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[Display omitted] • Detrital zircon with ages of ca. 3.8 Ga has been discovered in the Dengfeng area. • Hafnium data reveal the presence of source rocks as old as ca. 4.5 Ga in the southern North China Craton. • The silicate Earth has differentiated at 4.4 to 4.5 Ga almost immediately after accretion. The depleted mantle and the continental crust are largely geochemically and isotopically complementary. However, the question of when the depleted mantle reservoirs developed on Earth remains a topic of considerable debate. In this study, we report the existence of a ca. 3.8 Ga detrital zircon from the quartzite of the Paleoproterozoic Songshan Group in the southern North China Craton. In situ zircon hafnium isotopic characteristics of the 3.8–3.2 Ga detrital zircons indicate the presence of source rocks as old as ca. 4.5 Ga in the southern North China Craton. Together with the global zircon U-Pb-Hf isotope dataset from the North China Craton, Jack Hills, Acasta as well as available μ142Nd values of ancient rocks from Archean craton worldwide, the new results indicate that the silicate Earth has differentiated at 4.4–4.5 Ga almost immediately after accretion, developing continental crust and a complementary depleted mantle reservoir at that same time. [ABSTRACT FROM AUTHOR]

In this paper, we present new U-Pb zircon ages, Hf isotope data and major and trace elements for Early Mesozoic granitic rocks in Mohe area in the Erguna Massif of northeast China to elucidate the southward subduction of the eastern Mongol-Okhotsk Oceanic plate in Early Mesozoic. Zircons from two representative intrusions, syenogranites and monzogranites, in the Mohe area are euhedral-subhedral in shape, display oscillatory growth zoning in cathodoluminescence (CL) images, and have Th/U ratios of 0.10-0.72, and in combination these features indicating that the zircons are of igneous origin. U-Pb zircon dating results demonstrate that the syenogranites formed at 245.1 ± 1.4 Ma and monzogranites formed at 212.2 ± 1.7 Ma. These granitic rocks are characterized by high SiO2, Al2O3 and (Na2O + K2O), low TFeO, MgO, TiO2 and P2O5 concentrations, belonging to the high-K calc-alkaline series. They are enriched in LREE and large ion lithophile elements (e.g., Rb, K, and Sr), depleted in HREE and high field strength elements (e.g., Nb, Ta, Th, and Ti), as well as very weak negative Eu anomalies (Eu/Eu* = 0.48 ~ 1.01). Their zircon εHf(t) values range from −7.9 to −2.0 and range from 0.20 to 0.49, in response to their two-stage Hf model ages (TDM2) range from 1.40 Ga to 1.77 Ga range from 0.94 Ga to 1.24 Ga, respectively, indicating that primary magmas of syenogranites were derived from partial melting of newly accreted juvenile crustal material that formed from the enriched mantle during the Mesoproterozoic, monzogranites are generated by partial melting of newly accreted juvenile crustal material that formed from the depleted mantle during the Meso- to Neoproterozoic. We conclude, therefore, that the early Mesozoic granitic rocks of the Mohe area are associated with the continuous southward subduction of the Mongol-Okhotsk oceanic plate rather than the Paleo-Asian and circum-Pacific tectonic regimes. [ABSTRACT FROM AUTHOR]

U-Pb dating for fifty-six detrital zircons from a paragneiss in Nanxiong area, northern Guangdong Province, indicates that the latest Neoproterozoic sediments in Cathaysia hinterland are composed of numerous Grenvillian and Neoarchaean clastic materials, as well as some Mesoproterozoic detritus. Minor Paleoarchaean (3.76 Ga) and Mesoarchaean (3.0-3.2 Ga) zircons, which are the oldest zircons in South China, also are firstly found in the sediments, suggesting that the Cathaysia Block may contain very old materials. The Hf isotope compositions of thirty-seven zircons reveal that these clastic mate- rials have different origins. Minor zircons crystallized from magma generated from relatively juvenile crust, while the parental magma of most zircons was derived from ancient crust. Integration of U-Pb dating and Hf Isotope analysis of these zircons suggests that the generation of juvenile crust in the Cathaysia block mainly occurred at 2.5-2.6 Ga. Mesoarchaean (3.0-3.3 Ga), late Paleoproterozoic (~1.8 Ga) and Paleoarchaean (~3.7 Ga) may also be important episodes of crustal growth. Grenvillian magmatism is extremely intense, but it mainly involved recycling of ancient crustal components with little formation of juvenile crust. The marked presence of ~2.1 Ga Hf model ages and the absence of the zircons with crystallization ages at ~2.1 Ga suggest that the parental magma of many zircons was probably derived from the mixed source consisting of Neoarchaean and late Paleoproterozoic materials. [ABSTRACT FROM AUTHOR]

The occurrence of zircons with U-Pb ages of ~3.8 Ga and Hf model ages of ~4.0 Ga in South China suggests the existence of the Hadean crustal remnants in South China. Furthermore, a detrital zircon with a U-Pb age as old as 4.1 Ga has been found in Tibet. This is the oldest zircon so far reported in China. These results imply that continental crust was more widespread than previously thought in the late Hadean, but its majority was efficiently reworked into Archean continental crust. On the basis of available zircon U-Pb age and Hf isotope data, it appears that the growth of continental crust in South China started since the early Archean, but a stable cratonic block through reworking did not occur until the Paleoproterozoic. Thus the operation of some form of plate tectonics may occur in China continents since Eoarchean. The initial destruction of the South China craton was caused by intensive magmatic activity in association with the assembly and breakup of the supercontinent Rodinia during the Neoproterozoic. However, most of the Archean and Paleoproterozoic crustal materials in South China do not occur as surface rocks, but exist as sporadic crustal remnants. Nevertheless, the occurrence of Neoproterozoic magmatism is still a signature to distinguish South China from North China. [ABSTRACT FROM AUTHOR]

Metamorphic zircon from coesite-bearing eclogites in the Dabie Mountains encloses high-Pphases, and may have formed at the peak of ultrahigh-pressure (UHP) metamorphism. Morphologically, the metamorphic zircon typically occurs as small, multi-faceted, near-spherical grains with homogeneous internal structure and weak backscattered electron (BSE) luminescence. Geochemically, it is characterized by extremely high and relatively constant contents of hafnium (Hf) and very low contents of Y, U and Th, reflecting the contraction of the zircon lattice under the UHP conditions. High contents of Hf may be characteristic of zircon formed during UHP metamorphism, which has important consequences for interpretation of geochronological results. We propose that the metamorphic zircon extremely enriched in Hf may be used to date the peak of UHP metamorphism that produced the coesite-bearing eclogites in the Dabie Mountains, and potentially in other UHP terranes. [ABSTRACT FROM AUTHOR]

• The Alxa Block has a tectonic affinity with the North China Craton. • Protoliths of the middle and eastern Longshoushan Belt came from different provenance. • The middle Longshoushan was deposited in a Paleoproterozoic convergent basin. • The eastern Longshoushan was deposited in a Cambrian collision-related foreland basin. The NW-SE trending Longshoushan Belt is a significant transitional belt between the Alxa and Qilian blocks. Its basement rocks were predominated by greenschist- to amphibolite-facies metamorphosed volcanic-sedimentary rocks, which were named the Longshoushan Complex and sporadically exposed in the middle and eastern Longshoushan Belt. The U-Pb ages of detrital zircons from the middle Longshoushan are scattered in the period of 3006–1981 Ma, predominated by Paleoproterozoic (>95%) with a single peak of 2.0 Ga. These zircons have the 176Hf/177Hf ratios of 0.281150–0.281687, corresponding to hafnium model ages (T DM C) of 3.04–2.15 Ga. These age features are in accordance with those of the Alxa Block and the western North China Craton. In contrast, the protoliths of the eastern Longshoushan reveal a wide age range from 3389 Ma to 529 Ma, which can be apparently divided into four age populations of 2.5 Ga, 1.6 Ga, 1.0 Ga and 0.8 Ga. This is consistent with recent reported age data of the Hexi Corridor, indicating that the eastern Longshoushan is not a part of the Longshoushan Complex, but has affinity with the Hexi Corridor. The cumulative probability curves of measured crystallization ages and depositional ages of detrital zircons imply that the middle Longshoushan could be deposited in a convergent basin (e.g., back-arc basin) in the Paleoproterozoic, but the eastern Longshoushan was typical of tectonic setting of a collisional basin (e.g., a foreland basin) in the Cambrian. The closure of the North Qilian Ocean formed the North Qilian Orogen between the Central Qilian and Alxa blocks, resulting to a foreland basin in the Hexi Corridor (i.e., eastern Longshoushan). [ABSTRACT FROM AUTHOR]