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We have performed in situ analyses of Li-Be-B and Al-Mg isotope systematics, and abundances of rare earth elements (REEs) in two Ca-Al-rich inclusions (CAIs) from the Ornans-like carbonaceous chondrite Yamato-81020 (CO3.05). The present CO CAIs are depleted in ultra-refractory heavy REEs (group II REE pattern), suggesting condensation of these CAIs or their precursors from the solar nebula. Initial 26Al/27Al ratios, (26Al/27Al)0, of these CO CAIs are found to be (4.8 ± 0.5) × 10–5 and (4.9 ± 0.3) × 10–5 (95% confidence), indicating their contemporaneous formation with a majority of CAIs from Vigarano-like carbonaceous (CV) chondrites. Melilite grains in the present CO CAIs show clear excesses in 10B, ranging from ∼370 to ∼4300‰ relative to the chondritic B isotopic composition, which are correlated well with 9Be/11B ratios. The correlation indicates in situ decay of 10Be in the present CO CAIs and yields initial 10Be/9Be ratios, (10Be/9Be)0, for the individual CAIs of (2.9 ± 0.6) × 10–3 and (2.2 ± 1.0) × 10–3 (95% confidence), which are significantly greater than the average (10Be/9Be)0 = ∼0.7 × 10–3 recorded in CAIs from CV chondrites. The apparent variation in (10Be/9Be)0 between the CO and CV CAIs, despite having indistinguishable (26Al/27Al)0 of ∼5 × 10–5, provides evidence for heterogeneous distribution of 10Be in the CAI forming-regions at the very beginning of the Solar System. The elevated (10Be/9Be)0 and group II REE patterns in the CO CAIs may reflect that compared with the CV CAIs having unfractionated REEs the present CO CAIs have formed closer to the Sun where 10Be was produced more efficiently through solar cosmic ray irradiation caused by solar flares. Alternatively, if the present CO CAIs and CV CAIs formed in the same region, and 26Al was distributed homogeneously at the CAI-forming region, our results indicate that solar cosmic ray fluxes at the forming region have fluctuated by a factor of six within a short duration (∼0.2 million years) inferred from the Al-Mg chronology.

Acid leaching has been widely used in Pb–Pb chronology especially on meteorite samples, as it enhances the precision and accuracy of the chronology by separating radiogenic Pb from non-radiogenic Pb in the samples. Yet, the detailed mechanism of the radiogenic Pb separation remains elusive. Here we report scanning electron microscopy observations of acid-leached minerals from three achondrites that were previously analyzed for pyroxene Pb Pb dating (D'Orbigny, Ibitira and Northwest Africa 6704), and one stony‑iron meteorite (Brenham). Moreover, we present chemical analysis of acid leachates and residues of pyroxene and whole-rock fractions from the three achondrites using inductively coupled plasma mass spectrometry. The combined results reveal the resistance of minerals to acid treatments with HNO3, HCl, and HF and, in turn, allow us to explore the prospects and limitations of acid leaching for Pb Pb chronology. In particular, we show that (i) washing with dilute acids can efficiently liberate contaminant terrestrial Pb adsorbed on the mineral surface; (ii) hot and more concentrated (~6 M) HNO3 and HCl can separate pyroxenes from sulfides and anorthitic plagioclase that are highly enriched in initial non-radiogenic Pb; (iii) albitic plagioclase and pyroxenes show limited dissolution during the HNO3 and HCl treatments, but are progressively leached by hot 1 M HF, making it difficult to separate them from each other; and (iv) within single pyroxene grains having exsolved lamellar textures, high-Ca lamellae are more efficiently leached by the HF treatment than low-Ca ones. In the context of a two-stage Pb isotopic evolution model for pyroxene lamellae, we demonstrate that heterogeneous and incomplete dissolution of pyroxene lamellae with dilute HF can result in inaccurate Pb Pb age estimates. This may account for previously observed scattered Pb isotopic data for meteorite samples that were taken as evidence for isotope fractionation in a radiogenic Pb component during HF treatments.

Geographical traceability of marine bivalves is critical to guarantee their quality and safeguard the interest of both consumers and producers. The neodymium isotopic ratio (143Nd/144Nd) of the coastal water mainly reflects the geology of its neighboring watershed, displaying the distinct and systematic variability at high level of geographical detail and thereby shedding light on its potential as a geochemical tracer. For the first time, the present study investigated the utility and robustness of 143Nd/144Nd archived in mytilid mussel shells for geographical traceability purposes. The reproducibility of 143Nd/144Nd ratios maintained in mussels shells from the same cohort demonstrates that the Nd isotopic ratio meets the major requirement for an ideal geochemical tracer, i.e., the biologically induced variation should be rather minimal. The distribution and variability of mussel shell 143Nd/144Nd patterns were subsequently mapped along the Japanese and Chinese coastal waters. Neodymium isotopes of mussel shells record 143Nd/144Nd variations among local regions and between the two countries, which are rather compatible with the ages and lithology of the continental bedrocks. These findings highlight the great potential of 143Nd/144Nd for tracing the geographical origin of marine bivalves.

Northwest Africa (NWA) 6704 is a unique achondrite characterized by a near-chondritic major element composition with a remarkably intact igneous texture. To investigate the origin of this unique achondrite, we have conducted a combined petrologic, chemical, and (187)Re–(187)Os, O, and Ti isotopic study. The meteorite consists of orthopyroxene megacrysts (En(55–57)Wo(3–4)Fs(40–42); Fe/Mn = 1.4) up to 1.7 cm in length with finer interstices of olivine (Fa(50–53); Fe/Mn = 1.1–2.1), chromite (Cr# ~ 0.94), awaruite, sulfides, plagioclase (Ab(92)An(5)Or(3)) and merrillite. The results of morphology, lattice orientation analysis, and mineral chemistry indicate that orthopyroxene megacrysts were originally hollow dendrites that most likely crystallized under high super-saturation and super-cooling conditions (1–10(2) °C/h), whereas the other phases crystallized between branches of the dendrites in the order of awaruite, chromite → olivine → merrillite → plagioclase. In spite of the inferred high supersaturation, the remarkably large size of orthopyroxene can be explained as a result of crystallization from a melt containing a limited number of nuclei that are preserved as orthopyroxene megacryst cores having high Mg# or including vermicular olivine. The Re–Os isotope data for bulk and metal fractions yield an isochron age of 4576 ± 250 Ma, consistent with only limited open system behavior of highly siderophile elements (HSE) since formation. The bulk chemical composition is characterized by broadly chondritic absolute abundances and only weakly fractionated chondrite-normalized patterns for HSE and rare earth elements (REE), together with substantial depletion of highly volatile elements relative to chondrites. The HSE and REE characteristics indicate that the parental melt and its protolith had not undergone significant segregation of metals, sulfides, or silicate minerals. These combined results suggest that a chondritic precursor to NWA 6704 was heated well above its liquidus temperature so that highly volatile elements were lost and the generated melt initially contained few nuclei of relict orthopyroxene, but the melting and subsequent crystallization took place on a timescale too short to allow magmatic differentiation. Such rapid melting and crystallization might occur as a result of impact on an undifferentiated asteroid. The O–Ti isotope systematics (Δ(17)O = −1.052 ± 0.004, 2 SD; ε(50)Ti = 2.28 ± 0.23, 2 SD) indicate that the NWA 6704 parent body sampled the same isotopic reservoirs in the solar nebula as the carbonaceous chondrite parent bodies. This is consistent with carbonaceous chondrite-like refractory element abundances and oxygen fugacity (FMQ = −2.6) in NWA 6704. Yet, the Si/Mg ratio of NWA 6704 is remarkably higher than those of carbonaceous chondrites, suggesting significant nebular fractionation of forsterite in its provenance.

Geographical traceability of marine bivalves is becoming increasingly important to assure their quality and to defend the interest of consumers and producers. This study verifies the neodymium isotopic ratio (

Monazite [(Ce, La, Th) PO4], a common accessory mineral in low-Ca felsic rocks and a wide range of metamorphic rocks, is suitable for in situ U–Pb dating, rare earth element (REE) geochemistry, and Nd isotope tracer studies. To link monazite composition with igneous petrogenesis and differentiation, we carried out comprehensive LA-ICP-MS measurements of REE-Th-U abundances and Sm-Nd isotope ratios in monazites from magnetite-series (oxidized type) and ilmenite-series (reduced type) granitic rocks across the Japan arc. The data revealed systematic differences in monazite composition between magnetite-series and ilmenite-series samples, and between pegmatites and granites. In ilmenite-series granitic rocks, monazites from pegmatites showed larger negative Eu anomalies, lower light-REE/middle-REE ratios, and higher middle-REE/heavy-REE ratios than those from granites. These geochemical variations were attributed to significant fractional crystallization of feldspars, monazite, xenotime, and garnet during differentiation in relatively reduced peraluminous granitic magmas. In contrast, there was no remarkable difference in the REE fractionation pattern between magnetite-series pegmatites and granites. Furthermore, the magnitudes of the negative Eu anomalies in the magnetite-series monazites were smaller than those observed in the ilmenite-series samples. These features were interpreted to reflect the suppression of monazite, xenotime, and garnet fractionation and limited Eu incorporation into fractionating feldspars in relatively oxidized and non-peraluminous magmas. In addition, our data demonstrated intra-grain variations in REE-Th-U compositions in a monazite from the Masaki ilmenite-series pegmatite, despite its homogenous Nd isotope composition. These variations suggest that the core and rim of the grain crystallized from distinct magmas that were generated from similar crustal rocks, but were differentiated under different conditions. A comparison of the present data with previously reported data indicates that igneous monazites from granitic rocks are distinct from a wide range of metamorphic monazites in REE-Th-U composition, especially due to their larger negative Eu anomalies. This finding highlights the potential utility of monazite REE-Th-U systematics as a provenance indicator for detrital monazites.

Abundant porphyritic granites, including Grt-bearing and Bt-bearing porphyritic granites, and flesh-red porphyritic granites, as various scale batholiths are widely distributed within the Jiao-Liao-Ji belt (JLJB), which extends for a distance of at least 1000 km, rather than being limited to sporadic outcrops in southern Liaoning and Jilin as stated in previous studies. On the basis of morphology, CL and BSE zoning patterns, and mineral inclusions of dated zircon and monazite grains from samples of various porphyritic granites, the grains exhibit evident magmatic zones with distinct cores and rims and preserve felsic mineral inclusions of Qtz + Kfs + Pl + Qtz ± Ap in both domains. The magmatic zircon cores and rims from 18 dated samples yielded two distinct weighted mean age groups, from 1872 ± 9 to 1866 ± 7 Ma and 1851 ± 14 to 1842 ± 10 Ma, with age peaks at 1869 ± 1.7 and 1848 ± 2.4 Ma, respectively. Similarly, the magmatic cores and rims of monazites from 10 dated samples also showed two distinct weighted mean age groups, from 1870 ± 3 to 1864 ± 2 Ma and 1851 ± 6 to 1842 ± 12 Ma, with age peaks at 1868 ± 0.8 and 1847 ± 1.2 Ma, respectively. The numerous U-Pb age data of both zircons and monazites revealed that the JLJB experienced a major episode of granitic magmatism in the Paleoproterozoic with initial emplacement timing of melts at ∼1.87 Ga and crystallisation end timing of melts at ∼1.84 Ga as represented by the magmatic cores and rims of the zircons and monazites, respectively. A combined study of whole-rock geochemistry and zircon Lu-Hf isotopic analyses revealed that the three types of porphyritic rocks are enriched in HREE, Zr, Nb, Ga, and Y and are depleted in V, Cr, and Ni, and that most have high TFeO/MgO ratios and Zr-saturation temperatures of ∼850 °C, which is suggestive of an affinity with A-type granite. Moreover, the dominant e Hf (t) values of the magmatic zircons range from −4.8 to +3.3, which is consistent with those of the 2.2–2.1 Ga calc-alkaline meta-granites in the JLJB. Considering the high contents of garnet, Al-rich paragneiss enclaves, and ∼1.92 Ga inherited metamorphic zircons in the granites, these porphyritic rocks were most likely derived from the partial melting of the 2.2–2.1 Ga calc-alkaline meta-granites with abundant involvement of Al-rich pelitic granulites from the basement of the JLJB. As the result of a newly combined study of traditional geothermobarometers and phase equilibria modelling together with geochronological U-Pb dating, a precise clockwise P-T-t path with a subsequent near isothermal decompression process has been well determined in the HP-MP granulite facies metamorphic rocks in the JLJB. Thus, the following sequence of events can be inferred. Abundant ∼2.2–2.1 Ga granitic rocks and voluminous Paleoproterozoic sedimentary rocks were subducted to lower crustal depths and underwent a peak HP-MP granulite facies metamorphism at 1950–1900 Ma. These granulite facies rocks were exhumed to middle crustal levels and experienced a post-peak MP-LP granulite facies metamorphism at 1875–1840 Ma. The retrograde rocks continued to be exhumed to shallow crustal levels at 1830–1800 Ma and were finally overprinted by late amphibolite facies retrogression. The numerous magmatic zircons and monazites from the various porphyritic granites record a distinct Paleoproterozoic granitic magmatic event with two evident age peaks of ∼1.87 Ga and ∼1.84 Ga, which are completely consistent with the post-peak MP-LP granulite facies metamorphism (1875–1840 Ma), representing an anorogenic magmatic association formed in an extensional setting possibly resulting from mantle upwelling and lithospheric thinning and resulting in the violent partial melting of ∼2.2–2.1 Ga meta-granites along with abundant Al-rich pelitic granulites. Considering these data in combination with previous whole-rock geochemistry and age data, it can be stated that similar porphyritic granites are not only limited to the entire JLJB but are also widely distributed in North and South Korea. Thus, it can be concluded that the ∼1.87–1.84 Ga porphyritic granites, together with massive rapakivi granites, Kfs-megacrysts, and porphyritic monzogranites, as products of an anorogenic granitic magmatic event, may have widely formed in both the JLJB and Korean Peninsula in an extensional and thinning tectonic setting.

The Earth was born in violence. Many giant collisions of protoplanets are thought to have occurred during the terrestrial planet formation. Here we investigated the giant impact stage by using a hybrid code that consistently deals with the orbital evolution of protoplanets around the Sun and the details of processes during giant impacts between two protoplanets. A significant amount of materials (up to several tens of percent of the total mass of the protoplanets) is ejected by giant impacts. We call these ejected fragments the giant-impact fragments (GIFs). In some of the erosive hit-and-run and high-velocity collisions, metallic iron is also ejected, which comes from the colliding protoplanets' cores. From ten numerical simulations for the giant impact stage, we found that the mass fraction of metallic iron in GIFs ranges from ~ 1wt% to ~ 25wt%. We also discussed the effects of the GIFs on the dynamical and geochemical characteristics of formed terrestrial planets. We found that the GIFs have the potential to solve the following dynamical and geochemical conflicts: (1) The Earth, currently in a near circular orbit, is likely to have had a highly eccentric orbit during the giant impact stage. The GIFs are large enough in total mass to lower the eccentricity of the Earth to its current value via their dynamical friction. (2) The concentrations of highly siderophile elements (HSEs) in the Earth's mantle are greater than what was predicted experimentally. Re-accretion of the iron-bearing GIFs onto the Earth can contribute to the excess of HSEs. In addition, the estimated amount of iron-bearing GIFs provides significant reducing agent that could transform primitive CO2-H2O atmosphere and ocean into more reducing H2-bearing atmosphere. Thus, GIFs are important for the origin of Earth's life and its early evolution., Accepted for publication in Earth and Planetary Science Letters, 33 pages, 7 figures, 1 table

The similar, but not identical chemical properties of W compared with Mo suggest that the stable isotope system of W could be a novel proxy to explore the modern and ancient ocean as is the case in the well-established utility of Mo isotopes. We experimentally investigated the isotopic fractionation of W during adsorption on Fe and Mn (oxyhydr)oxides (ferrihydrite and δ-MnO 2 ), a key process in the global ocean budget of this element. Our adsorption experiments confirmed that W isotopes fractionate substantially on both ferrihydrite and δ-MnO 2 : lighter W isotopes are preferentially adsorbed on both oxides as a result of equilibrium isotopic exchange between dissolved and adsorbed species, and the obtained values of Δ 186/183 W liquid–solid ( = δ 186 W dissolved − δ 186 W adsorbed ) are 0.76 ± 0.09‰ for ferrihydrite and 0.88 ± 0.21‰ for δ-MnO 2 (2 σ , n = 6). Compared with the case of Mo isotopes, fractionation of W isotopes is (i) of comparable magnitude between ferrihydrite and δ-MnO 2 , and (ii) much smaller than that of Mo on δ-MnO 2 . Our previous XAFS observations and newly-performed DFT calculations both indicate that the observed W isotopic fractionations are caused by the symmetry change from Td (tetrahedral) WO 4 2− to distorted Oh (octahedral) monomeric W species via formation of inner-sphere complexes on both ferrihydrite and δ-MnO 2 . The similar isotopic fractionations between the two oxides relate to the strong tendency for W to form inner-sphere complexes, which causes the symmetry change, in contrast to the outer-sphere complex of Mo on ferrihydrite. The smaller isotopic fractionation of W compared with Mo on δ-MnO 2 despite their similar molecular symmetry seems to be due to their different degrees of distortion of Oh species. Our findings imply that the isotopic composition of W in modern oxic seawater is likely to become heavier relative to the input by removal of lighter W isotopes via adsorption on ferromanganese oxides in analogy with the Mo isotope budget. In contrast, the isotopic composition of W in ancient seawater should have evolved in response to the extent of deposition of both Fe and Mn oxides; this is likely to be different compared with that of the Mo isotopes, which is strongly associated with the occurrence of Mn oxides relative to Fe oxides.

The 176 Lu– 176 Hf radioactive decay system has been widely used to study planetary crust–mantle differentiation. Of considerable utility in this regard is zircon, a resistant mineral that can be precisely dated by the U–Pb chronometer and record its initial Hf isotope composition due to having low Lu/Hf. Here we review zircon U–Pb age and Hf isotopic data mainly obtained over the last two decades and discuss their contributions to our current understanding of crust–mantle evolution, with emphasis on the Lu–Hf isotope composition of the bulk silicate Earth (BSE), early differentiation of the silicate Earth, and the evolution of the continental crust over geologic history. Meteorite zircon encapsulates the most primitive Hf isotope composition of our solar system, which was used to identify chondritic meteorites best representative of the BSE ( 176 Hf/ 177 Hf = 0.282793 ± 0.000011; 176 Lu/ 177 Hf = 0.0338 ± 0.0001). Hadean–Eoarchean detrital zircons yield highly unradiogenic Hf isotope compositions relative to the BSE, providing evidence for the development of a geochemically enriched silicate reservoir as early as 4.5 Ga. By combining the Hf and O isotope systematics, we propose that the early enriched silicate reservoir has resided at depth within the Earth rather than near the surface and may represent a fractionated residuum of a magma ocean underlying the proto-crust, like urKREEP beneath the anorthositic crust on the Moon. Detrital zircons from world major rivers potentially provide the most robust Hf isotope record of the preserved granitoid crust on a continental scale, whereas mafic rocks with various emplacement ages offer an opportunity to trace the Hf isotope evolution of juvenile continental crust (from eHf [4.5 Ga] = 0 to eHf [present] = + 13). The river zircon data as compared to the juvenile crust composition highlight that the supercontinent cycle has controlled the evolution of the continental crust by regulating the rates of crustal generation and intra-crustal reworking processes and the preservation potential of granitoid crust. We use the data to explore the timing of generation of the preserved continental crust. Taking into account the crustal residence times of continental crust recycled back into the mantle, we further propose a model of net continental growth that stable continental crust was firstly established in the Paleo- and Mesoarchean and significantly grew in the Paleoproterozoic.

Northwest Africa (NWA) 7325 is a unique ungrouped gabbroic achondrite which has characteristics consistent with a possible link to the planet Mercury. In order to understand the origin of this meteorite and the nature of its parent body, we have determined its crystallisation age using the long-lived U–Pb and short-lived Al–Mg chronometers. An internal Pb–Pb isochron defined by six acid leached pyroxene fractions yields an age of 4563.4 ± 2.6 Ma, assuming that the 238U/235U ratio for NWA 7325 is identical to the bulk Earth and Solar System value of 137.794. The Al–Mg isotope analyses of seven fractions (four plagioclase, one pyroxene, one olivine and one whole rock) define a regression line corresponding to 26Al/27Al0 = (3.03 ± 0.14) × 10−7 and an initial δ26Mg∗ of 0.093 ± 0.004‰. When anchored to the D’Orbigny angrite, this initial 26Al/27Al yields an age of 4563.09 ± 0.26 Ma. The Pb–Pb age of 4563.4 ± 2.6 Ma and Al–Mg age of 4563.09 ± 0.26 Ma are in complete agreement, but the low U concentrations of NWA 7325 resulted in a relatively low precision Pb–Pb age. The observed excess in initial δ26Mg∗ can be explained by 27Al/24Mg fractionation and subsequent Mg isotopic evolution after planetary differentiation. Furthermore, the parental magma of NWA 7325 most likely formed within 1.72 Ma after calcium-aluminium rich inclusion (CAI) formation. NWA 7325 formed near simultaneously with quenched angrites and a number of ungrouped achondrites at ∼4563 Ma, suggesting that a multitude of planetary bodies had formed and differentiated by ∼4–5 Myr after CAI formation. This ancient age may be interpreted as an argument against NWA 7325 originating from Mercury, however it does not completely rule it out.

Slab-melting is considered to have played an important role in the formation of continental crust. The combination of oxygen (O) and hafnium (Hf) isotope signatures can provide key information relating to the melting components during slab-melting. To reveal the melting components, we used SIMS and LA-ICP-MS to determine O isotope ratios at 220 spots and Hf isotope ratios at 61 spots in zircons from five plutons in the Taitao Peninsula, where slab-melting occurred at ca. 4–5 Ma. In addition, we measured whole-rock Hf O isotope ratios in 11 rocks that were intruded by the granitoids. The zircon δ18O values of the Seno Hoppner pluton (5.37 ± 0.44‰) are identical to those of mantle-equilibrated zircons, whereas those of the other four plutons are relatively high (6.09–6.53‰). The ɛHf(t) values of zircons in the granitoids are negatively correlated with δ18O, and they fell along the mixing line between a juvenile component and sedimentary rocks. Therefore, the Hf O profiles can be attributed to mixing of juvenile granitoid magma and the sedimentary rocks, the amount of which was likely minimal in the Seno Hoppner pluton. As such, the δ18O values of the Seno Hoppner pluton could best reflect the juvenile component. In view of the δ18O variation in whole-rock samples of the Taitao ophiolite, the melting of hydrothermally altered basalt and dolerite is considered responsible for the juvenile magma generation. This further implies that juvenile granitoid magmas can be generated by the melting of the upper half of subducted oceanic crusts.

The late heavy bombardment (LHB) hypothesis, wherein the terrestrial planets are thought to have suffered intense collisions ca. 3.9 billion years ago, is under debate. Coupled with new dynamical calculations, re-examination of geochronological data seem to support an earlier solar system instability and a smooth monotonic decline in impacts, as opposed to a “cataclysm.” To better understand this collisional history, records from the asteroidal meteorites are required. Here, we report a uranium–lead (U–Pb) chronological dataset for eucrite meteorites thought to originate from the asteroid 4 Vesta; this dataset indicates to a continuous history of collisions prior to 4.15 Ga. Our 207Pb⁎/206Pb⁎ model ages of apatite [Ca5(PO4)3(F,Cl,OH)] and merrillite [Ca9NaMg(PO4)7] from three brecciated basaltic eucrites—Juvinas (4150.3 ± 11.6 million years ago (Ma); merrillite only), Camel Donga (disturbed around 4570–4370 Ma), and Stannern (4143.0 ± 12.5 Ma)—record multiple thermal metamorphic events during the period of ∼4.4–4.15 Ga. We interpret this to mean that Vesta or the vestoid cluster underwent multiple impacts and moderate high-temperature reheating during this time. The ages of ∼4.4–4.15 Ga are distinctly younger than the initial magmatic process on Vesta (>4.5 Ga) but are significantly older than a later “impact peak” based on some interpretations of 40Ar–39Ar chronologies (∼3.9–3.5 Ga). The intense collisions prior to 4.15 Ga on Vesta are at odds with the conventional LHB hypothesis but not inconsistent with the much earlier bombardment and monotonic decline scenario. Different radiometric chronologies of the asteroid likely represent the different stages of a continual collisional process. Conversely, the model 207Pb⁎/206Pb⁎ ages of apatite in the unbrecciated basaltic eucrite, Agoult, returned an age of 4524.8 ± 9.6 Ma. This may represent slow cooling from an earlier global reheating of the crust on Vesta at 4.55 Ga, as documented by other radiometric chronologies. The apatite in Juvinas recorded a coincident timing of 4516.9 ± 10.4 Ma, which could be due to either slow crustal cooling or impact.

Rare earth element (REE) mineralization is hosted within Neoproterozoic alkaline metaigneous rocks in the northwestern part of the Okcheon Metamorphic Belt (OMB), a polymetamorphosed fold-and-thrust belt transecting the Paleoproterozoic Gyeonggi and Yeongnam Massifs in the southern Korean Peninsula. The principal carrier phase of REEs is allanite. Allanite grains can be subdivided into several types based on the texture and mineral assemblage including quartz, K-feldspar, biotite, britholite, apatite, fergusonite, andradite, magnetite, zircon, titanite and fluorite. Electron microprobe analysis of allanite clearly distinguishes sample-to-sample variations in total REEs, Ca, Al, Fe and Y but the textural varieties from each rock sample do not show marked differences in those elements. Sensitive high-resolution ion microprobe dating of allanite and zircon reveals a complex history of multistage mineralization. Allanite grains from REE ores yielded Late Ordovician (444.6 ± 8.0 Ma), Permian to Triassic (ca. 300–220 Ma) and Early Jurassic (199–183 Ma) 208Pb/232Th ages. These multiple age components often coexist in single grains showing slight differences in backscattered electron brightness. The Ordovician components have distinctly higher Th/U than the younger domains in the same rock sample. The cores and rims of zircon from a syenite hosting REE ore bodies yielded Neoproterozoic (858.2 ± 6.3 Ma) and Early Jurassic (ca. 190 Ma) 206Pb/238U ages, respectively. The Early Jurassic ages (194–187 Ma) also obtained from zircon grains from granites taken from dykes occurring close to the ores and a drill core indicate the correspondence between granitic magmatism and REE mineralization. The Neoproterozoic zircon inheritance (weighted mean = 853.9 ± 3.8 Ma) in these granites is in sharp contrast to the dominant Paleoproterozoic inherited zircon from the widespread earliest Middle Jurassic granites enclosing the mineralized zone. The geotectonic significance of the Late Ordovician event recorded in the allanite, as well as in detrital zircon from the OMB, is still unclear but its temporal coincidence with intraplate volcanism and arc-related igneous activity, respectively, reported from the southwestern edge of the adjacent Taebaeksan Basin and the southwestern Gyeonggi Massif is noteworthy. The following Permian–Triassic and Early Jurassic mineralization events are probably linked to the continental suturing between the North and South China blocks and subsequent post-orogenic magmatism, and arc magmatism resulting from the paleo-Pacific plate subduction, respectively. Sub-grain Sm–Nd isotopic analyses of allanite by laser ablation multiple collector ICPMS yielded initial eNd values plotting along the Nd isotopic evolution path of the Neoproterozoic metaigneous rocks, indicating that REEs originating from the host rock have been recycled during multistage mineralization events. The profound differences in inherited zircon ages and Nd isotopic compositions between the Early and Middle Jurassic granites may reflect the presence of a major thrust-bounded crustal structure beneath the OMB.

Non-cumulate eucrites represent basaltic crust that experienced a complex thermal history involving multistage metamorphism and metasomatism, probably on asteroid Vesta. To better constrain the thermal history of these rocks and their parent body, we have integrated high-precision U–Pb age and trace element data for zircon grains with sizes up to 80 μm in the eucrite Agoult. All analyzed zircon grains yielded concordant U–Pb dates that correspond to the precise 207Pb/206Pb age of 4554.5 ± 2.0 Ma . The Ti contents in these zircon grains indicate their crystallization at subsolidus temperatures of ca. 900 °C, which are similar to the inferred conditions of pyroxene exsolution in most basaltic eucrites that occurred during protracted thermal metamorphism. The zircon crystallization temperatures, together with the presence of baddeleyite needles and variable Zr concentration in Agoult ilmenite grains, indicate metamorphic origin of the Agoult zircon through Zr release from ilmenite followed by reaction with silica. We therefore consider the zircon 207Pb/206Pb age as the timing of the widespread thermal metamorphism in Vesta's crust. The metamorphic age is coincident with the oldest Mn–Cr date for cumulate eucrites, supporting the view that the thermal metamorphism is a result of burial of basaltic crust and subsequent heating from the hot interior rather than collision of asteroids. The zircon rare earth element patterns with restricted Ce positive anomalies suggest that the metamorphism occurred at an oxygen fugacity below the iron–wustite buffer, implying the absence of oxidizing agents such as aqueous fluid within the crust at that time.

Ibitira is an unbrecciated, equilibrated vesicular basaltic achondrite that is considered to have originated on a parent body distinct from all other known meteorites. We present the first combined high-precision U and Pb isotopic data for this unique meteorite. The 238 U/ 235 U value of 137.777 ± 0.013 determined for the whole rock is comparable to values determined for bulk chondrites and other basaltic achondrites. This value results in corrections of −1.1 Ma for Pb–Pb dates calculated using the previously assumed invariant 238 U/ 235 U value of 137.88. Using the determined 238 U/ 235 U value, the 7 most radiogenic Pb isotopic analyses for acid-leached pyroxene-rich and whole rock fractions yield an isochron Pb–Pb age of 4556.75 ± 0.57 Ma, in excellent agreement with the results of Mn–Cr chronology which give the ages of 4557.4 ± 2.5 Ma and 4555.9 ± 3.2 Ma using the U-corrected Pb–Pb age of D’Orbigny as a time anchor. Along with the previously proposed thermal history of Ibitira and our closure temperature estimates for Pb diffusion, the Pb–Pb age is interpreted as the timing of the last chemical equilibration and coarse pyroxene exsolution that occurred during high temperature metamorphism. The metamorphism may have been caused by burial of Ibitira lava under successive lava flows and, if so, the Pb–Pb age should post-date the crystallization by a short time interval. The Pb isotopic data for acid leachates suggest partial re-equilibration of Pb between plagioclase and phosphate, perhaps during an impact event at 4.49 Ga, as recorded by K–Ar systematics. The whole rock 238 U/ 204 Pb indicates that compared to CI chondrites, Ibitira is less depleted in Pb than in some alkali elements despite a lower condensation temperature of Pb than the alkali elements. The restricted Pb depletion may reflect preferential concentration of metals with high fluid/melt partition coefficients including Pb and Zn as a result of fluid exsolution and migration within the parent magma. We discuss the implications of the U–Pb systematics for the origin and differentiation of the parent body.

The 3D lithological distribution model presented in this data article is related to “Stochastic modeling of 3-D compositional distribution in the crust with Bayesian inference and application to geoneutrino observation in Japan” by Takeuchi et al. (2019) [1]. Our target region is set to the crust and uppermost mantle beneath Japanese main islands and their vicinity. We discretized the target region into 79,968 grid points. We defined 31 rock types; 29 major crustal rock types, plus sediment and mantle. Our lithology model represents a probabilistic distribution map inferred from a seismic tomography model and allows quantitative studies with error estimations, making it fundamentally different from previous models. To enable such quantitative applications, we provide explicit numerical data for the probabilities of the 31 rock types for each grid point. We also provide explicit values of the bulk proportion lithology model at various depths and for the bulk whole crust. Further, a figure of synthetic gravity data is presented to correct a minor error in the related paper [1]. Keywords: Bayesian, Crustal structure, Crustal lithology, Rock composition, Geoneutrinos

Mount Narryer and Jack Hills metasedimentary rocks in the Narryer Gneiss Complex of the Yilgarn Craton, Western Australia, contain zircons with ages up to 4.4 Ga, the oldest known crustal materials on Earth, and monazites up to 3.6 Ga. In this study, we have investigated 147 Sm– 143 Nd systematics of detrital and metamorphic monazites from these metasedimentary rocks using laser ablation-multicollector-inductively coupled plasma mass spectrometry (LA-MC-ICPMS). All detrital monazites have negative initial eNd(t) values, indicating that their parental magmas formed by remelting of older crustal materials. A comparison between the initial eNd(t) values of the detrital monazites and granitoids in the Narryer Gneiss Complex indicates that the Mt. Narryer and Jack Hills sediments were partly derived from the most isotopically enriched surrounding granitoids with ages of ca. 3.6 and 3.3 Ga. The metamorphic monazites generally have lower initial eNd(t) values when compared to the detrital monazites. However, the detrital and metamorphic monazites show similar distributions of eNd(t) at the ages of sediment deposition (3.28 Ga for Mt. Narryer and 3.05 Ga for Jack Hills). In addition, multiple analyses on single monazite grains having core-rim structures reveal that the cores and the recrystallized rims had identical Nd isotopic compositions at the time of recrystallization. These findings indicate that older monazites are source of light rare earth elements for younger metamorphic monazite formation and, therefore, that monazite can inherit its primary Sm–Nd isotopic signature during the recrystallization processes. We calculated the Nd model ages for all analyzed monazites to estimate crustal residence time of their source materials. We find that no igneous monazites older than 4.0 Ga were recrystallized to form the monazites. This implies that the lack of Hadean monazites is not due to recrystallization of ancient monazites during later metamorphism, but due to high-Ca compositions of the parental magmas of Hadean detritus, which prevent growth of magmatic monazite.

The 147Sm–143Nd radioactive decay system has been widely used in the Earth sciences as a geochronometer and isotopic tracer. Recent studies have shown that laser ablation-multiple collector-inductively coupled plasma mass spectrometry (LA-MC-ICPMS) is capable of precise and rapid 143Nd/144Nd measurements with high spatial resolution, but its ability to measure 147Sm/144Nd accurately is still poorly constrained. A critical analytical issue is the fractionation effects between 147Sm and 144Nd in LA-MC-ICPMS, which must be carefully corrected to determine robust initial 143Nd/144Nd particularly for ancient geological samples. Here we show that LA-MC-ICPMS can produce substantial (> 5%) 147Sm/144Nd fractionation during analysis of monazite and that the fractionation can be corrected with uncertainty of ~ 1% by using an independently defined 147Sm–143Nd isochron for an Archean monazite standard. In addition, we describe a method for improving the precision and accuracy of LA-MC-ICPMS isotopic measurements by calibration of Faraday amplifier response and isotopic ratio normalization using a synthetic standard. This method has been applied to one Neogene and two Archean monazites, which were also analyzed by isotope dilution-thermal ionization mass spectrometry (ID-TIMS). The LA-MC-ICPMS data were acquired from 16–37 μm single spots. The LA-MC-ICPMS determinations of the 145Nd/144Nd for all samples and 143Nd/144Nd for the Neogene monazite compare well with the ID-TIMS results, indicating the robustness of our method to measure Nd isotopic ratios. For the Archean monazites, the method yields initial 143Nd/144Nd values identical to the ID-TIMS values with reproducibilities (2 s.d.) of 39 and 58 ppm. Analytical precisions of individual spot analyses for initial 143Nd/144Nd were calculated by taking into account the uncertainty in (i) the Nd isotopic normalization to the synthetic monazite, (ii) the correction factor for 147Sm/144Nd fractionation and (iii) the age, which results in 2σ of 45–87 ppm. These results clearly demonstrate the capabilities of the LA-MC-ICPMS technique applied to monazite Sm–Nd isotope systematics for early crustal evolution studies.

A large portion of Earth's crust is formed at convergent plate boundaries that are accompanied by the subduction of sediments that can contain evolved crust-derived detritus. Partial melting of such sediments can strongly affect the trace element and isotope geochemistry of new arc rocks. Here, we present high-precision Lu–Hf–Zr concentration data and Hf isotope compositions for a series of volcanic rocks from the Banda arc, East Indonesia, to quantify the transfer of subducted Hf to the Banda arc crust and address the influence of recycled Hf in subduction zones on the Hf isotope systematics of arc rocks. Along-arc from NE to SW, the 176Hf/177Hf decreases from 0.28314 to 0.28268 ranging from predominantly mantle-like ratios towards more crustal signatures. Hf–Nd isotope co-variations require low Nd/Hf in the arc magma source, inconsistent with fluid addition to the arc melts, but in agreement with the involvement of partial sediment melts. The systematic decrease in Hf–Nd isotopes infers a NE–SW along-arc increase in the involvement of subducted continental material (SCM) in the arc magma source, consistent with δ18O and Nd–Sr–Pb isotope constraints. The along-arc decrease in Hf isotopes coupled with increasing Zr/Hf (from 31.9 to 36.1) and decreasing Lu/Hf suggests that the newly produced arc lavas contain crustal-derived Hf as a result of partial melting of SCM associated with the breakdown of zircon. Based on recent experimental estimates of temperatures required to achieve zircon breakdown, we infer that slab surface temperatures in the Banda arc region need to be as high as 925 °C. As a consequence of the inheritance of non-radiogenic Hf from SCM, the juvenile Banda arc crust exhibits Hf isotope model ages biased by hundreds of millions of years. We conclude that crust-formation ages derived from Hf isotope ratios of convergent margin rocks and their constituent minerals (such as zircon) can be geologically meaningless mixing ages, even when they readily preserve low δ18O values (i.e.

Accurate determination of the absolute ages of the oldest Solar System objects — chondrules and Ca–Al-rich inclusions (CAIs), requires knowledge of their 238U/235U ratios. This ratio was assumed to be invariant in all U–Pb dating of meteorites so far, but the recent discovery of U isotope variations in CAIs (Brennecka et al., 2010a) shows that this assumption is invalid. We present the first combined high-precision U and Pb isotopic data for a CAI, and U isotopic data for chondrules and whole rock fractions of the Allende meteorite. The Pb–Pb isochron age of the CAI SJ101 is 4567.18 ± 0.50 Ma, calculated using the measured 238U/235U = 137.876 ± 0.043 (2σ), reported relative to 238U/235U = 137.837 of the CRM 145 standard. Our best current estimate of the average terrestrial value is: 238U/235U = 137.821 ± 0.014.The error in the age includes uncertainties in the Pb–Pb isochron intercept and in the 238U/235U ratio. Allende bulk rock and chondrules have 238U/235U = 137.747 ± 0.017 (2σ), distinctly lower than the CAI. The difference in the 238U/235U ratio of 0.129 ± 0.046 (2σ) between the CAI and chondrules and bulk meteorite increases the 207Pb–206Pb age difference by ~ 1.4 Ma, and eliminates apparent disagreement between the CAI–chondrule formation time interval determinations with the U–Pb and extinct nuclide (26Al–26Mg and 182Hf–182W) data. We discuss standardisation of 238U/235U measurements for U–Pb geochronology and cosmochronology, elemental and isotopic fractionation induced by intensive acid leaching, ages of CAIs in the context of 238U/235U variability, and possible causes of U isotopic variations in CAIs and meteorites.

We have measured 182W/184W for Eoarchean rocks from the Itsaq Gneiss Complex (3.8–3.7 Ga pillow meta-basalts, a meta-tonalite, and meta-sediments) and Acasta Gneiss Complex (4.0–3.6 Ga felsic orthogneisses) to assess possible W isotopic heterogeneity within the silicate Earth and to constrain W isotopic evolution of the mantle. The data reveal that 182W/184W values in the Eoarchean samples are uniform within the analytical error and indistinguishable from the modern accessible mantle signature, suggesting that the W isotopic composition of the upper mantle has not changed significantly since the Eoarchean era. The results imply either that chemical communication between the mantle and core has been insignificant in post-Hadean times, or that a lowermost mantle with a distinctive W isotope signature has been isolated from mantle convective cycling. Most terrestrial rock samples have a 0.2e142Nd/144Nd higher than the chondrite average. This requires either the presence of a hidden enriched reservoir formed within the first 30 Ma of the Solar System, or the bulk Earth having a ∼ 5% higher Sm/Nd than the chondrite average. We explored the relevance of the 182Hf–182W isotope system to the 146Sm–142Nd isotope system during early silicate differentiation events on Earth. In this context, we demonstrate that the lack of resolvable 182W excesses in the Itsaq rocks, despite 142Nd excesses compared to the modern accessible mantle, is more consistent with the view that the bulk Earth has a non-chondritic Sm/Nd. In the non-chondritic Sm/Nd Earth model, the 182W–142Nd chronometry constrains the age of the source mantle depletion for the Itsaq samples to more than ∼ 40 Ma after the Solar System origin. Our results cannot confirm the previous report of 182W anomalies in the Eoarchean Itsaq meta-sediments, which were interpreted as reflecting an impact-derived meteoritic component.

The Cretaceous Luobusa Ophiolite is a tectonic slice less than 1.2 km thick. The structurally underlying unit is the Tertiary Luobusa Formation and the overlying unit is composed of feebly metamorphosed Triassic sedimentary rocks. The top and bottom contacts of the ophiolite dip gently to the south. The major part of the Luobusa Ophiolite is mantle peridotite, including podiform chromitite. This chromitite has received much attention because it contains an ‘unusual mineral assemblage’ which includes diamond and moissanite. A serpentinite melange zone, including clasts of basaltic and sedimentary rocks, occurs underneath the mantle peridotite. Mesoscopic–microscopic structures were observed in the sheared rocks. Shear-indicating structures (C′-type shear bands and σ-type porphyroclasts) in the rocks near the top and bottom boundaries of the Luobusa Ophiolite show consistent top-to-the-north (or northeast) reverse displacement. The results reveal that the Luobusa Ophiolite was overturned and intercalated into an imbricate structure. The thrust faults on the top and bottom of the ophiolite can be correlated with north-vergent back-thrusting which was associated with crustal shortening along the Main Central Thrust due to the continued northward movement of India, after the welding of India to Asia.

A suite of Early Paleozoic island arc volcanic rocks, consisting mainly of basaltic lavas and some intermediate-silicic rocks, crops out in the North Qaidam basin, northeastern Tibet Plateau. These rocks have been extensively metamorphosed under greenschist facies conditions, and hence differ from the older Proterozoic intermediate-mafic volcanic rocks, which have generally experienced amphibolite facies metamorphism. The Early Paleozoic volcanic rocks are divided into three groups based on their geochemical characteristics: (1) VTG-I, consists of island arc tholeiitic basalts, basaltic andesites and andesites that crop out in Jilusu and Shuangkoushan; (2) VTG-II, which are high-Al, alkaline and sub-alkaline basalts in Jilusu; and (3) VTG-III, an assemblage of highly depleted, MORB-type basalts, andesites and dacites that occurs mostly in Shuangkoushan. Groups VTG-I and -II are considered to be the products of mature island arcs produced in two stages. In the first stage, following initiation of ocean–continent subduction, the island arc tholeiites were generated by partial melting of the subsiding oceanic crust and mantle wedge beneath the island arc. As subduction progressed and accelerated, calc-alkaline and high-Al basalts were formed and the crust beneath the island arc was thickened. The highly depleted MORB-type lavas (VTG-III) have boninitic affinities and are believed to have been generated from depleted mantle material modified by subduction zone fluids, possibly in the fore-arc region. The island arc tholeiites are dated at 514.2±8.5 Ma whereas UHP eclogite in the North Qaidam Belt has been dated at 494 Ma. These ages suggest that ocean–continent subduction took place in the North Qaidam Basin in the Early Paleozoic and was followed shortly by continent–continent collision and subduction, which produced the UHP rocks.

In situ X-ray diffraction measurements on a calcium aluminosilicate (CAS) phase have been carried out using a laser-heated diamond anvil cell up to a pressure of 44 GPa, employing a synchrotron radiation source. CAS is the major mineral formed from sediments subducted into the Earth's mantle. The sample was heated using a YAG laser after each pressure increment to relax the deviatoric stress in the sample. X-ray diffraction measurements were carried out at T = 300 K using an angle-dispersive technique. The pressure was calculated using an internal platinum metal pressure calibrant. The Birch–Murnaghan equation of state for the CAS phase obtained from the experimental unit cell parameters showed a density of ρ 0 = 3.888 g/cm 3 and a bulk modulus of K 0 = 229 ± 9 GPa for K ′ 0 = 4.7 ± 0.7. When the first pressure derivative of the bulk modulus was fixed at K ′ 0 = 4, then the value of K 0 = 239 ± 2 GPa. From the experimental compressibility, the density of the CAS phase was observed to be lower than the density of co-existing Al-bearing stishovite, calcium perovskite, calcium ferrite-type phases, and (Fe,Al)-bearing Mg-perovskite in subducted sediments in the lower mantle. Therefore, the density of subducted sediments in the lower mantle decreases with increasing mineral proportion of the CAS phase.

In situ X-ray diffraction of orthorhombic perovskite, which is the dominant phase in the Earth’s lower mantle, was carried out on a sample with a KLB-1 peridotite composition up to a pressure of 80 GPa using a laser-heated diamond anvil cell (LHDAC) with X-rays from a synchrotron radiation source. At each pressure increment, the sample was heated using a YAG laser to relax the deviatoric stress in the sample. The bulk modulus of the orthorhombic perovskite, which contained FeO, Al 2 O 3 , TiO 2 , CaO, and Na 2 O, was nearly equal to, or slightly larger than that of pure MgSiO 3 perovskite. The density of the KLB-1 peridotite at the top of the lower mantle estimated using thermoelastic parameters, is in good agreement with a density profile (PREM) determined from seismic observations. The KLB-1 peridotite composition is, therefore, consistent with the bulk composition of the upper part of the lower mantle.