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Granites are keys to the understanding of crustal stabilization and cratonization processes. Here we present an integrated study of the lithology, geochronology and geochemistry of late Neoarchean granites and associated TTGs (tonalite-trondhjemite-granodiorite) and migmatites from the western Shandong Province (WSP) of the North China Craton (NCC). The TTG xenoliths in the Lushan massive granite formed at 2529 ± 7 Ma. The Menglianggu and Yishan migmatite, containing 2.70-2.52 Ga inherited zircons, defines regional anatectic event at 2512 ± 6 Ma. The Menglianggu, Lushan and Yishan granites yield 207 Pb/ 206 Pb ages ranging between 2517 to 2488 Ma, which are indistinguishable from the regional metamorphic/anatectic events of the WSP. Based on the SiO 2 contents and REE patterns, the late Neoarchean granites exposed in Wande, Sishui, Qixingtai and Menglianggu areas can be subdivided into three groups. Group 1 exhibits, low SiO 2 (68.6-69.2 wt.%), high ΣREE (345.4-475.3 ppm) contents, moderate negative Eu anomalies (0.55-0.73) and depletion in U, Nb, Ta and Sr contents. Group 2 is composed of most of the studied samples and show moderate SiO 2 (70.1-75.7 wt.%) and ΣREE (135.8-357.1 ppm) content with obvious negative Eu anomalies (0.33-0.58) (excluding an outlier sample TS1310) and pronounced depletions in Ba, Sr, Nb and Ta contents. Group 3 displays high SiO 2 (74.9-76.3 wt.%) and low ΣREE (18.6-71.6 ppm) abundance. They are characterized by lack of negative Eu and Sr anomalies. Geology and Geochemical comparisons suggest that the major part of the granitic magma originate from re-melting of TTG type rocks at low pressure. The negative U anomalies of Group 1 granite are inherited from the source which is different from the case of TTGs. The correlation of Sr vs. Ba and Rb suggests fractional crystallization of K-feldspar, plagioclase and minor hornblende in the precursor magmas of Group 2. These geochemical features are similar to those associated with crustal stabilization in other cratons. Our studies on the WSP also suggest that the coeval to slightly earlier regional anatexis is also an important process during cratonization.

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

The Neoarchean era is an important period for the formation of continental crust in the early earth. The North China Craton (NCC) records magmatism during 2.8–2.7 Ga and 2.6–2.5 Ga with the latter more extensive. However, the ∼2.7 Ga rock assemblages are significantly different from those of the ∼2.5 Ga rocks. Based on detailed field investigation, we present results of zircon geochronology by using SHRIMP and LA-ICP–MS techniques on the Shanggang pluton in the central belt of the western Shandong Province (WSP). The Shanggang pluton is composed of 2.71–2.69 Ga strongly deformed tonalite on the eastern and northern margins with the central part occupied by younger (2.67–2.65 Ga and 2.63–2.61 Ga) trondhjemite. Most zircon grains with apparent 207Pb/206Pb ages of 2.67–2.66 Ga in our samples have low Th/U ratios (0.05–0.20) resulted from low to moderate Th contents of 10–130 ppm and relatively higher U contents of 100–3000 ppm, consistent with those of anatectic zircons. Some of grains carry ∼2.7 Ga inherited cores. Our study reveals that the crustal re-working event at 2.67–2.66 Ga might have been more widespread than currently known, although the 2.67–2.66 Ga zircons have positive eHf(t) values close to that of coeval depleted mantle (Wan et al., 2014). Together with data from previous studies, it is notable that more trondhjemite and even some granite were generated during 2.67–2.60 Ga. Relative to the older TTG suites (2.72–2.69 Ga), the younger ones (2.67–2.60 Ga) are dominated by trondhjemite. The compositional variations of TTG suites through the early to middle Neoarchean suggest that the 2.67–2.60 Ga magmatic and anatectic events should be related to the compositional differentiation of the Archean continental crust of the WSP.

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.

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 207Pb/206Pb 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 ɛHf(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.

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 SiO2 and very low FeOt + MgO. The magmatic zircon grains from all these rocks are similar in their Hf isotopic compositions and have ɛHf(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.

Metamorphosed clastic rocks provide important constrains on the composition of upper continental crust. Here we report and characterize a sequence of Neoarchean paragneiss in association with migmatite from the Qixingtai area in Western Shandong Province (WSP) in the North China Craton (NCC), that represent metamorphosed moderate- to fine-grained clayey clastic rocks. The garnet from the paragneiss is characterized by nil or weakly compositional zoning. The biotite shows low TiO2 content ( The paragneiss exhibits SiO2 contents in the range of ∼58 wt.% (garnet gneiss)–∼70 wt.% (sillimanite gneiss), and negative correlations with Al2O3 (23.4–15.4 wt.%), TiO2 (0.90–0.35 wt.%), MgO (4.5–1.1 wt.%), FeOt (8.3–2.6 wt.%) and Cr (382–131 ppm). The REE patterns also show a systematic change from garnet gneiss to sillimanite gneiss. In trace element discrimination diagrams, the paragneiss plots between the end-members of komatiite/basalt and TTG/granite, suggesting that the sediments sourced from a mixture of ultramafic–mafic and felsic protoliths. Combined with the geochronological data, we suggest that the 2.75–2.71 Ga komatiite–tholeiite sequence of the Taishan association and TTGs in the central terrane and the 2.56–2.53 Ga TTGs in the southwestern part of the WSP as the potential provenance for the clastics. The protolith of the paragneiss in the Qixingtai area belong to the sedimentary sequence of the Taishan association. Spatially associated coeval arc-like assemblage and other geological evidence suggest that, (1) the metasediments were likely deposited in a back arc basin, (2) the upper amphibolites-facies metamorphism, constrained by the mineral assemblages in the paragneiss, might be related to the closure of the basin, and (3) the generation of large volumes of matured K-rick continental crust occurred not earlier than 2.53 Ga in the WSP granite–greenstone belt.

Western Shandong Province (WSP) is one of the typical Neoarchean granite-greenstone belts in the North China Craton (NCC). The Taishan association, consisting of a ∼2.7 Ga komatiite–tholeiite sequence and a ∼2.5 Ga felsic volcanic-sedimentary sequence, is the major supracrustal assemblage in the WSP. The ∼2.7 Ga komatiite–tholeiite sequence can be subdivided into the Yanlingguan and Liuhang units. The 150–800 m thick basaltic lava sequence of the Liuhang unit is exposed in the Qixingtai area, with the bottom unit composed of massive and layered basalts. Pillow basalts and tuff dominate the upper parts of the sequence. We report a weighted mean SHRIMP 207Pb/206Pb zircon age of 2706 ± 9 Ma (MSWD = 0.61) for a trondhjemitic dike that intrudes the base of the pillow basalts, constraining the timing of this sequence to be older than this age. The basaltic lava sequence in the Liuhang unit is characterized by voluminous tholeiites and a minor component of enriched basalts. The tholeiites show relatively high MgO (5.5–9.0 wt.%), but low TiO2 (0.8–1.3 wt.%) and Nb (2.1–3.3 ppm) contents. They display co-variations between Zr and other immobile trace elements and flat REE and trace elements patterns on chondrite- and primary mantle-normalized diagrams, respectively. In contrast, the enriched basalts have low MgO (3.6–5.4 wt.%), but high TiO2 (1.6–2.2 wt.%) and Nb (8.4–11.6 ppm) contents. They display moderately enriched LREE and fractionated HREE patterns on chondrite-normalized diagrams. The basaltic sequence of the Liuhang unit displays a moderate range of initial ɛNd (−0.1 to +3.0) values. The element concentration and Nd isotopes of tholeiitic rocks in the Liuhang unit are comparable with the contemporaneous tholeiites in greenstone belts globally. In particular, the geochemical systematics of the tholeiite and enriched basalts show close similarity with those of the Wawa greenstone belt in the Superior Province. The Nb/Th, La/Smcn and Nb/La ratios of these basalts indicate that the basaltic lava sequence of the Liuhang unit has not been significantly affected by crustal contamination compared to the Yanlingguan komatiite–tholeiite sequence. The variation in lithology and geochemistry of basalts between the Liuhang and Yanlingguan units reflects a lateral change in composition of the ∼2.7 Ga basaltic eruption. We propose that the komatiite–tholeiite sequence in the Taishan association was derived from an upwelling mantle plume with eruption close to the continental margin within an ocean basin. Our study does not provide any evidence to support that the WSP granite-greenstone belt was subjected to significant arc–plume interaction during the early Neoarchean. Our results contribute to the understanding of early Neoarchean crustal growth globally identified from different regions.

The evolution of the North China Craton (NCC) is well known for a marked 2.55–2.50 Ga tectonothermal event. However, supracrustal and intrusive rocks of 2.75–2.70 Ga 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 2.75–2.70 Ga 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 2.70 Ga and 2.74 to 2.71 Ga, respectively. Zircons from most of the samples have high positive ɛ Hf ( t ) values (+4.7 to +10.0) and t DM (Hf) ages (2.85–2.60 Ga) 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 3.51–2.80 Ga. Therefore, the strong 2.75–2.70 Ga 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 ∼2.7 Ga are well developed. However, the main difference is that in the NCC, superimposed ∼2.5 Ga tectonothermal events were much stronger than in most other cratons.