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Incompatible trace-element modelling of TTG source a, Mantle-normalized⁴⁷ trace-element patterns for the averages of various rocks from the Pilbara Craton including all tholeiitic basalts (3.48–3.20 Gyr old), >3.45-Gyr-old tholeiitic basalts, primitive (K2O/Na2O < 0.35) and more evolved (0.35 ≤ K2O/Na2O < 0.6) TTG, sanukitoid, hornblende-bearing rocks of the high-MgO granite series (other than sanukitoid), and averages of primitive TTG samples analysed here from the Pilbara and Yilgarn Cratons (Supplementary Table 5). The orange shaded field encompasses trace-element modelling assuming 20% partial melting of average >3.45-Gyr-old Pilbara tholeiite and a wide range of garnet (gnt)-rich and hornblende (hbl)-rich residual mineral assemblages (see Methods). Partial melting of neither average nor voluminous preserved Archaean mafic crust can produce the large-ion lithophile element, Th and light rare earth element enrichment in average TTG. b, The composition of a lower crustal hybrid source formed through adding 17% sanukitoid to mafic crust with the composition of >3.45-Gyr-old Pilbara tholeiitic basalts remains basaltic in composition (Extended Data Fig. 2) and under 20% partial melting (purple field) reproduces the compositions of average Pilbara evolved TTG, leaving a residual mineral assemblage with plagioclase:clinopyroxene:hornblende:garnet proportions of 1:3:8:4. The grey field outlines data from the 3.5-Gyr-old Coucal basalt from the eastern Pilbara Craton⁹. The lined field reflects models with 5% sanukitoid. See Supplementary Table 6 for data citations. The widths of the fields indicate the range of each element on the plot. Source data
Source publication
Much of the current volume of Earth’s continental crust had formed by the end of the
Archaean eon (2.5 billion years ago), through melting of hydrated basaltic rocks at
depths of approximately 25–50 kilometres, forming sodic granites of the tonalite–
trondhjemite–granodiorite (TTG) suite. However, the geodynamic setting and
processes involved are d...
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Constraining deep-water recycling along subduction zones is a first-order problem to understand how Earth has maintained a hydrosphere over billions of years that created conditions for a habitable planet. The pressure-temperature stability of hydrous phases in conjunction with slab geotherms determines how much H2O leaves the slab or is transporte...
Citations
... Earth is the only planet in the solar system to contain granitic continental crust (Campbell and Taylor, 1983;Tang, 2021). Investigation of the petrogenesis of Archean granitoid rocks (Johnson et al., 2017;Smithies et al., 2021;Sun et al., 2021;Gao et al., 2022;Ge et al., 2023;Huang et al., 2023) is important for our understanding of the geodynamic processes of formation and evolution of early continental crust on Earth. Evidence from zircon age spectra suggests that the Neoarchean (2.7-2.5 Ga) was a period of rapid formation of the early continental crust (Condie et al., 2009), and preserved granitoid rock assemblages from the Archean show a change from predominantly sodic tonalite-trondhjemitegranodiorite (TTG) associations in the early Archean to diversified granitoid assemblages (enriched in K 2 O and other large ion lithophile elements [LILEs]) in the late Archean (Laurent et al., 2014;Halla et al., 2017;Hu et al., 2019;Sun et al., 2020a;Ge et al., 2022). ...
The composition of Archean granitoid rocks changed from predominantly tonalite-trondhjemite-granodiorite (TTG) gneisses in the early Archean (4−3 Ga) to diversified granitoid rock assemblages in the late Archean (3.0−2.5 Ga), marking a crucial transformation in the geodynamic processes of early Earth. However, the reason for this major transition remains enigmatic because the petrogenetic features of different granitoid assemblages and their crust-mantle interactions during different periods are poorly understood. We use variations in the spatial-temporal distribution, lithological association, chemical composition, and petrogenesis of Neoarchean (2.7−2.5 Ga) granitoids and inferred correlative crust-mantle interactions in the Eastern Liaoning Range (ELR) of the northeastern North China craton to explore this geodynamic transition. The early Neoarchean (ca. 2.7 Ga) ELR granitoids were dominated by TTG gneisses, and the late Neoarchean (2.6−2.5 Ga) ELR granitoid typology and compositions became more complex, changing into TTGs and more K2O-rich granitoid rocks. The TTGs can be subdivided into a high-Ca group and a low-Ca group: The 2.71−2.68 Ga high-Ca group TTG magma originated from partial melting of subducted juvenile oceanic crust, and the low-Ca group TTG magma was derived from fractionation crystallization of the high-Ca group TTG magma. The chemical composition of the magmatic sources played a dominant role on the 2.60−2.50 Ga TTG magmatism: the high-Ca and low-Ca group TTG magmas came from low-K mafic rocks and tonalites, respectively. The 2.58−2.49 Ga K2O-rich granitoids can be divided into three petrogenetic series: (1) The high-Ca-Mg group K2O-rich granitoid magma originated from partial melting of high-K mafic rocks, (2) the low-Ca-Mg group K2O-rich granitoid magma was derived from partial melting of sedimentary rocks, and (3) the transition group K2O-rich granitoid magma was sourced from metagreywackes. The 2.71−2.68 Ga TTGs were generated in an island arc belt, and subducted slab melting and subsequent magmatic differentiation were the dominant mechanisms of the TTG magmatism. The 2.60−2.50 Ga diversified granitoids were formed in the oceanic-continental subduction process under the active continental margin; the complicated oceanic slab subduction and arc-arc and arc-continent collisions contributed to the diversity of late Neoarchean granitoid magmatism.
... There is compelling evidence showing that the foundations of Earth's early continental crust were built by sodic tonalite-trondhjemitegranodiorite (TTG) granitoids that were formed through the melting of preexisting mafic crust, despite the fact that geodynamic settings of the TTG granitoids are still disputed (Moyen and Martin, 2012;Laurent et al., 2020;Smithies et al., 2021). However, for much of Earth's evolutionary history, the development of continental crust has been closely related to the highefficiency production of intermediate-felsic magmas at continental arc settings. ...
Continental arc magmatism is crucial in producing juvenile continental crust of andesitic to dacitic composition, yet its impact on the formation of the modern mature continental crust, which is more enriched in potassic and granitic components, remains poorly understood. We examined a suite comprised of norite gabbro, gabbroic diorite, high-Mg diorite, dioritic enclave, and medium-K to high-K granites (the Urad Houqi suite) from the Langshan arc in the southern Central Asian Orogenic Belt (CAOB). Zircon U-Pb geochronology indicates that the Urad Houqi suite was formed ca. 278−268 Ma by a continuous magmatic event, marking the final episode of the late Paleozoic continental arc magmatism in the southern CAOB induced by the subduction of the Paleo-Asian Ocean. The suite exhibits a more potassic and fertile composition compared to typical continental arc magmas, and shows a continuous increasing K2O/Na2O ratio and incompatible element concentrations, including K, Rb, Th, and U, with increasing SiO2 content. The geochemical evolution of the suite offers valuable insights into the maturation process of the juvenile arc crust. By combining zircon Hf and bulk-rock Sr-Nd-Pb isotope studies, we demonstrated that the various lithologies within the Urad Houqi suite recorded a three-stage enhancement of the geochemical fertility of the juvenile Langshan arc crust: (1) generation of the initially fertile primary melt from the mantle wedge metasomatized by the recycled subducted sediments; (2) trans-crustal open-system hybridization processes, including peritectic reaction and magma mixing, that further fertilized the derived melts in addition to fractional crystallization; and (3) diverse petrogenetic processes that contributed to the fertility of the granitic magmas, including polybaric fractionation of the primary magma, anatexis of ancient crust, and extraction of high-silica melts from the shallow mush system. The three-stage maturation of the juvenile Langshan arc crust was typically coupled with the accelerated subduction of the Paleo-Asian Ocean since the earliest Permian. Our study finds that the Urad Houqi suite can serve as an example of modern continental crust maturation at continental arc settings.
... One school argues that some form of subduction (e.g., mobile-lid tectonics) operated since the early Eoarchean (or even in the Hadean) (e.g., Arndt, 2023;Hastie et al., 2023). In contrast, the other workers favor the idea that the early Earth was dominated by stagnant-lid tectonics with different forms (e.g., heatpipe, drips and plumes, delamination and upwellings, etc.) (e.g., Smithies et al., 2021;Stern, 2018;Tarduno et al., 2023), with a change to mobile-lid tectonics postulated to occur around the early Mesoarchean (e.g., Dhuime & Storey, 2012;Tang et al., 2016), even though this geodynamic shift in the early Mesoarchean has been questioned by other works based on different proxies (e.g., Greber et al., 2017;C. B. Keller & Harrison, 2020;Reimink et al., 2023). ...
Plain Language Summary
In this study, we explore the Earth's continental crust evolution before 3.0 billion years ago, a period characterized by limited preserved ancient rocks. We focus on zircon from igneous rocks, which provides a more reliable petrogenetic record than detrital zircon. Our study challenges the widely observed increase in detrital zircon initial Hf isotopes during the Paleo‐to Mesoarchean transition, often interpreted as a shift in tectonic regimes. We present new data from 3.05 to 2.9 billion‐year‐old granitoids in the Yangtze Block, suggesting isotopically juvenile magmatic activity. Statistical analysis of a global database of igneous zircon Hf isotopes reveals a state‐shift increase in εHf(t) across the Paleo‐to Mesoarchean transition, indicating global crustal rejuvenation at that time. Contrary to prevailing theories, we propose that this rejuvenation can be attributed to elevated mantle temperatures, challenging the notion of a significant geodynamic change during this period. Our findings emphasize the need to consider mantle thermal evolution in understanding continental crust growth on early Earth.
... Based on previous statistics on detrital zircon ages, the early Neoarchean (~2.8-2.7 Ga) was recognized as the most crucial period of global continental growth (Condie et al., 2009(Condie et al., , 2018. As the major component of early continents, the tonalite-trondhjemite-granodiorite (TTG) magmatism reached a peak during the early Neoarchean, providing a window into the formation and evolution of early continental crust (Jahn et al., 1981;Moyen and Martin, 2012;Smithies et al., 2021). ...
... Zircon, a common accessory mineral in igneous rocks, has physio-chemical stability to retain the primary compositional and isotopic characteristics of its source, making it a key mineral in the investigations of successions that have experienced complex tectono-thermal histories (Valley et al., 2005). Stable isotopes (e.g., Si and O) are resistant to metamorphic and high-T (even >700°C) metasomatic processes and thus are robust tracers of Earth's major reservoirs and capable of unraveling the origin of TTGs and the evolution of geodynamics (André et al., 2019;Smithies et al., 2021;Y. S. Wang et al., 2021). ...
... Ga. Data sources of compiled δ 18 O from published TTG and TTG-like rocks are from Valley et al. (2005) and Smithies et al. (2021), and Data sources of compiled zirconδ 18 O from igneous samples through time are from Spencer et al. (2017Spencer et al. ( , 2022. All zircon O isotope data are listed in Tables S4-S6. ...
... Approximately half of the δ 18 O zircon data for Archean TTGs are within the uncertainty of the mantle range (Smithies et al., 2021). Moreover, O isotope values higher than mantle values are common in Archean TTGs since ca. ...
The start of the Paleoproterozoic supercontinent cycle is typically taken as the initiation of orogenesis at ca. 2.1 Ga leading to the assembly of Earth's first supercontinent, Columbia. However, the dearth of ca. 2.5–2.2 Ga geological records makes it difficult to deduce tectonic factors during the onset of the Paleoproterozoic supercontinent cycle. The petrogenesis of tonalite–trondhjemite–granodiorite (TTG) provides useful proxies for tracing prevailing geodynamic regimes of early continental evolution. However, marked decreases of TTG and other magmatism occurred across the Archean–Paleoproterozoic transition and have previously precluded forming testable hypotheses. Early Paleoproterozoic TTGs have been identified in the North China Craton (NCC) and other cratons, which may represent the last major pulse of TTGs globally. Here we present low δ¹⁸O and δ³⁰Si ca. 2.3 Ga TTGs from the NCC, together with thermodynamic modeling and compilation of stable O and Si isotopes for TTGs globally through time. The ca. 2.3 Ga TTGs were derived from the partial melting of Archean basaltic crust and give lighter average zircon δ¹⁸O (3.15 ± 0.35‰) and whole‐rock δ³⁰Si values (−0.17 ± 0.08‰) than most Archean TTGs. Considering coeval mafic‐felsic igneous rocks, and lithospheric thinning since ca. 2.5 Ga based on estimated crustal thickness through the Neoarchean–Paleoproterozoic, we posit the onset of an intraplate rifting consistent with the anomalous low‐δ¹⁸O magmatism. Continental rifting of Archean cratons/supercratons plausibly hints at the formation of rifts driving subduction initiation as the veritable onset of the Paleoproterozoic supercontinent cycle.
... Oxygen isotopes are typically situated below the magma source region, with a few data points exhibiting lower oxygen isotope values, potentially associated with zircon alteration caused by high-temperature hydrothermal fluids. According to Smithies et al. [71], TTG can host zircons akin to the mantle's δ 18 O value, with the potential for relatively high zircon content δ 18 O values (approximately 5.9‰). Subsequently, these droplets traverse the lower crust and descend into the mantle, releasing fluids and melts with high δ 18 O. ...
... The low ε Hf (t) values of tonalite gneisses (-9.3 to -3.3; Figure 6) indicate that the magma sources for the TTG rocks are primarily ancient crust. Smithies et al. [71] observed that TTG rocks with mantle-like δ 18 O values can also exhibit relatively high zircon δ 18 O values (about 5.9‰). They proposed that the TTG magma sources area with slightly enriched δ 18 O are hydrated partial melts formed from the source lithospheric mantle, leading to the formation of sanukitoids [6,71]. ...
... Smithies et al. [71] observed that TTG rocks with mantle-like δ 18 O values can also exhibit relatively high zircon δ 18 O values (about 5.9‰). They proposed that the TTG magma sources area with slightly enriched δ 18 O are hydrated partial melts formed from the source lithospheric mantle, leading to the formation of sanukitoids [6,71]. Based on zircon Hf-O isotope data, it is suggested that ancient crust may have been the source of these rocks. ...
The 2.45–2.20 Ga period during the early Paleoproterozoic era is considered to have witnessed a global “Tectono-Magmatic Lull (TML)” and thus marks a relatively quiescent period. Our study unveils a 2.45–2.20 Ga magmatic suite from the Xiong’ershan area in the southern North China Craton, offering some key constraints on localized active tectonics during the TML. Zircon U-Pb dating shows Paleoproterozoic ages for the meta-basalt (2.31, 2.28 Ga), Na-rich meta-andesite (~2.33 Ga), tonalite-trondhjemite-granodiorite (TTG) gneisses (2.36, 2.30 Ga), K-rich granodiorite (~2.29 Ga), and monzogranite (2.33, 2.27 Ga). The meta-basalts geochemically and petrographically belong to calc-alkaline basalts and show distinctive Nb, Ta, and Ti contents and primitive mantle normalized patterns from different places in the Xiong’ershan area. Combined with their enriched εHf(t) values, the magmas were derived from subduction-related enriched mantle sources within a convergent plate boundary. The meta-andesites display high MgO content (average 4.5 wt%) and Mg# (44–57), strongly fractionated rare-earth pattern, calc-alkaline affinity, and negative Nb, Ta, and Ti anomalies. The TTG gneisses are of high SiO2 type (>62 wt%), high (La/Yb)N (17.5, 39.2), and Sr/Y (50.2, 104.3) and mostly display positive Eu anomalies and high-pressure type. Zircons from these rocks show a relatively narrow range of δ18O isotope values (5.35‰, 6.79‰) with εHf(t) isotope characteristics (−9.3, −3.3), suggesting derivation from partial melting of a thickened mafic lower crust. The youngest K-rich granodiorite and monzogranite show high K2O/Na2O ratios (0.65, 2.45). Variable molar ratio Al2O3/(CaO+Na2O+K2O) (A/CNK) and low zircon εHf(t) values suggest that the K-rich granitoids formed from the partial melting of different levels of crust. The presence of meta-basalt to andesite assemblages and diverse intermediate to felsic magmatic rocks implies magmatic activity within a convergent plate boundary tectonic environment with potential influence from plume-triggered extensional processes, supported by evidence of slab rollback and upwelling of mantle material.
... The Stimsons Granite (DH50) and Round Granite (DH27) yield emplacement ages of 2666 ± 4 Ma (Fig. 7K) and 2660 ± 22 Ma (Fig. 7L), respectively. DH50 has higher average δ 18 O values than DH27 (5.8 ± 0.4 and 5.0 ± 0.9‰), but average εHf values are similar (+1.9 ± 0.4 and (Lu et al., 2021c;Smithies et al., 2021a;Johnson et al., 2022;Lu et al., 2022c). Individual δ 18 O zircon analyses are shown as well as the average of a sample population. ...
... In order to understand better the adjacent crustal blocks in the eastern Yilgarn Craton, Hf (n = 28) and O (n = 5) isotopes were determined on zircon samples, previously dated by U-Pb using SHRIMP, across the Yamarna and Burtville Terranes from GSWA (n = 23) and GA (n = 5; Table 1). These data are combined with existing Hf (n = 12) and O (n = 5) isotope data from previous studies (Table 1; Wyche et al., 2012;Mole et al., 2019;Lu et al., 2021c;Smithies et al., 2021a;Johnson et al., 2022;Lu et al., 2022c;Lu et al., 2022a;Lu et al., 2022b). Zircon O and Hf isotopic compositions are mostly homogeneous within samples, with 2SD comparable to the DHGB samples (δ 18 O: 0.5 -1.0; εHf: 0.5 -2.5 for n > 5 analyses). ...
... +3.1) compared to the earlier monzogranitic rocks. It is interpreted that these TTG-like rocks formed by melting of isotopically juvenile, metamorphosed mafic rocks in the garnet or amphibole stability field, which may have been hydrated by primordial mantle-derived water (e.g., Moyen & Martin, 2012;Smithies et al., 2021a). Interestingly, these TTG rocks formed after the 'A-type' granites, suggesting increasingly deeper melting from ca. 2830 Ma to ca. 2775 Ma. ...
... Unlike the sources of TTGs, which are mantle-derived, the source rocks of the high-K granites would include buried sediments and other surface-altered materials, which have high δ 18 O and contain old detritus. The transition in melting processes in the wake of delamination thus can explain the increase in δ 18 O values and concomitant loss of juvenile Hf isotope compositions in late K-rich granites within TTG terranes 54,67 . If Archaean TTGs indeed formed by the melting of the gabbroic lower crust, then K-rich granitoid magmatism and the development of "modern" andesitic continental crust from mafic proto-crust likely represent natural consequences of the magmatic differentiation of the crust. ...
Large swaths of juvenile crust with tonalite-trondhjemite-granodiorite (TTG) composition were added to the continental crust from about 3.5 billion years ago. Although TTG magmatism marked a pivotal step in early crustal growth and cratonisation, the petrogenetic processes, tectonic setting and sources of TTGs are not well known. Here, we investigate the composition and petrogenesis of Archaean TTGs using high field-strength-element systematics. The Nb concentrations and Ti anomalies of TTGs show the overwhelming effects of amphibole and plagioclase fractionation and permit constraints on the composition of primary TTG melts. These melts are relatively incompatible element-poor and characterised by variably high La/Sm, Sm/Yb and Sr/Y, and positive Eu anomalies. Differences in these parameters are not indicative of melting depth, but instead track differences in the degree of melting and fractional crystallisation. Primary TTGs formed by the melting of rutile- and garnet-bearing plagioclase-cumulate rocks that resided in proto-continental roots. The partial melting of these rocks is part of a causal chain that links TTG magmatism to the formation of sanukitoids and K-rich granites. Together, these processes explain the growth and differentiation of the continental crust during the Archaean without requiring external forcing such as meteorite impact or the start of global plate tectonics.
... The other end-member argues that such processes were not possible for early Earth's hotter mantle and instead invoke vertical tectonic ('stagnant-lid') processes, by which lower-crustal drips or delamination enriched mantle source regions and were the dominant mechanisms for heat loss and crustal recycling, and where the tonalitic Archean felsic crust results mainly through deep crustal reworking (e.g. Hamilton, 2003;Stern, 2008;Bédard, 2006Bédard, , 2018Bédard et al., 2013;Mole et al., 2021) at least before c. 3.2 Ga (Johnson et al., 2017;Smithies et al., 2019Smithies et al., , 2021. Yet other models argue that both groups of processes may have operated, or dominated, in some form, at certain times and or regions throughout the Archean (e.g., Smithies et al., 2018;O'Neill et al., 2018). ...
... Recently, stagnant-lid processes, such as crustal drips, have been proposed to explain stratigraphically limited arc-like magmas in broader Archean (and particularly Paleoarchean) geological sequences that are otherwise devoid of clear subduction-like signatures and/or where outcrop and regional scale evidence such as 'dome and keel' structures point towards a dominance of vertical tectonic processes (e.g., Johnson et al., 2017;Smithies et al., 2021). In the northwestern Youanmi Terrane, apart from syn-transitional TTG structural kinematics in the Yalgoo dome area (discussed below), there are no such geological features, or geochemical sequences that might not be credibly associated with a subduction-like setting, or that would indicate a dominance of stagnant-lid processes. ...
This study defines a comprehensive chemostratigraphic framework for the 2820-2738 Ma magmatic rocks of the northwestern Youanmi Terrane of the Yilgarn Craton. Sixteen chemostratigraphically distinct units can be correlated between greenstone belts that are separated by later voluminous granitic plutons. On a regional scale, the chemostratigraphic units define discontinuous, broadly NNE striking zones up to 350 km long and 50 km wide (including later granitic plutons). Neodymium isotope and trace element systematics of magmatic rocks require an increasing component of metasomatised mantle from c. 2820 to 2738 Ma and variable recycling of a 3050-2920 Ma crustal component. We interpret the first magmatic episode at 2820-2782 Ma to reflect litho-spheric thinning and asthenosphere upwelling in a back-arc-like setting and attribute the metasomatism of sources for multiple mafic units to subduction of 3050-2920 Ma, predominantly isotopically juvenile, mafic crust. Following an approximate 16 Ma hiatus, a second magmatic episode at 2766-2738 Ma is dominated by crustal-derived transitional TTGs with lower volumes of mantle-derived shoshonitic and sanukitoid-like rocks, and LILE-LREE enriched tholeiitic mafic to felsic rocks. The compositions of the transitional TTG and shoshonitic rocks in this study area are similar to potassic granites and shoshonitic rocks (including shoshonitic lamp-rophyres) from post-orogenic continental collision settings, such as the Mesozoic Tibetan Plateau. We interpret this later episode as reflecting post-orogenic melting of crustal and upper (modified) mantle sources caused by upwelling mantle related to delamination of arc-crust or slab breakoff. The northwestern Youanmi Terrane preserves an extensive package of Archean magmatic rocks that can be confidently attributed to subduction-magmatism and provides a reference point to show that some form of subduction occurred in the Meso-Neoarchean.
... Ga primary magmatic zircon oxygen values from the Yilgarn Craton highlights a statistically (p << 0.05) significant temporal variation with a change point at 2670 Ma when δ 18 O values rose from 5.3 ‰ to 5.7 ‰. Primary magmatic zircon oxygen values in the Pilbara Craton (Smithies et al., 2021) also show a statistically significant change (p << 0.05) at 3060 Ma when δ 18 O values rose from 5.4 ‰ to 6.5 ‰. Similarly, zircon oxygen isotope data from the Barberton granite-greenstone terrane, South Africa (Wang et al., 2021) reveal a statistically significant change at 3232 Ma when average δ 18 O values rose from 5.5 ‰ to 6.4 ‰. ...
... Early (≥3990 Ma) oxygen isotopic signatures within the Acasta gneiss, which at the upper (heavy) limit of mantle values are consistent with deep melting with or without a minor supracrustal component that underwent low-temperature oxygen exchange with the hydrosphere (e. g. altered greenstones) (Smithies et al., 2021). Importantly, however, a ≥ 3965 Ma sub-mantle oxygen signature in zircon requires assimilation or direct melting of altered near-surface crust that had interacted with meteoric water (Taylor, 1971). ...
... A broad secular shift to average heavier oxygen is implied. Data from: Yilgarn , Pilbara (Smithies et al., 2021), Barberton (Wang et al., 2021). Mu is the statistic representing the population mean of a distribution.(For ...
