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[Display omitted] • A new complex, named as the Hujiamiao Complex, was discovered in the Anshan area, NCC. • Trondhjemitic rocks of different ages from 3.79 to 3.11 Ga have been identified. • It is the first time in Anshan to identify trondhjemitic rocks with relatively high (La/Yb) n ratios. • Magmatic zircons have ε Hf (t) of −12.3 to 1.6, t DM (Hf) and t CC (Hf) ages of 4.1 to 3.6 Ga and 4.3 to 3.7 Ga. • All the Anshan 3.8–3.3 Ga complexes are the relics of the same larger complex in the area. Anshan is located in the northeastern North China Craton and has a long-term geological history back to 3.8 Ga. Four complexes with ages of 3.8–3.1 Ga have been identified previously, namely the Baijiafen, Dongshan, Shengousi and Guodishan complexes. Being similar to the neighbouring Beijiafen Complex, the newly-discovered Hujiamiao Complex extends in a northwest-southeast direction and shows tectonic contacts on one side with the Chengtaigou granite and on the other with the Chengtaigou supracrustal rocks. In the Hujiamiao Complex, trondhjemitic rocks of 3789 Ma, 3786 Ma, 3698 Ma, 3617 Ma, 3566 Ma, 3504 Ma and 3106 Ma have been identified. More work is required to establish if a gabbro also has a formation age of 3.8 Ga. The trondhjemitic rocks show similar compositional features in being high in SiO 2 (72.37–76.71 %) and Na 2 O (5.00–6.47 %) and low in K 2 O (0.60–1.95 %), ∑REE contents (32.83–91.83 ppm) and (La/Yb) n ratios (11.09–48.64). They have whole-rock ε Nd (t) values of 0.35–4.43, t DM (Nd) of 3.74–3.46 Ga and t CC (Nd) ages of 3.74–3.43 Ga, and in situ magmatic zircon ε Hf (t) values of −12.3 to 1.56, t DM (Hf) ages of 4.2 to 3.5 Ga and t CC (Hf) ages of 4.6 to 3.7 Ga. Combined with previous work, it is concluded that all the Anshan area 3.8–3.3 Ga complexes are the relics of a larger complex which was once more widely distributed in the Anshan area. The trondhjemitic rather than tonalitic character of the Anshan Eoarchean rocks shows diversity in the formation and evolution of the earliest continental crust with a range of T/P for crustal anatexis. [ABSTRACT FROM AUTHOR]

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 <0.3), c) rare idiomorphic morphologies, and d) commonly containing inherited (xenocrystic) cores. We conclude that the strong late Neoarchean event is widespread in western Shandong and is limited between ∼2.50 and 2.54 Ga. In contrast, apparent 2.45–2.48 Ga metamorphic zircon ages in some other areas of the North China Craton may be the result of overprinting and partial recrystallization of Neoarchean metamorphic zircons during the late Paleoproterozoic event. The Archaean rocks of western Shandong can be divided into three belts, namely Belts A, B and C from the northeast to the southwest. The difference between Belts A and B in ∼2.5 Ga metamorphic and anatectic intensity may indicate that the former was elevated to a higher crustal level compared with the latter at the end of the Neoarchean. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Lower Wulashan Group in Daqingshan, northwestern NCC records magmatic zircon ages of 2455–2382 Ma. • Intrusive rocks intruding the Lower Wulashan Group have magmatic zircon ages of 2436–2362 Ma. • It is for the first time to identify early Paleoproterozoic supracrustal rocks in the area. • The Lower Wulashan Group and related intrusive rocks formed in a continental environment. • Three main magmatic episodes of the late Neoarchean to late Paleoproterozoic have been identified. Early Paleoproterozoic supracrustal rocks are relatively rare worldwide and only a few have been reported in the North China Craton (NCC). Daqingshan is a typical area of the Khondalite Belt, northwestern NCC, where early Precambrian supracrustal and intrusive rocks are widely distributed, although the precise age of all units remains unconfirmed. The Lower Wulashan Group is mainly composed of acidic to mafic volcanic and volcano-sedimentary rocks that have undergone amphibolite to granulite facies metamorphism; it was previously considered to be of Mesoarchean age. This study utilized integrated field and petrographic work, whole-rock geochemistry, and Nd whole-rock and zircon U-Pb-Hf isotopic analyses on the Lower Wulashan Group and related intrusive rocks. SHRIMP U-Pb dating of eight samples from the supracrustal rocks, interpreted as metavolcanics, yielded magmatic zircon ages of 2455–2382 Ma, thus for the first time identifying early Paleoproterozoic supracrustal rocks in the Daqingshan area. Thus it is of great importance for understanding the Precambrian evolution of the NCC as well as the Earth because this is within the period when magmatism was globally weak. Six samples from a variety of intrusive rocks have zircon U-Pb ages of 2436–2362 Ma, thus further confirming the depositional ages of the supracrustal rocks. These rocks include meta-alkali basalt, and are high in total rare earth element contents and have magmatic zircon ε Hf (t) values of −3.00 to +6.62 and crustal model ages of 3.12–2.52 Ga (38 analyses), and whole-rock ε Nd (t) of +1.0 to +2.6 with crustal model ages of 2.74–2.60 Ga (5 analyses). It is considered that the early Paleoproterozoic supracrustal rocks of the Lower Wulashan Group and related intrusive rocks formed in a continental environment, but more work is required to determine the tectonic regime (extension or subduction). [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]

Abstract: At the end of the Neoarchean continental evolution, voluminous syenogranites were emplaced in the North China Craton, together with other magmatic rocks (trondhjemite–tonalite–granodiorite (TTG), monzogranite, diorite, gabbro). Syenogranites are widely distributed in Anshan-Benxi, Qinhuangdao and western Shandong, and also occur in southern Jilin, northern Liaoning, northwestern Hebei and central Henan. Based on geological relationships, degree of metamorphism, deformation and magmatic zircon ages, two phases of syenogranite magmatism are recognized. Rocks produced during the first phase show a gneissic texture and were formed between 2.53 and 2.52Ga and locally comprise abundant TTG. Rocks of the second phase cut late Neoarchean TTG and supracrustal rocks, display a massive structure, and mainly formed between 2.52 and 2.50Ga. All syenogranites share the same features in major element compositions, being high in SiO2 and low in CaO, total FeO, MgO, TiO2 and P2O5. However, they are different in trace and REE compositions and can be subdivided into three types. (1) Type 1 shows a large variation in total REE contents, low (La/Yb) n ratios, strong negative Eu*/Eu anomalies and Ba depletion; (2) Type 2 is similar to Type 1 but has higher (La/Yb) n ratios. (3) Type 3 shows a large variation in total REE and (La/Yb) n ratios and significantly do not show strongly negative Eu*/Eu anomalies and Ba depletion. Whole-rock Sm–Nd isotopic compositions show large variations in ɛ Nd(t) values and t DM(Nd) modal ages, ranging from −9.49 to −4.72 and 3.70 to 3.25Ga (Type 1), 0.55–1.03 and 2.77–2.71Ga (Type 2) and −2.35 to 1.23 and 2.93–2.66Ga (Type 3), respectively. Hf isotopic compositions of zircons from three samples have ɛ Hf(t) values and t DM1(Hf) ages of 0.7–7.2 and 2.84–2.56Ga (Type 1), 2.6–7.4 and 2.74–2.56Ga (Type 2) and 2.1–6.3 and 2.76–2.60Ga (Type 3). It is concluded that syenogranites were generated by melting of continental crust with different mean crustal residence ages, and most of them were emplaced during the second phase (2.52–2.50Ga) in an extensional tectonic regime. The formation of these voluminous syenogranites marks a tectono-magmatic event resulting in stabilization of the North China Craton at the end of the Neoarchean. [Copyright &y& Elsevier]

Abstract: In the Daqingshan area within the Khondalite Belt of the North China Craton, Paleoproterozoic gabbro and dolerite intrusions show amphibolite to granulite-facies metamorphism. U–Pb zircon dating and whole-rock geochemistry were undertaken on these rocks in order to understand the timing of mantle magmatism and thermal processes. Ten samples yielded zircon U–Pb formation ages of 2.46–2.44Ga, 1.97–1.92Ga and 1.84Ga and metamorphic ages of 1.95–1.83Ga. They are variable in geochemical composition with some being enriched in light rare earth and large ion lithosphere elements but depleted in Nb–Ta. Combined with previous results, it is concluded that mafic magmatism at 2.45–2.37Ga and 1.97–1.92Ga indicates two Paleoproterozoic extensional phases, with the latter accompanied by HT–UHT metamorphism as a result of underplating of mantle magma. [Copyright &y& Elsevier]

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]

Eastern Shandong is one of the important early Precambrian areas in the North China Craton, where extensive 2.5, 2.7 and 2.9 Ga magmatic activities have been identified, followed by very strong late Neoarchean and Paleoproterozoic tectono-thermal events. We carried out SHRIMP zircon dating, Hf-in-zircon isotope analysis and a whole-rock geochemical study on ca. 2.9 Ga Mesoarchean magmatic rocks. These include gneissic diorite, gneissic quartz diorite, gneissic tonalite and gneissic high-Si trondhjemite and were identified in five new areas. All these rocks contain ca. 2.5 Ga metamorphic zircons. The dioritic and tonalitic rocks are enriched in large ion lithosphile (LIL) elements (K, Rb, Ba) and depleted in Nb and P with moderate to highly fractionated REE patterns, similar in chemical compositions to Archean TTG rocks worldwide. The high-Si trondhjemites are characterized by very high SiO 2 and very low FeOt + MgO. The magmatic zircon grains from all these rocks are similar in their Hf isotopic compositions and have ɛ Hf ( t ) values ranging from + 1.3 to +9.9. Combined with previous work, our main conclusions are: (1) eastern Shandong underwent a major magmatic event at ca. 2.9 Ga; (2) diorites and tonalites formed by melting of thickened lower crust or the root of an oceanic plateau, whereas the high-Si trondhjemites were derived from melting of intermediate to felsic rocks; (3) the Mesoarchean (ca. 2.9 Ga) was a major period of juvenile crustal addition from the depleted mantle, earlier than the major crustal growth period at 2.7–2.8 Ga in the North China Craton; (4) the 2.7–2.9 Ga rocks underwent strong metamorphism at ca. 2.5 Ga, probably as a result of magmatic underplating. [ABSTRACT FROM AUTHOR]

Highlights: [•] ∼2.7 Ga rocks have been identified in eight areas of the North China Craton. [•] They are mainly tonalitic in composition and frequently underwent late alteration. [•] Their formation was a result of juvenile additions to the continental crust. [•] The North China Craton is similar in main period of crustal growth to other cratons. [ABSTRACT FROM AUTHOR]

Abstract: The eastern part of the North China Craton in eastern Hebei Province contains metamorphosed and deformed Neoarchaean to earliest Palaeoproterozoic rocks (∼2550–2490Ma) with some older Archaean rocks. Numerous precise U–Pb zircon ages, structural observations, Nd and Hf isotopic data and whole rock geochemistry (our new data with reassessment and integration of previous work) show that there is not a single protracted event at the end of the Archaean lasting ∼60 million years, but that from east to west there are several separate events with their own unique character. The eastern coastal region is dominated by weakly deformed 2530–2510Ma granites with subordinate granodiorites, diorites and magnesian-gabbros. This suite has inclusions of older 2550–2540Ma plutonic rocks. ∼80km inland to the west, there are amphibolite facies biotite-rich schists, lenses of BIF, siliceous fuchsite bearing rocks with 3880–3540Ma zircons, peridotites and orthogneisses, all intruded by younger granites and monzonites. Three amphibolite–granulite facies gneisses and schists with volcano-sedimentary protoliths have 2548–2534Ma igneous zircon populations, rare inheritance back to >3600Ma and 2506±6Ma zircon equated with granulite facies metamorphism. Older tonalitic to granitic polyphase orthogneisses contain 3287±11Ma to ∼2940Ma igneous components. Late kinematic high Fe/Mg gabbros, monzonites and granites have ages of 2499±7 to 2491±13Ma. 160–100km inland, gneissose 2550–2530Ma quartz-diorite to tonalitic rocks occur as intrusions into, or intercalations with, mafic rocks. These were affected by granulite facies metamorphism but then widely retrogressed. Abundant syn-granulite facies neosome and later shear zones disrupt the early geological relationships. The granulite facies metamorphism is dated at 2503±5Ma from several samples, including a syn-granulite facies pegmatite. The Neoarchaean igneous rocks show marked negative Nb, Ti anomalies, LIL enrichment and enrichment of the light REE relative to the heavy REE across the entire ultramafic, basaltic, tonalitic and granitic compositional spectrum: 2550–2530Ma tonalites and quartz diorites are most important in the west and 2530–2510Ma granites are most important in the east. Their composition resembles those formed at various stages of magmatic arc evolution at a convergent plate boundary, rather than being plume products. The eastern Hebei rocks thus formed in a complex arc with distinct pulses of plutonism at 2550–2540 and 2530–2510Ma, with local incorporation of older continental crust. The 2500–2490Ma thermal event with its associated higher Fe/Mg magmas involved interaction of underplated fractionated gabbroic melt with deep crustal melts, possibly during extension of an already ∼50 million years old arc. [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]