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Dating of igneous rocks from paleo-island arc complexes of orogenic belts makes it possible to determine the precise timing of subduction processes that occurred during the formation of the orogen. Within the central (East Transbaikal) part of the Mongol–Okhotsk orogenic belt, the Kamenka island-arc terrane is an example of such a complex. Its intrusive part is included into the Bereya complex, represented by a gabbro-diorite-tonalite-plagiogranite series of rocks demonstrating subduction geochemical characteristics. The dating of zircons from acidic rocks of this complex by the U–Pb classical method showed that they were formed in a narrow time interval of 203 ± 1–205 ± 1 Ma, which corresponds to the Norian–Rhaetian boundary of the Late Triassic. Taking into account the previously obtained age of the diorites (254 ± 5 Ma), the timing of formation of the entire series of the intrusive rocks is about 50 Ma, thus indicating the probable subduction along the northern (in modern coordinates) margin of the Mongol–Okhotsk Paleocean under the Siberian paleocontinent in the Late Permian – Late Triassic. The diorites of the first phase have positive values of εND(254 Ma) = 3.2–3.6 (TNd(DM) = 879–994 Ma), and the plagiogranites have ɛND(205 Ma) = 2.3–3.5 (TNd(DM) = 859–1028 Ma), which points to the relationship between these rocks and the substance of the depleted mantle source and is consistent with the Sm–Nd isotope characteristics of the juvenile crust of the Central Asian orogenic belt. [ABSTRACT FROM AUTHOR]

Abstract\nKEY POINTSNew allanite geochronology is presented for four mineral deposits in the Mount Isa Inlier (SWAN, Mary Kathleen, Koppany and Elaine Dorothy). The data indicate the occurrence of multiple phases of allanite formation: one at 1732 ± 8 Ma at Koppany, one at ca 1520 Ma at Mary Kathleen, Koppany and SWAN, and one at ca 1473 Ma at Mary Kathleen and Elaine Dorothy associated with vein calcite. In the Mary Kathleen–Koppany–Elaine Dorothy skarn system, there are chemical and textural differences between the three allanite generations; the ca 1520 Ma generation formed by dissolution–reprecipitation of 1732 Ma allanite, with no addition of externally sourced rare earth elements, as shown by the identical Nd isotopic compositions of these two populations. Allanite at SWAN yielded a 207Pb/206Pb ID-TIMS age of 1519.6 ± 1.1 Ma; its homogeneity, low common Pb contents and near-concordance make it a suitable reference material. Repeated remobilisation of rare earth elements in the Mary Kathleen system is surprising, given the widely accepted low solubility of these elements, but may have been restricted in spatial extent.New ages for allanite formation at four REE-rich deposits near Mount Isa.Some localities show multiple generations of allanite with distinct compositions.Nd isotopes link these generations to each other and to the source of the ore-forming fluids. [ABSTRACT FROM AUTHOR]

The Canindé Domain is crucial for understanding the pre-collisional events in Sergipano Belt, Borborema Province, especially during the Late Stenian/Early Tonian (740–680 Ma). We present thermobarometric, geochronology, and isotopic studies of the metavolcanosedimentary rocks of the Novo Gosto unit. The calculated metamorphic conditions resulted in a range of T: 600–740°C and P: 3.5–10.0 kbar for non-mylonitic amphibolites and values of T: 636–808°C and P: 7.0–12.0 kbar for mylonites, both of amphibolite facies. The minimum metamorphic conditions imprint in these rocks are T: 390°C and P: 2.5 kbar, indicating retrometamorphism in greenschist facies. The probable age of the peak metamorphic event was obtained in zircon rims from a quartzite at 692 ± 8.5 Ma. U-Pb detrital zircon and Nd model ages of the metasedimentary rocks point out Early Tonian as primary source rocks. Subordinate contributions of Mesoproterozoic, Paleoproterozoic, and Neoarchean sources were also recognized. These primary sources are related to Cariris Velhos event rocks, whereas the subordinate sources are from the Pernambuco-Alagoas superterrane. Early Tonian and Late Stenian ages were recognized for the first time in the Canindé Domain, with U-Pb zircon ages of 1005 ± 3 and 989 ± 6 Ma in amphibolites and mylonitized granites, mostly outcropping at the southwestern limit of the area. New ages were also obtained in the Novo Gosto surrounding intrusions: Canindé Layered Gabbroic Intrusion (~718 Ma), Garrote (~715 Ma) and Curralinho/Boa Esperança (~708 Ma) metagranites, and Gentileza metavolcanic rock (~700), which integrate the early pre-collisional magmatism of the Sergipano Belt (~740-680 Ma). Finally, U-Pb zircon ages were obtained in the Poço Redondo Domain, potential source area of the Novo Gosto metasedimentary rocks, resulting in ages of 957 ± 11 and 988 ± 15 Ma. The new data bring perspective to future correlations with adjacent belts and the understanding of the structuration of West Gondwana during the Brasiliano-Pan-African Orogeny. [ABSTRACT FROM AUTHOR]

Silicate weathering has long been considered to maintain the Earth's climate stability, yet how the weathering responds to the late Cenozoic cooling remains unclear, partly because of the complicated factors which obscure the weathering records. Large rivers in East Asia integrate continental weathering history, but how the source-to-sink system evolution affected the weathering signals need to be clarified. We compile proxy data of Nd isotopes, zircon ages and Chemical Index of Alteration (CIA) in East Asian margin and source terranes, along with new proxy data from core CSDP-2 in the shelf region, to understand the large river evolution and assess their influence on weathering proxy records. The median εNd values of East Asian marginal sediments increased from −18.8 in pre-3.6 Ma period to −11.3 since the 1.0 Ma, corresponding to the isotopic signatures in North China Craton and Northeastern (NE) Tibetan Plateau/Loess Plateau terranes, respectively. The zircon ages further confirmed the provenance shift, hinting that the modern-like Huanghe (Yellow River) system has been fully integrated during early Pleistocene, no later than ∼1.0 Ma. This integration facilitated the sediment transportation from plateaus into the continental margin. Consequently, the CIA records in marginal regions show a more significant decrease than other Asian regions, within the context of Plio-Pleistocene cooling. Our study found that the upland expansion of large river system and global cooling jointly controlled the decline in the weathering intensity records, highlighting the importance to understand the evolution of source-to-sink system before interpreting the weathering signals from the continental margin sediments. • Detrital Nd isotopes and zircon ages are compiled to constrain the sediment sources in East Asian margin. • The sediment provenance shifted from proximal lowlands to uplands, links to the Huanghe integration. • Large river expansion in East Asia amplified the decline in weathering intensity proxy records since the Pliocene. [ABSTRACT FROM AUTHOR]

The Fraser Zone of the Albany-Fraser Orogen of Western Australia contains an extensive suite of mafic and mafic–ultramafic intrusions. This includes the Nova-Bollinger intrusions (ca 1300 Ma), which host economic Ni-sulfide mineralisation, a prime example of magmatic sulfide liquids emplaced into the deep crust under ambient granulite facies conditions. Sulfur, Sr and Sm–Nd isotopes, and trace elements have been used to evaluate the role of crustal contamination of the parental magmas to Nova-Bollinger and other sulfide-bearing mafic–ultramafic bodies within the Fraser gabbro suite. All ore types have δ34S values between +1.6 and +8.0‰ VCDT with a positively skewed distribution and a median value of +2.3‰ VCDT, anomalous relative to uncontaminated mantle values near 0‰ VCDT. No significant Δ33S anomalism was observed. The initial 87Sr/86Sr and 147Sm/143Nd ratios of most of the Nova-Bollinger igneous rocks have an age of formation of 1300 Ma, which is similar to those of CHUR1300Ma and record limited contamination by lower continental crustal material. The country rocks of the Snowys Dam Formation, locally enriched in iron and sulfur, are likely candidates as crustal contaminants. These metasedimentary sulfides show similar ranges in values for both δ34S and Δ33S to the ores, but their Sr isotopic range is greater than observed in the host intrusions at Nova-Bollinger and in most of the other sampled intrusions. Bollinger globular sulfides with ɛSr values of 63.1 and 144.5 and ɛNd values of −5.7 and −1.8 are suggestive of localised crustal contamination from adjacent wall rock marbles, but otherwise high ɛSr country rocks do not appear to have been dominant contaminants. Bulk assimilation of the country rocks, as modelled in both silicate and sulfide portions of the system, of up to 30% contamination of a primitive mantle melt by siliceous country gneisses, would have been sufficient to produce the degree of crustal contamination recorded in the Nova-Bollinger ores, and more regionally within the Fraser gabbros. Beyond indications that S was crustally derived, it is not possible to identify a specific source, but Snowys Dam sediments are the most likely. There is no compelling evidence for Archean S in the ores, unsurprisingly given the mid-Proterozoic age. It is likely that much of the contamination of the magma and generation of sulfide liquid took place during lateral flow through linked sill complexes within the deeply buried Snowys Dam metasediments, prior to the emplacement of the magmas to form the orebodies. Nova-Bollinger Ni–Cu–Co sulfide ores have δ34S values between +1.6 and +8.0‰ VCDT, with a median value of +2.3‰ VCDT, anomalous relative to uncontaminated mantle values but similar to the range in the country rock metasediments. Values are consistent with equilibration of sulfide xenomelts at R factors of 200–700. There is no detectable mass-independent fractionation of δ33S in the Nova-Bollinger ores. The initial 87Sr/86Sr and 147Sm/143Nd ratios of most of the Nova-Bollinger igneous rocks at the age of formation of 1300 Ma are similar to those of CHUR1300 Ma and record contamination of a primitive mantle melt by up to 30% lower continental crustal material. Unusual globular ores at Bollinger have anomalous ɛSr indicating localised contamination from adjacent wall rock marble; however, this contamination is not pervasive through the orebody. It is likely that much of the contamination of the magma and generation of sulfide liquid took place during lateral flow through linked sill complexes within the deeply buried Snowys Dam metasediments, prior to the emplacement of the magmas to form the orebodies. [ABSTRACT FROM AUTHOR]

The Pauzhetka Caldera (27 × 18 km) was formed in the South Kamchatka during the Golygin Ignimbrite eruption (420–440 ka), the largest known eruption in the region in the past 1 Myr. The eruption was preceded by the 3 Ma-old mafic and intermediate volcanism. After the caldera-forming eruption, a variety of products, from basalt to rhyolite, were ejected within the caldera. For understanding the origin of voluminous silicic magmatism in thin mafic South Kamchatka crust, we used geochemical and isotope data. Our research has characterized the major and trace element composition of Golygin ignimbrite, intra-caldera hydrothermally altered deposits, pre-caldera (Mt. Orlinoe Krylo, Mt. Klyuchevskaya) and post-caldera (Kambalny Ridge, Chernye Skaly) eruptive centers. The Sr–Nd isotope composition of the Golygin ignimbrite and some eruptive post-caldera products was investigated. The isotope variations indicate that parental magmas for all rocks of the Pauzhetka area were obtained from a weakly evolved source derived through fluid-assisted melting of a subducted slab. Geochemical data support that the formation of most magmas of the Pauzhetka caldera was mainly controlled by fractional crystallization in the lower to middle crust. MELTS-modelling agrees with geochemical data. The fractional crystallization of Kambalny basalt with 2 wt % H2O at 6 kbar provides the best fit to the observed composition of the Golygin dacite. [ABSTRACT FROM AUTHOR]

A bulk composition for the upper continental crust (UCC) is often constructed using sediments and associated river waters, which are both assumed to efficiently average contributions from a multitude of bedrock components. Many potential biases, however, exist in sedimentary systems, rendering this approach less than optimal. In order to further investigate these phenomena, we estimate the bulk Pb, Sr, and Nd isotopic composition of the Australian UCC using archived National Geochemical Survey of Australia (NGSA) regolith samples, collected so as to represent 1186 catchments covering an area approaching 6.17 million km2. The size of the dataset and its systematic nature provide a high level of confidence that it is statistically representative, while the relative tectonic stability of the Australian continent, preserving a wide range of sample ages and lithologies, suggests that the data may form a reliable proxy for the global bulk UCC composition. Calculated median values for the Pb isotope system based on 1229 NGSA samples (some catchments were sampled in duplicate) representing an area of 5.65 million km2 (206Pb/204Pb = 18.838, 207Pb/204Pb = 15.686, 208Pb/204Pb = 38.989, 207Pb/206Pb = 0.83210, 208Pb/206Pb = 2.0669) are comparable to previous estimates of the global UCC, providing a strong validation of our methodology. We believe these new global bulk UCC values to be considerably more robust, however, given the much larger and more spatially representative dataset they derive from. In contrast, however, our Sr and Nd isotope results (median 87Sr/86Sr = 0.7377, 143Nd/144Nd = 0.511817), derived from significantly smaller subsets of the NGSA sample suite (576 and 93 samples, respectively, in turn representing areas of 2.6 million and 490 thousand km2), are considerably more radiogenic/evolved than previous UCC estimates. We discuss potential reasons for these discrepancies and conclude that the present data appear to confirm the possibility of multiple potential biases in current global assessments of bulk UCC isotopic values, related to methodological approach, over-sampling of younger, tectonically active regimes, and significant non-gaussian behaviour in sedimentary datasets. • Continental-scale isotopic analysis of regolith samples. • Provide a good proxy for the Upper Continental Crust (UCC) composition. • Pb isotope ratios in agreement with previous global estimates. • Sr and Nd isotopes show more isotopically evolved ratios than previous estimates. • Further investigation of global UCC compositions appears to be warranted. [ABSTRACT FROM AUTHOR]

The near closure of the Panama Seaway during the late Miocene resulted in the modification of deep-ocean currents and the formation of modern oceanic circulation. However, it is unclear how this closure impacted the north Pacific western-boundary deep circulation since the late Miocene. Here, we combine Nd isotope records in the north Pacific and a newly developed water-mass proxy (amorphous Fe hydroxide content, AFHs) from the western Pacific to investigate deep-current evolution since the late Miocene. These proxies consistently indicate a significant deep water-mass change in the north Pacific at ∼5 Ma, reflecting shoaling of the Panama seaway that curtailed intermediate and deep-water exchange between the East Equator Pacific and Atlantic. Although intensification of Antarctic bottom water since ∼3.4 Ma (Northern Hemisphere Glaciation) has been widely documented, a decrease in western-boundary currents has occurred since ∼3 Ma. We suggest that this phenomenon is likely due to the increased mixing of south-ward and north-ward deep western-boundary currents in the north Pacific. This water mass mixing may have a significant impact on the western Pacific biogeochemical cycling. • Records of amorphous Fe hydroxide from a Fe-Mn nodule elucidate western Pacific deep-current evolution since the late Miocene. • Nd isotope records indicate east-west mixing of deep-waters in the north Pacific before the closure of the Panama seaway. • Nd isotope and amorphous Fe hydroxide results suggest enhanced south-north mixing of deep western-boundary currents in the north Pacific since ∼3 Ma. [ABSTRACT FROM AUTHOR]

The causes of the Mid-Pleistocene Transition, the shift from ~41-ky to 100-ky interglacial-glacial cycles and more intense ice ages, remain intensely debated, as this fundamental change occurred between ~1,250 and 650 ka without substantial changes in astronomical climate forcings. Recent studies disagree about the relative importance of events and processes in the Northern and Southern Hemispheres, as well as whether the shift occurred gradually over several interglacial-glacial cycles or abruptly at ~900 ka. We address these issues using a north-to-south reconstruction of the Atlantic arm of the global meridional overturning ocean circulation, a primary means for distributing heat around the globe, using neodymium (Nd) isotopes. Results reveal a period of intense erosion affecting the cratonic shields surrounding the North Atlantic between Marine Isotope Stages (MIS) 27 and 25 (~980 and 950 ka), reflected by unusually low Nd isotope ratios in deep North Atlantic seawater. This episode preceded a major ocean circulation weakening between MIS 25 and 21 (950 and 860 ka) that coincided with the first ~100-ky-long interglacial-glacial onset of Northern Hemisphere glaciation at around 2.4 to 2.8 Ma. The data point to a Northern Hemisphere-sourced initiation for the transition, possibly induced through regolith loss and increased exposure of the crystalline bedrock, which would lead to increased friction, enabling larger ice sheets that are characteristic of the 100-ky interglacial-glacial cycles. [ABSTRACT FROM AUTHOR]

[Display omitted] • Apatite REE + Y variations are determined primarily by elemental partitioning. • Mineral fractionation can cause apatite Sr, Pb, Th, and U variations. • Apatite Nd isotopes have the potential to serve as geological indicators. Compositional variations of apatite are mainly determined by parameters such as partition coefficients and the composition of parental magma. However, the relative importance of these parameters in relation to apatite geochemistry in different lithologies of magmatic rocks is not well constrained. In this study, six Mesozoic (219–154 Ma) mafic–felsic intrusions from the eastern North China Craton, were selected for detailed apatite microanalyses (trace elements and Nd isotopes). Apatite from the studied intrusions has uniform textures in the cathodoluminescence image. They exhibit high abundances of rare earth elements (REE) and are characterized by light REE enriched patterns, indicative of a magmatic origin. Alongside compiled apatite data, these findings suggest that compositional variations of REE + Y in apatite from mafic to felsic magmatic rocks are controlled primarily by elemental partitioning between apatite and melts. The competitive crystallization of other accessory minerals prior to apatite can be responsible for compositional variations of Sr, Pb, Th, and U. New Nd isotope data for apatite are discussed and compared with whole-rock Nd and zircon Hf isotope data for the same sample. The Nd isotopic compositions between the whole-rock and apatite are identical. The integrated dataset provides an alternative interpretation for the isotopic decoupling between apatite Nd and zircon Hf isotope systems. In conclusion, apatite REE concentrations and Nd isotopes have the potential to serve as geological indicators. [ABSTRACT FROM AUTHOR]

• First comprehensive study of Nd stable isotopes in wide range of terrestrial basalts. • Partial melting modelling demonstrates that δ146Nd is unfractionated upon melting. • Confirmation the bulk silicate Earth and chondrites have the indistinguishable δ146Nd. • Variations in δ146Nd induce no analytical artefacts when calculating radiogenic isotope compositions. Accurate knowledge of the composition of Earth's major chemical reservoirs is fundamental for constraining all modern geochemical cycles. Basaltic rocks provide a direct way of sampling the composition of Earth's inaccessible interior. Here, we present the first comprehensive neodymium (Nd) stable isotope analyses for a global compilation of mid-ocean ridge, ocean island, continental intraplate and island arc basalts using a double-spike technique. In these primitive magma compositions magmatic differentiation has no resolvable effect on δ146/144Nd. Mid-ocean ridge basalts possess an extremely homogenous δ146/144Nd with an average composition of δ146/144Nd = −0.025 ± 0.013‰ (±2 s.d.; n = 33). Ocean island and continental intraplate magmas possess more variable compositions (δ146/144Nd = 62 ppm) that are related to the variable incorporation of recycled components in their source regions. Island arc basalts from New Britain (δ146/144Nd = 61 ppm) reflect the complex interplay between source composition, degree of melting and slab-fluid inputs. Variations are uncorrelated with indicators of magmatic differentiation or slab-fluid addition, rather increasing δ146/144Nd with slab depth is attributed to a higher proportion of metasomatized sub-arc mantle in the melting region. A partial melting model for Nd stable isotopes has been constructed using Nd O force constants calculated using the Born-Lande approximation. Melting of typical mantle peridotite will induce no resolvable fractionations of Nd stable isotopes (Δ146/144Nd melt-mantle < 0.003‰ at 1200 °C). The lack of fractionation upon partial melting means primitive magmatic rocks can be used to calculate the average composition of the bulk silicate Earth (BSE), which is δ146/144Nd = −0.024 ± 0.031‰ (±2 s.d.; n = 80). This BSE composition is indistinguishable at the 95 % confidence level from that of chondritic meteorites, the building blocks of Earth. Therefore, sequestration of significant quantities of Nd into the sulfide matte did not occur, this combined with recent experimental evidence for no Sm-Nd fractionation means the sulfide matte cannot be considered a plausible solution for the 142Nd/144Nd offset between the Earth and chondrites. Despite resolvable variations in δ146/144Nd from the canonical value being widespread in terrestrial materials, they are not large enough to generate the difference in radiogenic Nd isotope ratios between the BSE and chondrites. [ABSTRACT FROM AUTHOR]

• Shikebutai iron formations was chemical sediments of authigenic origin. • This Late Carboniferous-aged IFs intimate association with submarine volcanic activity. • Enhanced hydrothermal activity can shape the marine redox landscape and of the development ferruginous conditions. Iron formations (IFs) are iron-rich chemical sediments that were widespread throughout the Precambrian. The deposition of IFs has provided key evidence about the prevalence of anoxic and ferruginous marine conditions throughout Earth's history. Here, we describe the Shikebutai IF, hosted in a Late Carboniferous volcano-sedimentary sequence in the Western Tianshan region of northwest China. The IF is largely composed of hematite, jasper, and siderite. The chemical composition of the Shikebutai IF is dominated by Fe 2 O 3 and SiO 2 , and very low concentrations of Al 2 O 3 , TiO 2 , Th, Nb, and Sc were observed, indicative of an authigenic origin. High Fe/Ti, Fe/Al, Co/Zn, and Ni/Zn ratios, along with positive Eu anomalies and ε Nd (t) values point to a significant submarine volcanic and hydrothermal contribution. The absence of negative Ce anomalies and heterogeneous δ56Fe values suggest progressive oxidation of hydrothermally sourced Fe(II) and deposition in an anoxic to low oxygen basin. Low P/Fe ratios in the Shikebutai IF, comparable to those found in the Precambrian, are consistent with Si inhibition of P sorption and P drawdown with high hydrothermal inputs. The intimate association of this Late Carboniferous IF with submarine volcanic activity suggests an origin that is analogous to Precambrian Algoma-type IFs. Further, the Shikebutai IF provides evidence for an episode of basin-scale anoxic, ferruginous conditions coinciding with the generally well-oxygenated deep oceans of the Phanerozoic, with deposition driven by enhanced submarine volcanic and hydrothermal activity in the Western Tianshan region during the Late Carboniferous. This demonstrates how, even with near modern surface oxygen levels, enhanced hydrothermal activity can shape the marine redox landscape and cause the development of ferruginous conditions without quantitative sulfate drawdown. [ABSTRACT FROM AUTHOR]

Eoarchean mantle and mantle-derived rocks can provide primary information on geodynamic processes operating on the early Earth. This study combines new petrological observations, comprehensive major and trace element data as well as Lu-Hf and Sm-Nd isotope compositions of >3.81 Ga ultramafic rocks from the Itsaq Gneiss Complex (IGC) in southern West Greenland. The sample set includes mantle peridotites and associated amphibolites from the Narssaq ultramafic body (Færingehavn terrane) and from the region south of the Isua supracrustal belt (Isukasia terrane). Lutetium-Hf whole rock age regression lines mainly yield Eoarchean ages of ca. 3.9–3.8 Ga, in good agreement with minimum ages inferred from field relationships (>3.8 Ga). Major and trace element signatures, the Lu-Hf isotope inventory as well as most major elements, MREE, HREE, and HFSE were only slightly disturbed during metamorphic overprint. Nearly flat primitive mantle-normalized REE patterns obtained for the mantle peridotites resemble those of refertilized modern abyssal peridotites and may reflect re-enrichment of initially depleted peridotite by melt-like subduction components, as also indicated by Th-HFSE-REE characteristics. Based on a simple evolution-model for the investigated mantle rocks, we suggest that the compositions are best explained by partial hydrous melt depletion in the spinel stability field, followed by refertilization by low quantities of adakite-like melt. Altogether, the geochemical data can be put in the framework of a geodynamic model, where Eoarchean mantle underwent significant melt extraction and subsequent re-fertilization by subduction-like components. Based on this finding, we propose that the Eoarchean mantle peridotites from SW Greenland represent remnants of a mantle wedge, confirming that subduction-like processes were in operation since at least the Eoarchean. [ABSTRACT FROM AUTHOR]

The Nové Město Unit and the northern part of the Zábřeh Unit comprise back-arc basin mafic rocks metamorphosed during Variscan times. In both units, nearly identical metabasites comprise variously enriched tholeiites (from N-MORB to transitional E-MORB-OIB), high-Ca, low-silica boninites and low-Ti tholeiites. The tholeiites (Ti/V: 22–58, εNd540: + 7.6 to − 4.7) represent 10–15% melting at ca. 30–60 km and temperatures of 1380–1230 °C of a depleted MORB mantle-type (DMM) wedge heterogeneously modified shortly before fusion by OIB-like melts (enriched mantle possibly of EM1–EM2 type) presumably derived from decompression melting of upwelling asthenosphere. Much less common meta-boninites (Ti/V: 6–23, εNd540: + 6.7 to − 2.9) formed by 15–25% re-melting of residual mantle (DMM after ~ 15% melt extraction) at depths of 40–65 km and temperatures of ~ 1420–1300 °C. Scarce low-Ti meta-tholeiites (Ti/V: 18–19, εNd540: + 7.1) resulted from < 10% melting of an unenriched DMM-type source or re-melting of residual mantle (after < 15% of former melting). Trace elements and Nd isotope compositions imply random fluxing of tholeiitic- and boninitic magma sources by components released from a subducted slab. The metasomatic enrichment (Th, LREE–MREE) was induced not only by sediment-derived melts but also by fluids supplied by subducted sediments or juvenile crust. The Nové Město–Zábřeh association of metabasites points to an easterly prolongation (in present-day coordinates) of the Cadomian subduction system of the Teplá–Barrandian. Boninite-type magmatism and OIB-like input into mantle beneath an extensional back-arc basin suggest an upflow of hot asthenosphere through subducted ridge (slab window) followed by a cessation of subduction zone activity. [ABSTRACT FROM AUTHOR]

Geochemical and Nd isotope data are presented for Palaeoproterozoic ultramafic to mafic rocks and granitoids which are associated with volcanic rocks in the southern part of the Ashanti greenstone belts of Ghana. The Prince's Town granitoids display subduction‐zone geochemical features, with some showing signatures similar to high‐SiO2 adakites (HSA). Their initial εNd (2.1 Ga) values range from −1.01 to +2.92, and they have TDM2 of 2.17–2.51 Ga. The gabbros show slightly LREE‐depleted and ‐enriched patterns, Th–U troughs, negative Nb, Zr–Hf and Ti anomalies, spikes in Sr and Pb, have εNd (2.1 Ga) values ranging from −1.23 to +5.23, and TDM2 values from 2.08 to 2.57 Ga. The Ahama ultramafic body is characterized by two groups of pyroxenites. Both groups show LREE enrichment patterns, display Th–U and Nb–Ta troughs, minor or pronounced negative Zr–Hf and Ti anomalies. However, the Group I pyroxenites exhibit minor Ce anomalies and lower total REE contents (28.1–32.8 ppm) whereas Group II pyroxenites show significant negative Ce anomalies and relatively higher total REE contents of 57.1–124 ppm. The pyroxenites show negative initial εNd (2.1 Ga) values (−0.58 to −5.68) and have TDM2 values of 2.52 to 2.75 Ga. The pyroxenitic and gabbroic rocks were most likely originated from a subduction‐related lithospheric mantle. The Aketakyi ultramafic–mafic complex is made up of mainly cumulate dunite, harzburgite, pyroxenites, and gabbro. The rocks display LREE‐depleted to flat patterns with low total REE contents (1.71 to 22.3 ppm) and demonstrate a supra‐subduction affinity. They show high positive initial εNd (2.1 Ga) values (+3.69 to +4.93), and TDM2 values of 1.99 to 2.04 Ga, which suggest that they were derived from depleted mantle magmas and were juvenile at their time of formation. The Nd isotopic data provides evidence for a possible contamination of the juvenile Birimian crust of the southern Ashanti belt by some amount of a pre‐Birimian (or Archaean?) crustal material. The trace element and isotopic signatures as well as the field relations of the studied granitoids and mafic–ultramafic rocks show they were derived through supra‐subduction‐related magmatism during the Palaeoproterozoic. [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD) has been proposed as a potential source of strategic rare earth elements (REEs) due to its high concentrations (>1000 µg/L) of dissolved REEs, as well as the middle rare earth element (MREE) enriched pattern exhibited by both coal mine- and metal mine-derived AMD, in which some of the most energy-critical REEs are significantly concentrated. However, the source of REEs and the origin of the MREE enrichment observed in AMD discharges is poorly understood; suggestions include dissolution of MREE-enriched surface coatings, fractionation by colloids, solid-liquid exchange reactions, incongruent dissolution of pyrite, and selective leaching of MREE-enriched phases. Filtration experiments on acidic to circumneutral AMD (unfiltered to <0.002 µm) indicate that REEs are in a dissolved state. Thus, colloids are not a significant carrier of REEs in these samples and are not responsible for the observed MREE-enriched patterns. The similarity of MREE-enriched patterns exhibited by AMD to those of laboratory sulfuric acid (simulated AMD) leachates of corresponding overburden samples suggest that these lithologies are a major contributor of REEs to AMD. Isotopes of strontium (87Sr/86Sr) and neodymium (143Nd/144Nd) in AMD discharges are distinct from whole-rock values of associated lithologies, but fall within the range of values of the leachates. Whole rocks, leachates, and AMD define a trend on a Sm-Nd isochron diagram consistent with the ∼310 Ma depositional age of the coal. These data suggest that MREE enrichment of AMD results from preferential leaching of a readily dissolvable, MREE-enriched mineral phase, most likely apatite or a related phosphate phase, that formed during or shortly after deposition of the coal and associated units. [ABSTRACT FROM AUTHOR]

The Yellowstone hotspot track in the northwestern US has a 17-myr history that began with eruption of the voluminous Columbia River basalts (CRB), and produced an eastward track with the bimodal rhyolite and basaltic eruptive centers of the Snake River Plain (SRP) as the North American Plate drifted westwards. We have generated the first Hf isotopic data on basalts in this large igneous province along with bulk-rock trace-element abundance patterns and Sr-Nd isotopic ratios to assess the hypothesized kinship with co-located rhyolites throughout the hotspot track. The isotopic compositions for all three elements span much of the compositional range observed in mantle-derived basalts worldwide. Varying between a high of +11.3 in parts of the CRB and a low of −8.3 in some of the late SRP basalts, the new ε Hf values are geographically controlled, similar to the shift first documented with Sr and Nd isotopes across the "0.706 Sr line," which marks the boundary between thin- accreted young ocean lithosphere and arc terranes in the west to thick, old cratonized crust in the east. This observation shows that there is significant lithospheric control on the isotopic compositions of both basalts and rhyolites associated with the Yellowstone hotspot track. Modeling of assimilation and fractional crystallization (AFC) processes in seven basaltic lava flows filling the 2-Ma Big Bend Ridge Caldera at Mesa Falls, Idaho, near the eastern end of the hotspot track suggests that the crustal contribution to the Nd and Hf concentration budgets increases systematically with time and was significant. A comparison of new and previously published bulk-rock major-oxide concentrations (e.g., the alkalis Na 2 O and K 2 O) with our previously published data for H 2 O, Cl, F and S in olivine-hosted melt inclusions suggests that the volatiles are sub-crustal, possibly from the lithospheric mantle, and degas extensively during magma ascent and crystallization. • New trace element and Nd-, Hf- and Sr-isotope data for Yellowstone hotspot and Columbia River basalts. • First Hf isotopic ratios on basalts in region agree with new and previous Nd and Sr isotopic results that crustal thickness influences composition. • Seven basaltic lava flows in Big Bend Ridge Caldera show crustal contamination grew in significance through time. • Isotopic data compared with olivine-hosted melt inclusion volatile compositions indicate a sub-crustal source for H 2 O. [ABSTRACT FROM AUTHOR]

Abstract The recurrent deposition of organic-rich sapropel layers in the eastern Mediterranean Sea (EMS) has been attributed to deep-water stagnation and enhanced biological production. However, the underlying climatic interactions, paleoceanographic processes, and associated ventilation dynamics are still debated. Here, we present a basin-wide reconstruction of circulation systematics during sapropel S1 formation (∼10.8–6.1 kyr BP), using the Nd isotope composition (ε Nd) as paleo-seawater tracer. Our ε Nd data from fish debris and foraminifera tests are remarkably radiogenic compared to today, and spatially and temporally constant. These results predominantly reflect enhanced Nile versus Atlantic contributions, and indicate that EMS deep-water stagnation prevailed below ∼800 m water-depth during S1 formation. Additional ε Nd records obtained from bulk sediment leachates show that such stagnation was preconditioned thousand(s) of years prior to S1 initiation by intensified Nile flooding, whereas it terminated with a basin-wide, deep-water renewal. In addition, decoupling of deep waters between the EMS and western Mediterranean Sea (WMS) is evident for the S1-period. Using a box-model for Nd in the EMS, the observed ε Nd distribution can be most adequately explained by a 2-fold increase in Nile discharge, and a 50% decrease in the EMS–WMS exchange that was mostly limited to the surface waters alone. The corresponding circulation during S1 was more sluggish and shallow for the EMS, but largely unaffected for the WMS. This implies that deep-water stagnation is a prerequisite for sapropel formation. Highlights • A basin-wide reconstruction of Mediterranean circulation during sapropel S1. • The most-reliable archive of paleo-seawater Nd isotopes – fish debris – is used. • Stagnation below ∼800 m depth in the eastern Mediterranean Sea (EMS) during S1. • Deep EMS and western Mediterranean Sea (WMS) were decoupled during S1. • S1 stagnation related to 2-fold increased Nile and 50% decreased EMS–WMS exchange. [ABSTRACT FROM AUTHOR]

Neodymium (Nd) isotopic composition (εNd) is an important tracer for water mass mixing and the reconstruction of past ocean circulation. To allow for a direct model‐data comparison, we have implemented Nd isotopes in the ocean component of the Community Earth System Model (CESM1.3). The model is able to capture the major features of the observed modern distribution of both εNd and Nd concentrations. Our model provides a useful tool for the interpretation of εNd reconstructions. For example, we show that in an idealized North Atlantic freshwater hosing experiment, εNd changes in the Atlantic are documenting primarily the changes in water mass mixing and are hardly affected by the concomitant and large changes in the marine biological productivity and organic matter fluxes. However, the hosing experiment also shows that the end‐member changes due to the change of ocean circulation can influence the interpretation of εNd in the Atlantic, depending on the location. The implementation of Nd, together with other existing tracers, such as δ18O, 231Pa/230Th, δ13C, and radiocarbon in the same model, can improve our understanding of past ocean circulation significantly. Plain Language Summary: The Climate model is an important tool to study past climate. However, previous model‐data comparison suffers from indirect comparison since reconstructions measures proxy records and climate model simulate physical variables, both of which have uncertainties and it is hard to address the model data discrepancies. To meet this challenge, we implement the Nd isotopes, which is more and more used in paleoceanography, in the ocean component of the Community Earth System Model (CESM). Our model is able to simulate εNd in good agreement with observations. With other isotopes, such as δ18O, 231Pa/230Th, δ13C, and radiocarbon in the same model, this isotope‐enabled CESM provides a powerful tool to improve the understanding of past ocean circulation changes. Furthermore, the hosing experiment suggests that the interpretation of εNd changes in the Atlantic as changes in the water mass mixing can be complicated by the changes in the end‐member values in some locations. Key Points: Nd isotopes are implemented in the CESM1, which simulate the Nd concentration and εNd in reasonable agreement with observationsIn idealized water hosing experiment, εNd changes in the Atlantic mainly reflect changes in the mixing between different water massesEnd‐member changes due to the change of ocean circulation can influence the interpretation of εNd in some locations [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • We use isotopic and geophysical data to map the location of a lithospheric boundary. • The boundary separates a Mesoarchaean and a Neoarchaean-Palaeoproterozoic terrane. • The boundary coincides with a low resistivity zone in mid-crust to upper mantle. • The position of the boundary is not reflected by potential field data. • Sub-vertical low resistivity and TMi lineaments reflect Proterozoic deformation. Abstract Major lithospheric boundaries play a fundamental role in localizing crustal deformation and metal enrichment in the crust. Their identification in poorly exposed terranes remains challenging and typically relies on a combination of sparse outcrop and drill hole data extrapolated using regional gravity and magnetic datasets. The high complexity in potential field data as well as the limited depth sensitivity to mostly upper to mid-crustal levels increases the ambiguity in identifying coherent lithospheric domains as well as the trans-lithospheric boundaries that cross into the subcontinental lithospheric mantle. Here we present a different approach using a combination of deep-probing magnetotelluric and seismic reflection methods, integrated with Nd isotope and inherited zircon ages of crustally-derived felsic igneous rocks, to locate and characterize a concealed Archean-Proterozoic lithospheric boundary within the Gawler Craton, South Australia. The boundary extends for approximately ∼600 km in the eastern part of the craton, from the supergiant iron oxide-copper-gold-uranium (IOCG-U) Olympic Dam deposit in the north to outcrops of the Kalinjala Shear Zone on southern Eyre Peninsula in the south. Using our approach we show a significant reduction in the uncertainty of the location of this boundary between these two end-points. While a range of locations are permissible based on potential field data across northern Eyre Peninsula, our integrated approach points towards a precise location east of previous interpretations, beneath the upper crustal Roopena Fault. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Carrancas Group chronostratigraphy: significant variations in the source. • Lower Unit: juvenile Palaeoproterozoic detritus. • Intermediate and Upper units: evolved Palaeoproterozoic and juvenile Mesoproterozoic. • Passive margin basin at the São Francisco craton's W-S margin facing an open sea. • Deposition: after 0.92 Ga. Main source: São Francisco craton. Abstract Sedimentary basins are, in many cases, the only preserved record of the geological processes active through geological time. These deposits preserve age, isotopic and geochemical signatures of the source rocks, providing insights into tectonic setting. In this context, we investigate the lithostratigraphy, provenance and tectonic environment of the Carrancas Group, a meta-sedimentary sequence characterised by a basal psammitic unit (Lower Unit) passing up into interbedded psammo-pelites (Intermediate Unit), which are overlain by a further psammitic unit (Upper Unit). This succession, along with the Canastra, Paranoá and Vazante groups (Brasília orogen), comprises a mature passive margin developed at the western-southern margin of the São Francisco craton during the Neoproterozoic. Detrital zircon U-Pb ages and Nd-Hf isotope data enable revised stratigraphic correlations across the basin, highlighting variations in the source of detritus. Deposition began after 0.92 Ga, with the sedimentation of the Lower Unit, with input of juvenile ∼2.1 Ga detritus (εNd t = −0.1 to +3.2) derived from the São Francisco craton. A marine transgression characterises the transition to the Intermediate Unit, which gradually covered over juvenile ∼2.1 Ga terrains and rendered them unavailable as possible source rocks for detrital zircons. Evolved Archaean-Palaeoproterozoic basement rocks, the Espinhaço Supergroup and evolved Neoproterozoic granitoids, all belonging to the São Francisco craton, acted as sources for the Intermediate and Upper units (U-Pb = 2.7 Ga to 0.9 Ga; εNd t = −10.4 to +7.1). The Goiás massif might also have acted as a source, providing juvenile Mesoproterozoic detritus. The sediments of the Upper Unit register a significant shift in source, with incoming of juvenile Mesoproterozoic and crustal 1.9 – 1.7 Ga detritus. This change in the ages of the detrital material may be related to exhumation of the Espinhaço Supergroup during the evolution of the passive continental margin basin. The whole-rock Nd T DM model ages become progressively younger from the base to the top of the sequence (Nd T DM = 2.6–1.8 Ga). The collisional events between Amazonian and São Francisco cratons and the Paranapanema block set the minimum age of deposition along this passive continental margin at around 0.67 Ga. [ABSTRACT FROM AUTHOR]

The Ylitornio area in northern Finland is a typical example of a poorly outcropping, multiply deformed, complex Precambrian terrain. U-Pb, Sm-Nd and geochemical data from metavolcanic, metasedimentary and plutonic rocks combined with structural data define the lithodemic units and tectonostratigraphy of the area. The Mellajoki, Martimo, Hosiojoki, Kierovaara and Uusivirka suites form the Ylitornio nappe complex. Although main thrust stacking had occurred between 1.921.89 Ga, later reverse faulting probably continued until 1.78 Ga. The Váystájá bimodal volcanic rocks (2.09-2.05 Ga) from the Martimo suite are plume-related EMORB-OIB rocks formed during a continent breakup. The Kaskimaa greywacke of the Martimo suite is inferred to represent sedimentation in a deepening rift basin in the continental margin. The coeval Hosiojoki felsic rocks with A-type affinity and the Kierovaara suite granites (2.00-1.98 Ga) represent dry melting of a dominantly 2.1-2.05 Ga contaminated mafic underplate, and hydrous melting of both the mafic underplate and a refractory lower crust of Archean age, respectively. The older rocks of the Uusivirka suite are early-collisional (1.92-1.91 Ga) and derived from poorly mixed local sources, whereas younger psammite-pelite associations (Ristivuoma) are syn-collisional (1.911.89 Ga) and derive from multiply recycled and thoroughly mixed sources. These rocks were deformed during continued collision with the development of foreland fold- and thrust belt. [ABSTRACT FROM AUTHOR]

• The Kangilleq Formation documents Paleoproterozoic subaqueous, basaltic volcanism. • The Kangilleq Formation is correlative with the Bravo Lake Formation of Baffin Island. • It records the initiation of an extension in an intracontinental backarc. • Initial extension and volcanism recorded in the OIB-like rocks of the Umiammakku member. • Followed by the eruption and deposition of the E-MORB-like rocks of the Kangiusap member. Mafic volcanic rocks of the Paleoproterozoic Kangilleq Formation of the Karrat Group of West Greenland represent a submarine mafic volcanic sequence, erupted and deposited on the Rae craton of Greenland. The formation ranges from <100 m-thick to ∼500 m-thick, and consists of mafic volcaniclastic rocks, pillow lavas and massive basalt lavas that have undergone greenschist facies metamorphism, yet preserve primary volcanic textures such as pillows, drainage cavities, lobes, flow banding, autoclastic breccias, hyaloclastite, scoria and layering. Rocks of the Kangilleq Formation overlie the Archean Qeqertarssuaq Complex and are interleaved with and overlain by the ca. 1950 Ma Nûkavsak Formation. Based on detailed (1:200) mapping and high-precision geochemistry, rocks of the Kangilleq Formation are subdivided into the Kangiusiap and Umiammakku members. The Kangiusiap member is dominated by mafic, scoria-rich breccias, has sulfide mineralization, and is bound at the bottom and top by the Nûkavsak Formation. This member has subalkaline, transitional to tholeiitic, mid-ocean ridge basalt (MORB) to back arc basin basalt (BABB) signatures with a Nd-isotope value similar to the depleted mantle at 1.88 Ga. The Umiammakku member is dominated by pillow lavas, with subordinate amounts of massive lavas and volcaniclastic rocks, overlies the Qeqertarssuaq Complex and is overlain by, and interleaved with, the Nûkavsak Formation. It is alkaline with characteristics similar to modern ocean island basalts and Nd-isotopic values slightly lower than the depleted mantle at 1.88 Ga. The rocks of the Kangilleq Formation represent non-arc suites or suites that have only minor subduction zone or crustal input, and display geochemical signatures similar to basalts found in modern intracontinental back arc settings. Lithofacies, bedforms, internal stratigraphy, and the identification of synvolcanic faults, suggest it is the product of volcanic eruptions during incipient rifting within a back arc setting, and seafloor mass wasting events at fault scarps related to rifting. Based on the geological characteristics and its petrogenetic and tectonic history, the Kangilleq Formation is interpreted to be correlative with the Bravo Lake Formation of the Piling Group of northeastern Canada and records incipient rifting of the southern margin of the Rae craton in the Paleoproterozoic. [ABSTRACT FROM AUTHOR]

Abstract The Bose Basin in southern China is within a region influenced by the winter westerly monsoon and, thus, potentially subject to eolian dust accumulation. A red earth sequence developed on terraces of the Youjiang River (a branch of the Pearl River) records information about climate variation during the Pleistocene and its relationship to contemporaneous global climate changes. In this study, geochemical characteristics and U-Pb geochronology of detrital zircons of the red earth sequence at Xiaomei were investigated using X-ray diffraction (XRD), X-ray fluorescence (XRF), inductively coupled plasma mass spectrometry (ICP-MS), thermal ionization mass spectrometry (TIMS), and detrital zircon U-Pb dating analyses. Our results show that the red earth sediments are composed of quartz and clay minerals (kaolinite, illite, and mixed-layer illite/vermiculite) with minor hematite and goethite. Mobile elements such as CaO, MgO, Na 2 O, K 2 O, Sr and Ba are depleted and immobile elements such as TiO 2 , Al 2 O 3 , Fe 2 O 3 (t) and Zr are enriched in comparison with loess-paleosols of the Chinese Loess Plateau (CLP), the upper continental crust (UCC), and post-Archean Australian shale (PAAS). These data indicate that the Xiaomei red earth sediments have experienced intense chemical weathering, similar to that of the Xuancheng and Jiujiang red earth sections on the middle to lower reaches of the Yangtze River. The Xiaomei sediments have similar La/Th ratios, U/Pb vs. Th/Pb relationships, and rare earth element (REE) distributions to the CLP, UCC, and PAAS, and their low ε Nd (0) values are indicative of an upper crustal origin. The 147Sm/144Nd and 87Sr/86Sr ratios of the Xiaomei sediments are different from loess-paleosols of the CLP but similar to those of well-mixed river sediments. U-Pb dating of detrital zircons in the Xiaomei sediments shows that crystals from different units have slightly different age distributions. The full Xiaomei section yields a distribution similar to that of Upper Permian-Triassic clastic rocks in the Youjiang area, and the distribution of the middle to upper Xiaomei section additionally shows similarities to upper crust of the South China Craton. Our results indicate that the Xiaomei red earth sequence, which dates to the late Early to early Middle Pleistocene (~ 1.0–0.6 Ma), accumulated predominantly from fluvially transported, locally weathered materials and, therefore, that the sediment-carrying capacity of the East Asian winter monsoon has been overestimated in previous provenance studies of red earth sediments in South China. Highlights • The Xiaomei red earth represents intensely leached tropical soils of Quaternary age in southern China. • Their major and trace element distributions differ from CLP loess-paleosols, UCC and PAAS. • Their detrital zircon age distributions show peaks at 240–300, 420–480, and 900–1000 Ma. • This pattern differs from CLP loess-paleosols but resembles other red earth deposits in southern China. • These red earth deposits were fluvially sourced from Permian-Triassic siliciclastics regionally. [ABSTRACT FROM AUTHOR]

Abstract Resolving the possible mantle and crustal sources for shergottite meteorites is crucial for understanding the formation and early differentiation of Mars. Orbiter and rover characterization of the martian surface reveal that the major element composition of most of its surface does not match the shergottites (McSween et al., 2009) leaving the relationship between them poorly understood. The identification of the meteorite NWA 7034 and its pairs as a Mars surface rock (Cartwright et al., 2014) provides access to a representative sample of Mars' crust (Agee et al., 2013; Humayun et al., 2013). Utilizing the short-lived 146Sm–142Nd, and long-lived 147Sm–143Nd and 176Lu–176Hf chronometers, which are sensitive to silicate differentiation, we analyzed three fragments of NWA 7034. The very negative mean isotopic compositions for this breccia, μ 142 Nd JNdi-1 = − 45 ± 5 (2SD), ε 143 Nd CHUR = − 16.7 ± 0.4 (2SD) and ε 176 Hf CHUR = − 61 ± 9 (2SD) point to an ancient origin for this martian crust. However, modeling of the data shows that the crust sampled by NWA 7034 possesses a Hf/Nd ratio and coupled ε 143 Nd – μ 142 Nd model age that are incompatible with this crustal reservoir being an end-member that generated the shergottite source mixing array. In addition, this crust is not juvenile, despite its rare earth element profile, but has had a multistage formation history. Therefore, early crustal extraction alone was not responsible for the creation of the reservoirs that produced the shergottites. Instead mantle reservoirs formed via other early differentiation processes such as in a Mars magma ocean must be responsible for the trace element and isotopic signatures present in shergottites. Highlights • ε 176 Hf , ε 143 Nd , and μ 142 Nd in NWA 7034 meteorite consistent with ancient crust. • Sm–Nd and Lu–Hf rule out bulk NWA 7034 as partial melt of primitive mantle. • NWA 7034 crustal reservoir is not the enriched end member for shergottites. • Martian magma ocean necessary to generate enriched end-member for shergottites. [ABSTRACT FROM AUTHOR]

Ordovician megacrystic granitoids intrude the Neoproterozoic-Paleozoic Acatlán Complex of southern Mexico, which consists of rift-passive margin, clastic rocks and rift-related igneous rocks. Most of the Neoproterozoic-Ordovician rocks were folded at greenschist-amphibolite facies metamorphism, however some rocks underwent polyphase deformation, underthrusting under high-pressure metamorphism followed by extrusion during the Late Devonian-Carboniferous (365–330 Ma). Most of our new Nd isotopic data for Ordovician granitoids have Ɛ Nd(T) ranging between −4.5 and −7.2 with T DM ages of 1.3–1.6 Ga that are similar to most published data from such Ordovician plutons: Ɛ Nd(T) of −0.2 to −6.6 and T DM ages of 1.2–1.8 Ga. These values are comparable to the range shown by the Oaxacan Complex, which confirms the conclusion reached using zircon U-Pb isotopic data indicating an Oaxacan source. One exception is the Ordovician Teticic granitoid that has Ɛ Nd(T) of −4.8 to −5.8 and T DM ages of 2162–2946 Ma. The combination of ca. 1.5 and 2–3 Ga T DM ages is also recorded in northwestern Amazonia, which is consistent with previous correlations of Oaxaquia with Amazonia. The transfer of Oaxaquia from Amazonia to southern Laurentia occurred during the amalgamation and breakup of Pangea, where the suture was roughly parallel to their relative motion: this resulted in dextral strike-slip faulting generally attributed to the Mojave-Sonora megashear. [ABSTRACT FROM AUTHOR]

The Silurian volcanic rocks of the Prague Basin represent within-plate, transitional alkali to tholeiitic basalts, which erupted in a continental rift setting through the thick Cadomian crust of the Teplá-Barrandian Unit (Bohemian Massif). Despite the variable, often intense alteration resulting in post-magmatic replacement of the basalt mass due to carbonatization, the geochemical signatures of Silurian basalts are still sufficiently preserved to constrain primary magmatic processes and geotectonic setting. The studied interval of Silurian volcanic activity ranges from Wenlock (Homerian, ~431 Ma) to late Ludlow (Gorstian, ~425 Ma) with a distinct peak at the Wenlock/Ludlow boundary (~428 Ma). Trace-element characteristics unambiguously indicate partial melting of a garnet peridotite mantle source. Wenlock basalts are similar to alkaline OIB with depleted radiogenic Nd signature compared to Ludlow basalts, which are rather tholeiitic, EMORB-like with enriched radiogenic Nd signature. The correlation of petrogenetically significant trace-element ratios with Nd isotopic compositions points to a mixing of partial melts of an isotopically heterogeneous, possibly two-component mantle source during the Wenlock-Ludlow melting. Lava eruptions were accompanied by intrusions of doleritic basalt and meimechite sills. The latter represent olivine-rich cumulates of basaltic magmas of probably predominantly Ludlow age. Meimechites with dolerites and, to a lesser extent, some lavas were subject to alteration due to wall-rock-fluid interaction. The trigger for the Wenlock-to-Ludlow (431-425 Ma) extension and related volcanism in the Prague Basin is related to far-field forces, namely slab-pull regime due to progressive closure of the Iapetus Ocean. The main stage of the Baltica-Laurentia collision then caused the Prague Basin rift failure at ca. 425 Ma that has never reached an oceanic stage. [ABSTRACT FROM AUTHOR]

According to the temporal-spatial distribution of Neoproterozoic igneous rocks and relative rocks in South China, including ophiolites, arc volcanic and intrusive rocks and subsequent bimodal magmatism, we identified the presence of a Neoproterozoic intra-oceanic arc, continent-arc-continent collision and three tectono-magmatic zones between the Yangtze Block and Cathaysia Block. We have also unraveled the amalgamation and tectono-magmatic histories between the Yangtze and Cathaysia blocks: At ∼1000–860 Ma, northwestward ocean-ocean subduction and southeastward ocean-continent subduction resulted in the intra-oceanic arc magmatism and active continental margin magmatism in the Cathaysia Block respectively. At ∼860–825 Ma, the steepening subduction caused development of back-arc basin in the intra-oceanic arc zone and the slab rollback induced the arc and back-arc magmatism in the Cathaysia Block. Meanwhile, a shallow dip northwestward ocean-continent subduction formed active continental margin magmatism in the Yangtze Block. At ∼825–805 Ma, the continent-arc-continent collision and final amalgamation between the Yangtze and Cathaysia blocks yielded the Jiangnan Orogen. At ∼805–750 Ma, the Jiangnan Orogen collapsed, and the Nanhua rift basin formed. Our study also rules out any Grenvillian Orogenic event and mantle plume activity in South China and indicates a marginal position of South China in the Rodinia supercontinent. [ABSTRACT FROM AUTHOR]

Monazite [(Ce, La, Th) PO 4 ], 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. [ABSTRACT FROM AUTHOR]

The property of 134−140 Neodymium nuclei have been studied in framework Interacting Boson Model (IBM) and a new method called New Empirical Formula (NEF). The energy positive parity bands of 134−140 Nd have been calculated using (IBM) and (NEF) while the negative parity bands of 134−140 Nd have been calculated using (NEF) only. The E-GOS curve ( E γ / I ) as a function of the spin (I) has been drawn to determine the property of the positive parity yrast band. The parameters of the best fit to the measured data are determined. The reduced transition probabilities B ( E 2 ) of these nuclei was calculated. The critical point has been determined for 140 Nd isotope. The potential energy surfaces (PESs) to the IBM Hamiltonian have been obtained using the intrinsic coherent state. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Yindonggou orogenic-type Ag–Au–Pb–Zn lodes occur in the southern Qinling Orogen. • It is hosted in Neoproterozoic rocks and yields sericite 40Ar/ 39Ar age of 234.65 ± 3.51 Ma. • The Sr–Nd isotopes indicate that initial ore-fluids were mainly sourced from oceanic crust. • The deposit was formed in Triassic oceanic subduction-related accretionary orogeny. The Yindonggou deposit, located in the northwestern margin of the Wudang Block, is the largest Ag–Au deposit (reserves: 2000 t Ag and 20 t Au) in the area. Quartz vein- and altered rock-type orebodies are hosted in the meta -volcanic rocks of the Wudang Group, and are controlled by the Yindongyan anticline and ductile shear zone along the anticlinal axis. The metamorphosed quartz keratophyre tuff from the Wudang Group yield LA-ICP-MS zircon concordant 206Pb/238U age of 738.30 ± 5.90 Ma, indicating a Neoproterozoic volcanic event. Four stages of mineralized quartz veins were found in the deposit. One hydrothermal sericite sample collected from the stage 2 smoke-gray quartz Ag–Au veins yield a well-defined 40Ar/39Ar isotopic plateau age of 234.65 ± 3.51 Ma, and 39Ar/36Ar-40Ar/36Ar normal isochron age of 220.11 ± 14.32 Ma, suggesting a Middle to Late Triassic (ca. 234 Ma) mineralization at Yindonggou. The difference between diagenetic and mineralization ages indicates that the Yindonggou deposit is not a volcanic eruption-related deposit, but a vein type epigenetic ore deposit. Five wall-rock samples from the Wudang Group of the Yindonggou deposit yield I Sr (234 Ma) ratios of 0.714890–0.723704, averaging 0.719938; the (143Nd/144Nd) i values ranging from 0.512018 to 0.512078, averaging 0.512055, with the ε Nd (234 Ma) values of −6.22 to −5.05. Galena from stage 1 have I Sr (234 Ma) values of 0.710801–0.718999, (143Nd/144Nd) i values of 0.511954–0.512234, and ε Nd (234 Ma) values of −7.47–2.01. Pyrite and sphalerite from stage 2 yield I Sr (234 Ma) ratios of 0.704389–0.719884, (143Nd/144Nd) i values of 0.511920–0.512402 and ε Nd (234 Ma) values of −8.13 to 1.28. Both ε Nd (234 Ma) and I Sr (234 Ma) values of the sulfides indicate that the ore-forming fluids were contaminated by wall rocks from the Wudang Group. The early stage sulfides are representative of the initial ore-forming fluids, which is similar to metamorphosed basic rocks and Mian-Lue ophiolite. This indicates that the deep-sourced initial ore-forming fluids with high ε Nd (234 Ma) and low I Sr (234 Ma) were derived from the metamorphic devolatilization of the subducted oceanic crust. The Yindonggou is an orogenic-type deposit formed in Triassic oceanic subduction-related accretionary orogeny. [ABSTRACT FROM AUTHOR]

The Pernambuco–Alagoas (PEAL) Domain, southern Borborema Province, northeastern Brazil, bears the most voluminous Cryogenian–Ediacaran granitic rocks in this province, which was formed during the convergence of the São Francisco Craton and the Borborem Province, during the western Gondwana amalgamation. New geochemical and isotopic data along those from the literature, for one of the largest intrusions, the Correntes composite batholith, at the southern part of this domain, indicate that the granitic rocks are intermediate to acid, oxidized, metaluminous to peraluminous, magnesian, and are high-K calc alkalic to shoshonitic with I-type signature. They are enriched in large-ion lithophile elements, exhibit lightly negative Eu in rare-earth element patterns and negative Ta–Nb, P, and Ti anomalies in spidergrams. Average initial 87Sr/86Sr is 0.7055 and rocks present values of whole-rock εNd (0.6 Ga) that fall into two groups. The pre-to syn-collisional, 635–628 Ma plutons present εNd (0.6 Ga) values from +1.3 to −2.5, with Nd model ages varying from 1.29 to 0.92 Ga, while the late-to post-collisional, 602–580 Ma, plutons show more negative values (−8.2 to −9.5), and older Nd model ages from 1.95 to 1.81 Ga. This Nd-isotope pattern is also observed in other plutons of the southern PEAL Domain and indicates a change in the lower crust source rock with time, with larger contributions of crustal components in the late-to post-collisional rocks. The chemical and isotopic characteristics of the studied granitic rocks and other granitic batholiths in the southern PEAL Domain are compatible with modern magmatic arcs of continental active margins. We propose that in earlier stages of convergence, melting has further affected the younger (Stenian –Tonian), likely less refractory rocks associated with abundance of volatiles, whose segregation would have differentiated to form the oldest plutons. Slow cooling allowed the accumulation of heat from mantle-derived magma in the pre-collisional period, which, together with radiogenic heat from thickened crust, led to partial melting of older crustal rocks, and the formation of magmas whose segregation and differentiation of the melt would originate the younger plutons in this part of the PEAL Domain. Older plutons formed during a Cryogenian-Ediacaran flare-up event that occurred in the southern PEAL Domain. • A flare-up Cryogenian-Ediacaran magmatism ocurred during convergence between the São Francisco Craton and the PEAL Domain. • Early-to syn-collisional, 635–628 Ma, plutons are mostly derived from younger (Stenian-Tonian) sources. • Syn-collisional, 602–580 Ma, plutons are mostly derived from Paleoproterozoic sources. • Crustal reworking, with minor crustal growth, and granite genesis, occurred in the PEAL Domain during the Brasiliano orogeny. [ABSTRACT FROM AUTHOR]

The geological history of the Amazon River is a complex story driven by geodynamic processes operating in the South American plate. In spite of recent research, the pre-Neogene structure of Amazon paleodrainage is still underconstrained. A recent study has suggested that the western Amazonian paleodrainage system was reversed, cratonic in origin during the Cretaceous. However, the extent and duration of this system are not well-constrained. To add new constraints, we investigated the sources of Cretaceous sedimentary rocks in the Brazilian Acre and Peruvian Madre de Dios basins, based on major and trace element concentrations, Sm–Nd isotopic compositions, and U–Pb detrital zircon dating. The late Cretaceous samples of the Acre Basin have ε Nd (0) values between −21.2 and −8.4 and zircon grains derived from terranes situated in the easternmost part of the Amazonian Craton: Ventuari–Tapajos (2.0–1.82 Ga) and Rio Negro–Juruena (1.82–1.54 Ga). In contrast, the Madre de Dios Basin samples have ε Nd (0) values ranging from −15.2 to −7.1 and a wide range of U–Pb zircon age distributions. The samples from the northern part of the basin (MD234 and MD238) are dominated by zircon ages between 0.9 and 1.3 Ga (Grenville/Sunsás, 30 %–43 %) and 0.5 and 0.7 Ga (Brazilian/Pampean, 26 %–16 %) with felsic provenance. The oldest MD234 sample also shows a dominant contribution from Paleozoic zircon (20 %). On the other hand, the samples from the southern part of the Madre de Dios Basin (samples MD-2019-4A; MD-2019-10; MD-2019-13; MD-2019-11D and MD-2019-12A) have U–Pb age distributions dominated by zircon ages between 0.9 and 1.3 Ga (Grenville/Sunsás, 30 %–45 %) and 1.54 and 1.3 Ga (Rondonia–San Ignácio, 16 %–43 %), pointing to a cratonic origin for these sedimentary rocks. To elucidate the distinction in provenance between the samples from the northern and southern parts of the Madre de Dios Basin, we suggest that a structural barrier (the Madidi Arch (?)) was active during the late Cretaceous. In this scenario, the northern part of the Madre de Dios Basin had similar sedimentary sources as the nearby basins like Huallaga, Bagua, Ucayali, and Marañón, whereas, in the southern part of the basin, sedimentation was influenced by local sources. Together with previously published studies, these data indicate that the continent-wide cratonic drainage developed between the Cenomanian and Maastrichtian in response to the Purus Arch uplift was probably driven by a geodynamic process related to the post-rift opening of the Atlantic Equatorial Ocean. [ABSTRACT FROM AUTHOR]

Based on the geological, geochemical and isotopic data, multi-stage magmatism, crustal reworking and growth events occurred in the Ntem Complex at ∼3.90–3.25 Ga ∼3.25 –3.0 Ga, ∼2.95–2.85 Ga and ∼2.75–2.72 Ga from the Eoarchean to the Neoarchean. [Display omitted] Hafnium and neodymium isotopes provide robust tool tracers for tracking the mechanisms of crustal generation and differentiation, from mantle extraction to the late geological processes undergone by the studied rocks. Though these two isotope systems commonly behave similarly and define a positive correlation between 143Nd/144Nd and 176Hf/177Hf referred to as the "terrestrial array", they may differ in terrains having a complex geological history, such as Archean cratons. This study presents the first combined whole-rock Hf and Nd isotopic analyses of Archean mafic and felsic igneous rocks from the Sangmelima terranes in the Ntem Complex (located in the Northwest of Congo Craton (NW CC) in southern Cameroon). It mainly consists of Mesoarchean charnockites and tonalite-trondhjemite-granodiorite (TTG) suites, greenstone belts, mafic enclaves or dykes, and potassic granitoids. Mesoarchean charnockite and TTG suites have subchondritic initial 176Hf/177Hf and 143Nd/144Nd ratios with a mean initial (suffix (i)) ε176Hf (i) and ɛ143Nd (i) of –3.30 ± 1.40 and –3.85 ± 0.65 (2SD) respectively, implying the involvement of Eo- to Paleoarchean components in their petrogenesis. The bulk rock initial Hf and Nd isotope compositions of the gabbro and gabbronorites are suprachondritic (ε176Hf (i) = +3.4 to + 8.2; ε143Nd (i) = +0.9 to + 1.6), indicate that they were derived from a depleted mantle source. Coupled with pre-existing data from the literature, these new Hf-Nd isotopic data indicate that two episodes of mantle-derived mafic magmatism in the Ntem Complex occurred during the Mesoarchean period (i.e., at ∼ 3.1 and 2.86 billion years (Ga)). Neoarchean dolerite dykes show broadly chondritic to supra-chondritic ε176Hf (i) and ε143Nd (i) values of –0.28 to + 4.53 and T CHUR ages of 2.74 – 2.76 Ga, suggesting the derivation of doleritic magma from a depleted mantle source with either none or limited crustal residence time. Considering other Archean domains of the NW CC, there were multi-stage magmatism events and crustal growth events occurred at ∼3.75 – 3.31 Ga, ∼3.26 – 3.0 Ga, ∼2.92 – 2.85 Ga, and ∼2.75 – 2.72 Ga from Eoarchean to Neoarchean in the NW Congo Craton. [ABSTRACT FROM AUTHOR]

The non-chondritic neodymium (Nd) 142 Nd/ 144 Nd ratio of the silicate Earth potentially provides a key constraint on the accretion and early evolution of the Earth. Yet, it is debated whether this offset is due to the Earth being formed from material enriched in s -process Nd isotopes or results from an early differentiation process such as the segregation of a late sulfide matte during core formation, collisional erosion or a some combination of these processes. Neodymium stable isotopes are potentially sensitive to early sulfide segregation into Earth's core, a process that cannot be resolved using their radiogenic counterparts. This study presents the first comprehensive Nd stable isotope data for chondritic meteorites and terrestrial rocks. Stable Nd measurements were made using a double spike technique coupled with thermal ionisation mass spectrometry. All three of the major classes of chondritic meteorites, carbonaceous, enstatite and ordinary chondrites have broadly similar isotopic compositions allowing calculation of a chondritic mean of δ 146/144 Nd = −0.025 ± 0.025‰ (±2 s.d.; n = 39 ). Enstatite chondrites yield the most uniform stable isotope composition (Δ 146/144 Nd = 26 ppm), with considerably more variability observed within ordinary (Δ 146/144 Nd = 72 ppm) and carbonaceous meteorites (Δ 146/144 Nd = 143 ppm). Terrestrial weathering, nucleosynthetic variations and parent body thermal metamorphism appear to have little measurable effect on δ 146/144 Nd in chondrites. The small variations observed between ordinary chondrite groups most likely reflect inherited compositional differences between parent bodies, with the larger variations observed in carbonaceous chondrites being linked to varying modal proportions of calcium–aluminium rich inclusions. The terrestrial samples analysed here include rocks ranging from basaltic to rhyolitic in composition, MORB glasses and residual mantle lithologies. All of these terrestrial rocks possess a broadly similar Nd isotope composition giving an average composition for the bulk silicate Earth of δ 146/144 Nd = −0.022 ± 0.034‰ ( n = 30 ) . In the samples here magmatic differentiation appears to only have an effect on stable Nd in highly evolved magmas with heavier δ 146/144 Nd values observed in samples with >70 wt% SiO 2 . The average stable Nd isotope composition of chondrites and the bulk silicate Earth are indistinguishable at the 95% confidence level. However, mantle samples do possess variable stable Nd isotope compositions (Δ 146/144 Nd = 75 ppm) with an average δ 146 / 144 Nd value of −0.008‰. If these heavier values represent the true composition of pristine mantle then it is not possible to completely rule out some role for core formation in accounting for some of the offset between the mantle and chondrites. Overall, these results indicate that the mismatch of 142 Nd between the Earth and chondrites is best explained by a higher proportion of s -process Nd in the Earth, rather than partitioning into sulfide or S-rich metal in the core. [ABSTRACT FROM AUTHOR]

The Gogó da Onça Granite (GOG) comprise a stock located in the Carajás Province in the southeastern part of Amazonian Craton near its border with the Araguaia Belt. Three facies were identified in the pluton: biotite-amphibole granodiorite, biotite-amphibole monzogranite and amphibole-biotite syenogranite. The GGO crosscut discordantly the Archean country rocks and are not foliated. All Gogó da Onça Granite varieties are metaluminous, ferroan A2-subtype granites with reduced character. The major and trace element behavior suggests that its different facies are related by fractional crystallization. Zircon and titanite U–Pb SHRIMP ages show that the pluton crystallized at ∼1880–1870 Ma and is related to the remarkable Paleoproterozoic magmatic event identified in the Carajás Province. Whole-rock Nd isotope data ( T DM ages 2.78 to 2.81, ε Nd values of −9.07 to −9.48) indicate that the GOG magmas derived from an Archaean source compatible with that of some other Paleoproterozoic suites from Carajás Province. The GOG show significant contrasts with the Jamon and Velho Guilherme Paleoproterozoic suites from Carajás Province and the inclusion of the Gogó da Onça granite in any of these suites is not justified. The GOG is more akin to the Serra dos Carajás Suite and to the Seringa and São João granites of Carajás and to the Mesoproterozoic Sherman granite of USA and the Paleoproterozoic Suomenniemi Batholith of Finland. This study puts in evidence the relevance of precise geochronological data and estimation of magma oxidation state in the characterization and correlation of A-type granites. [ABSTRACT FROM AUTHOR]

This paper presents a systematic study of major and trace elements and Sm-Nd isotopes in leucogranites closely related to uranium mineralization in the Gaudeanmus area, Namibia. The results illustrate that the uraniferous leucogranites possess high SiO2 (68.8wt%-76.0wt%, average 73.1wt%) and K (4.05wt%-7.78wt%, average 5.94wt%) contents, and are sub-alkaline and metaluminous to weakly peraluminous, as reflected by A/CNK values of 0.96-1.07 with an average of 1.01. The leucogranites are rich in light rare earth elements (LREE/HREE = 2.53-7.71; (La/Yb)N = 2.14-10.40), have moderate Eu depletion and high Rb/Sr ratios (2.03-5.50 with an average of 4.36); meanwhile, they are enriched in Rb, K, Th, U and Pb, and depleted in Ba, Nb, Ta, and Sr. The ∊Nd( t) values of uraninites range from -14.8 to -16.5, and the two-stage Nd model ages are 2.43-2.56 Ga. Detailed elemental and Sm-Nd isotopic geochemical characteristics suggest that the leucogranites were formed in a postorogenic extensional environment. The U-rich pre-Damara basement was the main source of uranium during the primary mineralization event, which is disseminated in leucogranites, whereas the uranium mineralization in veins possibly resulted from remobilization of the primary uranium minerals. [ABSTRACT FROM AUTHOR]

Marine neodymium (Nd) isotope and rare earth element (REE) compositions are valuable tracers for present and past ocean circulation and continental inputs. Yet their supply via high latitude estuaries is largely unknown. Here we present a comprehensive dissolved Nd isotope (expressed as ε Nd values) and REE data set together with seawater stable oxygen isotope ( δ 18 O) compositions of samples from the Laptev Sea recovered in two Arctic summers and one winter. The Laptev Sea is a shallow Siberian Shelf sea characterized by extensive river-runoff, sea-ice production and ice transport into the Arctic Ocean. The large variability in ε Nd (−6 to −17), REE concentrations (16 to 600 pmol/kg for Nd) and REE patterns is controlled by freshwater supply from distinct riverine sources and open ocean Arctic Atlantic Water. Strikingly and contrary to expectations, except for cerium no evidence for significant release of REEs from particulate phases is found, which is attributed to low amounts of suspended particulate matter and high dissolved organic carbon concentrations present in the contributing rivers. Essentially all shelf waters are depleted in light (L)REEs, while the distribution of the heavy REEs shows a deficiency at the surface and a pronounced excess in the bottom layer. This distribution is consistent with REE removal through coagulation of riverine nanoparticles and colloids starting at salinities near 10 and resulting in a drop of all REE concentrations by ∼30%. With increasing salinity preferential LREE removal is observable reaching ∼75% for Nd at a salinity of 34. Although the delayed onset of dissolved REE removal contrasts with most previous observations from other estuarine environments, it agrees remarkably well with results from recent experiments simulating estuarine mixing of seawater with organic-rich river waters. In addition, melting and formation of sea ice leads to further REE depletion at the surface and strong REE enrichment near the shelf bottom as a function of ice melting and brine transfer, respectively. The ice-related processes significantly affect the distribution of dissolved REEs in high-latitude estuaries and likely also similarly contribute to the redistribution of other dissolved seawater constituents. [ABSTRACT FROM AUTHOR]

Detrital thermochronology is often employed to assess the evolutionary stage of an entire orogenic belt using the lag-time approach, i.e., the difference between the cooling and depositional ages of detrital mineral grains preserved in a stratigraphic succession. The impact of different eroding sources to the final sediment sink is controlled by several factors, including the short-term erosion rate and the mineral fertility of eroded bedrock. Here, we use apatite fertility data and cosmogenic-derived erosion rates in the Po river catchment (Alps–Apennines) to calculate the expected percentage of apatite grains supplied to the modern Po delta from the major Alpine and Apenninic eroding sources. We test these predictions by using a cutting-edge dataset of trace-element and Nd-isotope signatures on 871 apatite grains from 14 modern sand samples, and we use apatite fission-track data to validate our geochemical approach to provenance discrimination. We found that apatite grains shed from different sources are geochemically distinct. Apatites from the Lepontine dome in the Central Alps show relative HREE enrichment, lower concentrations in Ce and U, and higher 147 Sm/ 144 Nd ratios compared to apatites derived from the External Massifs. Derived provenance budgets point to a dominant apatite contribution to the Po delta from the high-fertility Lepontine dome, consistent with the range independently predicted from cosmonuclide and mineral-fertility data. Our results demonstrate that the single-mineral record in the final sediment sink can be largely determined by high-fertility source rocks exposed in rapidly eroding areas within the drainage. This implies that the detrital thermochronology record may reflect processes affecting relatively small parts of the orogenic system under consideration. A reliable approach to lag-time analysis would thus benefit from an independent provenance discrimination of dated mineral grains, which may allow to proficiently reconsider many previous interpretations of detrital thermochronology datasets in terms of orogenic-wide steady state. [ABSTRACT FROM AUTHOR]

We present high-precision Nd isotope compositions for ordinary and carbonaceous chondrites determined using thermal ionization mass spectrometry with dynamic and multistatic methods. The ordinary chondrites had uniform and non-terrestrial μ 142 Nd , μ 148 Nd , and μ 150 Nd values, with data that plot along the mixing line between s -process and terrestrial components in μ 150 Nd versus μ 148 Nd and μ 142 Nd versus μ 148,150 Nd diagrams. In contrast, the carbonaceous chondrites were characterized by larger anomalies in their μ 142 Nd , μ 148 Nd , and μ 150 Nd values compared to ordinary chondrites. Importantly, the data for carbonaceous chondrites plot along the s -process and terrestrial mixing line in a μ 150 Nd versus μ 148 Nd diagram, whereas they have systematically lower μ 142 Nd values than the s -process and terrestrial mixing line in μ 142 Nd versus μ 148,150 Nd diagrams. This shift likely results from the incorporation of calcium- and aluminum-rich inclusions (CAIs), indicating that the Nd isotopic variability in the ordinary chondrites and CAI-free carbonaceous chondrites was caused solely by the heterogeneous distribution of s -process nuclides. The isotopic variation most likely results from nebular thermal processing that caused selective destruction of s -process-depleted (or r -process-enriched) dust grains in the inner Solar System where the parent bodies of ordinary chondrites formed, whereas such grains were preserved in the region of carbonaceous chondrite parent body formation. The Nd isotope dichotomy between ordinary and bulk aliquots of carbonaceous chondrites can be related to the presence of Jupiter, which may have separated two isotopically distinct reservoirs that were present in the solar nebula. After correcting for s -process anomalies and CAI contributions to the Nd isotopes observed in the chondrites, we obtained a μ 142 Nd value ( − 2.4 ± 4.8 ppm) that was indistinguishable from the terrestrial value. Our results corroborate the interpretation that a missing reservoir (e.g., a hidden enriched reservoir, erosional loss of crust) is not required to explain the observed differences in 142 Nd/ 144 Nd ratios between chondrites and terrestrial materials. [ABSTRACT FROM AUTHOR]

The history of the Amazon River is a much-discussed subject, and the timing of the development of a transcontinental system in particular is a matter of some controversy, with estimations varying between the Early Miocene and the Pliocene or even the Pleistocene. To shed further light on this, we studied the sediment provenance of an Oligocene to Late Pleistocene marine sedimentary section from the Ceará Rise (ODP Site 925), a topographic high in the central Atlantic Ocean, using major element concentrations and Nd isotopic composition in 85 samples. In addition, the carbon isotopic composition of bulk organic matter and changes in the distribution of glycerol dialkyl glycerol tetraethers (GDGTs) were used to identify periods of increased river outflow. On the basis of these results, we suggest that the history of the development of the Amazon River is characterized by specific steps. During the late Oligocene/Early Miocene (30–18.3 Ma), the terrigenous mass accumulation rates (TARs) were high, and sediment and GDGT compositions suggest that a large river system existed, which at times received weathering products from a younger and probably Andean sediment source. A shift to a younger Andean sediment provenance after 8.7 Ma indicates that the Amazon River became permanently connected with the Andes. Between 18.3 and 4.5 Ma, TARs were generally low, and GDGTs were derived for the most part from in situ production in marine waters. Around 4.5 Ma, the river expanded, probably due to ongoing tectonic activity, and uplift in the Andes increased Andean rock erosion. This led to a strong increase in terrigenous sediment deposition and enhanced organic matter preservation on the Ceará Rise, and the delivery of terrestrial (both soil and riverine) branched GDGTs to the Ceará Rise. [ABSTRACT FROM AUTHOR]

Neodymium isotopic compositions ( 143 Nd/ 144 Nd or ε Nd ) have been used as a tracer of water masses and lithogenic inputs to the ocean. To further evaluate the faithfulness of this tracer, we have updated a global seawater ε Nd database and combined it with hydrography parameters (temperature, salinity, nutrients and oxygen concentrations), carbon isotopic ratio and radiocarbon of dissolved inorganic carbon. Archive ε Nd data are also compiled for leachates, foraminiferal tests, deep-sea corals and fish teeth/debris from the Holocene period (< 10,000 years). At water depths ≥ 1500 m, property-property plots show clear correlations between seawater ε Nd and the other variables, suggesting that large-scale water mass mixing is a primary control of deepwater ε Nd distribution. At ≥ 200 m, basin-scale seawater T-S-ε Nd diagrams demonstrate the isotopic evolution of different water masses. Seawater and archive ε Nd values are compared using property-property plots and T-S-ε Nd diagrams. Archive values generally agree with corresponding seawater values although they tend to be at the upper limit in the Pacific. Both positive and negative offsets exist in the northern North Atlantic. Applying multiple regression analysis to deep (≥ 1500 m) seawater data, we established empirical equations that predict the main, large-scale, deepwater ε Nd trends from hydrography parameters. Large offsets from the predicted values are interpreted as a sign of significant local/regional influence. Dominant continental influence on seawater and archive ε Nd is observed mainly within 1000 km from the continents. Generally, seawater and archive ε Nd values form gradual latitudinal trend in the Atlantic and Pacific at depths ≥ 600 m, consistent with the idea that Nd isotopes help distinguish between northern/southern sourced water contributions at intermediate and deep water depths. [ABSTRACT FROM AUTHOR]

The water masses passing the Fram Strait are mainly responsible for the exchange of heat and freshwater between the Nordic Seas and the Arctic Ocean (the Arctic Mediterranean, AM). Disentangling their exact sources, distribution and mixing, however, is complex. This work provides new insights based on a detailed geochemical tracer inventory including dissolved Nd isotope ( ε Nd ), rare earth element (REE) and stable oxygen isotope (δ 18 O) data along a full water depth section across Fram Strait. We find that Nd isotope and REE distributions in the open AM primarily reflect lateral advection of water masses and their mixing. Seawater-particle interactions exert important control only above the shelf regions, as observed above the NE Greenland Shelf. Advection of northward flowing warm Atlantic Water (AW) is clearly reflected by an ε Nd signature of −11.7 and a Nd concentration ([Nd]) of 16 pmol/kg in the upper ∼500 m of the eastern and central Fram Strait. Freshening and cooling of the AW on its way trough the AM are accompanied by a continuous change towards more radiogenic ε Nd signatures (e.g. −10.4 of dense Arctic Atlantic Water). This mainly reflects mixing with intermediate waters but also admixture of dense Kara Sea waters and Pacific-derived waters. The more radiogenic ε Nd signatures of the intermediate and deep waters (reaching −9.5) are mainly acquired in the SW Nordic Seas through exchange with basaltic formations of Iceland and CE Greenland. Inputs of Nd from Svalbard are not observed and surface waters and Nd on the Svalbard shelf originate from the Barents Sea. Shallow southward flowing Arctic-derived waters (<200 m) form the core of the East Greenland Current above the Greenland slope and can be traced by their relatively radiogenic ε Nd (reaching −8.8) and elevated [Nd] (21–29 pmol/kg). These properties are used together with δ 18 O and standard hydrographic tracers to define the proportions of Pacific-derived (<∼30% based on Nd isotopes) and Atlantic-derived waters, as well as of river waters (<∼8%). Shallow waters (<150 m) on the NE Greenland Shelf share some characteristics of Arctic-derived waters, but exhibit less radiogenic ε Nd values (reaching −12.4) and higher [Nd] (up to 38 pmol/kg) in the upper ∼100 m. This suggests local addition of Greenland freshwater of up to ∼6%. In addition to these observations, this study shows that the pronounced gradients in ε Nd signatures and REE characteristics in the upper water column provide a reliable basis for assessments of shallow hydrological changes within the AM. [ABSTRACT FROM AUTHOR]

Results from new geologic mapping, SHRIMP U-Pb geochronology, and petrologic studies indicate that Mesoproterozoic basement in the northern French Broad massif near Mount Rogers consists of multiple, mostly granitic plutons, mapand outcrop-scale xenoliths of pre-existing crustal rocks, and remnants of formerly overlying meta-sedimentary lithologies. Zircon and titanite ages demonstrate that these rocks collectively record nearly 350 m.y. of tectonic evolution including periods of igneous intrusion at ca. 1190 to 1130 Ma (Early Magmatic Suite) and ca. 1075 to 1030 Ma (Late Magmatic Suite) and three episodes of regional metamorphism at ca. 1170 to 1140, 1070 to 1020, and 1000 to 970 Ma. The existence of ca. 1.3 Ga age crust is indicated by (1) orthogranofels of ca. 1.32 Ga age in a map-scale xenolith, (2) inherited zircons of ca. 1.33 to 1.29 Ga age in Early Magmatic Suite plutons, and (3) ca. 1.36 to 1.30 Ga age detrital zircons in meta-sedimentary lithologies. Mineral assemblages developed in amphibolites and granofelses indicate that metamorphism during both Mesoproterozoic episodes occurred at upper amphibolite- to lower granulite-facies conditions. Syn-orogenic Early Magmatic Suite plutons emplaced at ca. 1190 to 1145 Ma are characterized by high-K, variably magnesian, dominantly calc-alkalic compositions, and have trace-element characteristics indicative of continental-arc magmatic origin involving melting of thick continental crust. In contrast, ca. 1140 Ma age quartz syenite displays A-type features indicating derivation from depleted crustal sources with increased mantle input during waning stages of regional contraction. Plutons of the compositionally bimodal Late Magmatic Suite include (1) ca. 1060 Ma meta-granite with geochemical characteristics transitional between silicic rocks of arc systems and post-collisional granites of A-type lineage, and (2) ca. 1055 Ma monzodioritic rocks with A-type compositional characteristics that likely reflect derivation from fertile, mafic sources in the lower crust. Collectively, these data suggest that Mesoproterozoic rocks of the study area preserve evidence of multiple orogenic episodes that likely involved continental-arc development and deformation at ca. 1150 Ma followed by crustal thickening at ca. 1060 Ma. Field relations and geochronologic data indicate that regional uplift and sedimentation occurred at ca. 1100 Ma between the two episodes of overlapping magmatism and orogenesis. The nature and timing of Mesoproterozoic events recorded in basement rocks of the study area illustrate significant differences in the lithologic assemblages and geologic history preserved by Mesoproterozoic basement of the adjacent Shenandoah and French Broad massifs, suggesting that the Blue Ridge massifs occupied different locations within the regional Grenville-age orogen until about 1070 Ma when the effects of Ottawan-age tectonics began to affect both areas. The near ubiquity of Ottawan-age orogenic activity recorded in Mesoproterozoic rocks of the Blue Ridge, other Appalachian inliers such as the New Jersey Highlands, and the Grenville province of Canada, including the Adirondacks, suggests that these formerly disparate terranes were amalgamated to form a common, regional orogen by this time. [ABSTRACT FROM AUTHOR]

Dust deposition in north-eastern Canada was estimated from the geochemical signature of a boreal peat bog from the James Bay lowlands. The rare earth elements and other lithogenic elements, as well as Nd isotopes were measured by Q-ICP-MS, ICP-OES and MC-ICP-MS, respectively along a 4.20 m peat core covering the last 7000 years. A principal component analysis performed on the geochemical dataset shows that REEs display the same chemical behavior as other lithogenic elements such as Al and Ti, which suggests that they are immobile in the peat column and can be used as tracers of dust deposition. After 4000 cal yr BP, peaks in dust deposition associated with greater variability in testate amoebae assemblages and plant macrofossil composition as well as a change in ɛNd values are observed. Between 7000 and 4100 cal yr BP, the ɛNd values varied from −36 to −29, while they gradually increased from 4100 cal yr BP until 1500 cal yr BP, suggesting proportionally less dust from local source(s) is deposited in favor of more regional source(s). From 1500 cal yr BP, ɛNd values remained relatively stable around −15 and −12. Most of the dust peaks correspond to documented cold and dry periods likely linked to intrusion of arctic air masses. A migration of the polar front might explain the more frequent intrusion of Arctic air masses in the region and the greater variability in the LG2 record over the last 4000 years. [ABSTRACT FROM AUTHOR]

It is well-established that lanthanide rare earth elements (REEs) have the potential to record the nature and source characteristics of their host magmas, in both whole-rock and their minerals. Accessory minerals that concentrate REEs are especially useful in crustal evolution studies, both for their elemental and isotopic information; the classic and unrivalled example being zircon. Approaches using a single radiogenic isotopic system, or one radiogenic and one stable isotope system (e.g., Hf and O) in one REE-bearing mineral (usually zircon) are common, but those involving multiple isotopes in several minerals remain scarce despite offering many advantages. Importantly, the latter approaches also allow comparing different techniques and provide evidence on whether isotopic systems were disturbed by secondary processes. This contribution documents several isotopic systems within the abundant accessory mineral of Caledonian high Ba-Sr granitoids from Northwest Scotland. We present a multi-isotope study of titanite, zircon and apatite from two localities (Strontian and Rogart), which were selected for their contrasting whole-rock isotopic signatures - the former deriving from a depleted mantle source, whereas the latter derived from a strongly enriched mantle source. New in-situ Sm-Nd in titanite and apatite and Hf in zircon isotope data are discussed and compared with in-situ oxygen isotope data previously published for the same samples. An internal consistency is observed for Nd isotopes in apatite and titanite. Nd isotopes values for both minerals strongly correlate with Hf isotopes in zircon. Isotopic data at the mineral scale confirm the Strontian and Rogart source characteristics previously defined from whole-rock isotope data, with the Rogart having a more enriched signature than the Strontian source along the "Caledonian Parental Magma Array"(CPMA). In contrast, a significant discrepancy exists between whole-rock and REE-mineral oxygen isotope data as the latter can be affected by post emplacement alteration and hence can be misinterpreted. Importantly, the contribution of sediments in the CPMA source(s) can be estimated from a diagram combining Sm-Nd isotopic signatures and (La/Sm) N in apatite and titanite. Overall, we demonstrate that detailed petrogenetic records are not only available in zircons but also in magmatic titanite and apatite, and we suggest that integrated multi-mineral approaches have potential to maximise constraints from in-situ mineral isotope geochemistry. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two episodic Nb-Ta-Li-W-REE mineralization occurred in the Jiabusi-Narenwula district. • The first and major Nb-Ta-W-forming episode occurred at 148–132 Ma, the second but subordinate REE-forming episode occurred at ∼116 Ma, which is associated with F-rich hydrothermal alteration. • The Jiabusi-Narenwula multiphase granites were originated by partial melting of the same sources. The Jiabusi Nb–Ta–Li deposit is a medium-sized rare-metal deposit discovered in central Inner Mongolia in recent years, and it is accompanied by Rb-Cs-REEs mineralization. Its magmatic and metallogenetic ages, magmatic source attributes, and mechanisms of magmatic evolution and related mineralization are not known. To identify these characteristics, with multi-stage granitic intrusions of the Jiabusi deposit as study objects, investigations relating to petrography, lithogeochemistry, monazite–cassiterite–hydrothermal bastnasite LA-ICP-MS U–Pb geochronology, and Nd isotopes were systematically conducted. The following results were obtained: The LA-ICP-MS monazite U–Pb ages of the metallogenetic Li-mica albite granite and granitic pegmatite are 148±7 and 141±2 Ma and 141±3, 137±2, 136±3, and 132±2 Ma, respectively; the cassiterite U–Pb ages of the Ta–Rb ore bodies are 148±2 and 146±1 Ma; and the bastnasite U–Pb age of the magmatic hydrothermal fluid is 116±1 Ma. These ages indicate that there were two episodes of granitic magmatism and related rare (rare-earth) metal mineralization in the Jiabusi area during the Yanshanian period (Jurassic–Cretaceous). Geochemical analysis results reveal that the barren biotite granite is characterized by high SiO 2 (75.89 wt%) and high alkali (Na 2 O + K 2 O = 8.48 wt%) and a relatively high FeOT/(MgO + FeOT) value (0.92) and a relatively high Zr + Nb + Ce + Y content (393×10−6), whereas Al 2 O 3 (12.35 wt%), CaO (0.51 wt%), and MgO (0.13 wt%) contents are all relatively low. These results indicate that the biotite granite is A-type granite, with characteristics similar to those of A1-type granite. The Li-mica albite granite is characterized by high F (0.95%-2.76%) and strongly peraluminous nature (A/CNK = 1.26–2.34). Meanwhile, it is strongly enriched in Cs, Li, Rb, Nb, and Ta but extremely depleted in Ba, Sr, P, Ti, Zr, and light REEs, with quite a strong negative Eu anomaly (δEu <0.01), an evident lanthanide tetrad effect (TE 1,3 = 1.36–1.44), and Zr/Hf (3.0–4.0) and Nb/Ta (0.5–1.0) ratios deviating from those of a normal magmatic system. X-ray fluorescence and electron probe microanalysis surface scanning imaging analysis revealed the activity of F-REE-rich hydrothermal fluid and related REE mineralization in the uppermost part of altered granites. These features indicate that the metallogenetic ore bodies underwent higher degrees of magmatic fractionation and F-rich fluid–present melt–hydrothermal interaction. The Li-mica albite granite and multi-stage granitic pegmatite have consistent Nd isotope characteristics (ε Nd (t) = −3.4 to −3.9) and relatively concentrated two-stage model ages (T DM,2 = 1174–1247 Ma), suggesting that they are quite likely syngeneic multi-stage products with different degrees of fractional crystallization. Through comprehensive analysis of the results in this study and from previous research, the Yanshanian (Jurassic–Cretaceous) granite in the Jiabusi area is inferred to quite likely have originated from the partial melting of the ancient lower crust caused by lithospheric thinning and asthenospheric upwelling along the northern margin of the North China Craton, and it is revealed that a large amount of juvenile crustal materials had contributed to this process. [ABSTRACT FROM AUTHOR]

The article presents a research report conducted on the Nd (Neodymium) isotopic characteristics of granitoids rocksfrom the New foundland Appalachians. It mentions the general characteristics and composition of the granitoids which include its spatial-temporal variation and deep crustal composition. The National Natural Science Foundation carried out field surveys of granite rocks for the characteristics.

The Moon is a key example of a planetary body that originated from a giant impact collisional event. By better understanding its bulk composition, we gain critical constraints on the building blocks of the Earth-Moon system. Combined measurements of long-lived 147Sm-143Nd and short-lived 146Sm-142Nd isotope compositions of Earth and Moon have lead to controversial interpretations in the past and it remains ambiguous, whether or not the Moon is similar to primitive chondrites in its refractory lithophile element composition. We investigated coupled 138La-138Ce and 147Sm-143Nd isotope and trace element compositions across a wide range of lunar rock types to provide an independent assessment of the bulk Moon composition. All measured lunar rocks define a tight array in 138Ce-143Nd space, intersecting initial ε Nd = 0 at an initial ε Ce = − 0.26 ± 0.04 , significantly lower than the currently accepted chondritic 138Ce reference value. The results of combined modeling of 138Ce-143Nd-176Hf isotope and trace element behavior during lunar magma ocean (LMO) crystallization are in good agreement with the bulk silicate Moon having a slight depletion in its highly incompatible trace element inventory. Our calculated composition of the silicate Moon evolves towards ε Ce = − 0.26 and ε Nd =+1.4 at 3.30 Ga, the approximate age of most lunar samples investigated here. This proposed lunar isotope composition at 3.30 Ga agrees well with the intersection of the 3.30 ± 0.25 Ga lunar array and the terrestrial array defined by rocks from the Archean Pilbara and the Kaapvaal Cratons. We take this as evidence that accessible silicate Earth and the Moon may share a common reservoir slightly depleted in highly incompatible trace elements, named here Slightly Depleted Earth-Moon reservoir (SDEM). The SDEM reservoir proposed here is generally in line with previous models claiming a depleted composition of the accessible silicate Earth, but the degree of depletion is significantly smaller than previously proposed. • Cerium-Nd isotope array of the Moon is non-chondritic. • Lunar and terrestrial rocks share a common slightly depleted trace element composition. • Earth and Moon share the same non-chondritic trace element characteristics. [ABSTRACT FROM AUTHOR]

Nd model ages are valuable tools for studying the structure and evolution of the continental crust. However, their calculation is severely affected by the 147Sm/144Nd lack of constancy during crustal evolution because it results in spurious Nd model ages that may induce wrong geodynamic and geochemical interpretations. An extensive database of granite analyses shows that 147Sm/144Nd may vary significantly in the high-SiO 2 range of granite rocks and that these variations are far more common in peraluminous than in metaluminous varieties. Only a tiny fraction of the latter has anomalously low ratios, likely resulting from apatite, perhaps titanite, fractionation. In contrast, many high-SiO 2 peraluminous granites also show abnormally high, even superchondritic 147Sm/144Nd ratios that likely resulted from monazite fractionation. A Sm and Nd residence study in peraluminous sources revealed that Sm/Nd ratios are lower in monazite and the feldspars than in the bulk rock but higher in apatite and garnet. Monazite carries 90% of Nd and 80% of Sm, apatite carries about 3–5% of Nd and up to 16% of Sm, and garnet may concentrate up to 27% of Sm. Accordingly, the interplay among monazite, apatite and garnet determines the 147Sm/144Nd of resulting magmas, obscuring the role of the other phases. Garnet is expected to be primarily a residual or early crystallized phase, although some can be entrained in melts. Apatite may also behave as a residual phase in high-SiO 2 metaluminous systems. However, it is highly soluble in peraluminous systems. Monazite may dissolve partially, remaining in the residua of peraluminous melts and crystallizing early from these, as seen in leucosome-melanosome pairs from the Ivrea-Verbano Zone, NW Italy, and Peña Negra, Central Iberia, and the upwards differentiated Pedrobernardo granite sill, also in Central Iberia. Garnet or apatite retention in residua, or segregated from a crystallizing magma, produces melts with low 147Sm/144Nd that may cause anomalously young Nd model ages, as exemplified by the Roccapietra granite of the Ivrea-Verbano zone, NW Italy. Monazite retention or crystallization, in contrast, produces high 147Sm/144Nd melts that yield anomalously old Nd model ages. The effects of intracrustal 147Sm/144Nd variations may be softened or eliminated by employing the two-stage Nd model age calculation method (DePaolo et al., 1991) with a Sm/Nd evolution model adapted to each specific crustal segment. • Realistic Nd model ages require the constancy of Sm/Nd during crustal evolution. • The constancy does not hold during the generation and evolution of peraluminous magmas. • Monazite fractionation causes abnormally high Nd model ages. • Garnet and, likely, apatite fractionation cause abnormally low Nd model ages. • These effects can be corrected using the two-step Nd model age calculation. [ABSTRACT FROM AUTHOR]