Archaean multi-stage magmatic underplating drove formation of continental nuclei in the North China Craton

Domain: earth_science
Published: 2024-07-24
Editorial outcome: accept

Abstract
The geodynamic processes that formed Earth’s earliest continents are intensely debated. Particularly, the transformation from ancient crustal nuclei into mature Archaean cratons is unclear, primarily owing to the paucity of well-preserved Eoarchaean–Palaeoarchaean ‘protocrust’. Here, we report a newly identified Palaeoarchaean continental fragment—the Baishanhu nucleus—in northeastern North China Craton. U–Pb geochronology shows that this nucleus preserves five major magmatic events during 3.6–2.5 Ga. Geochemistry and zircon Lu–Hf isotopes reveal ancient 4.2–3.8 Ga mantle extraction ages, as well as later intraplate crustal reworking. Crustal architecture and zircon Hf–O isotopes indicate that proto-North China first formed in a stagnant/squishy lid geodynamic regime characterised by plume-related magmatic underplating. Such cratonic growth and maturation were prerequisites for the emergence of plate tectonics. Finally, these data suggest that North China was part of the Sclavia supercraton and that the Archaean onset of subduction occurred asynchronously worldwide.

Introduction
Earth is the only known planet to have evolved a felsic continental crust. While the majority of continental crustal growth occurs today at convergent plate margins, the dominant crust-forming mechanisms that operated during the Archaean (and even Hadean) are strongly disputed1. Some authors argue that subduction and plate tectonics has operated on Earth since at least the Eoarchaean2,3. By contrast, numerical modelling and field investigation of some Palaeoarchaean cratons suggest that a ‘stagnant lid’ regime operated, where lithospheric plates moved very slowly across Earth’s surface—if at all. In such an environment, the formation of felsic/TTG-like crust was driven by mantle plume activity4 and/or melting within lithospheric drips5,6. This latter geodynamic scenario finds support from the study of Mars and Venus, which can be considered analogues for the early Earth7. Determining when, where, and why certain geodynamic regimes dominated at different points in time has key implications for other critical events in Earth history, such as continental emergence, atmospheric oxygenation, changes in ocean composition, and the appearance and evolution of life8. The primarily obstacle in resolving this dispute is the scarcity of preserved Hadean to early Archaean continental crust on the modern Earth. Even in cratons that contain such Eoarchaean rocks, they often only comprise a volumetrically minor component of the terrane itself9. Therefore, any newly discovered ancient nuclei can provide invaluable insights into the crustal evolution of early Earth, and how cratons grew and eventually matured. The North China Craton preserves a continuous record of successive magmatic events that span almost all (3.8–2.5 Ga) of the Archaean Eon10. Two major continental nuclei have been previously established: the Anshan continental nucleus (in the Anshan–Benxi areas) and the Eastern Hebei continental nucleus (Fig. 1a), both of which have ancient geologic histories dating back to as old as 3.8 Ga (ref. 10). The region stretching from Anshan to Jiapigou (Fig. 1b) preserves the most comprehensive record of Archaean magmatism within North China and represents an ideal natural laboratory for investigating the formation and evolution of an Archaean craton.

Here, we report a Palaeoarchaean continental nucleus, named the Baishanhu nucleus (occurring in the Jiapigou–Baishanhu areas), which has been identified in northeastern North China Craton. This study presents zircon U–Pb geochronology from a suite of granitoids, alongside zircon Lu–Hf and O isotopic analyses and whole-rock geochemistry. These results establish a spatiotemporal framework for the formation of the Baishanhu nucleus, which provides constraints on cratonic growth and maturation, and shed light on the geodynamic regime that likely operated on Earth during the early Archaean.

Results
Geochronological framework
To establish craton growth and maturation processes of the Baishanhu nucleus, we conducted a total of 870 zircon U–Pb geochronological analyses from 21 samples. Detailed description of zircon U–Pb dating, as well as newly acquired and compiled zircon Hf–O data, can be found in the Supplementary Notes and Supplementary Data 1–6. The results reveal at least five discrete magmatic episodes at 3.6–3.5, 3.3–3.2, 2.8–2.7, 2.63, and 2.55–2.50 Ga (Fig. 2a). An early Palaeoarchaean magmatic event is recorded by abundant 3.6–3.5 Ga xenocrystic zircons found within younger (3.3–3.2 and 2.55–2.50 Ga) granitoids. These xenocrysts exhibit concentric oscillatory internal zonation, suggestive of crystallisation from a felsic melt (Fig. 2b). Evidence for a subsequent late Palaeoarchaean/early Mesoarchaean magmatic event comes from 3.3–3.2 Ga monzogranites and 3.3–3.2 Ga xenocrystic zircons within younger 2.55–2.50 Ga potassic granitoids. These 3.3–3.2 Ga monzogranites are the oldest potassic granites documented within the North China Craton, and primarily consists of plagioclase (35%), microcline (25%), quartz (30%), biotite (5%), and minor hornblende. An early Neoarchaean magmatic event (2.8–2.7 Ga) is evidenced by c. 2.78 Ga trondhjemitic gneiss from the Jiapigou area11, c. 2.72 Ga monzogranite, and 2.8–2.7 Ga xenocrystic zircons within 2.55–2.50 Ga potassic granitoids. The c. 2.72 Ga monzogranite exhibits a massive structure and has a mineral assemblage of quartz (30%), plagioclase (30%), microcline (35%), and minor biotite (5%). Finally, two episodes of late Neoarchaean magmatism within the Baishanhu nucleus are documented by minor c. 2.63 Ga magmatism (monzogranite), and intensive and widespread magmatism at 2.55–2.50 Ga, similar to other terranes within North China. The dominant lithologies of this young c. 2.5 Ga episode include TTG, meta-mafic volcanic rocks, and potassic granitoids.

Crustal evolution of Baishanhu nucleus revealed by zircon Hf isotopes
The zircon Lu–Hf isotopic system is a useful and robust tool for deciphering the evolutionary history of the continental crust12. Here, we acquired 321 new zircon Hf isotope analyses for the Baishanhu nucleus (Fig. 2b). Generally, the two-stage depleted mantle model (TDM2) age of granitoids represents the timing of extraction of their mafic precursors from a depleted mantle source, which in turn signifies the timing of crustal growth6; however, we note that the Hf TDM2 age is affected by the assumed mantle depletion history and the 176Lu/177Hf ratio of the crust. Currently, the community’s understanding of the evolution of the Earth’s depleted mantle through time is uncertain. Several studies of Eoarchaean TTGs (e.g., the Itsaq gneiss, North Atlantic Craton13, and the Aktash gneiss, Tarim Craton14) have indicated that their mafic precursors were derived from a near-chondritic mantle. Further, Hf–Nd isotopes of Palaeoarchaean (c. 3.6 Ga) mafic–ultramafic rocks from the Pilbara Craton also indicate the existence of a chondritic to near-chondritic mantle at that time15,16. Thus, these authors interpret that any global depletion of the mantle had not begun during the Eoarchaean or Hadean, such that a depleted mantle signature began to progressively develop since c. 3.9 Ga (ref. 16), although see ref. 17 for the potential caveats involved when zircon is used to estimate mantle depletion.
To directly address this issue, we compiled a global dataset of igneous zircon Hf isotopes of early Archaean TTGs from all major cratons on Earth. The compilation reveals that most zircons display very low sub-chondritic εHf(t) values (Fig. 2c), indicating that the mafic precursors of these early Archaean TTGs likely had a long crustal residence time. These unradiogenic Hf isotopes indicate that some crust-mantle differentiation must have occurred in the Hadean to early Archaean, and the inferred source ages for these unradiogenic zircons vary depending on the assumed degree of mantle depletion. Several Palaeoarchaean mafic–komatiitic (e.g., Barberton Greenstone Belt18 and Western Pilbara Craton19) and TTG rocks (e.g., Dharwar Craton20 and Singhbum Craton21) that display depleted mantle signatures also argue for the existence of a depleted mantle in the early Archaean. After excluding analyses that show clear Pb loss and samples with heterogeneous Hf isotopic compositions, many Eoarchaean zircons from North China still record highly depleted Hf isotope signatures (Fig. 2d). Measured 142Nd–143Nd isotopes of c. 3.8–3.0 Ga rocks from the Anshan Complex suggest multiple mantle-crust differentiation events between 4.3 Ga and 3.8 Ga, and indicate the existence of a depleted upper mantle during this period22. Thus, we interpret that the early Archaean mantle was heterogeneous with some domains (e.g., North China and Dharwar Cratons) that exhibited depleted Hf isotopes, whereas other domains (e.g., North Atlantic and Tarim Cratons) exhibited chondritic compositions. Therefore, the TDM2 age calculation performed in this study assumes that early Archaean mafic protocrust within North China formed from a depleted mantle.
Additionally, a plot of zircon ages against their initial 176Hf/177Hf ratios demonstrates that the 3.6–2.7 Ga zircon from the Baishanhu nucleus, the 3.8–2.9 Ga zircon from the Anshan nucleus, and the 3.8–2.9 Ga detrital zircon of the Caozhuang sequence from the Eastern Hebei nucleus all fall along a crustal evolution line with a 176Lu/177Hf ratio of 0.022 (Fig. 2e). This trend is consistent with the 176Lu/177Hf ratio observed in Archaean mafic crust23. Thus, we consider it reasonable to use a 176Lu/177Hf ratio of 0.022 for calculating the TDM2 ages of the Archaean zircon from North China.
The 3.6–3.5 Ga zircon grains from the Baishanhu nucleus have sub-chondritic εHf(t) values ranging from −3.6 to −0.1, with TDM2 ages of 4.2–3.9 Ga. In contrast, the 3.3–3.2 Ga and c. 2.72 Ga groups display more unradiogenic Hf isotopic features with sub-chondritic εHf(t) values ranging from −6.0 to −1.5 and −10.2 to −4.2, and both groups have similar TDM2 ages of 4.2–3.8 Ga. Zircons from the c. 2.63 Ga monzogranite exhibit sub-chondritic εHf(t) values ranging from −4.5 to −0.5 with TDM2 ages of 3.7–3.3 Ga. Some of the 2.55–2.50 Ga potassic granites also exhibit unradiogenic Hf isotopes, yielding sub-chondritic εHf(t) values ranging from −7.7 to −1.1, with TDM2 ages of 3.7–3.3 Ga. In contrast, several 2.55–2.50 Ga potassic granites have more radiogenic Hf isotopes with positive εHf(t) values ranging from 0 to +5.7 with TDM2 ages of 3.2–2.8 Ga. Together, these data show that the 3.6–3.5, 3.3–3.2, and c. 2.72 Ga zircons have a similar TDM2 age range (4.2–3.8 Ga), and they also display a common evolution as demonstrated by well-defined 4.2 and 3.8 Ga crustal evolution lines (Fig. 2d). The 4.2–3.8 Ga TDM2 ages thus represent the mantle extraction age of the mafic protocrust, which subsequently experienced multiple stages of recycling at 3.6–3.5, 3.3–3.2, and c. 2.72 Ga. In addition, the Hf isotopes of the c. 2.78 Ga trondhjemitic gneiss11, the c. 2.63 Ga monzogranite, and the 2.55–2.50 Ga potassic granites with sub-chondritic εHf(t) values reflect another mantle extraction event that occurred from 3.7–3.3 Ga (Fig. 2d). Moreover, the 2.55–2.50 Ga potassic granites with radiogenic Hf compositions, as well as the previously reported 2.55–2.50 Ga mafic volcanic rocks and TTGs from the Baishanhu nucleus (refs in Supplementary Data 4), suggest significant juvenile crustal growth between the Mesoarchaean and Neoarchaean. Together, these data demonstrate that the Baishanhu nucleus experienced multiple phases of crustal growth and reworking/recycling processes throughout the Archaean, leading to its geochemical maturation and facilitation of cratonization. Similar Archaean crusts with secular evolved Hf isotopes are also developed in other cratons, such as the Yilgarn and Slave24.

Geochemical constraints on petrogenesis of the 3.3–2.5 Ga potassic granites
In this study, a total of 20 samples were analyzed for major and trace elements. Detailed results of geochemistry can be found in Supplementary Data 7. The 3.3–2.5 Ga potassic granites exhibit similar geochemical features, such as high SiO2 (70.38–77.94 wt. %), low MgO (0.18–1.21 wt. %), TFeO (1.24–4.00 wt. %), Cr (3.16–26.4 ppm), and Ni (1.22–17.20 ppm) contents. They are enriched in light rare earth elements (e.g., La and Ce), Sr, Zr, and Hf, but depleted in heavy rare earth elements (e.g., Lu, Yb, and Y), Nb, and Ta (Fig. 3a), with mainly positive Eu anomalies. On a Al2O3/(FeOT+MgO)–(3CaO)–(5K2O/Na2O) ternary diagram25 (Fig. 3b), the 3.3–3.2 Ga and c. 2.72 Ga monzogranites plot mainly within the field of melts derived from tonalite. As the 3.3–3.2 Ga and c. 2.72 Ga zircons exhibit a similar Hf crustal evolutionary pattern to the 3.6–3.5 Ga xenocrystic zircons, it is reasonable to propose that the 3.6–3.5 Ga TTG was the source for the 3.3–3.2 Ga and c. 2.72 Ga monzogranites. The source rock for the c. 2.63 Ga monzogranite could have been a high-K mafic rock (Fig. 3b), which had a mantle extraction age of 3.7–3.3 Ga. The c. 2.5 Ga potassic granites exhibiting negative εHf(t) values might have been sourced from TTG rocks (Fig. 3b), whereas the other c. 2.5 Ga potassic granites displaying positive εHf(t) values, higher Al2O3 values and K2O/Na2O ratios, likely formed from juvenile metasediments. All of the 3.3–2.5 Ga potassic granites display high Sr/Y ratios (32–132, except for one analysis of 18) and LaN/YbN (35–201, except for one analysis of 17), and can thus be classified as adakitic granites26 (Fig. 3c). Generally, such adakitic geochemical characteristics suggest substantial garnet but minor plagioclase in the source region during partial melting, classically interpreted to occur at a pressure greater than 1.0 GPa (ref. 26). Based on the computational method of ref. 27, the average Zr saturation temperatures (TZr) of the 3.3–3.2, c. 2.72, c. 2.63, and c. 2.5 Ga adakitic granites are 794°C, 847°C, 818°C, and 808°C, respectively. Moreover, the characteristics of high SiO2 contents but low MgO, Cr, and Ni contents suggest a thickened crust origin for these adakitic granites28 (Fig. 3d). This interpretation is also supported by abundant xenocrystic zircons within the 3.3–2.5 Ga potassic granites and their unradiogenic zircon Hf isotopes (e.g., negative zircon εHf(t) values and Hadean to Palaeoarchaean TDM2 ages). As such, these adakitic granites indicate that the Baishanhu nucleus maintained a notably thick continental crust (>30 km) from at least 3.3 Ga to 2.5 Ga.

Crustal architecture of northeastern North China and its affinity with other nuclei of the North China Craton
To contextualise our new data, we present contour maps of zircon U–Pb ages and Lu–Hf data derived from Archaean igneous rocks spanning the region from Anshan to Jiapigou, which illustrate the architecture of the early Archaean basement of the North China Craton (Fig. 4). Although the oldest magmatic record in the Baishanhu nucleus is slightly younger than that in the Anshan nucleus (Fig. 4a), both continental nuclei appear to have initially originated from Hadean to early Eoarchaean protocrust (4.2–3.8 Ga) (Fig. 4b). An εHf(t) contour map (Fig. 4c) also supports the interpretation that the Anshan and Baishanhu nuclei are dominated by reworked ancient crust, as they show strongly negative εHf(t) values. Additionally, two small regions in the Qingyuan and Helong areas display ancient TDM2 ages of 3.8–3.3 Ga and unradiogenic Hf isotopes, probably indicating the existence of ancient crustal fragments (Fig. 4). This interpretation is further supported by the identification of the c. 3.1 Ga TTG and amphibolite assemblage29 and abundant 2.9–2.7 Ga xenocrystic zircons within the c. 2.7 Ga meta-mafic volcanic rocks30. The Baishanhu nucleus and the other two ancient crustal fragments occur as isolated fragments on the northern margin of the North China Craton, and are separated from the Anshan nucleus and each other by the late Neoarchaean North Liaoning to South Jilin granite–greenstone belt (Fig. 4). This crustal architecture suggests that these ancient nuclei are surrounded by a younger and juvenile granite–greenstone belt. Then, the tectono-thermal event that transpired during the late Neoarchaean (2.7–2.5 Ga) facilitated a significant expansion and growth of the North China Craton, extending it from its original Eoarchaean-to-Mesoarchaean cratonic nuclei.
The three nuclei within the North China Craton (i.e., Anshan, Baishanhu, and Eastern Hebei) are connected by Neoarchaean granite–greenstone belts; however, it remains unclear whether these nuclei belonged to a single coherent continental terrane or represented three individual terranes. In favour of the former argument, we note that these nuclei experienced many similar Eoarchaean-to-Mesoarchaean magmatic events, such as the c. 3.8 Ga magmatic event recorded in the Anshan and Eastern Hebei nuclei10. The oldest c. 3.6 Ga magmatic event in the Baishanhu nucleus also correlates with that identified from the Hujiamiao Complex of the Anshan nucleus10. Also, intensive crustal reworking events occurred in all three nuclei during 3.3–2.9 Ga (refs. 31–33), leading to the formation of large-scale potassic granitoids and reflecting the existence of voluminous continental crust in each region during the Mesoarchaean. Finally, zircon Hf isotopes suggest similar TDM2 ages (4.2–3.8 Ga), 176Lu/177Hf ratios (0.022), and crustal evolution histories (Fig. 2d) for these three nuclei. Therefore, the three North China nuclei may have once constituted a coherent Eoarchaean-to-Mesoarchaean proto-craton. Considering that c. 2.7–2.6 Ga potassic granites have only been identified from the Baishanhu nucleus, and the existence of a 2.7–2.6 Ga granite-greenstone belt between the Baishanhu and Anshan nuclei, we suggest that Baishanhu might have rifted away from Anshan during the early Neoarchaean, and then later reunited during late Neoarchaean cratonization of North China. Such a scenario involving rifting and breakup of an ancient continental nucleus resembles the processes that have been proposed for the Yilgarn Craton6.

Hadean to early Eoarchaean mafic protocrust in early Earth
As shown by our new data, zircon Hf isotopes indicate that the Anshan, Baishanhu, and Eastern Hebei nuclei originated from a Hadean to early Eoarchaean mafic protocrust (Fig. 2d). 142Nd and 143Nd isotopes for the 3.8–3.0 Ga Anshan Complex suggest 4.5–4.4 Ga model ages for the precursor of the oldest components and multiple mantle-crust differentiation events from 4.3 to 3.8 Ga (ref. 22). Several Hadean detrital zircons10 and xenocrystic zircons34 identified from the Eastern Hebei and Anshan nuclei and the southern margin of North China provide direct evidence of a Hadean to early Eoarchaean heritage for the craton. This interpretation is further corroborated by the Xinyang Eoarchaean xenoliths from southern North China35 that display more evolved Hf isotopes than the other three northern continental nuclei (Fig. 2d). Our new compilation of zircon Hf isotopes of Eoarchaean-to-Mesoarchaean TTGs worldwide show that the vast majority of Eoarchaean–Palaeoarchaean TTGs from most cratons (e.g., Slave, Yilgarn, East Antarctica, Superior, and Kaapvaal) generally display TDM2 ages >4 Ga (Fig. 2c). Studies of the Eoarchaean Acasta Gneiss Complex of the Slave Craton suggest that these oldest rocks on Earth were generated from a Hadean mafic protocrust9,36. In light of these earliest records and our new findings from North China Craton, we propose the existence of a Hadean to early Eoarchaean mafic protocrust that was crucial for the formation of the earliest continental crust nuclei preserved in individual cratons37.

Repeated Archaean underplating in a plume-dominant regime
Our new data show that the cores of the Baishanhu and Anshan nuclei experienced multiple stages of crustal reworking since the Eoarchaean. The 3.8–3.6 Ga TTG and the c. 3.3 and 3.1–2.9 Ga potassic granites in the Anshan nucleus, as well as the 3.3–2.7 Ga granitoids within the Baishanhu nucleus all exhibit consistent linear crustal evolutionary trends (melting trend #1 in Fig. 2d), and were therefore derived from repeated melting of a 4.2–3.8 Ga mafic precursor(s), without significant addition of juvenile materials in any magmatic episode. In addition, the c. 3.45 Ga migmatite, the c. 3.3 Ga trondhjemite, and the c. 3.1 Ga trondhjemite from the Anshan nucleus, the c. 2.9 Ga TTG and diorite from the Eastern Hebei nucleus, as well as the c. 2.78 Ga trodhjemite, c. 2.63 monzogranite, and some 2.5 Ga potassic granites from the Baishanhu nucleus define another reworking episode with a distinct crustal evolution array (melting trend #2 in Fig. 2d). They represent repeated melting products of former (3.8–3.3 Ga) underplated mafic crusts. This tectono-magmatic history of repeated intervals of the reworking of ancient continental crust best fits a scenario involving multiple underplating episodes within a plume-dominated environment, most parsimoniously characteristic of a stagnant lid geodynamic regime. The alternative scenario involving crustal growth and reworking driven by arc magmatism above a subduction zone would typically involve the incorporation of more juvenile components with radiogenic Hf isotopes, which is not observed until c. 2.6 Ga. Furthermore, the lithospheric architecture, characterised by younger and juvenile granite–greenstone belts surrounding ancient, long-lived, and reworked continental nuclei (Fig. 4), notably differs from linear arcs and collisional orogens typically associated with Phanerozoic convergent plate margins6.
Our data, expanding on previous interpretations, allow us to propose a tectonic model for the North China Craton (Fig. 5). (i) The Anshan and Baishanhu nuclei initially formed in a stagnant lid environment in an oceanic plateau setting due to partial melting of a 4.2–3.8 Ga mafic protocrust at 3.8 Ga and 3.6 Ga, respectively (Fig. 5a). (ii) Underplating of mafic magmas during the late Palaeoarchaean to Mesoarchaean drove reworking of the existing Anshan and Baishanhu Eoarchaean–Palaeoarchaean continental crusts, causing crustal anatexis and the production of voluminous 3.3–2.9 Ga potassic granites (Fig. 5b). (iii) A final stage of magmatic underplating would have driven further recycling of Eoarchaean–Palaeoarchaean continental crust in the Baishanhu nucleus and the generation of c. 2.72 and 2.63 Ga monzogranites, and caused the Baishanhu and Anshan nuclei to separate (Fig. 5c). Similar processes also dominated the growth and maturation of other ancient cratons. For instance, the 3.5–2.8 Ga granitoids from the East Pilbara Craton display a secular trend towards more evolved Hf isotopes, transitioning from TTG to K-rich granite with limited addition of juvenile materials under a plateau-type setting38; in the Yilgarn Craton, several episodes of crustal reworking events occurred during 3.7–2.8 Ga, driven by mantle plume activities6,39; multiple episodes of underplating from 3.6 to 3.2 Ga were also recognised from the Kaapvaal Craton40. Therefore, we propose that the growth and maturation of Archaean cratons required multiple cycles of underplating under a vertically-dominated, plume-related regime. Such mantle processes also resulted in the stabilisation of thick subcontinental lithospheric mantle roots. Stabilisation of such cratonic nuclei and the appearance of more rigid, plate-like crustal fragments was likely the tipping point for allowing the global transition to plate tectonics and the onset of the supercontinent cycle41.

Archaean supercratons and the asynchronous onset of subduction
It has been proposed that the presently separated Archaean cratons might have once constituted a larger ancestral land mass(es), either a single supercontinent (“Kenorland”)42 or else several individual supercratons43, during the late Archaean. A recent paleomagnetic study performed on the c. 2.62 Ga Yandinilling dike swarm of the Yilgarn Craton in western Australia supports the hypothesis of multiple, long-lived supercratons having existed through the Archaean–Proterozoic transition44. Three or so supercratons, such as Superia, Sclavia, and Vaalbara, have been proposed based on their distinct histories of amalgamation and breakup43. Some plate reconfiguration schemes suggest the Superia supercraton, including the Superior, Hearne, and Kola/Karelia cratons, and the Vaalbara supercraton, mainly consisting of the Kaapvaal and Pilbara cratons, were joined together as a larger Supervaalbara supercraton45. Separately, the Sclavia supercraton is thought to have included the Slave (Canada), Yilgarn (Australia), Zimbabwe, Dharwar (India), and São Francisco (Brazil) cratons43,44,46,47. Within these supercraton reconstructions, North China has been conspicuously absent; however, several key geological similarities lead us to argue that North China appear to have a close affinity with the Sclavia supercraton, consistent with recent speculation48. For example, (i) similar Hadean–Eoarchaean tectono-thermal events, as evidenced by U–Pb ages and Hf isotopes of igneous zircons (Fig. 2c, d) from the Acasta complex in the Slave Craton9,12, the Narryer terrane in the Yilgarn Craton39, the Anshan and Eastern Hebei nuclei in North China, as well as the Mairi gneiss complex in the São Francisco Craton49; (ii) similar c. 2.7 Ga basaltic volcanism, including komatiite, is preserved within the North China Craton50 and elsewhere in Sclavia supercraton51,52; (iii) North China and other cratons of the Sclavia supercraton share similar cratonization ages during the late Neoarchaean (2.6–2.5 Ga; refs. 51,53); and (iv) both North China and the Sclavia supercraton lack early Paleoproterozoic glaciogenic sequences, which are characteristic of the Superior-like cratons45 (whereas deposits of the Hutuo Group of North China are of ambiguous glacial origin and likely a distinctly younger age than the Huronian Group of Superior54). Together, our new data suggest that North China belonged to the Sclavia supercraton, and affirm previous hypotheses that the supercontinent-like cycle of continental assembly has operated on Earth since at least the late Archaean.
Our new data from the North China Craton can further shed light on a key question within the geosciences: when did the transition between a stagnant lid and mobile lid (plate tectonic) geodynamic regime occur on Earth? Zircon oxygen isotope analysis has been proposed to track subduction zone processes55. In this study, we compiled a dataset that includes new zircon oxygen isotopes and data from various terranes within North China, as well as other cratons worldwide. Globally, >2.7 Ga zircons primarily display mantle-like or slightly elevated δ18O values, whereas those with ages <2.7 Ga show an increasing trend in δ18O values (Fig. 2f), as similarly demonstrated in previous analyses41. In North China specifically, zircon δ18O values only begin to show significant elevation by the end of the Neoarchaean (c. 2.5 Ga), while 3.6–2.6 Ga zircon exhibit mantle-like or only slightly elevated δ18O values (Fig. 2f). Significant elevation of δ18O values during the Neoarchaean is consistent with the observation from triple-oxygen-isotopes recorded in Archaean shales56 that reflect substantial emergence of subaerial landmass, allowing for subaerial weathering. The appearance of more exposed continent during the Neoarchaean is contemporaneous with the assembly of the Kenorland supercontinent42 or multiple supercratons43 (i.e., Superia, Sclavia, and Vaalbara). Thus, the diachronous increase of δ18O values in different cratons at different times in the Neoarchaean suggests the asynchronous emergence of large-scale subaerial land.
There is broad consensus that plate tectonics had become established on Earth by around 3 Ga (refs. 1,57,58), even if localised subduction began in some cratons at an earlier time59–61. The δ18O values of the c. 2.5 Ga igneous rocks from North China show notably higher values than those in older zircon (Fig. 2f), which suggest that considerable volumes of supracrustal materials have been incorporated into magma source regions. This process can be achieved through several geodynamic processes (e.g., subduction, sagduction, or thrust stacking), of which, subduction is considered the most effective way. Several independent lines of evidence confirm that subduction initiated locally within the North China Craton by the end of the Neoarchaean, including evidence of paired metamorphism in Dengfeng62, Alpine-style subhorizontal arc-affinity nappe structures in central North China63,64, and the widespread presence of subduction-related potassic granites and sanukitoids53—all occurring at c. 2.5 Ga. Therefore, the initiation of subduction in North China might have occurred notably later than in many other cratons. Our new data thus add to a growing set of observations supporting the onset of subduction being asynchronous from a global perspective59,65. This later tectono-magmatic age is interestingly also when the global δ18O database on the whole exhibits a positive step-change increase towards more supracrustal reworking taken to indicate a geodynamic shift into the “supercontinent state”, whereafter the three large supercontinents are known to have formed41. This relationship underscores how North China Craton represents one of the last places in a globally highly asynchronous process to have experienced the onset of subduction.

Methods
Zircon U–Pb dating
Zircon U–Pb analysis of samples 21LJ38-1, 21LJ39-1, 21LJ35-1, 21LJ06-3, 21LJ18-1, and 21LJ19-1 was conducted using a PlasmaQuant MS series ICP–MS with a NWR193 laser-ablation microprobe at Yanduzhongshi Geological Analysis Laboratories Ltd, Beijing, China. The diameter of laser beam was set at 30 μm. The analysis of samples 22BS20-3, 22BS15-1, 22BS19-1, 22BS23-1, 22BS27-1, 22BS28-1, 22BS29-1, 22BS32-1, 22BS18-4, 23HX22-1, 23HX23-1, 23HX28-1, and 23HX29-1 was carried out using an Agilent 7500c quadrupole ICP–MS and a 193-nm ArF Excimer laser at the Key Laboratory of Mineral Resources Evaluation in Northeast Asia at Jilin University, Changchun, China. The analytical spot size was set at 32 μm, with a laser energy density of 10 J/cm2 and a repetition frequency of 8 Hz. Zircon U–Pb dating of Sample Z2010-3 was performed using an Agilent 7900 ICP–MS with an ATL (ATLEX 300) excimer laser at Nanjing Hongchuang Exploration Technology Service Co., Ltd., Nanjing, China. Zircon standards 91500 and Plešovice were utilised as primary and secondary reference materials in all three above laboratories, respectively. In addition, Samples 21LJ39-1, 22BS20-3, and 22BS15-1 were also analyzed using the Sensitive High Resolution Ion MicroProbes (SHRIMP) II instrument at the Beijing SHRIMP Center of the Chinese Academy of Geological Sciences (GAGS), Beijing, China. During the analysis, the intensity of the primary O2− ion beam was set to 3–5 nA, with beam spot sizes of 20 μm. Standard zircon TEMORA was utilised to correct the U, Th, and Pb contents as well as the ages of zircon. The detailed analytical procedures for the zircon U–Pb isotopes are presented in Supplementary Methods.

Zircon Lu–Hf isotope analysis
In situ Lu–Hf isotope ratio analysis was conducted using a Neptune Plus MC–ICP–MS in conjunction with a Geolas HD excimer ArF laser ablation system at the Wuhan Sample Solution Analytical Technology Co., Ltd, Wuhan, China. All data were collected on zircon in single spot ablation mode at a spot size of 44 μm. The energy density of laser ablation used in this study was approximately 10 Jcm−2. Each measurement consisted of a 20-s acquisition of the background signal followed by a 50-s acquisition of the ablation signal. Plešovice was utilised for external standard calibration to optimise the analytic results. 91500 and GJ-1 served as secondary standards to monitor the quality of data correction. The εHf(t) values are calculated using 176Lu decay constant (λ176Lu) of 1.865×10−11 (ref. 66) and the chondrite parameters used are 176Hf/177Hf=0.282772 and 176Lu/177Hf=0.0332 (ref. 67). The zircon Hf two-stage depleted mantle model ages (TDM2) were calculated using ratios of 176Hf/177Hf=0.283251 and 176Lu/177Hf=0.0384 for present depleted mantle suggested by ref. 68, and 176Lu/177Hf value of 0.022. The detailed analytical procedures for the zircon Lu–Hf isotopes are described in Supplementary Methods.

Major and trace element analyses
Whole-rock major and trace element analyses were conducted at Wuhan Sample Solution Analytical Technology Co., Ltd, China. The Zsx Primus II wavelength dispersive X-ray fluorescence spectrometer was used to analyze the major elements. The standard curves were derived using the national standard materials GBW07103, GBW07105, GBW07111, and GBW071112. The relative standard deviation was less than 2%. An Agilent 7700e ICP–MS equipment was used to analyze the trace elements. The standard materials GSR-3, RGM-2, BHVO-2, and JA-2 were used for quality control. The detailed analytical procedures for the whole-rock geochemistry are described in Supplementary Methods.

Zircon O isotope analysis
The analysis of zircon oxygen isotope was conducted using the SHRIMP II equipment at the Beijing SHRIMP Center, CAGS, China. The Cs+ primary ion beam’s intensity was approximately 3 nA, which resulted in secondary 16O1− count rates exceeding 109 cps. The diameter of the spot analyzed was 20 μm. The standard zircon TEMORA was used as reference material for calibrating instrumental mass fractionation. The standard was analyzed either two or three times at the beginning of each analytical session, and then after every third analysis of the unknown samples. The detailed analytical procedures for the zircon O isotopes are presented in Supplementary Methods.

Compilation of zircon Hf–O data
Zircon Hf isotopic data have been compiled from various sources for the continental nuclei of the NCC and the Neoarchaean northern Liaoning to southern Jilin granite-greenstone belt. Additionally, Eoarchaean-Mesoarchaean TTG samples from other cratons have also been included in this compilation. These cratons include: (1) India: Bastar Craton, Bundelkhand Craton, Coorg Block, Dharwar Craton, and Singhbum Craton; (2) South Africa: Kaapvaal Craton; (3) North America: North Atlantic Craton, Slave Craton, Superior Craton, and Wyoming Craton; (4) Australia: Pilbara Craton and Yilgarn Craton; (5) China: Yangtze Craton and Tarim Craton; (6) Other locations: East Antarctica and Sao Francisco Craton (South America). The compiled zircon Hf isotopic data and references are presented in Supplementary Data 4. This compilation includes only the data of magmatic zircons with U–Pb age discordances <10%. Generally, crustal contamination or magma mixing could induce heterogeneous Hf isotope signatures. Thus, this study applies probability of fit (p) values of each sample to filter out those zircons with heterogeneous Hf compositions. The p values of each sample were calculated using Origin 2023. Only samples with p≥0.05 are considered statistically homogeneous, while those with p<0.05 are deemed heterogeneous and thus excluded from interpretation. The in situ zircon O isotopic data have been compiled from various terranes of the NCC and other ancient cratons/terranes worldwide. These cratons/terranes include the Slave craton, Barberton, Clearwater Block, Congo Craton, Coorg Block, Dharwar craton, East Antarctica, North Atlantic craton, Pilbara craton, Scandinavia, Superior craton, Tarim craton, Yangtz craton, and Yilgarn craton. The compiled zircon δ18O values and references for these data are provided in Supplementary Data 5. Only analyses for magmatic zircons or cores with U–Pb age discordances <10% were included.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "Please the file titled 'Review_document.docx' attached.", "reviewer_2": "This manuscript presents new zircon U-Pb age, Lu-Hf isotope and Oxygen isotope data for the newly recognized 3.57 Ga Tonalite, together with other younger rocks, in the North China Craton. It represents the finding of a new continental nucleus in the North China Craton. Based on the data, the authors addressed three problems: the widespread of Hadean to early Eoarchean proto-crust, the geodynamic process for the Paleoarchean to Mesoarchean magmatism and the initiation of plate tectonics. The data is interesting and the manuscript is well organized. This research is generally of broad interests for researchers who are interested in the early earth. I suggest the authors add some new issues in the revision. First, the readers would like to know if the Eoarchean to Paleoarchean rocks in the Jiapigou–Baishan Lake area of this study, and those reported in previous studies, mainly in the Anshan-Benxi area and the eastern Hebei area belong to the same coherent continental nucleus or three individual nuclei. The other issue is about the geodynamic process of the 3.57-2.72 Ga magmatism. The authors proposed the 3.57-2.72 Ga magmatism, including tonalite, monzogranite and trondhjemite, were formed by repeated plume underplating in a stagnant lid background, mainly based on their Hf isotopes. This seems acceptable but not enough. The readers would wonder what controls the major and trace element geochemical characteristics (which is missing in the presented data) of the 3.57 Ga tonalite, 3.23 Ga monzogranite, 2.78 Ga trondhjemite, 2.72 Ga monzogranite if they are all derived from the same proto-crust. What are the differences in their melting conditions? What are the implications of such differences? And I disagree with the authors on their discussion on the onset of plate tectonics. The authors proposed asynchronous onset of plate tectonics in different cratons based on asynchronous increase of Hf isotope and O isotopes. In my opinion, the asynchronous onset of plate tectonics is a fake proposition because plate tectonics is defined to be a global tectonics characterized by the creation and maintenance of a global network of narrow plate boundaries. The increase of Hf isotope ratios may signify the contribution of depleted mantle related to plate subduction. The increase of O isotope ratios suggests the emergence of large-scale subaerial landmass for low-temperature weathering.\nBelow are detailed comments and suggestions.\nLine 121: The title is not consistent with the contents of this section. I can only see the crustal architecture of northeastern NCC from this paragraph. I can see nothing about the structure of lithospheric mantle in the whole manuscript.\nLines 127-128: You need to provide the ages of these so-called “old crust”. Only unradiogenic εHf(t) values do not support they are very old.\nThe effective numbers: For example, the uncertainty of eHf(t) values is about 0.4-0.5. Therefore, the significant digit after the decimal point of eHf(t) should be 1. And the significant digit of 176Hf/177Hf and error is traditionally 6.\nFig. 3a: The design of this figure is not logical. The hot and cold color is designed to represent negative and positive eHf(t) values. However, the same eHf(t) values at different ages represent different mantle extraction age. If they are labelled as the same color, the authors would get the wrong information that the mantle extraction ages are the same. I strongly suggest the authors provide zircon U-Pb age map and TDM2 map in Fig. 3.\nLines 146-148: It is impossible for the existence of a “global-scale” Hadean to early Eoarchean proto-crust. This means that almost all continental crust were formed in the very early stage of the Earth history. If so, most of the continental crust should have modal age of Hadean to early Eoarchean, which was not observed in zircon Hf model age data base (e.g., Dhuime et al., 2012).\nDhuime, B., Hawkesworth, C.J., Cawood, P.A., Storey, C.D., 2012. A change in the geodynamics of continental growth 3 billion years ago. Science 335, 1334-1336.\nLines 152-154: The statement is not consistent with Fig. 2b. Not all the >2.6 Ga granitoids within the ABN exhibit a simple linear evolutionary εHf value trend. The 3.1-3.0Ga rocks in the ABN show obvious increase in εHf values.\nLines 160-161: I cannot see the crustal architecture characterized by “younger and juvenile granite-greenstone belts surrounding ancient, long-lived, and reworked continental nuclei” from Fig. 3.\nLines 195-206: I personally agree that the NCC may belong to the Sclavia supercraton. But I cannot agree with the logics of the first evidence. The identification of Hadean-Eoarchean rocks and detrital zircons in these cratons, do not mean that they are in the same supercraton in the Neoarchean. The Hadean detrital zircons might be transported to other cratons at any time if they were in the same supercontinent.\nLines 213-215: Subduction is not a pre-requirement for the increase of δ18O values. Other geodynamic processes for recycling of supracrustal materials (e.g., sagduction) are also capable to incorporate supracrustal materials into magmatic sources. The key point is the emergence of subaerial landmass for low-temperature weathering. Therefore, the synchronous increase of δ18O values in different cratons suggest the asynchronous emergence of large-scale subaerial land rather than asynchronous initiation of subduction.\nBindeman, I.N., Zakharov, D.O., Palandri, J., Greber, N.D., Dauphas, N., Retallack, G.J., Hofmann, A., Lackey, J.S., Bekker, A., 2018. Rapid emergence of subaerial landmasses and onset of a modern hydrologic cycle 2.5 billion years ago. Nature 557, 545-548.\nLine 225: onset of plate tectonics or onset of subduction? Plate tectonics is defined to be a global tectonics characterized by the creation and maintenance of a global network of narrow plate boundaries. According to its definition, if plate tectonics begun, it is globally. Therefore, you can say asynchronous onset of subduction but cannot say asynchronous onset of plate tectonics.\nGPS coordinates should be provided in the supplementary tables.\nThe age of 22BS20-3: From the field photo of Fig. S3b and d, I cannot see any difference between the 3.57 Ga tonalite and the 3.2 Ga monzogranite. There are three groups of ages in Fig. S6a and b, which group really record the crystallization age? To support your interpretation that the 3.57 Ga group is the crystallization age, you need to provide more zircon CL images and describe their Th/U ratios.\nLu-Hf isotope and Oxygen isotope results for the metamorphic domains should not be plotted on the figures. If the zircon metamorphic domain is of recrystallization origin, its 176Hf/177Hf isotope ratios should be similar with its igneous predecessor whereas its U-Pb age is reset. If the Hf isotope is plotted on the eHf(t)-age diagram, it will mislead the readers that the magmatism of this age have such eHf(t) values."}, "author_response": "Review of Liu et al., - Nature Communications (January ’24)\nThis manuscript presents new zircon U-Pb, Hf and O isotopic data from the Jiapigou–Baishan Lake nucleus (JBLN) of the North China Craton (NCC). Hf isotopic compositions of zircon from Paleoarchean tonalitic rocks and zircon xenocrysts in younger potassic granites indicate repeated reworking of 3.8-4.2 Gyr old mafic source rock over a period of 1 billion years. This data is inferred to support the existence of a Hadean to early Eoarchean heritage for the NCC and the long history of crustal reworking is inferred to reflect repeated remelting in an intraplate/stagnant lid environment. Overall, I found the manuscript well written and easy to understand. However, there are a few issues that need to be addressed.\nThe U-Pb and Hf isotope data for the standard materials are not reported in the supplementary dataset so it is not possible to verify how robust the data are. Please report Hf isotope data for all standard material and unknowns, preferably in a format similar to Table 3 in (Fisher et al., 2014), that includes the stable Hf isotope ratios (e.g. 178Hf/177Hf and/or 180Hf/177Hf) , so that it is easy to assess the quality of the data. There appears to be a plotting / normalisation error with the Hf isotope data. On the diagram of 176Hf/177Hf versus Age shown in Fig. S1 (supplementary material), the 3.5-3.6 Ga rocks cluster above the CHUR model evolution line, whereas in Fig 2b of the main text the same rocks plot below the CHUR model evolution line (please see the comparison in Figure below). Whilst this doesn’t necessary influence the inferred tectonic history, it needs to be investigated because it could have a profound influence on the apparent model ages and need for a Hadean source, which is a significant part of the novelty of this study. Based on Fig S1, it doesn’t appear as though there is any need for a Hadean source.\nFurther to this point, Hf isotope models ages are fraught with uncertainty and very sensitive to the assumed mantle depletion history. Although there is some justification for the chosen mantle depletion history in the supplementary information. I think there needs to be a more nuance discussion around the calculation of Hf isotope models ages (after the issue above has been addressed) and the inferred mantle depletion history in the main text.\nWhile I tend to agree with the authors view that the development of plate tectonics was highly asynchronous globally, I think that if one takes this stance, it is also reasonable to think that the history of mantle depletion could have progressed in a similar fashion. My sense is that modelling mantle depletion as a single global event at 4.5 Ga is a bit simplistic, and doesn’t consider more recent work attempting to address this issue through Hf-Nd isotope systematics in ancient crustal rocks (Kemp et al., 2023; Petersson et al., 2019). For example, in East Pilbara Terrane of the Pilbara Craton — which is arguably the archetypal example of intraplate continental growth processes (Van Kranendonk et al., 2007) — it appears as though there is a relatively long history of chondritic magmatism throughout the Paleoarchean, with evidence of only moderate mantle depletion starting around 3.8 Ga (Kemp et al., 2023). Indeed, in Figure 2b it appears like the preferred crustal evolution line (176Hf/177Hf = 0.022) for the most evolved zircon Hf compositions intersects the chondrite evolution curve at a slightly younger date (around 3.9–4.0 Ga) and that a mantle depletion history starting around this time still provides a reasonable fit for the most juvenile compositions observed in the NCC (see modified version of Figure 2b below). Such a depletions history will shift the model ages to younger values. Provided the plotting / normalisation issue isn’t to blame it might not affect the need for a Hadean source, but this needs to be properly evaluated. I think having some discussion around this is warranted and will ultimately make for a more robust and hopefully compelling discussion.\nAnother point to consider is that the data point yielding the inferred Hadean age is not from the 3.5–3.6 tonalites (partial melts of mafic crust), but rather from the c. 3.2 Ga monzogranites. Again, this may be influenced by the plotting/normalisation issue, but it is also worth considering if it is justified to model Hf isotope evolution using a single stage model with mafic composition, when the petrology of the rocks requires at least two stage evolution, involving reworking of more evolved (felsic) material?\nFinally, it strikes me that 142Ndisotope data on some of these rocks could provide a critical test for the hypothesis presented in this manuscript. Are any such data from the JBLN or one of the other cratonic nuclei in the NCC available? If so, it could be useful to cite as additional evidence for a Hadean source if there is some.\nAdditional minor comments in the attached pdfs.\nReferences\nFisher, C. M., Vervoort, J. D., & Hanchar, J. M. (2014). Guidelines for reporting zircon Hf isotopic data by LA-MC-ICPMS and potential pitfalls in the interpretation of these data. Chemical Geology, 363, 125-133.\nKemp, A. I., Vervoort, J. D., Petersson, A., Smithies, R. H., & Lu, Y. (2023). A linked evolution for granite-greenstone terranes of the Pilbara Craton from Nd and Hf isotopes, with implications for Archean continental growth. Earth and Planetary Science Letters, 601, 117895.\nPetersson, A., Kemp, A. I., Hickman, A. H., Whitehouse, M. J., Martin, L., & Gray, C. M. (2019). A new 3.59 Ga magmatic suite and a chondritic source to the east Pilbara Craton. Chemical Geology, 511, 51-70.\nVan Kranendonk, M. J., Smithies, R. H., Hickman, A. H., & Champion, D. C. (2007). Paleoarchean development of a continental nucleus: the East Pilbara terrane of the Pilbara craton, Western Australia. Developments in Precambrian Geology, 15, 307-337.\nComments in black\nResponses in blue\nRevisions in red\nLine numbers refer to the “clean” version of the manuscript without tracked changes.\nReviewers’ comments:\nReviewer #1 (Remarks to the Author):\nThis manuscript presents new zircon U-Pb, Hf and O isotopic data from the Jiapigou–Baishan Lake nucleus (JBLN) of the North China Craton (NCC). Hf isotopic compositions of zircon from Paleoarchean tonalitic rocks and zircon xenocrysts in younger potassic granites indicate repeated reworking of 3.8-4.2 Gyr old mafic source rock over a period of 1 billion years. This data is inferred to support the existence of a Hadean to early Eoarchean heritage for the NCC and the long history of crustal reworking is inferred to reflect repeated remelting in an intraplate/stagnant lid environment. Overall, I found the manuscript well written and easy to understand. However, there are a few issues that need to be addressed.\nResponse: We sincerely thank the reviewer for this comprehensive assessment.\nComment 1:\nThe U-Pb and Hf isotope data for the standard materials are not reported in the supplementary dataset so it is not possible to verify how robust the data are. Please report Hf isotope data for all standard material and unknowns, preferably in a format similar to Table 3 in (Fisher et al., 2014), that includes the stable Hf isotope ratios (e.g. 178Hf/177Hf and/or 180Hf/177Hf), so that it is easy to assess the quality of the data.\nRevision: We appreciate the reviewer’s attention to the data of standard materials. We have added U–Pb and Hf isotope data for all standard materials at the end of Supplementary Table S1-3, respectively. We also provide weighted average diagrams of the U–Pb and Hf isotope data of standard materials for easily assessing the quality of the data. In addition, we added the stable Hf isotope ratios (178Hf/177Hf) for all standard materials and unknowns (Supplementary Table S3), and reformatted the Hf isotope data according to Fisher et al. (2014) as the reviewer suggested. LA–ICP–MS U–Pb data of standard materials are provided at the end of Supplementary Table S1. See the following image below as a demonstration.\nRevision: SHRIMP U–Pb and O data of standard materials are provided at the end of Supplementary Table S2. See the following image as a demonstration.\nRevision: The Hf data of standard materials are provided at the end of reformatted Supplementary Table S3. See the following image as a demonstration.\nComment 2:\nThere appears to be a plotting/normalisation error with the Hf isotope data. On the diagram of 176Hf/177Hf versus Age shown in Fig. S1 (supplementary material), the 3.5-3.6 Ga rocks cluster above the CHUR model evolution line, whereas in Fig 2b of the main text the same rocks plot below the CHUR model evolution line (please see the comparison in Figure below). Whilst this doesn’t necessary influence the inferred tectonic history, it needs to be investigated because it could have a profound influence on the apparent model ages and need for a Hadean source, which is a significant part of the novelty of this study. Based on Fig S1, it doesn’t appear as though there is any need for a Hadean source.\nRevision: We greatly appreciate the reviewer for pointing out this plotting error in Fig. S1 (previous). We regret that we incorrectly used the present (i.e., dated) 176Hf/177Hf ratios rather the initial (i.e., calculated) ratios that should be used in the diagram of 176Hf/177Hf versus age. According to the new diagram of 176Hf/177Hf versus age (new Fig. 2e), the 3.5–3.6 Ga rocks of this study cluster below the CHUR model evolution line, which is consistent with the εHf versus age diagram (new Fig. 2d). Meanwhile, the depleted (t) mantle model ages of these 3.6–2.7 Ga zircons indeed suggest a Hadean to early Eoarchaean (4.2–3.8 Ga) source. In addition, several Eoarchaean zircons from the Anshan nucleus and Eastern Hebei nucleus show even lower εHf values than the 3.6 (t) Ga zircons of this study. This strongly suggests a Hadean protocrust (considered the mafic precursors derived from chondritic mantle) once existed in the NCC. Also, in case some additional geological signals can be detected, we plot all analyses rather than the mean values of each sample in new diagrams of 176Hf/177Hf vs. Age and ε vs. Age. Hf(t) (Those zircon with obvious Pb loss were excluded.) In addition, those zircon with heterogeneous Hf compositions (probability of fit (p) values < 0.05), which could be due to contamination, magma mixing, later metamorphism and/or alteration, were not considered in the interpretation. These heterogeneous zircons are plotted in the diagrams, but are displayed in light gray. Please see the comparison in the figures below.\nComment 3:\nFurther to this point, Hf isotope models ages are fraught with uncertainty and very sensitive to the assumed mantle depletion history. Although there is some justification for the chosen mantle depletion history in the supplementary information. I think there needs to be a more nuance discussion around the calculation of Hf isotope models ages (after the issue above has been addressed) and the inferred mantle depletion history in the main text. While I tend to agree with the authors view that the development of plate tectonics was highly asynchronous globally, I think that if one takes this stance, it is also reasonable to think that the history of mantle depletion could have progressed in a similar fashion. My sense is that modelling mantle depletion as a single global event at 4.5 Ga is a bit simplistic, and doesn’t consider more recent work attempting to address this issue through Hf-Nd isotope systematics in ancient crustal rocks (Kemp et al., 2023; Petersson et al., 2019). For example, in East Pilbara Terrane of the Pilbara Craton — which is arguably the archetypal example of intraplate continental growth processes (Van Kranendonk et al., 2007) — it appears as though there is a relatively long history of chondritic magmatism throughout the Paleoarchean, with evidence of only moderate mantle depletion starting around 3.8 Ga (Kemp et al., 2023). Indeed, in Figure 2b it appears like the preferred crustal evolution line (176Lu/177Hf = 0.022) for the most evolved zircon Hf compositions intersects the chondrite evolution curve at a slightly younger date (around 3.9–4.0 Ga) and that a mantle depletion history starting around this time still provides a reasonable fit for the most juvenile compositions observed in the NCC (see modified version of Figure 2b below). Such a depletions history will shift the model ages to younger values. Provided the plotting/normalisation issue isn’t to blame it might not affect the need for a Hadean source, but this needs to be properly evaluated. I think having some discussion around this is warranted and will ultimately make for a more robust and hopefully compelling discussion.\nResponse: We greatly appreciate the reviewer’s concern about the Hf isotope model age. We agree with the reviewer that more discussion about the mantle depletion history will make the interpretation more robust and convincing. Firstly, we moved the related discussion previously in the supplementary material into the main text now. Then, we compiled a new zircon Hf isotopic dataset of early Archaean TTG from cratons worldwide. This new compilation can give us more information about the crustal growth history of early Earth and provide some hints about the crustal residence time of the mafic precursors of these early Archaean TTGs. This compilation suggests long crustal residence times for these ancient TTGs, which can, as revealed by Liou et al. (2022)1, potentially lead to significant underestimation of zircon εHf values and the degree of (t) initial mantle depletion. Additionally, our new compilation of Archaean zircon Hf isotopes from the North China Craton suggests that a considerable proportion of Eoarchaean zircon have depleted Hf isotopes. Combined with the 142Nd–143Nd isotopes, such zircon Hf signatures demonstrate the existence of depleted mantle in the North China Craton during the Eoarchaean. Thus, collectively, the evidence available globally at this time appears to suggest that both depleted and chondritic mantle existed in different domains on Earth during the early Archaean. The related detailed text revisions are as follows.\nRevision: Lines 93-124 “however, we note that the Hf T 2 age is affected by the DM assumed mantle depletion history and the 176Lu/177Hf ratio of the crust. Currently, the community’s understanding of the evolution of the Earth’s depleted mantle through time is uncertain. Several studies of Eoarchaean TTGs (e.g. the Itsaq gneiss, North Atlantic Craton2, and the Aktash gneiss, Tarim Craton3) have indicated that their mafic precursors were derived from a near-chondritic mantle. Further, Hf–Nd isotopes of Palaeoarchaean (c. 3.6 Ga) mafic to ultramafic rocks from the Pilbara Craton also indicate the existence of a chondritic to near-chondritic mantle at that time4, 5. Thus, these authors interpret that any global depletion of the mantle had not begun during the Eoarchaean or Hadean, such that a depleted mantle signature began to progressively develop since c. 3.9 Ga (ref. 5), although see ref. 1 for the potential caveats involved when zircon is used to estimate mantle depletion.\nTo directly address this issue, we compiled a global dataset of igneous zircon Hf isotopes of early Archaean TTGs from all major cratons on Earth (Table S4). The compilation reveals that most zircons display very low sub-chondritic ε values (Fig. 2c), indicating Hf(t) that the mafic precursors of these early Archaean TTGs likely had a long crustal residence time, potentially leading to significant underestimation of zircon ε value and the degree Hf(t) of mantle depletion1. Several Palaeoarchaean mafic–komatiitic (e.g., Barberton Greenstone Belt6 and Western Pilbara Craton7) and TTG rocks (e.g., Dharwar Craton8 and Singhbum Craton9) that display depleted mantle signatures also argue for the existence of a depleted mantle in the early Archaean. After excluding analyses that show clear Pb loss and samples with heterogeneous Hf isotopic compositions, many Eoarchaean zircons from North China still record highly depleted Hf isotope signatures (Fig. 2d). Measured 142Nd–143Nd isotopes of c. 3.8–3.0 Ga rocks from the Anshan Complex suggest multiple mantle-crust differentiation events between 4.3 Ga and 3.8 Ga, and indicate the existence of a depleted upper mantle during this period10. Thus, we interpret that the early Archaean mantle was heterogeneous with some domains (e.g., North China and Dharwar Cratons) that exhibited depleted Hf isotopes, whereas other domains (e.g., North Atlantic and Tarim Cratons) exhibited chondritic compositions.\nTherefore, the T 2 age calculation performed in this study assumes that early Archaean DM mafic protocrust within North China formed from a depleted mantle. Additionally, a plot of zircon ages against their initial 176Hf/177Hf ratios demonstrates that the 3.6–2.7 Ga zircon from the Baishan nucleus, the 3.8–2.7 Ga zircon from the Anshan nucleus, and the Eoarchaean–Palaeoarchaean detrital zircon of the Caozhuang sequence from the Eastern Hebei nucleus all fall along a crustal evolution line with a 176Lu/177Hf ratio of 0.022 (Fig. 2e). This trend is consistent with the 176Lu/177Hf ratio observed in Archaean mafic crust11. Thus, we consider it reasonable to use a 176Lu/177Hf ratio of 0.022 for calculating the T 2 ages of the Archaean zircon from North China.” DM\nComment 4: Another point to consider is that the data point yielding the inferred Hadean age is not from the 3.5–3.6 tonalites (partial melts of mafic crust), but rather from the c. 3.2 Ga monzogranites. Again, this may be influenced by the plotting/normalisation issue, but it is also worth considering if it is justified to model Hf isotope evolution using a single stage model with mafic composition, when the petrology of the rocks requires at least two stage evolution, involving reworking of more evolved (felsic) material?\nResponse: We appreciate the reviewer’s concern about the inferred Hadean age. Firstly, we resolved the plotting issue mentioned in “Comment 2”. And we have a comprehensive discussion on the calculation of depleted mantle model ages. It is reasonable to regard two-stage depleted mantle ages as representing the mantle extraction ages of the mafic precursors of these granitoids. Almost all the 3.6–2.7 Ga zircons yield 4.2–3.8 Ga T 2 DM ages, not only the 3.2 Ga monzogranites. These 3.6–2.7 Ga zircons fall between the 4.2 Ga and 3.8 Ga crustal evolution lines on the ε vs. Age diagram (Fig. 2d; refer to Hf(t) following figure). We agree with the reviewer that single stage model age is suitable for mafic rocks, whereas a two-stage model age is suitable for felsic rocks. So, following this principle to make the contour map of T age (Fig. 4b; see below), we chose a single- DM stage model age for meta-mafic rocks and a two-stage model age for TTGs and other granitoids.\nFig. 2d\nFig. 4b\nComment 5: Finally, it strikes me that 142Nd isotope data on some of these rocks could provide a critical test for the hypothesis presented in this manuscript. Are any such data from the JBLN or one of the other cratonic nuclei in the NCC available? If so, it could be useful to cite as additional evidence for a Hadean source if there is some.\nResponse: We appreciate the reviewer for this useful suggestion. Currently, only one paper (Li et al., 2014) reported 142Nd and 143Nd isotope data for the 3.8–3.0 Ga Anshan Complex in the Anshan–Benxi nucleus. Their research also suggests a Hadean evolution history for the NCC. We added this evidence in the main text.\nLi, C.-F. et al. Differentiation of the early silicate Earth as recorded by 142 Nd- 143 Nd in 3.8–3.0 Ga rocks from the Anshan Complex, North China Craton. Precambrian Research 301, 86-101 (2017).\nRevision: Lines 215-217 “142Nd and 143Nd isotopes for the 3.8–3.0 Ga Anshan Complex suggest 4.5–4.4 Ga model ages for the precursor of the oldest components and multiple mantle-crust differentiation events from 4.3 to 3.8 Ga (ref. 10).”\nAdditional minor comments in the attached pdfs:\n1# Line 25-26 “primarily owing to the paucity of well-preserved crustal remnants from this eon.”: Reads as though Archean rocks in general are not well preserved. If you are referring to Eo-to-Paleoarchean 'protocrust' (crustal nuclei) I think it would be to be a bit more specific.\nResponse: We appreciate the reviewer for pointing out this ambiguous expression. We agree with you that it is better to be more specific. So, we adopt your suggestion, and replace “crustal remnants” by “Eoarchaean–Palaeoarchaean 'protocrust’”.\nRevision: Line 21 “primarily owing to the paucity of well-preserved Eoarchaean–Palaeoarchaean ‘protocrust’.”\n2# Line 30 “Further, zircon Lu–Hf isotopes reveal that these crustal fragments record Hadean to early Eoarchean (4.1–3.8 Ga) mantle extraction ages”: I would be a bit more cautious here...these 'ages' are fraught with uncertainty and highly model dependent.\nResponse: We appreciate the reviewer’s concern about the model ages. This comment is along the lines of Comments 3 and 4. According to the reviewer’s suggestion, we have included a comprehensive discussion on the uncertainty of calculation of mantle model age, and present reasons why the two stage depleted mantle ages are suitable for these early Archaean granitoids of this study—cited earlier in response to Comments 3 and 4. In addition, we replace “4.1–3.8 Ga” by “4.2–3.8 Ga” as suggested by the reprocessed T 2 ages. Please refer to Comment 3 and 4 for detailed discussion. DM\nRevision: Line 24-25 “ancient 4.2–3.8 Ga mantle extraction ages”.\n3#Line 57 “Even in cratons that contain such Eoarchean–Paleoarchean rocks, they often only comprise a volumetrically minor component of the terrane itself”: Maybe true for Eoarchean rocks but, there are plenty of relatively well-preserved Paleoarchean rocks in the East Pilbara Terrane and Barberton area.\nResponse: We appreciate the reviewer for pointing out this ambiguous expression. It’s true that Palaeoarchaean rocks are more abundant compared to Eoarchaean ones. We adopt your suggestion, and delete the reference to the Palaeoarchaean here.\nRevision: Lines 45-46 “Even in cratons that contain such Eoarchaean rocks, they often only comprise a volumetrically minor component of the terrane itself12.”.\n4# Lines 98-100 “Generally, the two-stage depleted mantle model (T DM2) age of granitoids represents the timing of extraction of their mafic precursors from a depleted mantle source, which in turn signifies the timing of crustal growth.”: Needs a reference.\nRevision: Good point. We added the following reference:\nMole, D.R. et al. (2019) Time-space evolution of an Archean craton: A Hf-isotope window into continent formation. Earth-Science Reviews 196, 102831.\n5# Lines 101-102 “The 3.6–3.5 Ga zircon grains have sub-chondritic ε values ranging Hf from −2.24 to −1.13, with T ages of 4.1–3.8 Ga.”: In Figure 2b is looks like the 3.8- DM 2 4.2 Ga evolution array is defined by all the newly acquired data (red circles), not just the 3.5-3.6 Ga rocks. These older rocks appear to have a more limited range of zircon Hf compositions and hence model ages. I would prefer to see the range of models ages for each magmatic pulse separately and then provide a summarily at the end. In Figure 2b, the evolution array is defined by 3.8 and 4.2 Ga crustal evolution lines? Moreover, in Figure 2b it looks like there is a pulse of chondritic magmatism at c.3.8 Ga, that matches what is observed in the the North Atlantic Craton (Fig 2c). Why can't these rocks have formed by reworking this 3.8 Ga chondritic mafic crust?\nResponse: We appreciate the reviewer’s concern about presenting the results and discussion more logically. According to your suggestion, we have displayed the Hf isotopes for each magmatic pulse separately, and then give a summary. We agree with you that all the 3.6–3.5 Ga, 3.3–3.2 Ga and c. 2.72 Ga zircons have similar Hf T 2 ages DM of 4.2–3.8 Ga, these analyses are well enveloped by 3.8 and 4.2 Ga crustal evolution lines in Fig. 2d. And we made some revisions. We partially agree with the reviewer that these 3.6–2.7 Ga zircons could be formed by reworking from a 3.8 Ga chondritic mafic crust, but only if a 3.8 Ga chondritic mantle existed in the North China Craton. However, as we discussed in Comment 3, several lines of evidence suggest a depleted mantle during the Eoarchaean in the North China Craton. What we can confirm at this stage based on Hf isotopes is the 4.2–3.8 Ga mantle extraction age (i.e., crustal growth age) of the mafic protocrust. These 3.6–2.7 Ga zircon could be generated by the partial melting of mafic protocrust, which could be crystallized at any point between 4.2 and 3.8 Ga.\nRevision: Lines 125-145 “The 3.6–3.5 Ga zircon grains from the Baishan nucleus have sub-chondritic ε values ranging from −3.6 to −0.1, with T 2 ages of 4.2–3.9 Ga. In Hf(t) DM contrast, the 3.3–3.2 Ga and c. 2.72 Ga groups display more unradiogenic Hf isotopic features with sub-chondritic ε values ranging from −6.0 to −1.5 and −10.2 to −4.2, and Hf(t) both groups have similar T 2 ages of 4.2–3.8 Ga. Zircons from the c. 2.63 Ga DM monzogranite exhibit sub-chondritic ε values ranging from −4.5 to −0.5 with T 2 ages of Hf(t) DM 3.7–3.3 Ga. Some of the 2.55–2.50 Ga potassic granites also exhibit unradiogenic Hf isotopes, yielding sub-chondritic ε values ranging from −7.7 to −1.1, with T 2 ages of Hf(t) DM 3.7–3.3 Ga. In contrast, several 2.55–2.50 Ga potassic granites have more radiogenic Hf isotopes with positive ε values ranging from 0 to +5.7 with T 2 ages of 3.2–2.8 Ga. Hf(t) DM Together, these data show that the 3.6–3.5, 3.3–3.2, and c. 2.72 Ga zircons have a similar T 2 age range (4.2–3.8 Ga), and they also display a common evolution as demonstrated DM by well-defined 4.2 and 3.8 Ga crustal evolution lines (Fig. 2d). The 4.2–3.8 Ga T 2 ages DM thus represent the mantle extraction age of the mafic protocrust, which subsequently experienced multiple stages of recycling at 3.6–3.5, 3.3–3.2, and c. 2.72 Ga. In addition, the Hf isotopes of the c. 2.78 Ga trondhjemitic gneiss13, the c. 2.63 Ga monzogranite, and the 2.55–2.50 Ga potassic granites with sub-chondritic ε values reflect another mantle Hf(t) extraction event that occurred from 3.7–3.3 Ga (Fig. 2d). Moreover, the 2.55–2.50 Ga potassic granites with radiogenic Hf compositions, as well as the previously reported 2.55–2.50 Ga mafic volcanic rocks and TTGs from the Baishan nucleus (refs in Supplementary Table S4), suggest significant juvenile crustal growth between the Mesoarchaean and Neoarchaean. Together, these data demonstrate that the Baishan nucleus experienced multiple phases of crustal growth and reworking/recycling processes throughout the Archaean, leading to its geochemical maturation and facilitation of cratonization.”\n6# “Analysis of zircon standard 91500 yielded a weighted mean 206Pb/238U age of 1062.3±2.1 Ma, aligning with the recommended 206Pb/238U ages of 1064 Ma for this standard within analytical errors (Wiedenbeck et al., 1995). Analysis of Plešovice yielded a weighted mean 206Pb/238U age of 339.3±4.1 Ma matched the recommended values (Sláma et al., 2008)”: This is different to the date reported above? (1060.3 +- 2.9 Ma). I think its helpful to state what the accepted ages of the standards are so readers can compare for themselves.\nResponse: We appreciate the reviewer for pointing out the lack of the analysis of standards. We have added the analyses results for all the standard materials into the Supplementary material. And we also added the accepted ages and values of standards for comparison.\nRevision:\nLines 41-47 in Supplementary material “The standard 91500 (1062.4 ± 0.4 Ma; Wiedenbeck et al. 14) and NIST 610 were used for external calibration of the U–Pb ages and trace element content calculations respectively. Corrections for instrument drift, mass bias, and fractionation of the U–Pb ratio were made using a standard-sample bracketing method. For quality control purposes, the zircon standard Plešovice (337.13 ± 0.37 Ma, Sláma et al. 15) was analyzed after every ten unknown samples. Based on the actual situation, a testing denuded diameter of 30 μm was selected. The measured weighted mean ages of standards 91500 (1060.4 ± 2.9 Ma) and Plešovice (339.6 ± 1.4 Ma) matched the recommended values.”\nLines 62-65 in Supplementary material “Analysis of zircon standard 91500 yielded a weighted mean 206Pb/238U age of 1062.2 ± 2.3 Ma, aligning with the recommended 206Pb/238U ages of 1062.4 ± 0.4 Ma for this standard within analytical errors14. Analysis of Plešovice yielded a weighted mean 206Pb/238U age of 335.9 ± 1.7 Ma matched the recommended values (337.13 ± 0.37 Ma; Sláma et al.15).”\nLines 82-84 in Supplementary material “The measured ages of zircon standards 91500 (weighted mean age = 1060.3 ± 5.0 Ma) and Plešovice (weighted mean age = 338.2 ± 3.9 Ma) are indistinguishable from accepted reference values suggested by Wiedenbeck et al. 14 and Sláma et al. 15.”\nLines 94-97 in Supplementary material “Standard zircon of TEMORA (206Pb/208U = 416.7 ± 1.3 Ma)16 was utilized to correct the U, Th, and Pb contents as well as the ages of zircon. The measured ages of zircon standards TEMORA (weighted mean age = 417.3 ± 2.6 Ma) are consistent with the recommended age.”\nLines 129-133 in Supplementary material “Lu-Hf data for these zircon standards are listed in Table S3. The test 176Hf/177Hf values of Plešovice (weighted mean value = 0.282478), 91500 (weighted mean value = 0.282297), and GJ-1 (weighted mean value = 0.282005) (Table S3) were consistent with the recommended values within the error range (Plešovice = 0.282478 ± 8, 91500 = 0.282300 ± 11, and GJ-1 = 0.282009 ± 10) suggested by Zhang and Hu 17.”\nLines 166-167 in Supplementary material “The analyses results of zircon standards TEMORA (weighted δ18O = 8.22 ± 0.11 ‰) are consistent with the recommended value (δ18O = 8.20‰)16”.\n7# “However, it’s worth noting that the mafic precursors of those earliest TTGs may had a long crustal residence time under a stagnant lid regime, potentially leading to significant underestimation of zircon εHf value and mantle depletion”: “may have”, If there was a long crustal residence prior to remelting to form TTG then this should be reflected in the Hf isotope composition.\nResponse: We appreciate the reviewer pointing out the error. We have replaced “may had” by “may have”. In order to better clarify the long crustal residence time, we compiled a new dataset of global igneous zircon Hf isotopes for Eoarchaean to Mesoarchaean TTGs from ancient cratons. The new compilation suggests that a considerable proportion of zircon display obviously low, sub-chondritic εHf values (Fig. 2c; see following figure). This indicates that the mafic precursors of these early Archaean TTGs may have a long crustal residence time, no matter whether their mafic precursors derived from a chondritic or depleted mantle (with both evolutionary trends depicted in the figure too).\nRevision: Lines 103-108 “To directly address this issue, we compiled a global dataset of igneous zircon Hf isotopes of early Archaean TTGs from all major cratons on Earth (Table S4). The compilation reveals that most zircons display very low sub-chondritic ε Hf(t) values (Fig. 2c), indicating that the mafic precursors of these early Archaean TTGs likely had a long crustal residence time, potentially leading to significant underestimation of zircon ε value and the degree Hf(t) of mantle depletion1.”\n8# Is DM modelled as a straight line connecting chondrite at 4.5 Ga and present day compositions, or modelled using the starting composition at 4.5 Ga and 176Lu/177Hf? Please provide more details.\nResponse: We appreciate the reviewer’s attention to the depleted mantle (DM) lines. The DM lines are based on the model of Griffin et al.18 with 176Hf/177Hf of 0.283251 and 176Lu/177Hf of 0.0384, and with depletion occurring at either 4.56 Ga or 3.8 Ga.\nRevision: Lines 575-578 “Depleted mantle (DM) lines are based on models of a present depleted mantle with a 176Hf/177Hf of 0.283251 and a 176Lu/177Hf of 0.0384 (ref. 18), and the 3.8 Ga DM curve is extrapolated from the assumption that growth of the depleted mantle began at 3.8 Ga (ε = 0) and evolved to the present-day depleted mantle Hf reservoir3”.\n9# “The weighted mean εHf value and probability of fit (p) values of each sample were calculated using Origin 2023. Only samples with p≥0.05 are considered statistically homogeneous, while those with p<0.05 are deemed heterogeneous and thus excluded. The compiled weighted mean εHf values are presented in Table S4 and Fig. 2b, c.”: I'm not familiar with this software package. Could you provide a reference for it? I'm not sure this is appropriate. There are several reasons why zircon from a given rock might exhibit heterogeneous Hf isotope signatures. 'Statistical homogeneity' is not necessarily a good measure of data quality and my sense is that by filtering the data in such a manner you could be excluding real geological signals from the dataset. I think it would be better to filter out analyses whose U-Pb systematics have been affect by Pb loss (as shown in Figure S1 above). My sense is that if there is still heterogeneity in 176Hf/177Hf after this step, then it could indeed reflect real.\nResponse: We appreciate reviewer’s questions about the data filtering process—and understand their concern about a heterogeneity being a potentially real effect. The Origin 2023 software includes basic data processing such as calculating means and standard variance, linear prediction, and hypothesis test (such as t-value test and variance test). Use of it is now cited in the Methods—although such stats calculations are not at all special to it. In term of statistical homogeneity, we have considered this comment carefully. According to the reviewer’s suggestion, we firstly filter out igneous zircon with obvious Pb loss as well as metamorphic/recrystallized zircon. This step can remove those zircons that experienced intensive later metamorphism and/or hydrothermal alteration. However, zircon that experienced significant crustal contamination and/or mixing may or may not display any Pb loss. Thus, we still need another method for filtering them out. Generally, crustal contamination or magma mixing can induce heterogeneous Hf isotope signatures with widely variable ranges—as the reviewer points out. So, we adopt a probability of fit (p) values to filter out those analyses that have a wide range of Hf isotopes. So, yes, we indeed agree with the reviewer that such statistical filtering principle might exclude some real geological signals. So, we also plot these samples with p <0.05, but in gray color on the diagrams and don’t include them in the interpretation. Actually, precluding these statistical heterogeneous zircons (gray color in Fig. 2d, e) do not affect any interpretations.\nRevision: Lines 384-388 “Generally, crustal contamination or magma mixing could induce heterogeneous Hf isotope signatures. Thus, this study applies probability of fit (p) values of each sample to filter out those zircons with heterogeneous Hf compositions. The probability of fit (p) values of each sample were calculated using Origin 2023 (www.originlab.com/2023). Only samples with p ≥ 0.05 are considered statistically homogeneous, while those with p < 0.05 are deemed heterogeneous and thus excluded from interpretation.”\nReferences\nFisher, C. M., Vervoort, J. D., & Hanchar, J. M. (2014). Guidelines for reporting zircon Hf isotopic data by LA-MC-ICPMS and potential pitfalls in the interpretation of these data. Chemical Geology, 363, 125-133.\nKemp, A. I., Vervoort, J. D., Petersson, A., Smithies, R. H., & Lu, Y. (2023). A linked evolution for granite-greenstone terranes of the Pilbara Craton from Nd and Hf isotopes, with implications for Archean continental growth. Earth and Planetary Science Letters, 601, 117895.\nPetersson, A., Kemp, A. I., Hickman, A. H., Whitehouse, M. J., Martin, L., & Gray, C. M. (2019). A new 3.59 Ga magmatic suite and a chondritic source to the east Pilbara Craton. Chemical Geology, 511, 51-70.\nVan Kranendonk, M. J., Smithies, R. H., Hickman, A. H., & Champion, D. C. (2007). Paleoarchean development of a continental nucleus: the East Pilbara terrane of the Pilbara craton, Western Australia. Developments in Precambrian Geology, 15, 307- 337.\nSincere thanks, for the critical and constructive comments.\nReviewer #2 (Remarks to the Author):\nThis manuscript presents new zircon U-Pb age, Lu-Hf isotope and Oxygen isotope data for the newly recognized 3.57 Ga Tonalite, together with other younger rocks, in the North China Craton. It represents the finding of a new continental nucleus in the North China Craton. Based on the data, the authors addressed three problems: the widespread of Hadean to early Eoarchean proto-crust, the geodynamic process for the Paleoarchean to Mesoarchean magmatism and the initiation of plate tectonics. The data is interesting and the manuscript is well organized. This research is generally of broad interests for researchers who are interested in the early earth. I suggest the authors add some new issues in the revision.\nWe are very encouraged that the reviewer finds the manuscript well-execute and of broad interest. We very much appreciate the issues raised to help improve during revision.\nComment 1: First, the readers would like to know if the Eoarchean to Paleoarchean rocks in the Jiapigou–Baishan Lake area of this study, and those reported in previous studies, mainly in the Anshan-Benxi area and the eastern Hebei area belong to the same coherent continental nucleus or three individual nuclei.\nResponse: Excellent question. Discussion on this new issue makes our manuscript more comprehensive, so the comment is greatly appreciated. Based on their similar ages of magmatic events and zircon Hf isotopes, these three nuclei might represent a coherent continental.\nRevision: Lines 194-211 “The three nuclei within the North China Craton (i.e., Anshan, Baishan, and Eastern Hebei) are connected by Neoarchaean granite–greenstone belts; however, it remains unclear whether these nuclei belonged to a single coherent continental terrane or represented three individual terranes. In favor of the former argument, we note that these nuclei experienced many similar Eoarchaean-to-Mesoarchaean magmatic events, such as the c. 3.8 Ga magmatic event recorded in the Anshan and Eastern Hebei nuclei19. The oldest c. 3.6 Ga magmatic event in the Baishan nucleus also correlates with that identified from the Hujiamiao Complex of the Anshan nucleus19. Also, intensive crustal reworking events occurred in all three nuclei during 3.3–2.9 Ga (refs. 20-22), leading to the formation of large-scale potassic granitoids and reflecting the existence of voluminous continental crust in each region during the Mesoarchaean. Finally, zircon Hf isotopes suggest similar T 2 ages (4.2–3.8 Ga), DM 176Lu/177Hf ratios (0.022), and crustal evolution histories (Fig. 2d) for these three nuclei. Therefore, the three North China nuclei may have once constituted a coherent Eoarchaean-to-Mesoarchaean proto-craton. Considering that c. 2.7–2.6 Ga potassic granites have only been identified from the Baishan nucleus, and the existence of a 2.7–2.6 Ga granite-greenstone belt between the Baishan and Anshan nuclei, we suggest that Baishan might have rifted away from Anshan during the early Neoarchaean, and then later reunited during late Neoarchaean cratonization of North China. Such a scenario involving rifting and breakup of an ancient continental nucleus resembles the processes that have been proposed for the Yilgarn Craton23.”\nComment 2: The other issue is about the geodynamic process of the 3.57-2.72 Ga magmatism. The authors proposed the 3.57-2.72 Ga magmatism, including tonalite, monzogranite and trondhjemite, were formed by repeated plume underplating in a stagnant lid background, mainly based on their Hf isotopes. This seems acceptable but not enough. The readers would wonder what controls the major and trace element geochemical characteristics (which is missing in the presented data) of the 3.57 Ga tonalite, 3.23 Ga monzogranite, 2.78 Ga trondhjemite, 2.72 Ga monzogranite if they are all derived from the same proto-crust. What are the differences in their melting conditions? What are the implications of such differences?\nResponse: We appreciate the question regarding the geochemistry. The geochemical data are provided in Supplementary Table S7. We have added discussion based on the major and trace elements for these granitoids, and provide related figures (Fig. 3, shown below). The 3.3–2.5 Ga potassic granites all exhibit geochemical features of adakitic granites derived from the partial melting of thickened crust with melting pressures >1.0 GPa and temperatures between 850 and 800℃. These 3.3–2.5 Ga adakitic granites reflect that the Baishan nucleus might maintain a thickened crust during 3.3–2.5 Ga.\nRevision: Lines 147-173 “Geochemical constraints on petrogenesis of the 3.3–2.5 Ga potassic granites\nIn this study, a total of 20 samples were analyzed for major and trace elements. Detailed results of geochemistry can be found in the Table S7. The 3.3–2.5 Ga potassic granites exhibit similar geochemical features, such as high SiO (70.38–77.94 wt. %), low 2 MgO (0.18–1.21 wt. %), TFe O (1.24–4.00 wt. %), Cr (3.16–26.4 ppm), and Ni (1.22– 2 3 17.20 ppm) contents. They are enriched in light rare earth elements (e.g., La and Ce), Sr, Zr, and Hf, but depleted in heavy rare earth elements (e.g., Lu, Yb, and Y), Nb, and Ta (Fig. 3a), with mainly positive Eu anomalies. On a Al O /(FeOT+MgO)–(3CaO)– 2 3 (5K O/Na O) ternary diagram24 (Fig. 3b), the 3.3–3.2 Ga and c. 2.72 Ga monzogranites 2 2 plot mainly within the field of melts derived from tonalite. As the 3.3–3.2 Ga and c. 2.72 Ga zircons exhibit a similar Hf crustal evolutionary pattern to the 3.6–3.5 Ga xenocrystic zircons, it is reasonable to propose that the 3.6–3.5 Ga TTG was the source for the 3.3– 3.2 Ga and c. 2.72 Ga monzogranites. The source rock for the c. 2.63 Ga monzogranite could have been a high-K mafic rock (Fig. 3b), which had a mantle extraction age of 3.7– 3.3 Ga. The c. 2.5 Ga potassic granites exhibiting negative ε values might have been Hf(t) sourced from TTG rocks (Fig. 3b), whereas the other c. 2.5 Ga potassic granites displaying positive ε values, higher Al O values and K O/Na O ratios, likely formed Hf(t) 2 3 2 2 from juvenile metasediments. All of the 3.3–2.5 Ga potassic granites display high Sr/Y ratios (32–132, except for one analysis of 18) and La /Yb (35–201, except for one N N analysis of 17), and can thus be classified as adakitic granites25 (Fig. 3c). Generally, such adakitic geochemical characteristics suggest substantial garnet but minor plagioclase in the source region during partial melting, classically interpreted to occur at a pressure greater than 1.0 GPa (ref. 25). Based on the computational method of Miller et al. 26, the average Zr saturation temperatures (T ) of the 3.3–3.2, c. 2.72, c. 2.63, and c. 2.5 Ga Zr adakitic granites are 794 ℃, 847 ℃, 818 ℃, and 808 ℃, respectively. Moreover, the characteristics of high SiO contents but low MgO, Cr, and Ni contents suggest a 2 thickened crust origin for these adakitic granites27 (Fig. 3d). This interpretation is also supported by abundant xenocrystic zircons within the 3.3–2.5 Ga potassic granites and their unradiogenic zircon Hf isotopes (e.g., negative zircon ε values and Hadean to Hf(t) Palaeoarchaean T 2 ages). As such, these adakitic granites indicate that the Baishan DM nucleus maintained a notably thick continental crust (>30 km) from at least 3.3 Ga to 2.5 Ga.”\nFig. 3\nComment 3: And I disagree with the authors on their discussion on the onset of plate tectonics. The authors proposed asynchronous onset of plate tectonics in different cratons based on asynchronous increase of Hf isotope and O isotopes. In my opinion, the asynchronous onset of plate tectonics is a fake proposition because plate tectonics is defined to be a global tectonics characterized by the creation and maintenance of a global network of narrow plate boundaries. The increase of Hf isotope ratios may signify the contribution of depleted mantle related to plate subduction. The increase of O isotope ratios suggests the emergence of large-scale subaerial landmass for low-temperature weathering.\nResponse: We appreciate the reviewer for clarifying the asynchronous onset of subduction rather than the asynchronous onset of plate tectonics. We agree with you that only the emergence of global network of plate boundaries represents the beginning of plate tectonics. Asynchronous onset of subduction in different terranes would promote the onset of the global network of plate boundaries. Therefore, we change “the onset of plate tectonics” to “the onset of subduction” throughout the manuscript. We accept that asynchronous increases of δ18O values in different cratons suggests the asynchronous emergence of large-scale subaerial land. To illustrate the role of subduction during the late Neoarchean in the NCC, we also consider other lines of geological evidence, such as ca. 2.5 Ga paired metamorphism in Dengfeng28, Alpine-style sub-horizontal arc-affinity nappe structures in central NCC29-31, and the widespread presence of subduction-related potassic granites and sanukitoids32. Therefore, we consider that the significant elevation of the δ18O values of the ca. 2.5 Ga igneous rocks from the NCC was most likely caused by subduction that incorporated large volumes of supracrustal materials into magma sources. Compared to other Archean cratons, the records of intensive subduction in the NCC occur later than those in other cratons, which is therefore consistent with the interpretation that the onset of subduction was asynchronous from a global perspective.\nRevisions:\nLine 271 “Archaean supercratons and the asynchronous onset of subduction”\nLines 303-326 “Globally, >2.7 Ga zircons primarily display mantle-like or slightly elevated δ18O values, whereas those with ages <2.7 Ga show an increasing trend in δ18O values (Fig. 2f), as similarly demonstrated in previous analyses33. In North China specifically, zircon δ18O values only begin to show significant elevation by the end of the Neoarchaean (c. 2.5 Ga), while 3.6–2.6 Ga zircon exhibit mantle-like or only slightly elevated δ18O values (Fig. 2f). Significant elevation of δ18O values during the Neoarchaean is consistent with the observation from triple-oxygen-isotopes recorded in Archaean shales34 that reflect substantial emergence of subaerial landmass, allowing for subaerial weathering. The appearance of more exposed continent during the Neoarchaean is contemporaneous with the assembly of the Kenorland supercontinent35 or multiple supercratons36 (i.e., Superia, Sclavia, and Vaalbara). Thus, the diachronous increase of δ18O values in different cratons at different times in the Neoarchean suggests the asynchronous emergence of large-scale subaerial land.\nThere is broad consensus that plate tectonics had become established on Earth by around 3 Ga (refs. 37-39), even if localized subduction began in some cratons at an earlier time40-42. The δ18O values of the c. 2.5 Ga igneous rocks from North China show notably higher values than those in older zircon (Fig. 2f), which suggest that considerable volumes of supracrustal materials have been incorporated into magma source regions. This process can be achieved through several geodynamic processes (e.g., subduction, sagduction, or thrust stacking), of which, subduction is considered the most effective way. Several independent lines of evidence confirm that subduction initiated locally within the North China Craton by the end of the Neoarchaean, including evidence of paired metamorphism in Dengfeng28, Alpine-style subhorizontal arc-affinity nappe structures in central North China29, 30, and the widespread presence of subduction-related potassic granites and sanukitoids32—all occurring at c. 2.5 Ga. Therefore, the initiation of subduction in North China might have occurred notably later than in many other cratons. Our new data thus add to a growing set of observations supporting the onset of subduction being asynchronous from a global perspective40, 43.”\nBelow are detailed comments and suggestions.\nComment 4: Line 121: The title is not consistent with the contents of this section. I can only see the crustal architecture of northeastern NCC from this paragraph. I can see nothing about the structure of lithospheric mantle in the whole manuscript.\nResponse: Fair point, thanks for pointing this out. We agree with the reviewer that this section is about the crustal structure rather than the structure of the lithospheric mantle. In addition, after clarifying the crustal architecture, we think that it is suitable for deciphering more about the affinities among the Baishan, Anshan, and Eastern Hebei nuclei here.\nRevision: The revised section title (Line 175) is: “Crustal architecture of northeastern North China and affinities among nuclei within the craton”.\nComment 5: Lines 127-128: You need to provide the ages of these so-called “old crust”. Only unradiogenic εHf(t) values do not support they are very old.\nResponse: Thanks for pointing out this unclear expression. Beside the ancient T 2 DM ages (3.7–3.3 Ga), these two regions also have some geological records that support that they are old than the surrounding Neoarchaean granite–greenstone belt: for example, the c. 3.1 Ga TTG and amphibolite assemblage in the North Qingyuan area44, and abundant 2.9–2.7 Ga xenocrystic zircon within the ca. 2.7 Ga meta-mafic volcanic rocks45. Thus, we think these two regions might represent two reworked ancient crustal fragments.\nRevision: Lines 183-187 “Additionally, two small regions in the Qingyuan and Helong areas display ancient T 2 ages of 3.8–3.3 Ga and unradiogenic Hf isotopes, probably DM indicating the existence of ancient crustal fragments (Fig. 4). This interpretation is further supported by the identification of the c. 3.1 Ga TTG and amphibolite assemblage44 and abundant 2.9–2.7 Ga xenocrystic zircons within the c. 2.7 Ga meta-mafic volcanic rocks45.”\nComment 6: The effective numbers: For example, the uncertainty of εHf(t) values is about 0.4-0.5. Therefore, the significant digit after the decimal point of εHf(t) should be 1. And the significant digit of 176Hf/177Hf and error is traditionally 6.\nRevision: Good point about sig figs. We revised this throughout the main text and supplementary materials and tables.\nComment 7: Fig. 3a: The design of this figure is not logical. The hot and cold color is designed to represent negative and positive εHf(t) values. However, the same εHf(t) values at different ages represent different mantle extraction age. If they are labelled as the same color, the authors would get the wrong information that the mantle extraction ages are the same. I strongly suggest the authors provide zircon U-Pb age map and T 2 DM map in Fig. 3.\nRevision: Good suggestion for better portraying the contour maps. Providing a zircon U–Pb age contour map is helpful to clarify the crustal architecture of this region. We assume that the reviewer might have missed the Hf T 2 map in the previous version. So, DM in the revision, we added a new zircon U–Pb age map and also added titles for each of the contour maps to help readers easily understand. Revised Figure 4 shown below:\nFig. 4\nComment 8: Lines 146-148: It is impossible for the existence of a “global-scale” Hadean to early Eoarchean proto-crust. This means that almost all continental crust were formed in the very early stage of the Earth history. If so, most of the continental crust should have modal age of Hadean to early Eoarchean, which was not observed in zircon Hf model age data base (e.g., Dhuime et al., 2012).\nDhuime, B., Hawkesworth, C.J., Cawood, P.A., Storey, C.D., 2012. A change in the geodynamics of continental growth 3 billion years ago. Science 335, 1334-1336.\nResponse: We appreciate the reviewer for pointing out this inappropriate expression. We agree with the reviewer that it cannot be true that almost all continental crust were formed in the Hadean to early Eoarchaean. Our original view was that the Hadean to early Eoarchaean protocrust might have existed widely within those oldest continental nuclei, such as the Slave, Yilgarn, and North China cratons. Therefore, we changed the title of this section to “Hadean to early Eoarchaean mafic protocrust in early Earth”, and revised this section accordingly.\nRevision: Lines 213-232 “Hadean to early Eoarchaean mafic protocrust in early Earth\nAs shown by our new data, zircon Hf isotopes indicate that the Anshan, Baishan, and Eastern Hebei nuclei originated from a Hadean to early Eoarchaean mafic protocrust (Fig. 2d). 142Nd and 143Nd isotopes for the 3.8–3.0 Ga Anshan Complex suggest 4.5–4.4 Ga model ages for the precursor of the oldest components and multiple mantle-crust differentiation events from 4.3 to 3.8 Ga (ref. 10). Several Hadean detrital zircons19 and xenocrystic zircons46 identified from the Eastern Hebei and Anshan nuclei and the southern margin of North China provide direct evidence of a Hadean to early Eoarchaean heritage for the craton. This interpretation is further corroborated by the Xinyang Eoarchaean xenoliths from southern North China47 that display more evolved Hf isotopes than the other three northern continental nuclei (Fig. 2d). Our new compilation of zircon Hf isotopes of Eoarchaean-to-Mesoarchaean TTGs worldwide show that the vast majority of Eoarchaean–Palaeoarchaean TTGs from most cratons (e.g., Slave, Yilgarn, East Antarctica, Superior, and Kaapvaal) generally display T 2 ages >4 Ga (Fig. 2c). Studies DM of the Eoarchaean Acasta Gneiss Complex of the Slave Craton suggest that these oldest rocks on Earth were generated from a Hadean mafic protocrust12, 48. In light of these earliest records and our new findings from North China Craton, we propose the existence of a Hadean to early Eoarchaean mafic protocrust that was crucial for the formation of the earliest continental crust nuclei preserved in individual cratons49.”\nComment 9: Lines 152-154: The statement is not consistent with Fig. 2b. Not all the >2.6 Ga granitoids within the ABN exhibit a simple linear evolutionary εHf value trend. The 3.1-3.0Ga rocks in the ABN show obvious increase in εHf values.\nResponse: We appreciate the reviewer for pointing out this ambiguous description. According to the zircon Hf isotopes, the ancient nuclei of the NCC might preserve 4.2–3.8 Ga mafic protocrust, and younger 3.8–3.3 Ga later underplated mafic crust. Thus, two different episodes of melting of these two different mafic sources would have two crustal evolutionary trends, as illustrated in the new Fig. 2d shown below. We have also revised this ambiguous description in the main text.\nFig. 2d\nRevision: Lines 233-242 “The 3.8–3.6 Ga TTG and the c. 3.3 and 3.1–2.9 Ga potassic granites in the Anshan nucleus, as well as the 3.3–2.7 Ga granitoids within the Baishan nucleus all exhibit consistent linear crustal evolutionary trends (melting trend #1 in Fig. 2d), and were therefore derived from repeated melting of a 4.2–3.8 Ga mafic precursor(s), without significant addition of juvenile materials in any magmatic episode. In addition, the c. 3.45 Ga migmatite, the c. 3.3 Ga trondhjemite, and the c. 3.1 Ga trondhjemite from the Anshan nucleus, the c. 2.9 Ga TTG and diorite from the Eastern Hebei nucleus, as well as the c. 2.78 Ga trodhjemite, c. 2.63 monzogranite, and some 2.5 Ga potassic granites from the Baishan nucleus define another reworking episode with a distinct crustal evolution array (melting trend #2 in Fig. 2d). They represent repeated melting products of former (3.8–3.3 Ga) underplated mafic crusts.”\nComment 10: Lines 160-161: I cannot see the crustal architecture characterized by “younger and juvenile granite-greenstone belts surrounding ancient, long-lived, and reworked continental nuclei” from Fig. 3.\nResponse: Thanks for pointing out this ambiguity. We assume that maybe due to the modification by younger orogenic belts, such an original crustal architecture might not be easy to recognize. Nonetheless, we would like to insist on our view. The Baishan nucleus and the two other ancient crustal fragments are distributed as isolated “fragment” on the northern margin of the NCC, and are separated from the Anshan nucleus by the late Neoarchean North Liaoning to South Jilin granite–greenstone belt (new Fig. 4). The zircon T 2 age contour map might be a clearer way to see that these nuclei (warm color) are DM surrounded by the younger and juvenile granite–greenstone belt (cold color). We sketched approximately such architecture in the following figure for illustration.\nRevision: Lines 187-191 “The Baishan nucleus and the other two ancient crustal fragments occur as isolated fragments on the northern margin of the North China Craton, and are separated from the Anshan nucleus and each other by the late Neoarchaean North Liaoning to South Jilin granite–greenstone belt (Fig. 4). This crustal architecture suggests that these ancient nuclei are surrounded by a younger and juvenile granite–greenstone belt.”\nComment 11: Lines 195-206: I personally agree that the NCC may belong to the Sclavia supercraton. But I cannot agree with the logics of the first evidence. The identification of Hadean-Eoarchean rocks and detrital zircons in these cratons, do not mean that they are in the same supercraton in the Neoarchean. The Hadean detrital zircons might be transported to other cratons at any time if they were in the same supercontinent.\nResponse: We appreciate the reviewer their concern about the logic of this evidence. We agree with the reviewer that if these cratons belonged to the same ancestral landmass (supercontinent or supercraton), detrital zircons with similar ages might be transported from other cratons. Thus, for this first potential line of evidence, we try to express it in a more logical way. These cratons recorded similar Hadean–Eoarchaean tectono-thermal events, as evidenced by U–Pb ages and Hf isotopes of igneous zircon (Fig. 2c, d) from the Acasta complex of the Slave Craton12, 50, the Narryer terrane of the Yilgarn Craton51, the Anshan and Eastern Hebei nuclei of the NCC, as well as the Mairi gneiss complex of the São Francisco Craton52.\nRevision: Lines 285-289 “(i) similar Hadean–Eoarchaean tectono-thermal events, as evidenced by U–Pb ages and Hf isotopes of igneous zircons (Fig. 2c, d) from the Acasta complex in the Slave Craton12, 50, the Narryer terrane in the Yilgarn Craton51, the Anshan and Eastern Hebei nuclei in North China, as well as the Mairi gneiss complex in the São Francisco Craton52;”\nComment 12: Lines 213-215: Subduction is not a pre-requirement for the increase of δ18O values. Other geodynamic processes for recycling of supracrustal materials (e.g., sagduction) are also capable to incorporate supracrustal materials into magmatic sources. The key point is the emergence of subaerial landmass for low-temperature weathering. Therefore, the asynchronous increase of δ18O values in different cratons suggest the asynchronous emergence of large-scale subaerial land rather than asynchronous initiation of subduction.\nBindeman, I.N., Zakharov, D.O., Palandri, J., Greber, N.D., Dauphas, N., Retallack, G.J., Hofmann, A., Lackey, J.S., Bekker, A., 2018. Rapid emergence of subaerial landmasses and onset of a modern hydrologic cycle 2.5 billion years ago. Nature 557, 545-548.\nResponse: We appreciate the reviewer for clarifying the meaning of the increase in δ18O values. We accept that the asynchronous increase of δ18O values in different cratons suggest the asynchronous emergence of large-scale subaerial land. To illustrate the role of subduction during the late Neoarchean in the NCC, we also consider other lines of geological evidence, such as ca. 2.5 Ga paired metamorphism in Dengfeng28, Alpine-style sub-horizontal arc-affinity nappe structures in central NCC29-31, and the widespread presence of subduction-related potassic granites and sanukitoids32. Therefore, we consider that the significant elevation of the δ18O values of the ca. 2.5 Ga igneous rocks from the NCC was most likely caused by subduction that incorporated large volumes of supracrustal materials into magma sources. Compared to other Archean cratons, the records of intensive subduction in the NCC occur later than those in other cratons, which is therefore consistent with the interpretation that the onset of subduction was asynchronous from a global perspective.\nRevision: Lines 303-329 “Globally, >2.7 Ga zircons primarily display mantle-like or slightly elevated δ18O values, whereas those with ages <2.7 Ga show an increasing trend in δ18O values (Fig. 2f), as similarly demonstrated in previous analyses33. In North China specifically, zircon δ18O values only begin to show significant elevation by the end of the Neoarchaean (c. 2.5 Ga), while 3.6–2.6 Ga zircon exhibit mantle-like or only slightly elevated δ18O values (Fig. 2f). Significant elevation of δ18O values during the Neoarchaean is consistent with the observation from triple-oxygen-isotopes recorded in Archaean shales34 that reflect substantial emergence of subaerial landmass, allowing for subaerial weathering. The appearance of more exposed continent during the Neoarchaean is contemporaneous with the assembly of the Kenorland supercontinent35 or multiple supercratons36 (i.e., Superia, Sclavia, and Vaalbara). Thus, the diachronous increase of δ18O values in different cratons at different times in the Neoarchean suggests the asynchronous emergence of large-scale subaerial land.\nThere is broad consensus that plate tectonics had become established on Earth by around 3 Ga (refs. 37-39), even if localized subduction began in some cratons at an earlier time40-42. The δ18O values of the c. 2.5 Ga igneous rocks from North China show notably higher values than those in older zircon (Fig. 2f), which suggest that considerable volumes of supracrustal materials have been incorporated into magma source regions. This process can be achieved through several geodynamic processes (e.g., subduction, sagduction, or thrust stacking), of which, subduction is considered the most effective way. Several independent lines of evidence confirm that subduction initiated locally within the North China Craton by the end of the Neoarchaean, including evidence of paired metamorphism in Dengfeng28, Alpine-style subhorizontal arc-affinity nappe structures in central North China29, 30, and the widespread presence of subduction-related potassic granites and sanukitoids32—all occurring at c. 2.5 Ga. Therefore, the initiation of subduction in North China might have occurred notably later than in many other cratons. Our new data thus add to a growing set of observations supporting the onset of subduction being asynchronous from a global perspective40, 43.”\nComment 13: Line 225: onset of plate tectonics or onset of subduction? Plate tectonics is defined to be a global tectonics characterized by the creation and maintenance of a global network of narrow plate boundaries. According to its definition, if plate tectonics begun, it is globally. Therefore, you can say asynchronous onset of subduction but cannot say asynchronous onset of plate tectonics.\nResponse: We appreciate the reviewer for clarifying the asynchronous onset of subduction rather than the asynchronous onset of plate tectonics. We agree with you that only the emergence of global network of plate boundaries represents the bona fide beginning of plate tectonics sensu strictu. Only the progressive propagation of subduction initiation in different terranes would eventually promote the onset of the global network of plate boundaries40, 53.\nRevision: Lines 29, 271, 326 and 331 “onset of subduction”\nComment 14: GPS coordinates should be provided in the supplementary tables.\nResponse: Thanks for pointing out the omission of the GPS coordinates, we have provided GPS coordinates in the Supplementary Tables.\nComment 15: The age of 22BS20-3: From the field photo of Fig. S3b and d, I cannot see any difference between the 3.57 Ga tonalite and the 3.2 Ga monzogranite. There are three groups of ages in Fig. S6a and b, which group really record the crystallization age? To support your interpretation that the 3.57 Ga group is the crystallization age, you need to provide more zircon CL images and describe their Th/U ratios.\nResponse: We appreciate the reviewer’s concern regarding the interpretation of these two groups of ages. We reevaluated the “3.57 Ga” tonalite, where both c. 3.57 Ga and c. 3.3 Ga zircon groups from sample 22BS20-3 display concentric oscillatory zones with narrow 2.5 Ga recrystallized zones or metamorphic rims (Fig. 2b). Both the c. 3.57 Ga and c. 3.3 Ga zircon groups have high Th/U ratios (0.11–0.81; except three analyses of 0.01, 0.07, and 0.08). We note that sample 22BS20-3 is a small xenolith (approximately 20 x 30 cm), and its zircon U–Pb ages are similar to the surrounding c. 3.23 Ga monzogranites. Although we haven’t found any c. 3.3 Ga zircons with 3.57 Ga zircon cores, it might be more acceptable that the c. 3.3 Ga group represents the crystallization age, whereas the 3.57 Ga group merely represents inherited zircons. It is worth noting that larger amounts of ca. 3.6–3.5 Ga xenocrystic zircons existed in the Baishan nucleus, and the younger c. 3.3 Ga and c. 2.73 Ga granites show similar Hf crustal evolution trends with these 3.6–3.5 Ga zircon. These lines of evidence also allow us to draw a conclusion that the oldest magmatic event of this region occurred at 3.6–3.5 Ga. Meanwhile, the other major conclusions are not affected if sample 22BS20-3 formed at c. 3.3 Ga with abundant 3.6–3.5 Ga xenocrystic zircon.\nRevision:\nLines 71-76 “An early Palaeoarchaean magmatic event is recorded by abundant 3.6–3.5 Ga xenocrystic zircons found within younger (3.3–3.2 and 2.55–2.50 Ga) granitoids. These xenocrysts exhibit concentric oscillatory internal zonation, suggestive of crystallization from a felsic melt (Fig. 2b). Evidence for a subsequent late Palaeoarchaean/early Mesoarchaean magmatic event comes from 3.3–3.2 Ga monzogranites and 3.3–3.2 Ga xenocrystic zircons within younger 2.55–2.50 Ga potassic granitoids.”\nLine 177 in Supplementary Materials “2.1 c. 3.3 Ga monzogranite (22BS20-3) with 3.6-3.5 Ga xenocrystic zircons”.\nLines 185-194 in Supplementary Materials “The cores display concentric oscillatory zones with high Th/U ratios (0.11–0.81, except three analyses of 0.01, 0.07, and 0.08) suggestive of a magmatic origin. Conversely, zircon rims and mantles are relatively luminescent or lack interior structures, indicating a metamorphic origin. Analyses on zircon cores can be divided into two groups. The older age group dated by LA-ICP-MS and SHRIMP yield 207Pb/206Pb ages of 3570–3364 Ma and 3573–3283 Ma with upper intercept ages of 3558±61 Ma and 3546±20 Ma, respectively. The four concordant analyses conducted by SHRIMP yielded a weighted mean age of 3571 ± 2 Ma (MSWD=1.06), which is interpreted as the age of xenocrystic zircons. The younger age group dated by LA-ICP-MS and SHRIMP yield 207Pb/206Pb ages of 3239–3076 Ma and 3252–2917 Ma with upper intercept ages of 3271±25 Ma and 3238±45 Ma, respectively. This younger ca. 3.3 Ga is interpreted as the crystallization age for Sample 22BS20-3.”\nFig. 2b\nComment 16: Lu-Hf isotope and Oxygen isotope results for the metamorphic domains should not be plotted on the figures. If the zircon metamorphic domain is of recrystallization origin, its 176Hf/177Hf isotope ratios should be similar with its igneous predecessor whereas its U-Pb age is reset. If the Hf isotope is plotted on the εHf(t)-age diagram, it will mislead the readers that the magmatism of this age have such εHf(t) values.\nResponse: We appreciate the reviewer for reminding us not to plot the results of metamorphic domains. According to your suggestion, we exclude the Hf and O isotopic data from metamorphic or recrystallized domains before plotting.\nReference\n1. Liou, P. et al. Zircons underestimate mantle depletion of early Earth. Geochimica et Cosmochimica Acta 317, 538-551 (2022).\n2. Fisher, C.M. & Vervoort, J.D. Using the magmatic record to constrain the growth of continental crust—The Eoarchean zircon Hf record of Greenland. Earth and Planetary Science Letters 488, 79-91 (2018).\n3. Ge, R. et al. Generation of Eoarchean continental crust from altered mafic rocks derived from a chondritic mantle: The ∼3.72 Ga Aktash gneisses, Tarim Craton (NW China). Earth and Planetary Science Letters 538 (2020).\n4. Petersson, A. et al. 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Science Advances 6, eabc5491 (2020).\nREVIEWERS' COMMENTS\nReviewer #1 (Remarks to the Author):\nThe authors have done a great job of improving the supplementary materials, and I think it is now much easier for readers to evaluate the quality of their data, which appears sound.\nI also think the additional discussion of 142,143Nd isotope data strengthens the argument that the rocks in the NCC were derived by reprocessing crust that originally fractionated from the mantle in the Hadean to very early Archean.\nI only have a few minor additional comments outlined below.\nSpecific comments:\nLine 55: the ‘thus’ in this sentence feels out of place. I would remove it.\nLine 66: craton growth and maturation processes?\nLine 106-107: I struggle to follow this. The eHf is an empirical measurement and its uncertainty is controlled by the uncertainty in the 176Hf/177Hf measurement, uncertainty in the age (which affects the correction to initial compositions) and the uncertainty in the CHUR model used for normalisation. Do you mean to say that while these unradiogenic zircon indicate that some crust-mantle differentiation must have occurred in the Hadean to early Archean, the inferred source ages for these unradiogenic zircon varies depending on the assumed degree of mantle depletion?\nLine 144-146: Similar secular eHf patterns are observed in other cratons (e.g. Mulder et al., 2020) so it might be worth mentioning that here.\nLine 268-270: Might be worth mentioning mantle processes here, and brining in the stabilisation of thick subcontinental lithospheric mantle roots?\nLine 301-302: I think this is debatable. Zircon oxygen can track melts generated from weathered rock, which probably requires some kind of crustal thickening / burial process, but I think linking it to subduction isn’t necessarily straightforward. In lines 320-322 you appear to be more circumspect about this link. Maybe better to say ‘has been proposed to track subduction…”\nReviewer #2 (Remarks to the Author):\nMost of my concerns have been well addressed in the revision. I am OK with it.\nJust a suggestion for Line 176: I suggest to revise “Crustal architecture of northeastern North China and affinities among nuclei within the craton” as “Crustal architecture of northeastern North China and its affinity with other nuclei of the NCC”.\nComments in black\nResponses in blue\nLine numbers refer to the “clean” version of the manuscript without tracked changes.\nReviewers’ comments:\nReviewer #1 (Remarks to the Author):\nReviewer #1 (Remarks to the Author):\nThe authors have done a great job of improving the supplementary materials, and I think it is now much easier for readers to evaluate the quality of their data, which appears sound.\nI also think the additional discussion of 142,143Nd isotope data strengthens the argument that the rocks in the NCC were derived by reprocessing crust that originally fractionated from the mantle in the Hadean to very early Archean.\nI only have a few minor additional comments outlined below.\nResponse: We sincerely thank the reviewer for this comprehensive assessment.\nComment 1:\nLine 55: the ‘thus’ in this sentence feels out of place. I would remove it.\nResponse: Thanks for your suggestion. We have removed ‘thus’.\nComment 2:\nLine 66: craton growth and maturation processes?\nResponse: According to your suggestion, we have modified this sentence. Please refer to Line 68: “To establish craton growth and maturation processes of the Baishan nucleus”.\nComment 3:\nLine 106-107: I struggle to follow this. The εHf is an empirical measurement and its uncertainty is controlled by the uncertainty in the 176Hf/177Hf measurement, uncertainty in the age (which affects the correction to initial compositions) and the uncertainty in the CHUR model used for normalisation. Do you mean to say that while these unradiogenic zircon indicate that some crust-mantle differentiation must have occurred in the Hadean to early Archean, the inferred source ages for these unradiogenic zircons vary depending on the assumed degree of mantle depletion?\nResponse: We appreciate the reviewer for clarifying this ambiguous expression. We agree with your suggestion. Please refer to Line 108-111: “These unradiogenic Hf isotopes indicate that some crust-mantle differentiation must have occurred in the Hadean to early Archaean, and the inferred source ages for these unradiogenic zircons vary depending on the assumed degree of mantle depletion.”\nComment 4:\nLine 144-146: Similar secular eHf patterns are observed in other cratons (e.g. Mulder et al., 2020) so it might be worth mentioning that here.\nResponse: We appreciate this suggestion, and we agree with the reviewer that it is worth mentioning the work of Mulder et al. (2021) here. Please refer to Lines 151-152: “Similar Archaean crusts with secular evolved Hf patterns are also developed in other cratons, such as the Yilgarn and Slave1.”\nComment 5:\nLine 268-270: Might be worth mentioning mantle processes here, and bringing in the stabilisation of thick subcontinental lithospheric mantle roots?\nResponse: Thanks for this good suggestion. We have made some modifications according to your suggestion. Please refer to Lines 276-277: “Such mantle processes also resulted in the stabilization of thick subcontinental lithospheric mantle roots. ”\nComment 6:\nLine 301-302: I think this is debatable. Zircon oxygen can track melts generated from weathered rock, which probably requires some kind of crustal thickening / burial process, but I think linking it to subduction isn’t necessarily straightforward. In lines 320-322 you appear to be more circumspect about this link. Maybe better to say ‘has been proposed to track subduction…”\nResponse: We agree with your suggestion, and replace “Zircon oxygen isotope analysis has been proven to be an effective method for tracing subduction zone processes” by “Zircon oxygen isotope analysis has been proposed to track subduction zone processes”. Please refer to Lines 312-313.\nReviewer #2 (Remarks to the Author):\nMost of my concerns have been well addressed in the revision. I am OK with it. Just a suggestion for Line 176: I suggest to revise “Crustal architecture of northeastern North China and affinities among nuclei within the craton” as “Crustal architecture of northeastern North China and its affinity with other nuclei of the North China Craton”.\nResponse: We sincerely thank the reviewer for this comprehensive assessment. We have changed the subtitle “Crustal architecture of northeastern North China and affinities among nuclei within the craton” into “Crustal architecture of northeastern North China and its affinity with other nuclei of the North China Craton”. Please refer to Lines 183-184.\nReference\n1. Mulder JA, Nebel O, Gardiner NJ, Cawood PA, Wainwright AN, Ivanic TJ. Crustal rejuvenation stabilised Earth's first cratons. Nat Commun 12, 3535 (2021)."}]

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