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Daqingshan is located in the northwestern North China Craton where late Neoarchaean supracrustal rocks occur widely, but where magmatic zircon ages have rarely been reported for plutonic rocks. In this study, we report SIMS U–Pb zircon ages and Hf isotope, whole-rock element and Nd isotope compositions for 12 magmatic samples, including TTG, quartz monzonitic and monzogranitic gneisses, and meta-gabbroic and dioritic rocks. They have magmatic zircon ages of 2530–2469 Ma; some samples have ages of Nd(t) and in situ magmatic zircon ϵHf(t) values of +1.2 to +2.4 and −1.1 to +6.2, respectively. Quartz monzonite and monzogranite gneisses and gabbroic to dioritic rocks have similar Nd–Hf isotope compositions to the TTG gneisses. The absence of zircon >2.6 Ga in the early Precambrian rocks suggests that the Sanggan Group may have formed in an oceanic environment, whereas the TTG rocks formed as a result of partial melting of the basaltic rocks of the Sanggan Group under relatively low-pressure conditions. Combined with previous studies, the main conclusions are that in the Daqingshan area, late Neoarchaean magmatism was widespread, the late Mesoarchaean – early Neoarchaean was an important period of juvenile continental crustal growth, and the late Neoarchaean supracrustal and plutonic rocks most likely formed in an arc environment. These are common signatures for Neoarchaean crustal evolution throughout much of the North China Craton, and also globally.

Qixia is a typical area of early Precambrian basement in eastern Shandong Province, eastern North China Craton. Many TTG (tonalite-trondhjemite-granodiorite) assemblages were once considered to be supracrustal rocks (the Jiaodong Group), and the formation ages of the rocks have only been determined in a few outcrops as shown on the early geological map of the area. We carried out geological mapping, geochemical study and SHRIMP U-Pb zircon dating in order to determine the temporal and spatial distribution and origins of the TTG rocks. In the newly compiled geological map (1:50,000), the main rock types of the Archean basement are ∼2.9 Ga, ∼2.7 Ga and ∼2.5 Ga tonalitic gneisses with local occurrences of trondhjemitic gneisses, granodioritic gneisses, (quartz) dioritic gneisses and meta-gabbro showing the same age range. Supracrustal rocks with ages of ∼2.9 Ga and ∼2.5 Ga are locally identified. All rocks broadly extend in a NW-SE direction as a result of strong tectonothermal events of the late Neoarchean and late Paleoproterozoic. Although the late Paleoproterozoic tectonothermal event strongly influenced all 2.7 to 2.9 Ga rocks in the area, metamorphic zircon ages are not widely recorded in these rocks because the high-grade metamorphism at ca. 2.5 Ga caused the older 2.7 to 2.9 Ga rocks to become relatively dry systems. The three generations of TTG rocks are similar in major element composition, characterized by high Na2O and low K2O, except for the late Neoarchean granodioritic gneisses, which locally occur and are relatively high in K2O. All the TTG rocks of different ages commonly have zircon O isotopic compositions within the range determined by Valley and others (2005) for Archean magmatic zircon. The ∼2.9 Ga TTG rocks show large Sr/Y and La/Yb variations and depletion in whole-rock Nd and zircon Hf isotopic compositions. The ∼2.7 Ga TTG rocks are similar in Nd-Hf isotopic compositions to the ∼2.9 Ga TTG rocks but have low Sr/Y and La/Yb ratios. The ∼2.5 Ga TTG rocks are similar in trace element composition to the ∼2.9 Ga TTG rocks, showing large variations in Sr/Y and La/Yb ratios. They can be further subdivided into two types in terms of Nd-Hf isotopic compositions with the depleted type mainly including tonalitic gneisses [eNd(t) = +1.86 to +4.59, eHf(t) = +1.0 to +8.7] and the enriched type including trondhjemitic and granodioritic gneisses [eNd(t) = −2.38 to −0.06, eHf(t) = −1.6 to −2.9]. It is concluded that the ∼2.9 Ga TTG rocks were formed in an oceanic environment (oceanic plateau or intra-ocean subduction), and the 2.7 Ga TTG rocks were formed by mantle underplating that resulted in partial melting of lower crustal mafic rocks under relatively low pressure conditions. More ancient continental materials played a role in the ∼2.5 Ga magmatic process, but more work is required to determine the tectonic environment (underplating or arc magmatism).

Santunying is an important area for revealing nature of the late Neoarchean tectono-magmato-thermal events in the eastern Hebei part of the North China Craton. It is mainly composed of meta-intrusive rocks. Supracrustal rocks sporadically occur in the meta-intrusive rocks. The meta-intrusive rocks are subdivided into the Santunying tonalitic gneiss, Qiuhuayu tonalitic-trondhjemitic gneiss, Xiaoguanzhuang dioritic gneiss and Qingyangshu meta-gabbro. Respectively, SHRIMP U–Pb zircon dating on fourteen samples yielded weighted mean 207Pb/206Pb ages of 2525–2537, 2532–2546, 2530–2544 and ~2531 Ma for magmatic zircons from them. Dioritic gneiss of the Xiaoguanzhuang gneiss contain abundant 2544–3487 Ma xenocrystic zircons. SHRIMP U–Pb dating on a garnet-biotite gneiss sample yielded a weighted mean 207Pb/206Pb age of 2537 Ma for detrital zircons. All rocks underwent strong metamorphism, deformation and anatexis, resulting in formation of leucosomes and residues, with some leucosomes concentrating to form large veins. They record a strong late Neoarchean event by metamorphic zircon ages of 2489–2519 Ma. Some rocks also record metamorphic zircon ages of 1772–1843 Ma. Magmatic zircons from the magmatic rocks show large variations in eHf(t) values ranging from −1.7 to +8.7. Combined with early studies, conclusions are: 1) Intrusive rocks with the involvement of mantle-derived materials have a narrow range of magmatic zircon ages from 2525 to 2546 Ma, and supracrustal rocks were formed during the same period. 2) Ancient crustal remnants (>2600 Ma) are present, consistent with the late Neoarchean arc magmatism involving older continental crust, similar to Phanerozoic Andean margins. 3) The Archean basement underwent a strong tectonothermal event at the end of the Neoarchean, with the metamorphic zircon ages being 10–30 million years younger than the timing of magmatism, a common feature of the North China Craton. 4) A late Paleoproterozoic tectonothermal event widely occurred in the western part of eastern Hebei, which is linked with regional ductile deformation.

Since the Apollo 14 mission delivered samples of the Fra Mauro formation, interpreted as ejecta of the Imbrium impact, defining the age of this impact has emerged as one of the critical tasks required for the complete understanding of the asteroid bombardment history of the Moon and, by extension, the inner Solar System. Significant effort dedicated to this task has resulted in a substantial set of ages centered around 3.9 Ga and obtained for the samples from most Apollo landing sites using a variety of chronological methods. However, the available age data are scattered over a range of a few tens of millions of years, which hinders the ability to distinguish between the samples that are truly representative of the Imbrium impact and those formed/reset by other, broadly contemporaneous impact events. This study presents a new set of U-Pb ages obtained for the VHK (very high K) basalt clasts found in the Apollo 14 breccia sample 14305 and phosphates from (i) several fragments of impact-melt breccia extracted from Apollo 14 soil sample 14161, and (ii) two Apollo 15 breccias 15455 and 15445. The new data obtained for the Apollo 14 samples increase the number of independently dated samples from this landing site to ten. These Apollo 14 samples represent the Fra Mauro formation, which is traditionally viewed as Imbrium ejecta, and therefore should record the age of the Imbrium impact. Using the variance of ten ages, we propose an age of 3922 ± 12 Ma for this event. Samples that yield ages within these limits can be considered as possible products of the Imbrium impact, while those that fall significantly outside this range should be treated as representing different impact events. Comparison of this age for Imbrium (determined from Apollo 14 samples) with the ages of another eleven impact-melt breccia samples collected at four other landing sites and a related lunar meteorite suggests that they can be viewed as part of Imbrium ejecta. Comprehensive review of 40Ar/39Ar ages available for impact melt samples from different landing sites and obtained using the step-heating technique, suggests that the majority of the samples that gave robust plateau ages are indistinguishable within uncertainties and altogether yield a weighted average age of 3916 ± 7 Ma (95 % conf., MSWD = 1.1; P = 0.13) and a median average age of 3919 + 14/-12 Ma, both of which agree with the confidence interval obtained using the U-Pb system. These samples, dated by 40Ar/39Ar method, can be also viewed as representing the Imbrium impact. In total 36 out of 41 breccia samples from five landing sites can be interpreted to represent formation of the Imbrium basin, supporting the conclusion that Imbrium material was distributed widely across the near side of the Moon. Establishing temporal limits for the Imbrium impact allows discrimination of ten samples with Rb-Sr and 40Ar/39Ar ages about 50 Ma younger than 3922 ± 12 Ma. This group may represent a separate single impact on the Moon and needs to be investigated further to improve our understanding of lunar impact history.

Abundant late Neoarchean granitoids occur in southwestern Liaoning Province, part of the Eastern Ancient Terrane of the North China Craton. These rocks include intermediate gneiss, TTG gneisses and potassic granitoids, and we report on the geochemistry and zircon SHRIMP ages as well as Hf-in-zircon isotopes of these granitoids in order to determine their petrogenesis. Field relationships suggest that most of these granitoids experienced widespread metamorphism and deformation, associated with anatexis at some localities. The intermediate gneisses, TTG gneisses and potassic granitoids were all emplaced at the end of the Neoarchean (2.50–2.53 Ga), and CL images document widespread recrystallization in the zircons. The intermediate and TTG gneisses yielded similar Hf isotopic systematics (eHf(t) = −3.73 to +6.42) as the associated potassic granitoids (eHf(t) = −2.44 to +7.80), and both rock types yielded mean Hf crustal model ages of 2.8–2.9 Ga. Combined with the geochemistry, we propose that the formation of the intermediate and TTG gneisses was related to partial melting of mafic rocks at different depth, whereas the potassic granitoids have variable petrogenesis. The nearly coeval TTG gneisses and potassic granitoids and their widespread metamorphism, deformation and zircon recrystallization suggest that a large-scale heat source must have been present at or near the base of the crust in southwestern Liaoning Province at the end of the Neoarchean. We propose that collision and post-collisional extension is the most likely tectonic environment for generation of the above granitoids, and the formation of widespread potassic granitoids played an important role in the maturation of continental crust in the North China Craton.

Metatonalite and amphibolite from the Taishan region of the Western Shandong Province in the North China Craton record c. 2.60 Ga fluid-present partial melting via the breakdown of biotite, plagioclase and quartz to produce peritectic hornblende and anatectic melt. Eight paired leucosome–melanosome samples from metatonalite and three paired samples from amphibolite were investigated to evaluate the composition of the melt. Hornblende, biotite and plagioclase in the leucosomes and hornblende and plagioclase in melanosomes from both rock types have similar compositions. Two leucosome samples from the metatonalite were influenced by the removal of heavy rare earth element-rich hornblende and the accumulation of plagioclase. The other leucosomes are interpreted to represent near initial melt compositions with a minor component of peritectic hornblende and are enriched in Si, Na and Sr and depleted in K, Ca, Ba and Rb relative to melanosomes. The enrichment of Na in the melt is inconsistent with experimental results of fluid-present melting of tonalite, but is broadly consistent with the experimental results of fluid-fluxed melting of amphibolite. The absence of K-feldspar in both rock types is a critical control on the composition of anatectic melt and initial melt compositions were probably similar for both rock types. Leucosomes inherited rare earth element patterns from their sources, which suggests that some trace element diagrams used to infer tectonic settings and depths of melting are not appropriate for reworked components of Archean grey gneisses. Whole-rockδ18O suggest that the fluids responsible for inducing local melting were derived from the intrusion and crystallization of ~2.60 Ga tonalites and trondhjemites in the Taishan region. One amphibolite sample has a relatively low δ18O suggestive of interaction with meteoric water or seawater possibly related to crustal extension and asthenosphere upwelling at ~2.60 Ga. Fluid-present partial melting reworked 2.75–2.60 Ga tonalites and amphibolites, generating ~2.60 Ga sodium-rich components of grey gneisses in the Western Shandong Province.

The Khondalite Belt is located in the northwestern North China Craton and contains late Paleoproterozoic metasedimentary rocks that generally underwent high-grade metamorphism. Only a few supracrustal sequences experienced low-grade metamorphism such as the Meidaizhao sequence in the Daqingshan area. The Erdaowa sequence north of Hohhot City, Inner Mongolia, is another late Paleoproterozoic supracrustal unit showing relatively low-grade metamorphism compared with the adjacent metapelitic khondalites. It is composed of metavolcanic as well as clastic metasedimentary rocks and marble. It was traditionally subdivided into the Halaqin and Hongshangou Formations. We undertook an integrated study of U-Pb zircon dating and O-Hf isotopic analysis, combined with whole-rock chemistry, on metasedimentary rocks of the Erdaowa sequence in order to understand the relationship between the low- and high-grade rocks and their tectono-thermal history in the Khondalite Belt. Cores and metamorphic domains of detrital zircons from a two-mica schist of the Halaqin Formation have 207 Pb/ 206 Pb ages of 2.0 and 1.86 Ga, δ 18 O values of 6.69–9.45‰ and 6.68–12.15‰, and ɛ Hf (t) values of +7.7 to +16.2 and +3.3 to +20.9, respectively. A recrystallized core, fir-tree domain and altered domain of zircon from a Grt-St-Ky two-mica gneiss have 207 Pb/ 206 Pb ages of >2.0 Ga, 1.88 Ga and 1.86 Ga, δ 18 O values of 12.10–12.75‰, 11.57–12.65‰ and 11.57–12.27‰, and ɛ Hf (t) values of +0.7 to +5.4, −2.0 to +4.7 and −2.0 to +0.5, respectively. These data limit the time of deposition of the sedimentary rocks between 2.0 and 1.88 Ga and show a high maturity, similar to khondalites of the same sequence. Compared with previous studies, we infer that the Erdaowa sequence consists of rocks of different origins and metamorphic grades (including khondalites), which were brought up to the same crustal level as tectonic slices due to late Paleoproterozoic tectonic processes.

High-temperature magma generation process and granulite-facies metamorphism can provide important information about mantle-crustal interaction and tectonic evolution. The strongly peraluminous monzonite pluton, the Jinshuikou cordierite granite on the southern margin of the Qaidam Block, can provide important information about the mantle-crustal interaction and constraints on tectonic transition from Proto-Tethys to Paleo-Tethys. This pluton develops enclaves of mafic granulite, amphibolite and quartzofeldspathic rocks, and is cut by massive monzonitic leuco-granite veins. Zircon and monazite U-Pb dating for the cordierite granite, the granulite enclaves and a massive monzonitic leuco-granite vein reveal that the cordierite granitic magma was generated from Mesoproterozoic continental crust with protolith derived from a provenance that was composed of >2.8 Ga old recycled crustal materials and recorded a ~1.7 Ga magmatic event. The continental crust underwent low-pressure granulite-facies metamorphism at ~380 Ma ago, whereas the cordierite granite magmas was generated and emplaced during 380 Ma, followed by intrusion of the massive monzonitic leuco-granite vein at circa 370–330 Ma. These data suggest that after the final closure of Proto-Tethys Ocean spreading along the southern Qaidam Block at ~420 Ma, break-off of the subducted slab or delamination of the lower crustal base and upwelling of the asthenospheric mantle beneath the southern Qaidam Block occurred before the Mid-Devonian, and that the initiation of the Paleo-Tethys tectonics might initiate near the end of Early-Carboniferous in the East Kunlun-Qaidam region, East Asia.

Granites generated by anatexis are ideal crustal probes to decipher the differentiation processes within deep continental crust. In this study, the successive emplacement of granites, including the porphyries and the coarse-grained granites, was found in the nucleus (the Kongling Complex) of the Yangtze Craton. The porphyries, intruding at 1840 ± 17 Ma (SHRIMP ages), occur as veins and contain phenocrysts of K-feldspar (∼15%), quartz (∼5%), plagioclase (∼4%) and garnet (∼1%) setting in a fine-grained groundmass (∼75%) of K-feldspar, plagioclase, quartz and biotite. The coarse-grained granites, emplacing at 1821 ± 8 Ma (SHRIMP ages), are outcropped as pluton and comprise K-feldspar (∼60%), quartz (∼30%), biotite (∼5%), plagioclase (∼5%). They are similar to A-type granites with relatively high SiO2 (69.2–71.5 wt%, 72.6–74.5 wt%), high Fe2O3T/MgO (21.5–27.7, 5.9–19.5), 104*Ga/Al ratios (3.6–4.3, 2.7–3.5) respectively and enriched HFSEs (Th, U, Pb, Ga). The porphyries contain higher total trace element contents and zirconium saturation temperature (mean 892 °C) than those of the coarse-grained granites (mean 803 °C). Magmatic zircons from the porphyries and coarse-grained granites have eHf(t) values of −17.6 to −11.7 and −21.0 to −14.8, which yield two-stage Hf model ages of 3.6–3.3 Ga and 3.8–3.4 Ga respectively, both falling into the evolutionary trend of the 2.9–2.8 Ga Kongling TTGs. It implies both granites are anatectic (crustal reworking) derivatives from partial melting of the Archean TTGs under sustaining extension in Paleoproterozoic. Applying trace element modelling, we further identify a unique tonalitic source for both granites which is analogous to the exposed natural Kongling tonalite, and find the porphyries slightly affected by the juvenile crust. Based on the intrusion of porphyry veins into granitic gneisses, we envisage the crustal structure beneath the craton is layered from older (∼2.94 Ga) tonalites upward to younger (∼2.87 Ga) granitic gneisses. Such hierarchical structure could shed new light on the imperceptible vertical differentiation process as cratonization.

The Archean Beitai-Waitoushan migmatite-syenogranite complex (BWMC) is located in the northeast of the Anshan-Benxi continent block (ABCB) where has ∼3.8 Ga rocks outcropped in the northeastern North China Craton (NCC). The BWMC consists chiefly of weakly migmatized tonalitic-trondhjemitic gneisses, migmatites with various volumes of potassium-rich granitoid veins from either syenogranite magma or anatexis of tonalitic- trondhjemitic gneisses, monzo- and syenogranitic intrusive rocks. LA-ICP-MS and SHRIMP zircon U-Th-Pb isotopic analyses reveal that the migmatized tonalitic-trondhjemitic gneisses were formed at 3454–3484 Ma, and were the partial sources of the syenogranitic rocks and entire protolith of the migmatites. The dominant monzo- and syenogranitic magmas were emplaced at 2500–2540 Ma and generally contain inherited Paleoarchean zircon grains with apparent 207Pb/206Pb ages of >3300 Ma. An amphibolite sample in the form of boudin in the migmatized tonalitic-trondhjemitic gneisses formed at 3414 Ma. These Paleoarchean rock samples and the inherited Paleoarchean zircons from the Neoarchean migmatites, monzo- and syenogranite samples indicate that a ∼3.45 Ga continent microblock existed prior to the ∼2.50 Ga migmatization and syenogranitic magmatism. When integrated with previous zircon Lu-Hf isotopic data from the study area, our new LA-ICP-MS zircon Lu-Hf isotope analyses for dated zircon spots from six dated samples reveal that the magmatic precursors of the ∼3.45 Ga samples and the ancient inherited zircons from the Neoarchean migmatites and intrusive granitoid rocks were primarily derived from ∼3.45 Ga partial melting of juvenile crustal materials from the depleted mantle, and either the mantle or more ancient continent crustal materials with CHUR-like Lu-Hf isotopic systematics. However, some of the Neoarchean monzo- and syenogranitoid rocks and the granitoid veins in the migmatites exhibit hybrid Lu-Hf isotopic features derived from both ancient ∼3.45 Ga continental and Neoarchean juvenile crustal materials, including partial mixing between the Neoarchean granitoid magma and plastic Paleoarchean gneiss relicts.

Mesoarchean and older potassic granites are important indicators of recycling of ancient continental crust early in Earth's history. This study of integrated whole rock and zircon geochemistry and geochronology reports the age and identification of the source materials of the > 200 km 2 Mesoarchean Tiejiashan-Gongchangling granite in the Anshan-Benxi area, North China Craton, the largest pre-Neoarchean granite domain in the craton. SHRIMP U-Pb zircon dating on 15 samples indicates the magmatic crystallization of the granites between 2.95 and 3.0 Ga and reveals a superimposed tectonothermal event at ~ 2.91 Ga. The granites are characterized by high SiO 2 and K 2 O, low CaO, FeOt, MgO and TiO 2 with peraluminuous features. They show large variations in (La/Yb) n and strong negative Eu and Ba anomalies and Nb, P and Ti depletions. Whole rock Nd and magmatic zircon Hf isotopic compositions show large variations, but with most having e Nd (t) and e Hf (t) values DM (Nd) and t DM (Hf) values varying from 3.3 to 3.9 Ga and 3.3 to 4.0 Ga, respectively. Magmatic zircons without very strong lead loss (discordance ≤ 20%) have δ 18 O values of + 3.14 to + 8.39. 3.3–3.7 Ga xenocrystic zircons occur in some samples. The granite formed as a result of recycling of Paleo- to Eoarchean continental material in an intracontinental environment, with little if any contribution from Mesoarchean mantle sources. The sources could be predominantly unaltered ancient gneisses, together with yet to be identified Paleo- to Eoarchean materials affected by early low temperature alteration (weathered rocks or clastic sediment).

There are different viewpoints on metamorphic and anatectic zircons recording ages of 2.45–2.48 Ga or even younger in some areas of the North China Craton where both late Neoarchean and late Paleoproterozoic tectono-thermal events are well developed. These are: 1) partial resetting of the U-Pb isotopic system in the late Neoarchean zircons, 2) metamorphism lasting from the late Neoarchean to the earliest Paleoproterozoic, and 3) earliest Paleoproterozoic metamorphism as separate different event. Western Shandong Province is an area where the late Neoarchean tectono-thermal event is widely developed but the late Paleoproterozoic event has not been identified. This provides an opportunity to understand the geological processes around the Archean-Proterozoic boundary. Based on a field study, we carried out SHRIMP U-Pb zircon dating on seventeen samples of ∼2.5 Ga old metamorphic and anatectic rocks, including tonalite, trondhjemite, granodiorite, gabbro, quartz diorite, granite and paragneiss with primary emplacement or depositional ages of 2.52–2.68 Ga. Anatectic zircons show some textural and compositional features: a) Homogenous or blurred oscillatory zoning, b) high U contents and low in Th/U ratios (commonly

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.

The Limpopo Belt of southern Africa is a typical early Precambrian orogen that experienced two high-grade metamorphic events which are a key for understanding its tectonic evolution. There has been a long-standing debate on whether the Neoarchean (c. 2.65 Ga) or the Palaeoproterozoic (c. 2.0 Ga) tectono-thermal event records continental collision. The clear field relationship between deformed mafic dykes and the surrounding rocks is a powerful tool to help reconstructing the deformation history. Mafic dykes intruded the 3.3–3.1 Ga Sand River Gneiss Suite in the Central Zone of the Limpopo Belt near Musina, South Africa, and were classified in the past into older Causeway dykes and younger Stockford dykes according to assumed field relationships, deformational patterns, and doubtful Rb-Sr dating. Our detailed field observations suggest that both dyke types belong to the same generation and cut the foliation and anatectic melt veins in the Sand River Gneiss Suite. They also experienced strong post-emplacement deformation and high-grade metamorphism, so they separate two high-grade metamorphic events. SHRIMP zircon dating yielded a likely emplacement age of ∼2.6 Ga for two Causeway dyke samples as well as metamorphic ages of 2002 ± 4 Ma and 2002 ± 8 Ma. The zircons of two Stockford dyke samples yielded igneous emplacement ages of 2607 ± 5 and 2604 ± 6 Ma, respectively, and metamorphic ages of 2014 ± 13 Ma and 2005 ± 11 Ma. Combining these data with similarities in the dyke geochemistry, we propose that the Causeway and Stockford dykes formed at the same time, but had different orientations. Our preferred tectonic model for the evolution of the Central Zone of the Limpopo Belt involves continental collision between the Zimbabwe and Kaapvaal Cratons at ∼ 2.65 Ga, followed by intracontinental transpressive orogeny and high-grade metamorphism at ∼2.0 Ga. We therefore propose that the widespread ∼2.6 Ga mafic dykes in the Central Zone formed in an extensional environment during post-collisional orogenic collapse. Both the Neoarchaean and Palaeoproterozoic orogenic events resulted in high-grade metamorphism and are separated in time by emplacement of the ∼2.6 Ga mafic dykes.

Among the various Precambrian crustal blocks in the North China Craton (NCC), the geology and evolution of the Ordos Block remain largely enigmatic due to paucity of outcrop. Here we investigate granulite-facies metapelites obtained from deep-penetrating drill holes in the Ordos Block and report petrology, calculated phase equilibria and in-situ monazite LA-ICP-MS geochronology. The rocks we studied are two samples of cordierite-bearing garnet–sillimanite–biotite metapelitic gneisses and one graphite-bearing, two-mica granitic gneiss. The peak metamorphic age from LA-ICP-MS dating of monazite in all three samples is in the range of 1930–1940 Ma. The (U + Pb)–Th chemical ages through EPMA dating reveals that monazite occurring as inclusions in garnet are older than those in the matrix. Calculated metamorphic phase diagrams for the cordierite-bearing metapelite suggest peak P–T conditions ca. 7–9 kbar and 775–825 °C, followed by decompression and evolution along a clockwise P–T path. Our petrologic and age data are consistent with those reported from the Khondalite Belt in the Inner Mongolia Suture Zone in the northern part of the Ordos Block, suggesting that these granulite-facies metasediments represent the largest Paleoproterozoic accretionary belt in the NCC.

Almost all evidence for the oldest traces of life on Earth rely on particles of graphitic carbon preserved in rocks of sedimentary protolith. Yet, the source of carbon in such ancient graphite is debated, as it could possibly be non-biological and/or non-indigenous in origin. Here we describe the co-occurrence of poorly crystalline and crystalline varieties of graphitic carbon with apatite in ten different and variably metamorphosed banded iron formations (BIF) ranging in age from 1,800 to >3,800 Myr. In Neoarchean to Palaeoproterozoic BIF subjected to low-grade metamorphism, C-13-depleted graphitic carbon occurs as inclusions in apatite, and carbonate and arguably represents the remineralisation of syngenetic biomass. In BIF subjected to high-grade metamorphism, C-13-depleted graphite co-occurs with poorly crystalline graphite (PCG), as well as apatite, carbonate, pyrite, amphibole and greenalite. Retrograde minerals such as greenalite, and veins cross-cutting magnetite layers contain PCG. Crystalline graphite can occur with apatite and orthopyroxene, and sometimes it has PCG coatings. Crystalline graphite is interpreted to represent the metamorphosed product of syngenetic organic carbon deposited in BIF, while poorly crystalline graphite was precipitated from C-O-H fluids partially sourced from the syngenetic carbon, along with fluid-deposited apatite and carbonate. The isotopic signature of the graphitic carbon and the distribution of fluid-deposited graphite in highly metamorphosed BIF is consistent with carbon in the fluids being derived from the thermal cracking of syngenetic biomass deposited in BIF, but, extraneous sources of carbon cannot be ruled out as a source for PCG. The results here show that apatite + graphite is a common mineral assemblage in metamorphosed BIF. The mode of formation of this assemblage is, however, variable, which has important implications for the timing of life's emergence on Earth. (C) 2019 Elsevier B.V. All rights reserved.

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.

The Xuting pluton, located at the north section of the Zanhuang Complex, contains potassic and sodic granite in both of which shallow level emplacement is shown by graphic texture feldspar and quartz intergrowth. Two potassic granite and one sodic granite samples yielded zircon 207 Pb/ 206 Pb ages of 2066 ± 17 Ma, 2092 ± 14 Ma, and 2071 ± 14 Ma, respectively, suggesting that the Xuting pluton emplaced between 2070 Ma and 2090 Ma, which is coeval with the Paleoproterozoic Gantaohe Group dominated by mafic volcanic and sedimentary rocks. The potassic granite is enriched in SiO 2 , total FeO, REEs (except Eu), Zr, Nb, Ga and Y, and depleted in MgO, CaO, Al 2 O 3 , Sr, V, Cr and Ni, with high TFeO/MgO ratios, consistent with the features of A-type granite. Except for the high MgO and low K 2 O contents, the sodic granite also presents most of the features of A-type granites. The zircon saturation temperatures from the potassic and sodic granites range from 855 to 998 °C and 853 to 933 °C respectively, indicating that they are from the high temperature magma. The potassic granites have the e Hf (t) ranging from − 5.9 to + 1.33 and Hf model ages of 2.5–2.8 Ga, which are identical with the ages of Neoarchean TTG gneisses in the Zanhuang Complex. We propose that the potassic granite in the Xuting pluton derived from the partial melting of Neoarchean TTG gneisses. The sodic granites also present negative e Hf (t) values from − 4.81 to − 0.76 and Hf model ages of 2.5–2.8 Ga, suggesting that they come from the partial melting of the Neoarchean crust. However, with relative enrichment in MgO and total FeO, and lower K 2 O and Rb, the sodic granite was derived from a mafic source in the lower crust. The likely heat source was high heatflow associated with mantle upwelling. The A-type Xuting pluton and mafic volcanic rocks in the Gantaohe Group constitute a bimodal lithologic association from a Paleoproterozoic continental rift environment. 2.2–2.0 Ga magmas are widely distributed along the Trans-North China Orogen (TNCO), and also present a bimodal character. We propose that 2.2–2.0 Ga bimodal magmas throughout the TNCO were likely formed in a Paleoproterozoic rifting setting. Considering the widespread 2.2–2.0 Ga magmatic rocks in the North China Craton (NCC), we infer that the magmatism likely occurs in tensional environment after the initial amalgamation of the NCC in the late Archean.

The Lomagundi-Jatuli Event (LJE) is one of the largest and earliest positive carbon isotope excursions preserving δ13Ccarb values between +5 and +16‰ in Paleoproterozoic carbonates worldwide. However, the duration, amplitude and patterns of these excursions remain poorly constrained. The 2.14–1.83 Ga Hutuo Group in the North China Craton is a >10 km thick volcano- sedimentary sequence, including >5 km thick well-preserved carbonates that were deposited in supra- tidal to sub-tidal environments. C-O isotopic and elemental analyses of 152 least altered samples of the carbonates revealed a three-stage δ13C evolution. It began with an exclusively positive δ13Ccarb (+1.3 to + 3.4‰) stage in the ~2.1 Ga carbonate in the Dashiling and Qingshicun Formations, followed by a transition from positive values to oscillating positive and negative values in ~3 000 m thick carbonates of the Wenshan, Hebiancun, Jianancun, and Daguandong Formations, and end with exclusively negative δ13Ccarb values preserved in > 500 m thick dolostones of the Huaiyincun and Beidaxing Formations. It appears that much of the LJE, particularly those extremely positive δ13Ccarb signals, was not recorded in the Hutuo carbonates. The exclusively positive δ13Ccarb values (+1.3 to + 3.4‰) preserved in the lower formations likely correspond to the end of the LJE, whereas the subsequent two stages reflect the aftermath of the LJE and the onset of Shunga-Francevillian event (SFE). The present data point to an increased influence of oxygen on the carbon cycle from the Doucun to the Dongye Subgroups and demonstrate that the termination of the LJE in the North China Craton is nearly simultaneous with those in Fennoscandia and South Africa.

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 ɛHf(t) values from −4.0 to +9.0 with depleted mantle model ages of 3.6–2.5 Ga, of which most ɛHf(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.

The Hutuo Group, located in the Wutai Mountains area, is characteristic of Paleoproterozoic strata in the North China Craton, and plays an important role in establishing evolutionary processes in the Trans-North China Orogen. We present petrological observations along with geochemical and Nd isotopic data for basalts in the Qingshicun and Hebiancun Formations of the Hutuo Group. These basalts are enriched in TFeO (11.97−18.01 wt.%), consistent with occurrences of iron-rich basalt world-wide. They also display relatively high MgO (4.95−12.25 wt.%), Ni (79−121 ppm) and Cr (37−101 ppm) and low in SiO 2 (41.37−51.95 wt.%). Therefore, the iron-rich character of the Hutuo Group basalts originated with their parental magma rather than via shallow crustal fractionation at low oxygen fugacity, as inferred for many high iron basalts. The Hutuo Group basalts exhibit weak to moderate differentiation of light REE over heavy REE ((La/Lu) cn = 2.61−6.79) with minor or slight Eu anomalies (Eu/Eu* = 0.77−1.41), and also show the Nb and Ti troughs without obvious Zr and Hf anomalies. The ɛ Nd ( t ) values of the basalts range from −1.23 to +0.81 with T DM of 2489−2664 Ma. The basalts most plausibly originated from the fertile subcontinental lithosphere mantle and, in the case of the Qingshicun Formation basalts, also underwent the crustal contamination. Basalts in the Hutuo Group also have the high Zr/Hf ratios, and present high Ti/V values of 24−55 and Zr/Y ratios ranging from 4.6 to 13.6, suggesting that they were emplaced in a within-plate setting. Considering the sedimentary associations and detrital fragments in the Hutuo and Gantaohe Groups, and bimodal magmatism along the Trans-North China Orogen, we propose that 2.2−2.0 Ga geological events within the orogen were rift-related, but did not result from subduction or island arc processes.

Sensitive High-Resolution Ion Microprobe (SHRIMP) U-Pb analyses of zircons from Paleoarchean (~3.4 Ga) tonalite-gneiss called the Older Metamorphic Tonalitic Gneiss (OMTG) from the Champua area of the Singhbhum Craton, India, reveal 4.24-4.03 Ga xenocrystic zircons, suggesting that the OMTG records the hitherto unknown oldest precursor of Hadean age reported in India. Hf isotopic analyses of the Hadean xenocrysts yield unradiogenic 176Hf/177Hfinitial compositions (0.27995 ± 0.0009 to 0.28001 ± 0.0007; ɛHf[t] = −2.5 to −5.2) indicating that an enriched reservoir existed during Hadean eon in the Singhbhum cratonic mantle. Time integrated ɛHf[t] compositional array of the Hadean xenocrysts indicates a mafic protolith with 176Lu/177Hf ratio of ∼0.019 that was reworked during ∼4.2-4.0 Ga. This also suggests that separation of such an enriched reservoir from chondritic mantle took place at 4.5 ± 0.19 Ga. However, more radiogenic yet subchondritic compositions of ∼3.67 Ga (average 176Hf/177Hfinitial 0.28024 ± 0.00007) and ~3.4 Ga zircons (average 176Hf/177Hfinitial = 0.28053 ± 0.00003) from the same OMTG samples and two other Paleoarchean TTGs dated at ~3.4 Ga and ~3.3 Ga (average 176Hf/177Hfinitial is 0.28057 ± 0.00008 and 0.28060 ± 0.00003), respectively, corroborate that the enriched Hadean reservoir subsequently underwent mixing with mantle-derived juvenile magma during the Eo-Paleoarchean.

The North China Craton is an ideal place for studying the transition of the Earth's thermal structure and tectonics at the Archean–Proterozoic boundary due to its good preservation of the ~ 2.5 Ga tectono-thermal events. We report the discovery of a high-pressure mafic granulite from the Jiaodong Terrain in the North China Craton. The mafic granulite occurs as garnet–clinopyroxene–orthopyroxene–hornblende gneiss enclaves within a late-Archean trondhjemite–tonalite–granodiorite (TTG) gneiss. Typical high-pressure mineral assemblage of garnet–clinopyroxene–plagioclase–quartz ± rutile has been identified. Plagioclase + clinopyroxene ± orthopyroxene ± hornblende symplectite surrounding garnet (“white eye”) is also observed. Using the conventional geothermobarometry and the pseudosection modeling, a clockwise metamorphic P–T path with the peak conditions at ~ 17 kbar and ~ 880 °C was determined. Zircon U–Pb analyses (SHRIMP) on the overgrowth rim of zircon grains of two samples from the same outcrop yielded a metamorphic age of 2473 ± 6 Ma (MSWD = 0.8). The analyses on magmatic core gave a probable magmatic age of 2527 ± 12 Ma (MSWD = 1.9). The high-pressure granulite facies metamorphism corresponds to a collisional event between the ~ 2.5 Ga crust and ~ 2.9 Ga crust at the dawn of Paleoproterozoic in the North China Craton. It also represents a new but rare case of a subduction–collision tectonics at the Archean–Proterozoic transition and provides insight into the change of the Earth's thermal structure.

We present an integrated study of zircon U-Pb dating and O-Hf isotopic analyses combined with whole-rock geochemistry and Nd isotopic systematics on widespread late Neoarchean syenogranites (Qidashan Pluton) and other granitoids (granodiorite, quartz monzonite, monzogranite) in the Anshan-Benxi area, eastern North China Craton. All these rocks were emplaced at ca. 2.5 Ga according to SHRIMP zircon U-Pb dating and other indirect methods. The syenogranites are characterized by high SiO2 and K2O/Na2O and low CaO, FeOt, MgO, TiO2 and P2O5. However, they differ in trace element and REE compositions and can be roughly subdivided into two types. Type 1 syenogranite has strongly negative Eu anomalies and Ba depletion, with large variations of LREE to HREE differentiation; type 2 syenogranite has no negative Eu anomaly and Ba depletion. Other granitoids are also rich in K2O and show similar trace element and REE compositional features as the type 2 syenogranite. Most syenogranite samples have whole-rock eNd(t) values of –10.5 to –2.7 and tDM(Nd) ages of 2.96 to 3.90 Ga, whereas the other granitoids have eNd(t) values of –5.2 to –2.2 and tDM(Nd) ages of 2.95 to 3.19 Ga. Magmatic zircon from the syenogranites has eHf(t) values and Hf crustal model ages ranging mainly from –11.0 to +4.4 and 2.70 to 3.46 Ga, respectively; those from other granitoids have eHf(t) values and Hf crustal model ages of –16.0 to +2.4 and 2.81 to 3.72 Ga, respectively. All these rocks contain Meso- to Paleoarchean xenocrystic zircon grains with eHf(t) values and Hf crustal model ages ranging from –14.3 to +8.3 and 2.79 to 3.93 Ga, respectively. Decoupling of whole-rock Nd and Hf-in-zircon isotopes occurs in some samples. Most low-U magmatic zircon (U