoscandian shield. Homogeneous initial Hf and Nd values suggest that sanukitoids are derived from well-mixed source(s). Limited scatter in the initial Pb isotope data within intrusions as well as in other radiogenic isotopes point to effective mixing processes in the mantle. O isotope data for zircon from Karelian sanukitoids indicate a dominant mantle source (δ 18O=+5.5–6.1‰) with minor contributions from sources with elevated δ 18O (+7.0‰ to +8.5‰), such as sediments and altered upper oceanic crust. Our results suggest that the parental melts of sanukitoids are mixtures of depleted mantle and recycled crustal components. A slab breakoff at the end-stage of subduction is a plausible trigger mechanism for sanukitoid magmatism and it explains variable contributions from different δ 18O sources. [Copyright &y& Elsevier]

Abstract: The Dunhuang block, in the easternmost segment of the Tarim craton, exposes Precambrian mafic granulite and felsic gneiss. To better understand the poorly known formation and evolution of the Tarim craton, we carried out detailed field-based petrological and geochronological investigations on the major lithologies of the Dunhuang block. U–Pb dating and Hf isotopic analyses on the mafic granulite and felsic gneiss (TTG gneiss) of the Dunhuang block reveal two distinct age populations: the Latest Neoarchaean (∼2.5Ga) and the Late Palaeoproterozoic (1.82–1.85Ga). The zircon magmatic cores and metamorphic rims of tonalitic gneisses yield similar ages of ∼2.5Ga, supporting the existence of Archean rocks in the Dunhuang block. The short time interval between Latest Neoarchean magmatism and high-grade metamorphism suggests that they were related to the same Latest Neoarchean tectonothermal event. The ∼2.5Ga zircons show Hf-depleted mantle model ages between 2.55Ga and 2.8Ga with a peak at ∼2.7Ga, suggesting that ∼2.7Ga juvenile crust of the Dunhuang block was reworked during a 200–300m.y. period at the end of the Neoarchean. The age of ∼1.85Ga obtained from the mafic granulites and felsic gneisses is interpreted as the age of high-pressure granulite facies metamorphism. Combined with the Hf isotopic data, these data suggest that the Dunhuang block experienced ∼2.7Ga crustal growth, a ∼2.5Ga magmatic–metamorphic event and a 1.82–1.85Ga (HP) granulite facies metamorphic event. This sequence of events is very similar to that of the North China Craton, implying that the evolutionary history of the Dunhuang block was consistent with that of the North China Craton from the Neoarchean to Paleoproterozoic. [Copyright &y& Elsevier]

Abstract: Voluminous Archean rocks (including orthogneisses and supracrustal rocks) are exposed in Eastern Hebei, northern part of the North China Craton (NCC), and nearly all of these Archean rocks have experienced high-grade metamorphism of granulite-facies or upper amphibolite facies from 2.54Ga to 2.52Ga. The Qinglong area of the eastern part of Hebei Province has a set of low-grade (greenschist- to lower amphibolite-facies) supracrustal rocks, e.g., the Qinglong volcano-sedimentary rock series (QVRS), unconformably overlying on the high-grade metamorphosed Qianxi Complex. Zircons yield a weighted mean 207Pb/206Pb age of 2511±12Ma meta-felsic volcanic rocks and 2503±13Ma meta-basic volcanic rocks. These ages indicate that the QVRS formed during the period from 2511Ma to 2503Ma. The meta-felsic volcanic rocks display low MgO (0.96–2.67wt.%), Cr (50.90–87.10ppm), and Ni (2.78–6.18ppm) contents, and low Nb/Ta ratios (13.56–14.54), and high light rare earth elements (LREEs) ((La/Yb) n =14.75–22.04), which are interpreted to have been produced by the partial melting of the lower crust. The meta-basic volcanic rocks (low-grade amphibolites) have abundance levels from 3.86wt.% to 7.74wt.% of MgO, and from 46.11wt.% to 51.99wt.% of SiO2. They are enriched in LREEs and depleted in high field strength elements (HFSEs) with positive ɛ Nd(t) values (+2.6 to +2.9). The volcanic rocks in the QVRS show bimodal compositions. The ɛ Hf(t) (t =2511Ma) values of amphibolite range from −4.7 to +5.7, and their single-stage Hf model ages vary from 2622Ma to 3030Ma (peak at 2835Ma). For the meta-felsic volcanic rocks, the ɛ Hf(t) values range from −3.2 to +5 with two-stage model ages changing from 2683Ma to 3180Ma (peak at 2872Ma). The QVRS is proposed to have formed during an intra-continent rift at 2500Ma, after the regional high-grade metamorphism from 2.52Ga to 2.54Ga. The QVRS probably formed during an intra-continental rift, as a part of the late Neoarchean cover of the NCC. [Copyright &y& Elsevier]

Abstract: The Miyun Geopark is located in the northern part of the North China Craton and includes a variety of Archean granitoids and metamorphic rocks. SHRIMP zircon dating documents their emplacement ages at 2567–2508Ma, metamorphic events at ca. 2.50Ga, 2.44Ga, and 1.82Ga. Late Neoarchean basement rocks elsewhere in the North China Craton document a similar evolutionary history with intrusion of granitoid rocks commencing at ca. 2590Ma and reaching three peaks at about 2550, 2520, and 2500Ma; these rocks then underwent regional metamorphisms at ca. 2.50Ga, 2.44Ga, 1.92Ga, and 1.82Ga. Positive ε Hf(t) values of +1.7 to +7.6, with model ages younger than 3.0Ga, for magmatic zircons from these late Neoarchean intrusive rocks indicate that they are predominantly derived from juvenile crustal sources and suggest that significant crustal growth occurred in the northern North China Craton during the Neoarchean. The intrusive rocks in the Miyun area are part of an extensive province of late Neoarchean magmatism and appear to be related to mantle plume activity at this time. [Copyright &y& Elsevier]

Abstract: The evolution of the North China Craton (NCC) is well known for a marked 2.55–2.50Ga tectonothermal event. However, supracrustal and intrusive rocks of 2.75–2.70Ga are in fact widely distributed in the western Shandong Province, the most important area of Archaean basement in the eastern part of the NCC. This paper reports SHRIMP U–Pb dating and LA-ICPMS Hf isotopic composition of zircons from 2.75–2.70Ga supracrustal and trondhjemite–tonalite–granodiorite (TTG) rocks in that area. Three fine-grained (hornblende) biotite gneiss samples (known locally as leptynite, with meta-volcanic or volcanosedimentary rock protoliths) and five TTG samples have SHRIMP zircon U–Pb ages varying from 2.75 to 2.70Ga and 2.74 to 2.71Ga, respectively. Zircons from most of the samples have high positive ɛ Hf(t) values (+4.7 to +10.0) and t DM(Hf) ages (2.85–2.60Ga) similar to their zircon U–Pb ages. This indicates that the rocks represent largely juvenile crustal additions derived from depleted mantle only a short time before. However, some granitoids show ɛ Hf(t) zircon values of −13.6 to +5.1 and t DM(Hf) of 3.51–2.80Ga. Therefore, the strong 2.75–2.70Ga tectonothermal event in the western Shandong Province involved not only juvenile addition to the continental crust but also intracrustal recycling of older components. Combined with craton-wide data, it is shown that the NCC is similar to many other cratons around the world where tectonothermal events of ∼2.7Ga are well developed. However, the main difference is that in the NCC, superimposed ∼2.5Ga tectonothermal events were much stronger than in most other cratons. [Copyright &y& Elsevier]

The Archean gneiss complex of West Greenland contains packages of unrelated rocks created during relatively short periods of time in arc-like magmatic environments, and having similarities to rocks formed at Phanerozoic convergent plate boundaries. The terranes of new Archean crust were amalgamated by collisional orogeny and then partitioned by post-assembly tectonic processes. Having summarized the origin of West Greenland Archean crust in arc-like environments, this paper then focuses on new data concerning the latest Neoarchean post terrane-assembly "intra-continental" tectonic and magmatic evolution of the region. Following the youngest documented high pressure metamorphism in a clockwise P-T-t loop at ~2650 Ma, attributed to tectonic thickening of the crust, there is in West Greenland a 150 million year record of intermittent production of crustally-derived granite, shearing and folding under amphibolite facies conditions. This is exemplified by the SSW-NNE orientated Neoarchean Qôrqut Granite Complex (QGC) which forms a myriad of closely spaced coeval sheets NE of Nuuk town. SHRIMP U-Pb zircon dating of a homogeneous gray granite sheet gives a magmatic age of 2561 ± 11 Ma, with 3800 to 3600 and 3070 to 2970 Ma zircon xenocrysts. The >40 km long Færingehawa straight belt, a lower amphibolite-facies vertical shear zone, runs from the QGC's SE margin and contains strongly deformed granite sheets with a U-Pb zircon age of 2565±8 Ma but is cut by undeformed granite sheets dated at 2555±12 Ma. The >60 km long Ivisaartoq fault consisting of lowermost amphibolite-facies mylonite runs from the northwestern end of the main mass of granite. It formed post-2630 Ma, because granites of that age are truncated by it. Near the QGC's northeastern extent, 2559±3 Ma granitic lithons in a folded mylonite are cut by 2521±72 Ma granite sheets. At a deep structural level at the northern end of the QGC, deformed granitic neosomes give ages of 2567±9 and 2563±5 Ma. Therefore, at ~2560 Ma, the ages within error for strongly deformed to non-deformed granite bodies shows that the QGC is not a largely post-kinematic intrusion as previously thought, but was coeval with lowermost amphibolite-facies metamorphism and shear zones with an important strike slip component, late in the development of regional non-cylindrical upright folds. The main body of the QGC appears to be essentially post-kinematic only because it was emplaced in a node of dilation during the heterogeneous predominantly strike slip deformation. Melting at this node may have been triggered by meteoric water percolating down dilational fractures, causing metasomatism. Melting of these altered rocks gave rise to the low δ18O signature of QGC igneous zircons. Due to the hydrous nature of the melting event, the QGC was emplaced immediately above its migmatitic generation zone. These late Neoarchean shear zones of the Nuuk region partition and disrupt the earlier-formed mosaic of amalgamated terranes of unrelated rocks. Such tectonic patterns are seen more recently, for example in Holocene Asian intra-continental tectonics along the north side of the Himalayas. [ABSTRACT FROM AUTHOR]

Abstract: The Pine Creek Orogen, located on the exposed northern periphery of the North Australian Craton, comprises a thick succession of variably metamorphosed Palaeoproterozoic siliciclastic and carbonate sedimentary and volcanic rocks, which were extensively intruded by mafic and granitic rocks. Exposed Neoarchean basement is rare in the Pine Creek Orogen and the North Australian Craton in general. However, recent field mapping, in conjunction with new SHRIMP U–Pb zircon data for six granitic gneiss samples, have identified previously unrecognised Neoarchean crystalline crust in the Nimbuwah Domain, the eastern-most region of the Pine Creek Orogen. Four samples from the Myra Falls and Caramal Inliers, the Cobourg Peninsula, and the Kakadu region have magmatic crystallisation ages in the range 2527–2510Ma. An additional sample, from northeast Myra Falls Inlier, yielded a magmatic crystallisation age of 2671±3Ma, the oldest exposed Archean basement yet recognised in the North Australian Craton. These results are consistent with previously determined magmatic ages for known outcropping and subcropping crystalline basement some 200km to the west. A sixth sample yielded a magmatic crystallisation age of 2640±4Ma. The ca. 2670Ma and ca. 2640Ma samples have ca. 2500Ma metamorphic zircon rims, consistent with metamorphism broadly coeval with emplacement of the volumetrically dominant ca. 2530–2510Ma granites and granitic gneisses. Neoarchean zircon detritus, particularly in the ca. 2530–2510Ma and ca. 2670–2640Ma age span, are an almost ubiquitous feature of detrital zircon spectra of unconformably overlying metamorphosed Palaeoproterozoic strata of the Pine Creek Orogen, and of local post-tectonic Proterozoic sequences, consistent with this local provenance. Neoarchean zircon is also a common detrital component in Palaeoproterozoic sedimentary units across much of the North Australian Craton suggesting the existence of an extensive, if not contiguous, Neoarchean crystalline basement underlying not only a large part of the Pine Creek Orogen, but also much of the North Australian Craton. [Copyright &y& Elsevier]

[Display omitted] • Metavolcanic rocks of the Tonghua area were formed at ca. 2.60 and 2.52 Ga, and metamorphosed at 2.53–2.47 Ga. • The SJB and NLB experienced two episodes of crustal growth at ∼ 2.7 Ga and ∼ 2.6–2.5 Ga, and were reworked at 2.53–2.47 Ga. • The Northern Liaoning Block and Southern Jilin Block have different tectonic setting. • Metavolcanic rocks formed in a transitional inner-oceanic arc to active continental margin geodynamic setting. The Tonghua area is located on the northeastern edge of the Eastern Block of the North China Craton (NCC), and connects the Northern Liaoning Block (NLB) in the west and Southern Jilin Block (SJB) in the north. The greenstone sequences in this region are voluminous metavolcanic rocks, which mainly comprise amphibolite, pyroxene amphibolite, pyroxene/amphibole–plagioclase gneiss, and biotite–plagioclase gneiss. Here we present zircon cathodoluminescence images, U–Pb dates, and Lu–Hf isotope data, as well as whole-rock geochemical data for these rocks, in order to constrain the geodynamic evolution of the Neoarchean crust and mantle and define the crustal evolution process of the northeastern NCC. Zircons from these metavolcanic rocks can be divided into two groups, with one having a typical magmatic origin and the other a metamorphic recrystallization origin. Zircon U–Pb dating and Lu–Hf isotopic results show that the magmatic zircons have two peak ages, dated at ca. 2.60 Ga and ca. 2.52 Ga, with the former have ε Hf =+3.04 to + 9.24 and single-stage model ages (T DM) of 2.80–2.54 Ga, the younger group have ε Hf values of + 2.41 to + 7.05 and T DM values of 2.73–2.56 Ga. While the metamorphic zircons document consistent metamorphic ages at 2.47–2.53 Ga, suggesting a regional metamorphic event. Their framing into the regional background has allowed us to explore the complete Neoarchean tectonic-thermal event and further contrast the NLB and SJB in the chronology, as well as to reveal crustal growth (∼2.7 Ga, ∼2.6–2.5 Ga) and reworking (∼2.53–2.47 Ga) history in the Neoarchean. The geochemical data indicate that the rocks were divided into three types, with affinities to mid-ocean ridge basalt (N-MORB), island arc tholeiites (IATs), and continental arc basalts (CABs). Taking into account the arc-related magmatism and the distribution of ancient crystalline basement (≥2.7 Ga), it is proposed that a long-lived, active continental-margin setting may have evolved along the northeastern margin of the NCC during the late Neoarchean (∼2.5–2.6 Ga), which distinguishes the NLB and SJB. Moreover, the geochemical and Lu–Hf isotope mapping results also indicate that the NLB and SJB have different tectonic setting. We consider that the metavolcanic rocks from the Tonghua area are related to an arc–continent collision, and formed in a transitional inner-oceanic arc to active continental margin geodynamic setting during the late Neoarchean (2.6–2.5 Ga). [ABSTRACT FROM AUTHOR]

The North China Craton (NCC) consists of Neoarchean to Paleoproterozoic basement, with rare Eo-Paleoarchean crustal relicts. However, the Precambrian tectonothermal evolution of the Central Orogenic Belt (COB) of the NCC is still hotly debated. In this contribution, we present new results of field-based litho-structural analysis, Th-U-Pb geochronology of accessory minerals including zircon, titanite and monazite from paragneiss and marble in a passive margin sequence in the Zanhuang Massif of the COB. Field studies show that two generations of deformation events occurred in the Zanhuang Massif. The earlier deformation is widely distributed in the entire Zanhuang Massif and developed with a top-to-SE shear sense resulting in foliation of the micaschist, metavolcanic rock, marble and paragneiss. The latter deformation is locally occurred in the central Zanhuang Massif and developed with a top-to-SW shear sense represented by the faulting and folding events which are similar to the fold-and-thrust structures of accretionary wedge during the formation of Zanhuang mélange. Zircons from paragneiss yield single-peak age populations with mean ages of 2.52 and 2.51 Ga, and a metamorphic age of 1.84 Ga. Zircon ages from marble are divided into four groups including a main peak of 2.54 Ga, two older groups of 2.77–2.82 and 2.60–2.70 Ga, and a younger metamorphic age of 1.81 Ga. Titanites from paragneiss and marble yield mean metamorphic ages between 1.94 and 1.88 Ga, representing an earlier thermal event. Monazites from paragneiss yield an isochron age of 1.80 Ga, representing a later thermal event. Based on our new litho-structural observations and geochronological data, coupled with previous studies, we suggest that the paragneiss and marble from the marble-siliciclastic unit represent the passive margin sequence, and were mainly deposited at 2.51–2.50 Ga. In addition, the Zanhuang Massif has experienced two tectonothermal events at ca. 1.94–1.88 Ga and ca. 1.83–1.80 Ga, which are widely distributed in the entire NCC, but gradually become weaker from north to south. [ABSTRACT FROM AUTHOR]

• SJC experienced multiple magmatism of ~2.78, ~2.69 and ~2.55 Ga. • Neoarchean magma derived from episodic juvenile crust growth and crustal reworking. • Recycling of sediments was not intense or extensive in SJC during Neoarchean. • A bottom-up tectonic regime related to plume activity is favored for NCC in Neoarchean. 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. [ABSTRACT FROM AUTHOR]

• The plutonic protoliths of the Huai'an gneisses were emplaced at 2.51–2.40 Ga. • The metamorphism was caused by continent-arc-continent collision at 1.86–1.80 Ga. • The Huai'an gneiss complex was formed in an intra-oceanic arc environment. • 2.8–2.6 Ga is a major period of juvenile crustal growth of Trans-North China Orogen. One of the major advancements in understanding the formation and evolution of the North China Craton was the recognition of a Himalayan-type collisional belt in the central part of the craton, called the Trans-North China Orogen (TNCO), along which two micro-continental blocks, named the Eastern Block and Western Block, joined together to form a coherent craton. However, controversy still remains about the pre-collisional tectonic setting and architectures of the TNCO. In this contribution, field-based zircon U–Pb and Lu-Hf isotopic investigations were carried out on the Huai'an gneisses from the Tianzhen-Xinpingbu area in the northern part of the TNCO. The Huai'an gneisses consist predominantly of tonalitic-trondhjemitic-granodioritic (TTG) gneisses with minor gabbroic, dioritic and granitic gneisses. Our zircon U-Pb results show that the plutonic protoliths of the Huai'an gneisses were emplaced at 2.51–2.40 Ga and experienced a granulite-facies metamorphic event at 1.86–1.80 Ga. The magmatic zircons of these samples yield ε Hf (t) values from +1.9 to +7.0 and T DM C ages of 2862–2619 Ma. These positive ε Hf (t) values, associated with the lack of old inherited zircons, suggest the derivation of their precursor magmas from a juvenile crust without contamination of old continental crust. The T DM C model ages indicate that 2.8–2.6 Ga is the best estimation of the mantle extraction time for the source rocks in the Huai'an gneisses, revealing a major period of juvenile crustal growth. Thus it can be inferred that the partial melting of subducted oceanic crust slab produced the magmas of the Huai'an gneisses, which subsequently interacted with overlying mantle wedge during the ascent, suggesting an intra-oceanic arc environment for the Huai'an gneiss complex. Taken together, the development of the Huai'an gneiss complex was involved in a subduction-related magmatic event in an intra-oceanic arc at ~2.5 Ga, followed by collision between the Eastern and Western blocks at ~1.85 Ga. [ABSTRACT FROM AUTHOR]