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The long-favored paradigm for the development of continental crust is one of progressive growth beginning at [approximately]4 billion years ago (Ga). To test this hypothesis, we measured initial ¹⁷⁶Hf/¹⁷⁷Hf values of 4.01- to 4.37-Ga detrital zircons from Jack Hills, Western Australia. [epsilon][subscript Hf] (deviations of ¹⁷⁶Hf/¹⁷⁷Hf from bulk Earth in parts per 10⁴) values show large positive and negative deviations from those of the bulk Earth. Negative values indicate the development of a Lu/Hf reservoir that is consistent with the formation of continental crust (Lu/Hf [approximately] 0.01), perhaps as early as 4.5 Ga. Positive [epsilon][subscript Hf] deviations require early and likely widespread depletion of the upper mantle. These results support the view that continental crust had formed by 4.4 to 4.5 Ga and was rapidly recycled into the mantle.

The authors became aware of a mistake in the data and axis labeling in Fig. 2 in the original version of the Article. Specifically, the authors mistakenly copied and pasted a formula for background correction instead of the actual values. As a result of this, Fig. 3 was updated to replace the incorrect label ‘sulfate flux (kg km −2 )’ with the correct ‘sulfate concentrations (ng g −1 )’ on the far-left y -axes in both panels, and to add the correct data for Δ 33 S, as given by the red dotted lines. The correct version of Fig. 3 is shown below as Fig. 1, which replaced the previous incorrect version, shown below as Fig. 2. This has been corrected in both the PDF and the HTML versions of the Article. The findings and interpretations in the original Article are based on the correct dataset, and this error does not affect the original discussion or conclusions of the Article. The authors apologize for the confusion caused by this mistake.

High quality records of stratospheric volcanic eruptions, required to model past climate variability, have been constructed by identifying synchronous (bipolar) volcanic sulfate horizons in Greenland and Antarctic ice cores. Here we present a new 2600-year chronology of stratospheric volcanic events using an independent approach that relies on isotopic signatures ( Δ 33 S and in some cases Δ 17 O) of ice core sulfate from five closely-located ice cores from Dome C, Antarctica. The Dome C stratospheric reconstruction provides independent validation of prior reconstructions. The isotopic approach documents several high-latitude stratospheric events that are not bipolar, but climatically-relevant, and diverges deeper in the record revealing tropospheric signals for some previously assigned bipolar events. Our record also displays a collapse of the Δ 17 O anomaly of sulfate for the largest volcanic eruptions, showing a further change in atmospheric chemistry induced by large emissions. Thus, the refinement added by considering both isotopic and bipolar correlation methods provides additional levels of insight for climate-volcano connections and improves ice core volcanic reconstructions. The estimation of volcanic contribution to climate variability requires identification of global-scale eruptions. Here the authors present a new 2600-year chronology of stratospheric volcanic events that relies on isotopic signature of ice core sulfate, that improves ice core volcanic reconstruction.

Determining the chronology for the assembly of planetary bodies in the early Solar System is essential for a complete understanding of star- and planet-formation processes. Various radionuclide chronometers (applied to meteorites) have been used to determine that basaltic lava flows on the surface of the asteroid Vesta formed within 3 million years (3 Myr) of the origin of the Solar System 1 , 2 , 3 . Such rapid formation is broadly consistent with astronomical observations of young stellar objects, which suggest that formation of planetary systems occurs within a few million years after star formation 4 , 5 . Some hafnium–tungsten isotope data, however, require that Vesta formed later 6 (∼16 Myr after the formation of the Solar System) and that the formation of the terrestrial planets took a much longer time 7 , 8 , 9 , 10 (62 -14 +4504  Myr). Here we report measurements of tungsten isotope compositions and hafnium–tungsten ratios of several meteorites. Our measurements indicate that, contrary to previous results 7 , 8 , 9 , 10 , the bulk of metal–silicate separation in the Solar System was completed within <30 Myr. These results are completely consistent with other evidence for rapid planetary formation 1 , 2 , 3 , 4 , 5 , and are also in agreement with dynamic accretion models 11 , 12 , 13 that predict a relatively short time (∼10 Myr) for the main growth stage of terrestrial planet formation.

Lead, oxygen, and osmium isotopic ratios measured on Hawaiian basalts can be matched with the isotopic ratios inferred for recycled ancient oceanic crust. High-precision hafnium isotopic data for lavas from several Hawaiian volcanoes identify old pelagic sediments in their source. These observations support the recycling hypothesis, whereby the mantle source of ocean island basalts includes ancient subducted oceanic crust. Hyperbolic lead-hafnium isotopic relations among Hawaiian basalts further indicate that upper mantle material is not involved in the production of hot spot basalts.

Valley et al . review the lines of evidence on which we drew to conclude that continental crust formed much earlier than previously thought. Their comment contains some misrepresentations that we correct, but new information they provide appears to bolster our hypothesis. Nothing in their comment refutes the presence of continental crust or plate boundary processes prior to 4 billion years ago.

Six garnet pyroxenites from Beni Bousera, Morocco, yield a mean lutetium-hafnium age of 25 ± 1 million years ago and show a wide range in hafnium isotope compositions ($\\varepsilon_{Hf}$ = -9 to +42 25 million years ago), which exceeds that of known basalts (0 to +25). Therefore, primary melts of garnet pyroxenites cannot be the source of basalts. The upper mantle may be an aggregate of pyroxenites that were left by the melting of oceanic crust at subduction zones and peridotites that were contaminated by the percolation of melts from these pyroxenites. As a consequence, the concept of geochemical heterogeneities as passive tracers is inadequate. Measured lutetium-hafnium partitioning of natural minerals requires a reassessment of some experimental work relevant to mantle melting in the presence of garnet.

The Earth's mantle is isotopically heterogeneous on length scales ranging from centimetres to more than 10 4 kilometres 1 , 2 . This heterogeneity originates from partial melt extraction and plate tectonic recycling, whereas stirring during mantle convection tends to reduce it. Here we show that mid-ocean ridge basalts from 2,000 km along the southeast Indian ridge (SEIR) display a bimodal hafnium isotopic distribution. This bimodality reveals the presence of ancient compositional striations (streaks) in the Indian Ocean upper mantle. The number density of the streaks is described by a Poisson distribution, with an average thickness of ∼40 km. Such a distribution is anticipated for a well-stirred upper mantle, in which heterogeneity is continually introduced by plate tectonic recycling, and redistributed by viscous stretching and convective refolding.

It remains controversial whether burial and exhumation in mountain belts represent episodic or continuous processes 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 . Regional patterns of crystallization and closure ages of high-pressure rocks may help to discriminate one mode from the other but, unfortunately, metamorphic geochronology suffers from several limitations. Consequently, no consensus exists on the timing of high-pressure metamorphic events, even for the Alps—which have been the subject of two centuries of field work. Here we report lutetium–hafnium (Lu–Hf) mineral ages on eclogites from the Alps as obtained by plasma-source mass spectrometry. We find that the Lu/Hf ratio of garnet is particularly high, which helps to provide precise ages. Eclogites from three adjacent units of the western Alps give (from bottom to top) diachronous Lu–Hf garnet ages of 32.8 ± 1.2, 49.1 ± 1.2 and 69.2 ± 2.7Myr. These results indicate that the Alpine high-pressure metamorphism did not occur as a single episode some 80–120Myr ago 6 , 7 , 10 , 18 , but rather that burial and exhumation represent continuous and relatively recent processes.

Up to 10 per cent of the ocean floor consists of plateaux 1 —regions of unusually thick oceanic crust thought to be formed by the heads of mantle plumes. Given the ubiquitous presence of recycled oceanic crust in the mantle source of hotspot basalts, it follows that plateau material should also be an important mantle constituent. Here we show that the geochemistry of the Pleistocene basalts from Logudoro, Sardinia, is compatible with the remelting of ancient ocean plateau material that has been recycled into the mantle. The Sr, Nd and Hf isotope compositions of these basalts do not show the signature of pelagic sediments. The basalts’ low CaO/Al 2 O 3 and Ce/Pb ratios, their unradiogenic 206 Pb and 208 Pb, and their Sr, Ba, Eu and Pb excesses indicate that their mantle source contains ancient gabbros formed initially by plagioclase accumulation, typical of plateau material. Also, the high Th/U ratios of the mantle source resemble those of plume magmas. Geochemically, the Logudoro basalts resemble those from Pitcairn Island, which contain the controversial EM-1 component that has been interpreted as arising from a mantle source sprinkled with remains of pelagic sediments 2 , 3 . We argue, instead, that the EM-1 source from these two localities is essentially free of sedimentary material, the geochemical characteristics of these lavas being better explained by the presence of recycled oceanic plateaux. The storage of plume heads in the deep mantle through time offers a convenient explanation for the persistence of chemical and mineralogical layering in the mantle.