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International audience; 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 2 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.

Floods are among the most destructive natural hazards on Earth. In paleohydrology, sediments are generally considered as one of the best archives to extend flood records to pre-historical timescales. Doing so requires being able to identify flood deposits from sediment archives and decipher between flood types. The latter is particularly important in glacierized regions, where meteorological floods frequently co-occur with glacial lake outburst floods (GLOFs). In Patagonia, results from a recent study suggest that GLOFs are recorded in downstream fjord sediments as fine-grained and organic-poor layers, representing the high amount of glacier rock flour transported during lake outbursts, whereas meteorological floods are represented by coarser and more organic deposits. However, not all fine-grained organic-poor deposits could be associated with historical GLOFs. Here, we reconstruct the provenance of these Baker River flood deposits using Sr-87/Sr-86 and epsilon Nd, taking advantage of the clear lithological differences that exist between both sides of the watershed. Our results show that both Sr-87/Sr-86 and epsilon Nd are suited to reconstruct sediment provenance in the Baker River watershed but that epsilon Nd is the most effective and the least affected by grain-size variations. Our provenance results confirm that the 21st-century fine-grained and organic-poor deposits represent GLOFs and that the largest winter meteorological flood on record has a distinct coarse and organic-rich signature. However, our results show that rain-on-snow events that occur in summer, and therefore primarily affect the western glacierized part of the watershed, have the same fine-grained organic-poor signature as GLOFs. Therefore, this study shows that the sedimentary signature of rain-on-snow floods in partially glacierized watersheds depends on the season during which they occur. We anticipate that our findings will contribute to a better interpretation of flood records from partially glacierized watersheds.

The role of Quaternary ice sheet fluctuations in driving meltwater pulses and ocean circulation perturbations is widely acknowledged. What is less clear is the role of these processes in driving changes in past atmospheric dust activity, and possible wider links between dust and climate. Terrestrial windblown dust (loess) deposits along the northern fringe of the European loess belt potentially record past atmospheric dust emission from regions close to the former Eurasian Ice Sheet (EIS) and provide a means to evaluate the role of ice sheet fluctuations in the past dust cycle. Numerical loess chronologies across this region generally agree on greatly enhanced dust deposition rates during MIS 2, when the EIS reached its maximum extent. Yet, uncertainties over the sources of this material prevent understanding of the precise causes of this greatly enhanced atmospheric dustiness, and any potential link to ice sheet fluctuations and climate. In southeast England, loess accumulation dominantly occurred in two phases centered on 25– 23.5 ka and 20–19 ka, matching the timing of coalescence of the Fennoscandian and British-Irish ice sheets and specifically advances and retreats of nearby ice lobes in the western North Sea. As such, these deposits provide an ideal test of the role of ice sheet fluctuations in atmospheric dust dynamics. Here we undertake such a test through a detailed provenance study of loess in southeast England and potential dust source sediments across the North Sea region. We group extensive new and published data sets of detrital zircon U–Pb ages from basement rocks and Cenozoic sediments in the North Sea area, which not only provide new insight into both loess source, but also the nature of sediment transport over NW Europe into the North Sea basin more widely. Multi-proxy evidence allows us to unambiguously identify ice sheet derived sediments in the exposed North Sea basin as the dominant source of loess in southeast England, while fluvial sediments delivered by rivers draining Continental Europe possibly contributed additional source material to the first loess accumulation phase. We propose that sudden retreats of the North Sea Lobe released substantial amounts of sediment rich meltwater into the southern North Sea and Channel basins, driving accelerated dust emission, loess deposition and provenance variability in NW Europe during MIS 2. Moreover, we propose that this model of dust activity driven by proglacial sediment availability may be applicable for EIS marginal regions more widely, even where resultant loess cover is rarely preserved due to extensive erosion and reworking along the ice marginal spillway. This implies the role of ice sheets in controlling wider dust emission may be underestimated. In addition to driving changes in ocean circulation through meltwater pulses, ice sheet dynamics in the Quaternary may have also driven substantial and abrupt changes in atmospheric dust activity. This mechanism may in part explain the coupling between dust and climate events widely seen in Quaternary dust sediment records and suggests a possible major role of high latitude dust emission in MIS 2 dustiness across Europe and beyond.

International audience; 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 143 Nd/ 144 Nd and 176 Hf/ 177 Hf 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 176 Hf/ 177 Hf and 143 Nd/ 144 Nd ratios with a mean initial (suffix (i)) ε 176 Hf (i) and ε 143 Nd (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 (ε 176 Hf (i) = +3.4 to + 8.2; ε 143 Nd (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 ε 176 Hf (i) and ε 143 Nd (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.

International audience; An ongoing debate concerns what initiated the Great Oxidation Event (GOE) and associated glaciation between ~ 2.45 and 2.2 Ga. One possibility is the emergence of continental landmasses and the increase of subaerial igneous province weathering during the Late Archean. We test this hypothesis in the Hamersley Basin by reporting Nd-isotope data from a succession of iron formations (IFs), mudstone/siltstones and glacial diamictites from the Boolgeeda Iron Formation and overlying Turee Creek Group deposited during the GOE. In a 147Sm/144Nd - εNd(t) diagram, the data define a negative trend indicating the contribution of a high εNd(t) ~ +3 hydrothermal component and a strongly negative εNd(t) ~ -9 crustal component, which is compatible with the Nd-isotope composition of the upper continental crust but also of the underlying felsic volcanics of the Woon-garra Rhyolite and crustally-contaminated mafic volcanics of the Fortescue Group. A less pronounced negative trend originating from the same hydrothermal source but correlated with non-contaminated ultramafic Fortescue volcanics (εNd(t) ~ -2) is observed for the older Joffre, Dales Gorge and Marra Mamba IFs. As Nd-isotopes are not sensitive to redox conditions, the major shift of Nd-isotopic compositions at ~ 2.45 Ga cannot be linked to a change in the weathering regime, rather to a change in the nature of the continental surface exposed to weathering. One explanation is that the Sm-Nd sources for sediments deposited before and during the GOE were locally derived from the underlying subaerial LIPs, reflecting a change in the geodynamic context of deposition and/or hydrographic network and catchment areas. Another explanation could be a significant change in the nature of fluid–rock interactions due to the increase role of weathering processes associated with the emergence of continental landmasses. Additional Nd isotope data from different cratons worldwide are needed, however, to infer as to whether or not the marked shift in Nd isotope compositions recorded in the Turee Creek Group reflect a change in the global hydrological cycle. Our data support the role of large subaerial magmatic provinces as triggers of the rise of atmospheric oxygen and the onset of glaciations at the beginning of the Proterozoic.

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 Yli-tornio nappe complex. Although main thrust stacking had occurred between 1.92–1.89 Ga, later reverse faulting probably continued until 1.78 Ga. The Väystäjä 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 (1.91–1.89 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.

Radiogenic lead (Pb) and neodymium (Nd) isotope compositions extracted from authigenic phases in marine sediments are sensitive tracers to reconstruct past ocean circulation and water mass mixing. Chemical reductive leaching of hydrogenetic ferromanganese oxyhydroxides from bulk sediments is the most practical way to recover past seawater Pb and Nd isotope signatures in the Southern Ocean, due to the scarcity of alternative archives. However, the leached signal could be compromised if substantial quantities of Pb and Nd were released from non‐hydrogenetic sediment fractions during chemical extraction. Here we developed a very short 10‐s leaching method to extract reliable seawater Pb and Nd isotope signals from sediments in the Atlantic sector of Southern Ocean. The effect of a previously recommended MgCl2 pre‐wash, the role of chelate ligands in the leaching solution and length of leaching time were investigated. The results show that 10‐s exposure time of sediments to reductive leaching extracted sufficient and more reliable hydrogenetic Pb and Nd compared with the commonly used 30‐min leaching approaches. The robustness of our improved leaching method was validated via direct comparison of Pb and Nd isotope signatures with actual seawater, porewater, and corresponding sediment leachates from three stations in front of the Antarctic Filchner‐Rønne Ice Shelf. Our findings also indicate that in contrast previously studied sites on the West Antarctic continental shelf, the bottom seawater Nd concentration is less elevated through benthic fluxes in the area of the southern Weddell Sea shelf., Plain Language Summary: Individual modern ocean water masses can often be identified by the isotopic signature of dissolved trace metals lead (Pb) and neodymium (Nd) supplied from surrounding continents. By analyzing past seawater Pb and Nd isotope ratios preserved in the sedimentary archives, we can understand how the ocean circulation changed. In the Southern Ocean, archives preserving past seawater Pb and Nd isotope compositions are very scarce. Thus, the chemical extraction of Pb and Nd from seawater‐derived ferromanganese oxyhydroxides within deep marine sediments becomes the most practical way to recover past seawater signal. However, Southern Ocean sediments commonly contain substantial quantities of Antarctic continental fine‐grained sediment, which easily partially dissolve during extraction, thereby releasing Pb and Nd, which did not originate from past ambient seawater. Here we established a gentle and efficient extraction method to obtain reliable past Southern Ocean seawater signatures. In addition, via analysis of regional seawater‐derived Pb and Nd signatures in the Atlantic sector of Southern Ocean, we found that the sediments further away from Antarctica and volcanically active regions are better suited to preserve unaltered seawater Pb and Nd isotope signals, which strongly supports the unique possibility of tracing past water mass sourcing in the Southern Ocean with our analytical approach., Key Points: 10‐s reductive leaching is capable of reliably extracting seawater Pb and Nd isotope signals from Southern Ocean sediments. Natural porewater Pb isotopic compositions are analyzed for the first time in front of the Antarctic Filchner‐Rønne Ice Shelf. Identify potential sites for extracting seawater Pb and Nd isotopic signatures from bulk sediments in the Atlantic sector of Southern Ocean., China Scholarship Council (CSC)

The Mozambique Channel plays a key role in the exchange of water masses between the Indian and Atlantic Oceans, which include the North Atlantic Deep Water (NADW) inflow from the south and the North Indian Deep Water (NIDW), an aged form of the NADW spreading poleward from the northern and equatorial Indian Ocean basin. Several authors assume that the Davie Ridge acts as a topographic barrier to the northward advection of NADW, which would therefore be absent in the Comoros Basin. Other studies suggest that the NADW flows from the south of the Mozambique Channel to the Comoros Basin, indicating that the Davie Ridge may not currently constitute a blocking topographic barrier to deep water mass circulation. To address this question, we studied ferromanganese (Fe, Mn) crusts collected over 2000 km in the Mozambique Channel, from the Agulhas Plateau to the Glorieuses Islands. Neodymium (Nd) isotope compositions (εNd) of surface scrapings range between εNd = −10.1 above the Agulhas Plateau, which might reflect the NADW inflow, and more radiogenic values between εNd = −8.0 and − 8.2 in the Glorieuses area, highlighting the NIDW influence. However, value of εNd = −9.4 measured north of the Davie Ridge cannot be explained by the sole influence of the NIDW and therefore highlights the advection of the NADW northeast of the Comoros Basin. We estimate that the contribution of the NADW through the channel is up to 68% in the Agulhas Plateau and 60% north of the Davie Ridge. These findings are consistent with previous hydrographic studies and suggest that the Davie Ridge does not currently act as topographic barrier to deep currents.

International audience; International Ocean Discovery Program (IODP) Expedition 356 Site U1461 represents one of the few records from the North West Australian shelf that provides information about aridity fluctuations in Australia during the Quaternary. A combination of chronostratigraphic indicators revealed the (partial) preservation of two major glaciations (Marine Isotope Stage (MIS) 2 and MIS 12) in the sedimentary record. The faunal content (mainly benthic foraminifera, corals and bryozoans) was analyzed to estimate paleo-environments and paleo-depths in order to determine if these sediments have been remobilized by reworking processes. Despite the occurrence of a depositional hiatus (including MIS 5d to MIS 9-time interval), the excellent preservation of faunal content suggests that the preserved sediment is in situ. The geochemical composition of the sediments (Nd and major elements) indicates that during MIS 12 riverine input was likely reduced because of enhanced aridity, and the sediment provenance (mainly atmospheric dust) is likely in the central (Lake Eyre) or eastern (Murray Darling Basin) parts of the Australian continent. MIS 2 is confirmed to be one of the driest periods recorded in Australia but with mixed dust sources from the eastern and western parts of the continent. More humid conditions followed the glacial maximum, which might correspond to the peak of the Indian-Australian Summer Monsoon..

The ability to trace and quantify sediment provenance in northwestern Patagonia is increasingly needed to properly understand modern sediment erosion and transport processes in this rapidly changing environment, and to accurately interpret sediment records from adjacent basins in terms of climate and environmental change. Nonetheless, no study so far has systematically evaluated the effectiveness of different tracers to reconstruct sediment provenance in this region. To fill this gap, we assess the effectiveness of commonly-used provenance indicators, including bulk mineralogy, major and rare earth element (REE) geochemistry, and Sr and Nd isotopes, to reconstruct sediment provenance in northwestern Patagonia. First, the ability of these tracers to discriminate between the main sources of sediment in the region is investigated, mostly using data compiled from the literature. Then, the potential of these tracers for provenance reconstruction is assessed by comparing the composition of sediments from six major Chilean rivers between 44 and 48°S to lithological proportions in their respective watersheds. The results suggest that mineralogy, major element geochemistry, and REE geochemistry can be used as qualitative tracers of sediment provenance. However, the compositional overlap between the sources and the relatively large variability within them prevent quantitative reconstructions. By comparison, 87Sr/86Sr and εNd allow to clearly differentiate between the sources, most likely due to significant age differences between the main lithologies, and to estimate the relative contribution of each source. End-member mixing results based on Sr and Nd isotopes show that the relative source contributions are in general agreement with the lithological proportions in the river watersheds. Differences between estimated contributions and lithological proportions in the watersheds are interpreted as the result of the high regional precipitation gradient and unequal glacier distribution, which lead to variable erosion rates across the study area. Our results demonstrate the suitability of 87Sr/86Sr and εNd for quantitative provenance reconstruction in northwestern Patagonia. They constitute a strong basis for the interpretation of sediment archives from the Patagonian fjords and from the eastern South Pacific, and they should be particularly useful to quantitatively investigate modern and past earth-surface processes., SCOPUS: ar.j, info:eu-repo/semantics/published

Financial support to DJW, TS, and TvdF was provided by the Natural Environment Research Council (NE/N001141/1), the Leverhulme Trust (RPG-398), the Grantham Institute for Climate Change and the Environment, and a Marie Curie Reintegration grant (IRG 230828). LFR acknowledges support from the Natural Environment Research Council (NE/N003861/1) and the European Research Council (278705). The sequence of deep ocean circulation changes between the Last Glacial Maximum and the Holocene provides important insights for understanding deglacial climate change and the role of the deep ocean in the global carbon cycle. Although it is known that significant amounts of carbon were sequestered in a deep overturning cell during glacial periods and released during deglaciation, the driving mechanisms for these changes remain unresolved. Southern Ocean sea-ice has recently been proposed to play a critical role in setting the global deep ocean stratification and circulation, and hence carbon storage, but testing such conceptual and modelling studies requires data constraining past circulation changes. To this end, we present the first deglacial dataset of neodymium (Nd) isotopes measured on absolute-dated deep-sea corals from modern Lower Circumpolar Deep Water depths in the Drake Passage. Our record demonstrates deglacial variability of 2.5 εNd units, with radiogenic values of up to during the Last Glacial Maximum providing evidence for a stratified glacial circulation mode with restricted incorporation of Nd from North Atlantic Deep Water in the lower cell. During the deglaciation, a renewed Atlantic influence in the deep Southern Ocean is recorded early in Heinrich Stadial 1, coincident with Antarctic sea-ice retreat, and is followed by a brief return to more Pacific-like values during the Antarctic Cold Reversal. These changes demonstrate a strong influence of Southern Ocean processes in setting deep ocean circulation and support the proposed sea-ice control on deep ocean structure. Furthermore, by constraining the Nd isotopic composition of Lower Circumpolar Deep Water in the Southern Ocean, our new data are important for interpreting deglacial circulation changes in other ocean basins and support a spatially asynchronous return of North Atlantic Deep Water to the deep southeast and southwest Atlantic Ocean. Postprint Postprint

International audience; The Iberian Pyrite Belt (IPB), located in the South Portuguese Zone of the Iberian Massif (Spain), is a world-class VHMS province containing numerous, huge mineral deposits hosted by bimodal volcanic sequences. The province can be subdivided in several domains, which differ from each other both in the nature and relative abundance of their volcanic sequences, and in the distribution of associated VHMS deposits. In spite of its geological and economic interest, information available for the northern part of the province is still relatively scarce. We present a new dataset of geochemical and Nd isotopic analyses on the Paymogo Volcano-Sedimentary Alignment (PVSA), an area that is considered to be representative of this northern segment of the IPB.Volcanic sequences in the PVSA contain very scarce mafic rocks. In contrast, felsic rocks are abundant and have been classified in two groups: (i) the Paymogo rhyolitic sequence, hosting most of the VHMS deposits and (ii) a dacitic sequence. Although approximately coeval, these groups of felsic rocks clearly differ in geochemical features and ƐNd signature. In view of these differences, it is suggested that felsic rocks were produced from different mid-crustal domains during a major event of partial melting related to a regional, late Devonian/Early Carboniferous transtensional event. It is further suggested that some volcanic rocks previously described as andesites, are better interpreted as dacites.The age (347.3 ± 0.8 Ma), geochemical features, (Zr

XX Seminario Ibérico de Química Marina (SIQUIMAR 2020) - XX Iberian Seminar on Marine Chemistry, 1-3 July 2020, Barcelona.-- 2 pages.-- Samples were collected during the NextData Cruise on R/V Minerva I in June 2016, The present study aims at shedding light on the central Mediterranean Sea (MS) functioning in terms of water mass mixing and potential lithogenic sources by means of new geochemical tracers such as dissolved Nd isotopes (εNd) and Rare Earth Element (REE: La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) concentrations. Although proved to be valuable tracers of oceanographic processes, their measurements are basically lacking in the MS water column. We analyzed 9 stations around the Tyrrhenian, Ionian and Ligurian seas. Dissolved REE were measured with an Agilent 7500 ICP-MS and εNd using a Nu Plasma-III MC-ICP-MS at UB. The obtained REE do not display nutrient-like profiles, likely suggesting relatively young waters with limited accumulation of remineralized REE. Light REE (LREE: from La to Gd) present a non-conservative behavior, largely peaking at surface waters and rapidly decreasing with depth. The negative linear correlation of surface LREE enrichment with offshore distance indicates their release from lithogenic sediments of the Italian coast to the Tyrrhenian waters. In contrast to other regions, this process does not modify the εNd values. On the other side, distributions of dissolved heavy REE (HREE: Tb to Lu) and εNd exhibit a conservative behavior that can be explained by mixing of western- (MAW and WMDW) and eastern- (LIW and EMDW) originated waters. We test this hypothesis with an Optimum Multi-Parameter Analysis (OMPA) including HREE and εNd parameters. Even though the limited data set, consistent results of water mass fractions are obtained for the four main water masses although with some particularities. While LIW take on major importance when considering HREE in the model, EMDW fractions are preferentially detected with εNd. This latter finding implies a noticeable deep-water flux across the Sicily Strait into the Western Mediterranean that was not clearly evidenced before, The authors thank financial support from the OPERA Project (CTM2013-48639-C2-1-R), the CHIMERA Project (CTM2016-75411-R) and Generalitat de Catalunya (2017 SGR 315). This work has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant agreement No. 683237)

12 pages, 6 figures, 2 tables, supplementary material https://doi.org/10.1016/j.pocean.2020.102340, Seawater rare earth element (REE) concentrations and Nd isotopic composition (εNd) are increasingly applied as valuable tracers of oceanographic processes such as water mass mixing and lithogenic inputs to seawater. However, their measurements are basically lacking in the Mediterranean Sea water column. This study analyzes 9 seawater stations around the central Mediterranean Sea to clarify the relative importance of external sources, vertical (biogeochemical) processes and lateral water mass transport in controlling REE and εNd distributions. Concentrations of REE do not show nutrient-like profiles with depth, likely indicative of relatively young waters with limited accumulation of remineralized REE. Light REE (LREE) present a non-conservative behavior, which largely peak at surface waters and rapidly decrease with depth. The negative correlation of surface LREE enrichment with offshore distance highlights the influence of continental input from the western Italian coast to the Tyrrhenian surface waters. In contrast to other regions with reported boundary exchange, this process does not modify the εNd values here. On the other side, distributions of dissolved heavy REE (HREE) and εNd display a conservative behavior that can be explained by mixing of western- (MAW and WMDW) and eastern- (LIW and EMDW) originated waters. We test this hypothesis with an Optimum Multi-Parameter Analysis (OMPA) including HREE and εNd parameters. Even though the limited data set, consistent results of water mass fractions are obtained for the four main water masses although with some particularities. While LIW takes on major importance when considering HREE in the model, EMDW fractions are preferentially detected with εNd. This latter finding implies a noticeable deep water flux across the Sicily Strait into the Western Mediterranean that was not clearly evidenced before, This research has been financially supported by the TIMED Project funded by the European Commission (ERC Consolidator Grant to I. Cacho; ID: 683237). The authors thank financial support from the CHIMERA Project (CTM2016-75411-R), Generalitat de Catalunya-Grups de Recerca Consolidats (2017 SGR 315) and the Project of Strategic Interest NextData PNR 2011-2013 (www.nextdataproject.it). [...]. E. Garcia-Solsona acknowledges support from a post-doctoral fellowship (FPDI-2013-15660) and L.D. Pena from the Ramón y Cajal program (MINECO, Spain). I. Cacho thanks the ICREA-Academia programme from the Generalitat de Catalunya. J.N. Pérez-Asensio has been funded by a Beatriu de Pinós postdoctoral fellowship from AGAUR (Generalitat de Catalunya) and the European Commission (Marie Curie-COFUND), With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

The Miocene is a key interval in the geodynamic and oceanographic evolution of the Mediterranean marking the transition from a wide open basin to the modern closed basin. We used the Sr and Nd isotope records of two Miocene carbonate successions in the Adriatic to document that the evolution of the Mediterranean Basin controlled its seawater chemistry. During the late Aquitanian (similar to 21Ma), a time of glaciation and sea level lowstand, increased runoff affected the Sr isotope ratios of Mediterranean waters, whereas during the Burdigalian (20.44-15.97Ma) volcanism in the circum-Mediterranean area mainly influenced the Sr isotopic signature. During the Langhian (15.97-13.82Ma), a time of sea level highstand associated with the Middle Miocene Climatic Optimum, the Nd isotope values indicate that waters exchanged between the Paratethys and the Central Mediterranean. The Central Mediterranean was well connected with the Atlantic Ocean between the Langhian and the early Tortonian (15.97-11.5Ma), but exchange of water with the Paratethys declined. In the Messinian (6.3Ma), connections between some marginal Mediterranean basins, for example, the proto-Adriatic basin, and the Central Mediterranean, became restricted. In this basin, the Sr isotope values fell below the global reference line, while Nd isotope ratios show a strong affinity with the Atlantic Ocean and also indicate freshwater input. We conclude that the Mediterranean Nd isotope signature differs from that in the open oceans and reflects the basin physiography, reflecting a mix of signals derived from the adjacent oceans and local signals.

Miocene is a key interval in the global climate evolution as well as in the geodynamic evolution of the Mediterranean basin. Therefore, global and regional factors controlled Miocene Mediterranean oceanography, which, in turn, affected carbonate production. In this work, we review the Miocene paleocenographic evolution of the Mediterranean starting from its Sr and Nd isotope records. Secondly, we discuss Mediterranean shallow-water carbonate production changes to identify the role of oceanographic conditions in controlling carbonate systems' evolution. During Aquitanian, Sr and Nd isotope records attest an open Mediterranean, mainly fed by the Indian Ocean. From the late Burdigalian, the intermittent connection with the Indian Ocean changed the overall circulation in the basin, leading to higher residence time of waters and smaller water exchanges with the adjacent oceans. In this newly established paleoceanographic framework, regional factors such as volcanism, significantly affected Mediterranean seawater chemistry. Local tectonics led to the development of small sub-basins in the Eastern Mediterranean, characterized by restricted water exchanges from the Tortonian in the easternmost part, to the early Messinian, as attested by the deviation of the Sr isotope record of the proto-Adriatic basin. Larger Benthic Foraminifera (LBF) assemblages dominated carbonate production in the Aquitanian, while they were the most affected by the Indo-Pacific closure, showing a demise after the Burdigalian. With the LBF demise, red algae and bryozoans dominated carbonate ramps from the middle Miocene to the Tortonian. Bryozoans in particular spread during the Monterey Event, favoured by global and regional factors. During early to middle Miocene, corals formed mounds in the oligophotic zone or coral carpets controlled by local conditions. Conversely, in the late Tortonian-early Messinian, they developed as huge reef complexes in the Western and Central Mediterranean, with the exception of small restricted sub-basins, such as the proto-Adriatic basin, where red algae and small benthic foraminifera persisted.

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 ( e Nd ) as paleo-seawater tracer. Our e 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 e 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 e 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.

International audience; 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 (εNdt = −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; εNdt = −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 TDM model ages become progressively younger from the base to the top of the sequence (Nd TDM = 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.

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, μ142NdJNdi-1=−45±5 (2SD), ε143NdCHUR=−16.7±0.4 (2SD) and ε176HfCHUR=−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 ε143Nd–μ142Nd 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., SCOPUS: ar.j, info:eu-repo/semantics/published

Rare earth elements (REE) concentrations were measured in surface waters collected across the salinity gradient in the Mississippi River estuary (i. e., Mississippi River plume, MRP), which includes the near-shore portion of the Louisiana Shelf. In addition, the neodymium (Nd) isotope compositions of two river water samples, and the acid leachable fractions of the associated suspended particulate matter (SPM), were quantified to compare Mississippi River water, and SPM with Gulf of Mexico waters. Despite the spatial limitations associated with sampling due to the size of the Mississippi River system, this study provides some important insights into the REE geochemistry of the MRP. The Mississippi River and its estuarine waters are enriched in the heavy REE (HREE) compared to the light REE (LREE) when normalized to shale composites. All water samples from the estuary also exhibit substantial negative Ce anomalies. In contrast to the majority of other estuaries investigated, removal of REE in the low salinity reaches of the Mississippi River estuary is less substantial. For example, approximately 50% of the river borne Nd is removed in the low salinity region (S < 10) of the Mississippi River estuary, compared to the estimated global average of ca. 70% removal of Nd for estuaries worldwide. We propose that the relatively low REE removal in the Mississippi estuary reflects the high pH (~8) of the Mississippi River, where REE complexation with carbonate ions and natural organic ligands act to stabilize REE in solution. The Nd isotope composition of Mississippi River water near its outflow to the Gulf of Mexico is εNd(0) = −10.5. The acid leachable fraction of the associated SPM is more radiogenic (−9.95 ≤ εNd(0) ≤ −9.77), and closer to the generally more radiogenic Gulf of Mexico [εNd(0) = −9.0]. Sequential extraction of the Mississippi River bank sediment reveals substantially different Sm/Nd ratios for the operationally defined fractions of the sediment, which suggests variations in Nd isotope compositions between the labile fractions and the bulk sediment.

VI Simposio Internacional de Ciencias del Mar - VI International Symposium of Marine Sciences (ISMS 2018), 20- 22 June 2018, Vigo.-- 2 pages, The purpose of this study is to use dissolved Rare Earth Elements (dREE) and Nd isotopes (εNd) in sea water to better understand water-mass exchange and pathways in the Central Mediterranean (CM) Sea. We have analyzed 9 hydrographic stations around the Tyrrhenian Sea, Strait of Sicily and Ionian Sea (NextData2016 Cruise). Pre-concentrated and purified dREE were measured with an Agilent 7500 quadrupole ICP-MS while Nd isotopes (εNd) were determined using a Nu Plasma III Multicollector ICP-MS. In general, dREE abundances in the CM are similar to the western Mediterranean [1] but clearly lower than in the eastern basin [2] pointing to an eastward enrichment of Atlantic Waters, as for other trace metals. In addition, inflowing Atlantic Waters (εNd≈-10) become more radiogenic within its circulation (εNdup to -6). Light REE (LREE) present highest concentrations at surface waters, probably indicating lithogenic inputs. This is specially marked at the station closest to the continental margin with LREE enrichments relative to the other stations of 20-50%, with no significant εNd modification. Far from continental margins and below the surface, well-developed oceanic dREE patterns are found displaying negative cerium anomalies (Ce*=0.20-0.30) and enrichment of Heavy REE (HREE) demonstrating that water mass mixing governs the REE distribution below the permanent thermocline. Levantine Intermediate Waters (LIW) can be traced through a substantial HREE peak and distinctive radiogenic neodymium signature (εNd=-6.4). This is coherent with older waters enhanced with conservative HREE. Concerning εNd, the radiogenic imprint of LIW is in accordance with either the influence of partially dissolved Nile river particles [2] or the rock signature in the LIW formation zone [3]. Finally, both dHREE and εNd can be used to distinguish deep water masses: EMDW present εNd≈-6.7 and WMDW show εNdof -8.5, with the first being 13% more enriched in dHREE than the later, We authors thank financial support from the Italian Project of Strategic Interest NEXTDATA (http://www.nextdataproject.it) “A national system for recovery, storage, accessibility and dissemination of environmental and climatic data from mountain and marine areas” and from the OPERA Project (CTM2013-48639-C2-1-R) and Generalitat de Catalunya-Grups de Recerca Consolidats (2017 SGR 315). This work has been partially funded by the European Commission through an ERC Consolidator Grant to I. Cacho (TIMED; ID: 683237). Support from the Spanish Government for a post-doctoral fellowship to E. G-S. (FPDI-2013-15660) is also recognized. L.P. acknowledges support from the Ramón y Cajal program (MINECO, Spain). J.N.P-A. has been funded by a Postdoctoral fellowship Beatriu de Pinós (Generalitat de Catalunya, Marie Curie-COFUND actions)

During the production of natron glass most features of the raw materials are lost and only some bulk geochemical characteristics have potential as provenance indicators. To determine the primary origin of archaeological glass artefacts, suitable sand raw materials have to be accurately characterised. In this respect, information about the possible variation in geochemical properties within a silica source is also vital to account for potential (partial) overlap of different sources. In this study, it is shown that the variation in major and minor elemental composition of beach sand on a local scale is smaller than the variation in Roman natron glass. Therefore, a single sand deposit can be seen as a relatively homogeneous source of silica for glass production. Nd isotopic signatures are identical for all samples analysed. The isotopic composition of Sr however varies considerably due to local variations in the relative proportions of carbonates and silicates (mostly feldspar). ispartof: STAR: Science & Technology of Archaeological Research vol:1 issue:2 pages:115-124 status: published

The Mediterranean Outflow (MOW) is generated by deep and intermediate waters from different basins in the Mediterranean Sea. Despite the number of studies on Mediterranean water masses, little work has been done on the source and properties of intermediate waters in the westernmost Mediterranean Sea and their links with MOW. Here we examine three marine sediment records spanning the last 20 kyr, located at key depths to trace intermediate waters along the Alboran Sea. We use a combination of redox-sensitive elements, which can serve as proxies to reconstruct variations in the water column oxygenation and the Nd isotopic composition of foraminiferal ferromanganese coatings, in order to reconstruct water mass provenance of Eastern/Western Mediterranean waters. As measured, eNd < − 9.2 and a low U/Th ratio during glacial periods can be attributed to the presence of Western Mediterranean Deep Water (WMDW) at the study sites. During deglaciation, higher Nd isotopic compositions and U/Th ratios point to an enhanced contribution of the modified Levantine Intermediate Water (LIW). The comparison between our data and other LIW and MOW records suggests that i) the lower branch of MOW is linked to WMDW during the glacial period, ii) the middle MOW branch follows LIW activity during deglaciation, while iii) the upper branch is more active during late Holocene, coinciding with LIW formation increase after sapropel deposits. This reconstruction has significant implications for an understanding of the MOW evolution.

Neodymium isotope data on exhalites and tuffs from the Cambrian Lemarchant volcanogenic massive sulphide (VMS) deposit provide insights into the tectonic environment of the Tally Pond group, Canada. New data from exhalites from the Lemarchant area show evolved values of εNd513 = 6.0 to 1.8, whereas the associated volcanic rocks have εNd513 of +0.4 to +1.4. The Lemarchant exhalite εNd compositions overlap the underlying Ganderian Neoproterozoic Sandy Brook Group (εNdt = 6.5 to 1.9) and Crippleback Intrusive Suite (εNdt = 5.9 to 5.2). The evolved Nd isotopic signatures suggest that the volcanic rocks of the Tally Pond group were formed upon Ganderian arc basement, which itself was possibly built upon, or proximal to, the Gondwanan Amazonian margin. Erosion of older crustal material and Tally Pond group volcanic rocks, together with coeval eruption of the volcanic rocks, released Nd-rich detritus into the water column. Uptake of eroded detrital and scavenged Nd resulted in mixed Nd sources (juvenile and evolved), which are archived in the exhalites. The results of this study are of significance not only for occurrences of exhalites within the Tally Pond group, but also have exploration implications for VMS districts globally. Postprint

Arc lavas form from melting of mélange rocks; sediment melts and slab-derived fluids are not major contributors., In subduction zones, sediments and hydrothermally altered oceanic crust, which together form part of the subducting slab, contribute to the chemical composition of lavas erupted at the surface to form volcanic arcs. Transport of this material from the slab to the overlying mantle wedge is thought to involve discreet melts and fluids that are released from various portions of the slab. We use a meta-analysis of geochemical data from eight globally representative arcs to show that melts and fluids from individual slab components cannot be responsible for the formation of arc lavas. Instead, the data are compatible with models that first invoke physical mixing of slab components and the mantle wedge, widely referred to as high-pressure mélange, before arc magmas are generated.

The warming of the Arctic region in the recent past has proceeded at rates double that of the global average and has been accompanied by rapid sea ice retreat and increased heat and freshwater fluxes to the Arctic Mediterranean (i.e. the Arctic Ocean and the Nordic Seas, AM). Further warming will have strong impacts on ocean circulation, freshwater pathways, and marine ecosystems in the AM. Disentangling the sources, distribution and mixing of water masses involved in the transport and transfer of heat and freshwater is therefore critical for the understanding of present and future hydrological changes in the high-latitude and polar regions and their consequences. This study refines the knowledge of water mass circulation and mixing in the AM and provides new insights into the processes occurring on the Arctic shelves and in high-latitude estuaries. A multi-proxy approach is used combining dissolved radiogenic Nd isotopes (εNd), rare earth elements (REEs) and stable oxygen isotopes (δ18O) together with standard hydrographic tracers. The sources, distribution and mixing of water masses that circulate in the AM and pass the Fram Strait are assessed through evaluation of dissolved εNd and REE, and δ18O data obtained from samples recovered in 2012 along a full water depth section extending between Svalbard and Greenland at ~79 °N, and through a compilation and reassessment of literature Nd isotope and concentration data previously reported for other sites within the AM. The Nd isotope and REE distribution in the central Fram Strait and the open AM primarily reflects the lateral advection of water masses and their mixing, whereas seawater-particle interactions exert important control only above the shelf regions. For example, on the NE Greenland Shelf, remineralization of biogenic and/or release from detrital particles is recorded in bottom waters. Advection of warm Atlantic Water (AW) in the upper water column of the eastern and central Fram Strait is clearly reflected by an εNd signature of -11.7 and a Nd concentration ([Nd]) of 16 pmol/kg. Freshening and cooling of the AW on its way through the AM are accompanied by a continuous change towards more radiogenic Nd isotope compositions (e.g. -10.4 of dense Arctic Atlantic Water). This change results from mixing with intermediate waters but also mirrors the admixture of dense Kara Sea waters and Pacific-derived waters. Exchange with basaltic formations of Iceland and southeastern Greenland is suggested to impart the intermediate and deep waters of the AM with more radiogenic εNd signatures, which reach -9.5 in the Fram Strait. Significant inputs of Nd from Svalbard are not observed and surface waters and Nd on the western Svalbard Shelf originate in the Barents Sea. Shallow (< 200 m) waters of Arctic origin form the core of the East Greenland Current above the Greenland slope and have relatively radiogenic εNd (reaching -8.8) and elevated [Nd] (21-29 pmol/kg), which together with δ18O and standard hydrographic tracers are used to determine the proportions of Pacific-derived (< 30 % based on Nd isotopes) and Atlantic-derived seawater, as well as of river waters (< 8 %). A change in the Nd isotope compositions to less radiogenic values (-12.4) and an increase in [Nd] (38 pmol/kg) are observed at water depths above 100 m near the Greenland coast documenting addition of Greenland-sourced freshwater (GFW). The amount of GFW contained in the upper water column on the NE Greenland Shelf reached 6 % in 2012. Data obtained for the years 2014 and 2015 for the northern and southern NE Greenland Shelf suggest similar fractions of GFW for shallow waters in the Norske Trough and east of Ob Bank, indicating southward and northward propagation of GFW along the Greenland coast assuming that the NE Greenland Ice Stream is the freshwater source. The Nd isotope compositions of Arctic-derived waters (εNd ~ -9) and other water masses were essentially constant over the time period 2012-2015, which provides a solid basis for quantitative estimates of GFW admixture. The GFW distribution suggests that future increased GFW supply forced by global warming will lead to additional freshening of shallow Arctic waters, which, once these waters have traversed the Nordic Seas, may ultimately affect overturning strength in the northern Labrador Sea. Overall, the results obtained from the Fram Strait demonstrate that the pronounced gradients in εNd and REE contents in the upper water column provide a reliable basis for assessments of short-term shallow hydrological changes within the AM. New insights into the processes occurring in high latitude estuaries are provided by dissolved Nd isotope and REE compositions together with δ18O data for the Laptev Sea based on filtered samples collected during two summers (2013 + 2014) and one winter (2012). The Laptev Sea is a Siberian Shelf sea characterized by extensive river-runoff, sea-ice production and ice transport into the Arctic Ocean. The broad range in εNd (-6 to -17), REE concentrations (16 to 600 pmol/kg for Nd) and REE patterns found in the frame of this study is attributed to freshwater supply from the Siberian rivers and advection of open ocean Arctic Atlantic Water. Strikingly and contrary to expectations, there is no evidence for significant release of Nd from particulate phases and Nd isotopes can thus be used to assess water mass mixing together with the salinity after correction for variations in the salinity caused by sea-ice formation and melting. High fractions of riverine contributions from the Lena River (up to 75 %) are determined for the surface layer of the eastern Laptev Sea with significant interannual variations, while the less variable advection of Yenisei and Ob freshwater (up to ~20 %) is restricted to the western Laptev Sea. Essentially all Laptev shelf waters are depleted in light (L)REEs, while the distribution of the heavy (H)REEs shows a deficiency at the surface and an excess in the bottom layer. A combination of REE removal through coagulation of nanoparticles and colloids and REE redistribution within the water column through formation and melting of sea ice and river ice is suggested to account for the distribution of all REEs. Estuarine removal of riverine REEs starts at salinities close to 10 and after a drop of all REEs by about 30 % transfers into preferential LREE removal, which for Nd reaches 75 % at salinities near 34. Although the delayed onset of dissolved REE removal contrasts with observations from most other estuarine environments, the distributions coincide remarkably well with results from recent experiments simulating estuarine mixing with organic-rich river waters. The melting and formation of sea ice and river ice lead to further REE depletion at the surface and enrichments in the bottom water layer as a function of ice melting and brine transfer, respectively. The ice-related processes contribute to the redistribution of other elements and may also affect macronutrient distribution and primary productivity in high latitude estuaries.

International audience; Neodymium isotopic compositions (143Nd/144Nd or εNd) 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 εNd database and combined it with hydrography parameters (temperature, salinity, nutrients and oxygen concentrations), carbon isotopic ratio and radiocarbon of dissolved inorganic carbon. Archive εNd 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 εNd and the other variables, suggesting that large-scale water mass mixing is a primary control of deepwater εNd distribution. At ≥ 200 m, basin-scale seawater T-S-εNd diagrams demonstrate the isotopic evolution of different water masses. Seawater and archive εNd values are compared using property-property plots and T-S-εNd 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 εNd 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 εNd is observed mainly within 1000 km from the continents. Generally, seawater and archive εNd 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.

The Arabian–Nubian Shield (ANS) represents a major site of juvenile Neoproterozoic crustal addition on Earth and documents Neoproterozoic tectonics bracketed by two supercontinent cycles, namely the fragmentation of Rodinia and the amalgamation of Gondwana. There is general consensus that the ANS formed by juvenile magmatic arc accretion and subsequent shield–wide post–tectonic magmatism. However, detailed understanding about the timing of events and the nature of magma sources in parts of the shield are lacking. To date, there are no isotopic data from the Paleozoic sedimentary sequences of the ANS, except those from the northern part. New zircon U–Pb, δ18O and whole–rock Nd isotopes are presented for plutonic rocks from the eastern Ethiopia, Yemen and southernmost Arabian Shield in Saudi Arabia. This thesis also presents the first combined in situ zircon U–Pb–O–Hf isotope data on the Cambrian–Ordovician sandstones of the Arabian Shield. The results are used to elucidate the crustal evolution of these parts of the ANS and to evaluate terrane correlations. Specifically, the nature of crustal growth, i.e., relative proportions of juvenile magmatic additions vs. crustal reworking, nature of the magma source and mechanism of crust formation (plume material vs. subduction zone enrichment) and understanding the provenance of the Cambrian–Ordovician sandstone sequences were important research questions addressed. The results from Paper I suggest that the eastern Ethiopian Precambrian basement is dominated by reworking of pre-Neoproterozoic supracrustal material unlike contemporaneous rocks in the remaining parts of Ethiopia— indicating the presence of two distinct lithospheric blocks of contrasting isotopic compositions in Ethiopia. Metamorphic age distributions suggest that the eastern Ethiopian block was amalgamated with the juvenile Western Ethiopian Shield during ca. 580–550 Ma. Importantly, the suture between them may represent the northern continuation of a major suture identified further south in Africa along which Gondwana amalgamated. Similarly, the Abas terrane in Yemen (Paper II) is dominated by reworking of pre–Neoproterozoic crust and shows age and isotopic compositions that are inconsistent with the Afif terrane of Saudi Arabia, precluding correlation between the two regions. The trace element systematics of plutonic rocks from the southernmost Arabian Shield (paper III) point to enrichment due to subduction component, bear no evidence of a plume component, and are consistent with the adakite-like chemistry of some of the subduction–related plutonic samples. This reinforces the notion that the shield grew through juvenile magmatic arc additions. The combined zircon U–Pb–O–Hf data of the Cambrian–Ordovician sandstones (Paper IV) indicate their derivation from both the adjacent juvenile ANS and the more southerly crustal blocks that are dominated by reworking of pre–Neoproterozoic crust. The remarkable similarity in age spectra and homogeneity of Cambrian sandstones deposited across the northern margin of Gondwana point to continental–scale sediment mixing and dispersal regulated by the supercontinent cycle. At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.

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 Ceara 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 Ceara Rise, and the delivery of terrestrial (both soil and riverine) branched GDGTs to the Ceara Rise.

Antarctic Intermediate Water (AAIW) is a key player in the global ocean circulation, contributing to the upper limb of the Atlantic Meridional Overturning Circulation (AMOC), and influencing interhemispheric heat exchange and the distribution of salinity, nutrients and carbon. However, the deglacial history of AAIW flow into the North Atlantic is controversial. Here we present a multicore-top neodymium isotope calibration, which confirms the ability of unclean foraminifera to faithfully record bottom water neodymium isotopic composition ( e Nd ) values in their authigenic coatings. We then present the first foraminifera-based reconstruction of e Nd from three sediment cores retrieved from within modern AAIW, in the western tropical North Atlantic. Our records reveal similar glacial and interglacial contributions of AAIW, and a pronounced decrease in the AAIW fraction during North Atlantic deglacial cold episodes, Heinrich Stadial 1 (HS1) and Younger Dryas (YD). Our results suggest two separate phases of reduced fraction of AAIW in the tropical Atlantic during HS1, with a greater reduction during early HS1. If a reduction in AAIW fraction also reflects reduced AMOC strength, this finding may explain why, in many regions, there are two phases of hydrologic change within HS1, and why atmospheric CO2 rose more rapidly during early than late HS1. Our result suggesting less flow of AAIW into the Atlantic during North Atlantic cold events contrasts with evidence from the Pacific, where intermediate-depth e Nd records may indicate increased flow of AAIW into the Pacific during the these same events. Antiphased e Nd behavior between intermediate depths of the North Atlantic and Pacific implies that the flow of AAIW into Atlantic and Pacific seesawed during the last deglaciation.

The oxygen (O) and neodymium (Nd) isotopic composition of monazite provides an ideal tracer of metamorphism and hydrothermal activity. Calibration of the matrix effect and monitoring of the external precision of monazite O&ndash, Nd isotopes with microbeam techniques, such as secondary ion mass spectrometry (SIMS) and laser ablation-multicollector-inductively coupled plasma-mass spectrometry (LA-MC-ICPMS), require well-characterized natural monazite standards for precise microbeam measurements. However, the limited number of standards available is impeding the application of monazite O&ndash, Nd isotopes. Here, we report on the RW-1 monazite as a potential new working reference material for microbeam analysis of O&ndash, Nd isotopes. Microbeam measurements by electron probe microanalysis (EPMA), SIMS, and LA-MC-ICPMS at 10&ndash, 24 &micro, m scales have confirmed that it is homogeneous in both elemental and O&ndash, Nd isotopic compositions. SIMS measurements yield &delta, 18O values consistent, within errors, with those obtained by laser fluorination techniques. Precise analyses of Nd isotope by thermal ionization mass spectrometry (TIMS) are consistent with mean results of LA-MC-ICPMS analyses. We recommend &delta, 18O = 6.30&permil, &plusmn, 0.16&permil, (2SD) and 143Nd/144Nd = 0.512282 &plusmn, 0.000011 (2SD) as being the reference values for the RW-1 monazite.

International audience; Major, trace element concentrations and Nd, Sr isotopic data are reported for Neoproterozoic high-pressure (HP) mafic granulites from the Agou Igneous complex (AIC), which marks the suture zone of the Pan-African Dahomeyide orogen in southwestern Togo. The main rock types consist of garnet-free and garnet-bearing metagabbronorites (GFM and GBM) that are cross cut by subordinate leucocratic to melanocratic veins and dykes of garnet-bearing microgabbroic rocks. Geochemical data suggest that the HP granulites may have preserved the geochemical imprints of their igneous protoliths. They display either cumulitic features or liquid compositions varying from primitive to evolved basalts and andesites and then to more differenciated dacitic magmas as supported by major and trace element contents. Primary basalts display LREE and LILE enriched patterns and no Eu anomaly, but are depleted in Y and Yb suggesting a slightly enriched mantle source or a weak crustal contamination. Mafic veins and dykes display REE flat patterns (LaN/YbN = 0.58-1.7) and a slightly negative Eu anomaly and ∑REE content ranging between 10 and 20. These features are consistent with protoliths of N- to E-MORB affinities. Mafic cumulates and andesitic basalts are characterized by various REE patterns which could be compared to those of the primary and/or the evolved basalts, probably identifying various igneous suites. The fractionated REE patterns (Ce/YbN ≈ 11.0-17.9) with slight LREE enrichment (Ce/SmN ≈ 3.1-3.8) and HREE depletion (Sm/YbN ≈ 3.6-4.8) could be induced by a garnet residue in the melt source. Neodymium isotopic data show that most mafic cumulative rocks have similar 143Nd/144Nd ratios between 0.5127 and 0.51289, corresponding to initial εNd(T) values between +2.26 and +6.33 that yielded TDM ages from 1.2 to 0.94 Ga. The mafic mesocratic vein displays 143Nd/144Nd values of 0.51227, corresponding to initial εNd(T) values of +6.87 that yielded TDM = 0.94 Ga, and constrains the minimum age. However primitive basalts samples A17 (GFM) and other mafic cumulate Ag224 (GBM) give an older depleted mantle source derivation age of 2.31 and 1.68 Ga respectively, suggesting crustal contamination by the surrounding gneissic Paleoproterozoic basement. The Nd isotopic compositions suggest that the parental magmas of the Agou Igneous Complex in southern Togo were derived from time-integrated depleted mantle source. Such geochemical features are consistent with an active continental margin environment and suggest that the AIC represents a magmatic body emplaced and cooled at the base of a continental crust above a subduction zone.

International audience; Hydroclimate variability has exerted a fundamental control on the alternating deposition of organic-lean marl and organic-rich sapropel sediments in the eastern Mediterranean Sea (EMS). However, the exact mechanisms regarding the freshwater sources and related changes are still debated. Here, Sr and Nd isotopes and high-resolution elemental data are used to constrain different riverine and eolian supplies to the central Mediterranean over the past 9.8 l

International audience; The stratoid granites of Madagascar are sheet-like granite sills emplaced conformably to the schistosity of the Antananarivo and Ikalamavony domains of the Precambrian basement. Most of them are fine-grained rocks with A-type affinities. They belong to two different plutonic suites: the Kiangara Suite north of Antananarivo and the Imorona–Itsindro Suite recognized in the whole central Madagascar. Stratoid granites are everywhere characterized by the same structural pattern evidencing two deformation events. The first event (D1 characterized by foliations mildly dipping to the west and lineations trending WSW) was coeval with synkinematic magma emplacement. The second one, responsible for local reworking in ductile conditions, is regarded as the result of late Pan-African transcurrent tectonics along N–S striking shear zones. New in situ U–Pb zircon dating from both suites yields similar results evidencing two group of ages: upper intercept ages of 790–780 Ma regarded as crystallization ages, and younger ages of ca. 555 Ma corresponding to a metamorphic overprint. These new data suggest that both plutonic suites in central Madagascar were emplaced at 790–780 Ma. New Sm–Nd isotopic data from the Kiangara Suite support the existence of two granite groups. The first group has εNd(t) at −15 and is likely derived from partial melting of the late Archaean crust. The second group made of granites with a more pronounced A-type nature and comagmatic syenites has εNd(t) at −12 evidencing the contribution of mantle melts. Mafic enclaves with εNd(t) ranging from −5 to −11 encompass the Nd isotopic signature of coeval Itsindro gabbros, which are regarded as derived from a subcontinental lithospheric mantle source. The interpretation of both structural and isotopic data is consistent with crustal thinning and extension during a Cryogenian Rodinia rifting stage at 790–780 Ma, that left a major imprint in central Madagascar. Separation from a conjugage margin represented by the North China craton is suggested. The Pan-African influence is limited to reheating, tectonic reworking and fluid transfer in the vicinity of late-Neoproterozoic (∼550 Ma) shear zones.

International audience; Early Proterozoic sedimentary basins are an important record of crust generation processes and consequently a fundamental key to unraveling Earth's evolution through geological time. Sediments within the basins are typically deformed and metamorphosed by subsequent tectonothermal events, which can obliterate their links to source terranes. Nd-whole-rock and detrital zircon U–Pb and Lu–Hf isotopic analyses are among the most reliable tools to be used in provenance investigations, since zircon is a resilient mineral and the Sm–Nd system is not extensively modified during metamorphism. These methods have been applied to a study of the provenance and tectonic setting of the São Vicente Complex, preserved in a Neoproterozoic passive margin related allochthon within the Southern Brasilia Orogen. The complex consists of siliciclastic and calc-silicate gneisses with mafic and minor ultramafic rocks, which were deformed and metamorphosed during late Neoproterozoic collision between the Paranapanema Block and the São Francisco-Congo plate. Detrital zircons indicate derivation from a juvenile Paleoproterozoic source terrane (peaks of crystallization ages of ca. 2130 Ma, 2140 Ma and 2170 Ma; ɛHft between +0.1 and +6.0; NdTDM = 2.31–2.21 Ga; ɛNdt = +1.6 to +2.8), with a minor contribution from older continental crust. Interlayered amphibolite rocks, with juvenile signatures (ɛHft = +5.8 to +8.2; NdTDM = 2.14 and 2.30 Ga; ɛNdt = +2.2 and +3.2), yielded similar ages of 2136 ± 17 and 2143 ± 14 Ma, suggesting syn-sedimentary magmatism. Thus, the maximum age of deposition at around 2130 Ma represents the best estimate of the depositional age of the complex. The dominance of detrital zircons ages close to the age of deposition, along with syn-sedimentary magmatism, imply a convergent margin basin tectonic environment for the São Vicente Complex, with similarities to fore arc basin and trench deposits. Amphibolite and meta-sedimentary rocks point to important juvenile magmatism around 2.14 Ga. Juvenile Rhyacian (ca. 2.1 Ga) granite-granodiorite-tonalite orthogneisses with arc-related geochemical signatures (Pouso Alegre Complex) that override the São Vicente Complex, are the probable main source of detritus within the complex. Both basin and source were part of the southern edge of the São Francisco plate during the assembly of West Gondwana, and served as sources for early Neoproterozoic passive margin related basins. The age of intrusive anorogenic A-type Taguar granite indicates that by 1.7 Ga the São Vicente Complex was in a stable tectonic environment.

A. Westin and M.C. Campos Neto acknowledge support from São Paulo Research Foundation (FAPESP) through grants 2011/13311-9, 2013/13530-8 and 2013/19095-1. A. Westin is a grant holder at FAPESP and M. C. Campos Neto is a CNPq researcher. P. A. Cawood, C. J. Hawkesworth and H. Delavault acknowledge support from Natural Environment Research Council grant NE/J021822/1. Early Proterozoic sedimentary basins are an important record of crust generation processes and consequently a fundamental key to unravelling Earth's evolution through geological time. Sediments within the basins are typically deformed and metamorphosed by subsequent tectonothermal events, which can obliterate their links to source terranes. Nd-whole-rock and detrital zircon U-Pb and Lu-Hf isotopic analyses are among the most reliable tools to be used in provenance investigations, since zircon is a resilient mineral and the Sm-Nd system is not extensively modified during metamorphism. These methods have been applied to a study of the provenance and tectonic setting of the São Vicente Complex, preserved in a Neoproterozoic passive margin related allochthon within the Southern Brasilia Orogen. The complex consists of siliciclastic and calc-silicate gneisses with mafic and minor ultramafic rocks, which were deformed and metamorphosed during late Neoproterozoic collision between the Paranapanema Block and the São Francisco-Congo plate. Detrital zircons indicate derivation from a juvenile Paleoproterozoic source terrane (peaks of crystallisation ages of ca. 2130 Ma, 2140 Ma and 2170 Ma; ɛHft between +0.1 and +6.0; NdTDM = 2.31-2.21 Ga; ɛNdt = +1.6 to +2.8), with a minor contribution from older continental crust. Interlayered amphibolite rocks, with juvenile signatures (ɛHft = +5.8 to +8.2; NdTDM = 2.14 and 2.30 Ga; ɛNdt = +2.2 and +3.2), yielded similar ages of 2136 ± 17 and 2143 ± 14 Ma, suggesting syn-sedimentary magmatism. Thus, the maximum age of deposition at around 2130 Ma represents the best estimate of the depositional age of the complex. The dominance of detrital zircons ages close to the age of deposition, along with syn-sedimentary magmatism, imply a convergent margin basin tectonic environment for the São Vicente Complex, with similarities to fore arc basin and trench deposits. Amphibolite and meta-sedimentary rocks point to important juvenile magmatism around 2.14 Ga. Juvenile Rhyacian (ca. 2.1 Ga) granite-granodiorite-tonalite orthogneisses with arc-related geochemical signatures (Pouso Alegre Complex) that override the São Vicente Complex, are the probable main source of detritus within the complex. Both basin and source were part of the southern edge of the São Francisco plate during the assembly of West Gondwana, and served as sources for early Neoproterozoic passive margin related basins. The age of intrusive anorogenic A-type Taguar granite indicates that by 1.7 Ga the São Vicente Complex was in a stable tectonic environment. Postprint

International audience; In the Sudetes, northeastern Bohemian Massif, three groups of (meta-)granitoids occur: 1) Cadomian orthogneisses, with a protolith c. 600-540 Ma old, 2) Early Ordovician (~500 Ma) orthogneisses, and finally 3) Variscan (~300 Ma) granitoids. The three groups exist together in the Karkonosze-Izera Massif in the West Sudetes and in the Strzelin Massif in the East Sudetes.In the Strzelin Massif, the ~600 Ma old granitoids belong to the Strzelin Complex ascribed to the Brunovistulian microcontinent, whereas the ~500 Ma orthogneisses are part of the allochtonous Stachów Complex, correlated with the Saxo-Thuringian Zone. During the Variscan Orogeny, the Stachów Complex was thrust onto the Strzelin Complex. Subsequently, both complexes were intruded by Variscan granitoids.Trace-element data support the crustal affinity of the three generations of granitoids but they do not provide evidence for their mutual relationships. Neodymium isotope data suggest that, while the 600 Ma orthogneisses were produced from ancient, purely crustal source materials, the genesis of the Ordovician metagranites involved protoliths that were isotopically less mature. Finally, Variscan granitoids required a significant contribution of juvenile (mantle-derived) components.The general increase of initial εNd values with decreasing age is reflected by the younging average crustal residence ages of the source materials to each particular group of granitoids in the Strzelin Massif. Although they are allochtonous in the massif, the 500 Ma gneisses fit very well to the scheme: the younger granites, the less negative values of the εNdi.The zircon inherited-core ages suggest that the protoliths of the 600 Ma and 500 Ma gneisses originated from different sources derived from Avalonia- and Armorica-type terranes, respectively.

The Gawler Craton forms the bulk of the South Australian Craton and occupies a pivotal location that links rock systems in Antarctica to those in northern Australia. The western Gawler Craton is a virtually unexposed region where the timing of basin development and metamorphism is largely unknown, making the region ambiguous in the context of models seeking to reconstruct the Australian Proterozoic. Detrital zircon data from metasedimentary rocks in the central Fowler Domain in the western Gawler Craton provide maximum depositional ages between 1760 and 1700 Ma, with rare older detrital components ranging in age up to 3130 Ma. In the bulk of samples, εNd(1700 Ma) values range between −4.3 and −3.8. The combination of these data suggest on average, comparatively evolved but age-restricted source regions. Lu–Hf isotopic data from the ca 1700 Ma aged zircons provide a wide range of values (εHf(1700 Ma) +6 to −6). Monazite U–Pb data from granulite-grade metasedimentary rocks yield metamorphic ages of 1690–1670 Ma. This range overlaps with and extends the timing of the widespread Kimban Orogeny in the Gawler Craton, and provides minimum depositional age constraints, indicating that basin development immediately preceded medium to high grade metamorphism. The timing of Paleoproterozoic basin development and metamorphism in the western Gawler Craton coincides with that in the northern and eastern Gawler Craton, and also in the adjacent Curnamona Province, suggesting protoliths to the rocks within the Fowler Domain may have originally formed part of a large ca 1760–1700 Ma basin system in the southern Australian Proterozoic. Provenance characteristics between these basins are remarkably similar and point to the Arunta Region in the North Australian Craton as a potential source. In this context there is little support for tectonic reconstruction models that: (1) suggest components of the Gawler Craton accreted together at different stages in the interval ca 1760–1680 Ma; and (2) that the North Australian Craton and the southern Australian Proterozoic were separate continental fragments between 1760 and 1700 Ma. Refereed/Peer-reviewed

The 618 Ma Curral de Cima tonalite and 577 Ma Lourenco monzodiorite, northeastern Brazil, are magmatic epidote-bearing plutons that carry ferrohornblende, biotite, titanite, and epidote. Major, trace, and isotope chemistry suggests that the major magmas of the two plutons followed similar differentiation trends but derived from source rocks that differed in age and isotopic composition. The mineral phases of the Curral de Cima tonalite, the presence of amphibole-rich clots, and juvenile component (average eNd = −3.55) point to an I-type source for these rocks. These data and high calculated δ 18 O(w.r.) (10.0‰) for the tonalite and high δ 18 O value for a clot (9.3‰) argue that the clots are fragments of a metabasaltic source rock that has been hydrothermally altered at a low temperature. In contrast, average calculated δ 18 O(w.r.) for the Lourenco monzodiorite = 7.8‰, 87 Sr/ 86 Sr = 0.7083, eNd = −14.6, and T DM = 1.92 Ga. These data are compatible with a long crustal residence time of lower crust amphibolites source. Epidote in the Curral de Cima pluton crystallized close to the NNO buffer, and hornblende chemistry, due to Al reequilibration, yielded sub-solidus temperature and pressure. In contrast, in the Lourenco pluton epidote crystallized close to the HM buffer and Al-in-hornblende points to near-solidus solidification (685 °C) around 4.4 Kbar. This study confirms that magmatic epidote in granitic plutons can crystallize at pressures lower than 5.5 Kbar under higher f O 2 as experimentally foreseen. Rapid magma transportation through hot continental crust during the peak of metamorphism in early stages of an orogenic cycle prevents epidote dissolution.

Devonian-Carboniferous granites are widespread in Tasmania. In eastern Tasmania, Devonian granites intrude Ordovician-Early Devonian quartz-rich turbidites of the Mathinna Supergroup. The earliest (*400 Ma) I-type granodiorites may be arc-related. Following the Tabberabberan Orogeny (*389 Ma), more felsic and, finally, strongly fractionated I- and S-type granites were emplaced until *373 Ma. In contrast, western Tasmania granites intrude a more diverse terrane of predominantly marine shelf successions, with depositional ages as old as Late Mesoproterozoic. They are mostly felsic and fractionated I- and S-types emplaced from *374-351 Ma, possibly in response to post-collisional crustal extension following juxtaposition of the eastern and western Tasmanian terranes. Granites from the two terranes are readily distinguishable by the age spectra of their inherited zircon, which are noticeably similar to those of the detrital zircon from sedimentary successions in their respective terranes. Furthermore, within each terrane, both I and S-types yield similar inheritance patterns. This suggests a pivotal role for the sedimentary successions in the petrogenesis of both types. Western Tasmanian granites are also enriched in *1600 Ma zircon, which is essentially unrepresented in the exposed supracrustal succession. Subtle differences between the inheritance and detrital age spectra in eastern Tasmania probably relate to unrepresentative sampling of the supracrustal rocks. Nd, Sr and Pb isotopic characteristics of the granites are consistent with their derivation by mixing of magmas derived from the mantle, possibly the lower crust, and from supracrustal rocks. Systematic isotopic trends in some eastern Tasmanian I-types, particularly in the Scottsdale Batholith, correlate well with major and trace element geochemistry and age. The isotopes are inconsistent with simple restite unmixing or crystal fractionation in a closed magma chamber, and indicate progressive contamination by the Mathinna Supergroup, or similar rocks. The isotopic characteristics of late, strongly fractionated granites, although sometimes obscured by hydrothermal alteration, are also consistent with concurrent assimilation-fractional crystallisation processes. Together with the close association of some strongly fractionated I- and S-types, this suggests that such granites were generated directly in the lower crust, and were not derived from unfractionated parental granite magmas.

The 1690–1670 Ma felsic Tunkillia Suite was generated through the central Gawler Craton, southern Australia, during or after the waning stages of the 1730–1690 Ma Kimban Orogeny. Previous models for the generation of the Tunkillia Suite used trace element tectonic discrimination diagrams to suggest a subduction-related petrogenesis. Subsequently, Tunkillia Suite magmatism was used to infer an active plate margin in paleotectonic reconstruction models. In part, this led to the suggestion of a long-lived active margin on the southern edge of paleo-Australia that was correlated with the long-lived active margin of south-western Laurentia. The more detailed geochemical and isotopic analyses used in this study highlight the shortcomings of analysis based upon simple application of trace-element tectonic discrimination diagrams. The combination of detailed geochemical assessment and new geochronology demonstrates that some intrusions previously used to characterise the tectonic setting of the Tunkillia Suite are in fact unrelated. Tunkillia Suite intrusions are typically high-K, alkali-calcic and magnesian and are dominantly felsic (>70 wt% SiO2), moderately peraluminous granitoids. Trace and rare earth element abundances display large variations. Sr and Y concentrations range from 40 to 550 ppm and from 4.7 to 41 ppm, respectively. Eu/Eu* values range from 0.2 to 1.6 and combined with REE patterns demonstrate the varying composition of restite associated with melt generation of the Tunkillia Suite. The majority of the Tunkillia Suite display chemical characteristics typical of a plagioclase- or hornblende-dominated restite with only three samples demonstrating garnet-rich restite composition. Nd-isotope characteristics of Tunkillia Suite intrusions suggest a crustal column of variable age exists in the Gawler Craton, as variation in ɛNd(T) values (−6.3 to +2.6) cannot be accounted for simply through assimilation and fractional crystallisation processes. The limited SiO2 compositional range of the Tunkillia Suite inhibits unequivocal tectonic classification due to the inability to determine mantle melt composition and infer mantle melting conditions leading to the generation of the Tunkillia Suite. Geochemical, isotopic and mineralogical characteristics of the Tunkillia Suite are most consistent with a ‘late- to post-tectonic’ setting for petrogenesis. The term ‘late- to post-tectonic’ is used in this instance as a genetic descriptor based upon the comparison with Phanerozoic granitoid suites formed in such a setting after collisional orogenesis. Contrary to the suggestion of previous studies, a subduction-related arc setting is not readily reconcilable with the chemical and mineralogical characteristics of the Tunkillia Suite. Refereed/Peer-reviewed

Dust deposition provides rock-derived nutrients such as phosphorus (P) to terrestrial ecosystems. Over pedogenic timescales, as bedrock sources of P are depleted, dust sources of P may support productivity in certain ecosystems, but controls on the spatial variability of dust in montane forested systems are largely unknown. Here, we use neodymium (Nd) isotope ratios in 31 ridgetop surface soils to evaluate the spatial variability of dust contributions to soil across ~ 100 km 2 in the Luquillo Mountains, Puerto Rico. Dust from the Sahara–Sahel region of Africa carries a distinct isotopic signature of − 12 e Nd . Local bedrock, in contrast, has a e Nd value of ~+ 7. End-member mixing calculations based on e Nd reveal a wide range in dust influence on surface soils, with between 0% and 92% of the top 20 cm of ridgetop soil Nd derived from African dust. Using e Nd paired with both dust and soil Nd content, the current soil dust content was calculated, ranging from 0 to 8%. There were no correlations between current dust content of soil and 10 Be-based denudation rate, elevation, rainfall, longitude, or forest type. Current soil dust content in the Luquillo Mountains is significantly higher in soils developed on volcaniclastic sandstone, breccia and mudstone than in soils developed on quartz diorite bedrock, which we attribute to greater retention capacity in the volcaniclastic soils. Current soil dust content also increases with increasing ridge-width, implying that small-scale topographic effects and other factors such as wind speed and turbulence influence local dust deposition rates. Higher current dust content of soil is also positively correlated with biologically cycled fractions of soil P on quartz diorite bedrock (r 2 = 0.24 and p = 0.002 for sum of extractable NaHCO 3 -P + NaOH-P), suggesting that atmospheric dust inputs contribute to the fertility of Luquillo Mountain ecosystems on the relatively P-poor quartz diorite bedrock.

The North Caribou Greenstone Belt (NCGB) lies at the core the granitoid-dominant North Caribou Terrane (NCT). Two sedimentary assemblages; the Eyapamikama (ELS) and Zeemal-Heaton Lake (ZHA) form the core of the NCGB. Geochemistry of garnets from the orogenic Au deposit at Musselwhite suggest that the auriferous fluids have a contribution of metamorphic fluids and mineralization consisted of prolonged, multi-stage periods. Chemical zoning suggests changes in the influx of chalcophile and lithophile elements and that Au/sulphide ratios during nucleation were lower relative to later growth events. Zircons from the ELS and ZHA suggest a c. 100 My hiatus in the onset of sedimentation, with the ZHA showing younger, “Timiskaming-type” ages. Age distributions from each assemblage reflect proximal, igneous sources. Nd isotopic compositions of the ZHA suggest a mixture of ancient and contemporaneous sources which are similar to external TTG rocks. Deplete mantle model ages of the ZHA rocks indicate a Mesoarchean inheritance.

International audience; A high-resolution peat record from Eastern Belgium reveals the chronology of dust deposition for the last 2500 years. REE and lithogenic elements in addition to Nd and Pb isotopes were measured in a 173 cm age-dated peat profile and provide a continuous chronology of dust source and intensity. Calculated dust flux show pronounced increases c. 300 BC, 600 AD,1000 AD, 1200 AD and from 1700 AD, corresponding to local and regional human activities combined with climate change. The Industrial Revolution samples (1700-1950 AD) are characterised by a significant enrichment in Sc-normalised REE abundance (sum REE/Sc > 25) due to intensive coal combustion. For the pre-Industrial Revolution samples, the Sc-normalised REE abundance (10 < Sum REE/Sc < 25) and the eNd variability (-13 to -9) are interpreted by a mixing between dust particles from local soils and long-range transport of desert particles. Three periods characterised by dominant-distal sources (c. 320 AD, 1000 AD and 1700 AD) are consistent with local wetter-than-average intervals as indicated by a lower degree of peat humification. Local erosion prevails during the drier (higher humification) intervals (100 AD,600 AD). On a global scale, more distal supplies are driven during colder periods, in particular during the Oort and Maunder minima, suggesting a potential link between dust deposition and global climate. Combining REE abundance, fractionation between Light REE and Heavy REE and Nd isotope data in ombrotrophic peat allows one to distinguish between dust flux changes related to human and climate forcings.

The Arabian-Nubian Shield is an excellent natural laboratory to study crust formation processes during the Neoproterozoic. It is one of the largest juvenile tracts of continental crust formed during this time. It diachronously evolved between the breakup of Rodinia (c.780 Ma) and amalgamation of Gondwana (c.550 Ma). New SIMS zircon U-Pb, whole-rock Sm-Nd isotopic and geochemical data are presented. The results are used to establish the geochronology of the Abas terrane and constrain its crustal evolution. The U-Pb data show bimodal age distribution: an older age group c. 790-760 Ma, which corresponds to the arc-forming stage of the ANS and a younger group c. 625-590 Ma, belonging to post-collisional episode in the region. The oldest sample in the post-collisional tectonomagmatic group is slightly deformed indicating that pervasive deformation in the area was decaying by c. 625 Ma. The inherited zircons documented range in age from Meso-to-Paleoproterozoic. Although few, these inherited zircons indicate that crust material of that age was assimilated during the Neoproterozoic magmatic events. The U-Pb geochronologic also resolved the temporal transition from high-K calc-alkaline to alkaline magmatism in the post-collisional suits. This transition commonly marks the end of orogeny. Almost all samples studied exhibit a strongly enriched initial εNd compositions and Nd model ages that predate the crystallization ages of the rocks by several hundred million years. These features highlight the sharp contrast in the magmatic sources between the Abas granitoids and the rest of the ANS, which is dominantly juvenile except that of the Afif terrane of Saudi Arabia. This suggests that the Abas terrane of Yemen had a distinctive crustal evolution history compared to the rest of the shield and these features provide evidence for the presence of pre-Neoproterozoic crust at depth in this region.

Present and past climate of the Earth has strongly depended on oceanic circulation and marine biological productivity. The formation of deep and bottom waters in high latitudes as a consequence of density changes and their pathways through the global ocean, the so called thermohaline circulation (THC) have been of primary importance for the redistribution of heat, for the Earth’s albedo through control on the sea ice distribution, and it serves as a reservoir of greenhouse gases such as CO2. The understanding of the mechanisms that have driven the THC in the past is crucial to reliably predict future climatic variations. For example, large amounts of CO2 were stored in the deep ocean during glacial periods, which depended on the structure of the water column but also on the availability of nutrients for primary producers in the surface ocean. Besides macronutrients, phytoplankton depends also on dust input to the ocean, which releases iron, one of the most important micronutrients, in particular in High Nutrient Low Chlorophyll areas. These issues have been poorly studied in the South Pacific, despite its importance for these processes. It represents a key area for the interchange of deep waters from all ocean basin because it is the main entrance and exit of deep waters to the largest of all oceans, the Pacific, which is also one of the principal CO2 reservoirs on Earth. For the study of present and past deep-water circulation regimes and the provenance of the dust input in this region, Rare Earth Element (REE) distributions and radiogenic isotopes of neodymium (Nd), lead (Pb) and strontium (Sr) have been analyzed in water and sediment samples obtained from a meridional transect of the South Pacific, spanning all the way from South America to New Zealand. Radiogenic isotopes have been proved to be very reliable traces for studying different surface earth processes, such as, in the case of Nd and Pb, the advection of water masses. These are labeled with characteristic isotope compositions through weathering of the lithologies of the surrounding continents in their formation regions, allowing to track the pathway of a certain water mass in the present day water column (not in the case of Pb due to anthropogenic inputs), as well as their presence and mixing in the past at a particular location given that these signatures are recorded by the sediments. Nd, Sr and Pb isotopes also allow identifying the provenance of lithogenic particles that arrive the bottom of the ocean brought by currents or wind due to the specific signature that different rocks carry as a consequence of their type and age. The concentrations of the REE including Nd in seawater also allow to distinguish water masses as well as vertical processes such as scavenging as their relative distributions vary coherently in the water column due to different affinities to particles. Chapter 4 of this study presents the first seawater REE concentrations and Nd isotope compositions in intermediate and deep waters of the South Pacific. The results show that Nd isotopes faithfully trace the different water masses displaying more negative Nd isotope compositions for those water masses originating in the Southern Ocean, such as Lower Circumpolar Deep Water (LCDW) and Antarctic Intermediate Water (AAIW), with εNd around -8.3; and more positive signatures for North Pacific Deep Water (NPDW)(εNd = -5.9), which exits the South Pacific in the east, close to South America. Nd isotope compositions also allowed identifying a remnant of North Atlantic Deep Water (NADW) entering the western South Pacific as part of LCDW. Dissolved REE concentrations indicate that NPDW were affected by scavenging processes underneath the high productivity area of the equatorial eastern Pacific that lowered the concentrations of the more particle reactive light REE (LREE) of this water mass before reaching the South Pacific. At the same time LREE are also released from oxides in the sediments of the Southeast Pacific Basin. Chapter 5 compares bottom seawater (chapter 4) and surface sediment Nd isotope compositions to identify the most reliable technique to obtain seawater-derived Nd isotopes from the sediment for the study of past circulation changes recorded in the sediment. Four different archives were tested in order to obtain the authigenic seawater Nd isotope signal that precipitates from seawater into the sediment in the form of early-diagenetic Fe-Mn oxide coatings: ‘decarbonated’ and ‘non-decarbonated’ bulk sediment leachates as well as ‘uncleaned’ planktonic foraminifera, which were also compared to the compositions of fossil fish teeth. None of them registered exactly the same Nd isotope compositions as those of the present day bottom waters due to the low sedimentation rates in the South Pacific that result in very old surface sediments (up to 24 kiloyears before present), which therefore integrate Nd isotope compositions from different circulation states of the ocean. However, independent evidence (REE patterns and Al/Ca ratios measured on unclean foraminifera), clearly indicates that the Nd isotope compositions of unclean foraminifera, fish teeth and ‘non-decarbonated’ leachates originated from bottom seawater, allowing the use of these methods to study past changes of deep water circulation. This study also suggests that contributions of the continental margins of the South Pacific to the Nd isotope composition of seawater, the so called ‘boundary exchange’ was small. The sources of fine lithogenic particles that arrive the South Pacific are studied in this chapter by combining Nd and Sr isotopes from the detrital fraction of the sediment. The results show that the lithogenic material found in the western and central Pacific originates from Southeast Australia and South New Zealand and was transported by the dominant Westerlies. The influence of these sources is also dominant in the eastern South Pacific, although in this region the proportions of detrital material from the Andes increase and contributions from Antarctica can also not be excluded. The last chapter of this thesis presents a reconstruction of the deep-water circulation and detrital provenances in the central South Pacific of the last 240 kyr based on Nd, Pb and Sr isotopes. The results show small but significant glacial-interglacial variations in the Nd and Pb isotope composition of the circumpolar deep water (CDW), which has been the dominating water mass in this region, caused by a decrease in the contribution of NADW during glacial stages. A deepening of the flow and advective incorporation of NPDW during glacial periods is not supported by the results of this study due to the location of the cores, which have remained within CDW. The combined detrital Nd-Sr isotope compositions indicate a dominance of Southeastern Australia and South New Zealand derived material, similar to the surface sediments over the past 240,000 years. Nevertheless, a small shift towards the Antarctic end-member during glacial periods is identified, which may indicate a stronger influence of Antarctic-derived material during cold periods, most probably transported northwards as suspended load of oceanic currents. Das Klima der Erde in der Gegenwart wird, wie auch in der Vergangenheit, stark von der ozeanischen Zirkulation und der marinen biologischen Produktivität beeinflusst. Die durch Änderungen der Dichte des Meerwassers verursachte Tiefenwasserbildung in den hohen Breiten und das dadurch getriebene globale Zirkulationsmuster der gesamten Wassersäule, die so genannte Thermohaline Zirkulation (THZ), spielt eine entscheidende Rolle als Wärmeverteiler, für die Albedo durch die Kontrolle der Eisausdehnung und auch als Speicher für Treibhausgase wie CO2. Das Verständnis der Mechanismen, die die THZ in der Vergangenheit gesteuert haben, ist entscheidend um zukünftige Änderungen des Klimas zu prognostizieren. Zum Beispiel wurden große Mengen an CO2 während der Glazialzeiten in der Tiefsee gespeichert, was zum Einen von der Tiefenwasserzirkulation abhängig war, zum anderen aber auch von der Verfügbarkeit von Nährstoffen für die Primärproduzenten an der Meeresoberfläche. Abgesehen von den Makronährstoffe ist das Phytoplankton auch von Staubeinträgen in den Ozean abhängig, die Eisen freisetzen, einer der wichtigsten Mikronährstoffe, besonders in sogenannten ‘High Nutrient Low Chlorophyll’-Gebieten. Der Süd-Pazifik wurde trotz seiner Bedeutung für diese Prozesse bis jetzt wenig untersucht obwohl er eine entscheidende Rolle für den Austausch und die Mischung von Tiefenwasserspielt. Dort finden Zufluss und Abfluss aller Tiefen-wassermassen in und aus dem Pazifik statt, dass das global größte Ozeanbecken ist und damit auch einer der wichtigsten CO2 Speicher der Erde ist. Um die gegenwärtige und vergangene Tiefenwasserzirkulation des Süd-Pazifiks und die Herkunft der Staubeinträge in dieser Region untersuchen zu können, wurden Konzentrationen der Seltenerdelemente (REE) und radiogene Isotopenverhältnisse von Neodym (Nd), Blei (Pb) und Strontium (Sr) an Wasser- und Sedimentproben gemessen, die entlang eines meridionalen Transekts über den Süd-Pazifik von Südamerika bis Neuseeland gewonnen wurden. Radiogene Isotopenverhältnissen haben sich als verlässliche Tracer für die Untersuchung verschiedener Prozessen an der Erdoberfläche erwiesen wie zum Beispiel, in Falle von Nd und Pb, als Advektionsindikatoren verschiedener Wassermassen. Diese werden von charakteristischen Isotopenverhältnissen gekennzeichnet, die sie durch Verwitterungeinträge von den umliegenden Kontinenten in ihren Entstehungsgebieten erhalten. Dies erlaubt die Verfolgung von bestimmten Wassermassen und deren Mischung sowohl in der heutigen Wassersäule (allerdings nicht im Fall von Pb- Isotopen, die von anthropogenen Einträgen kontaminiert wurden) als auch in der Vergangenheit dank der Speicherung der Meerwasserisotopenverhältnisse im Sediment. Dank der charakteristischen Nd-, Pb- und Sr-Isotopenverhältnisse der Gesteine als Folge ihres Typs und Alters ist auch die Bestimmung der Herkunft des lithogenen Anteils der Sedimente möglich, der durch Wind und Strömungen transportiert wird. Die Konzentrationen der Seltenerdelemente inklusive Nd im Meerwasser erlauben ebenfalls die Identifizierung von Wassermassen sowie von vertikalen Prozesse wie ‘Scavenging’, da deren Konzentrationen in Abhängigkeit ihrer Ionenradien durch unterschiedliche Affinitäten zu Partikeln in der Wassersäule variieren . Kapitel 4 dieser Arbeit zeigt die ersten systematischen Daten von Seltenerdelement-Konzentrationen und radiogenen Nd-Isotopenzusammensetzungen von Tiefen- und Zwischenwässern des Süd-Pazifiks. Die Ergebnisse zeigen, dass die Nd-Isotopie des Tiefenwassers im Südpazifik als verlässlicher konservativer Wassermassentracer dienen kann, da Wassermassen aus dem Antarktischen Zirkumpolarstrom, wie das untere zirkumpolare Tiefenwasser (LCDW) oder das antarktische Zwischenwasser (AAIW), negativere εNd-Signaturen um -8.3 zeigen. Dagegen zeigen die aus dem Nordpazifik stammenden Beiträge des Nordpazifischen Tiefenwassers (NPDW), die den Pazifischen Ozean an seinem östlichen Rand entlang Südamerika verlassen, positivere Werte (εNd = -5.9). Ein weiteres wichtiges Ergebnis ist die Identifikation von Zumischungen des Nordatlantischen Tiefenwassers (NADW) im oberen Teil des LCDW im westlichen Südpazifik. Die Konzentrationen der Seltenen Erden zeigen, dass NPDW von Scavengingprozessen unter der Hochroduktivitätszone des äquatorialen östlichen Pazifiks beeinflusst wird bevor es den Südpazifik erreicht. Dies verringert die Konzentrationen der stärker partikelreaktiven leichten REE (LREE). Zusätzlich wird aber auch beobachtet, dass LREE im südöstlichen Pazifischen Becken von Mn-Fe-Oxihydroxiden im Sediment freigesetzt werden. Kapitel 5 prüft die Verlässlichkeit von Extraktionsmethoden um Meerwasser-Nd-Isotopen-Signaturen aus Tiefseesedimenten zu gewinnen. Dazu wurde eine detaillierte Kalibration durchgeführt, in deren Rahmen die εNd-Signaturen des Meerwassers mit den aus den Oberflächensedimenten extrahierten Werten verglichen wurden. Hierzu wurden vier verschiedene Extraktions-Methoden angewandt und verglichen um sicherzustellen, dass verlässliche Daten für die Rekonstruktionen der Zirkulation der Vergangenheit erhoben werden können. Die Tiefenwasser-Nd-Isotopie der authigenen, frühdiagenetischen ‘Fe-Mn-coatings’ wurde durch verschiedene Laugungsmethoden extrahiert: Laugung des Gesamtsediments mit und ohne vorherige Entfernung der Karbonatfraktion, sowie Auflösung handverlesener planktonische Foraminiferengehäuse. Diese Ergebnisse wurden mit den εNd-Signaturen fossiler Fischzähne verglichen. Keine dieser Methoden spiegelte die exakten Nd-Isotopenzusammensetzungen des heutigen Bodenwassers exakt wider. Dies ist eine Folge der sehr niedrigen Sedimentationsraten im Südpazifik, die zu extremen Oberflächensedimentaltern von bis zu 24,000 Jahren führt was die Integration von Nd Isotopenzusammensetzungen verschiedener Zirkulationsmuster der Vergangenheit in den Oberflächensedimenten führt. Die REE-Muster und Al/Ca Verhältnisse der Mn-Fe Coatings der planktonischen Foraminiferengehäuse zeigen dass sowohl die Nd- Isotopenzusammensetzungen der Foraminiferengehäuse, der gelaugten Sedimente ohne vorheriger Entfernung der Karbonatfraktion und fossile Fisch Zähne aus dem Bodenwasser stammen. Diese Studie zeigt auch, dass Kontinentalränder des Südpazifiks zumindest an der Lokation dieser Studie nicht mit dem Bodenwasser austauschen und keinen Einfluss haben auf die Nd-Isotopenzusammensetzung des Tiefenwassers. Die kombinierten Nd- und Sr-Isotopenzusammensetzungen der lithogenen Fraktion des Sediments erlauben die Bestimmung der Herkunft der detritischen Partikel im Untersuchungsgebiet. Diese stammen hauptsächlich aus Südostaustralien und dem südlichen Neuseeland und wurden von den dominierenden ‘Westwinden’ geliefert, wobei aber auch der Einfluss der Anden vor allem in östlichen Südpazifik klar identifizierbar ist. Dort kann auch ein Einfluss von Material aus der Antarktis nicht ausgeschlossen werden. Das letzte Kapitel dieser Arbeit präsentiert die Änderungen in der Tiefenwasserzirkulation des Südpazifiks auf glazial/interglazialen Zeitskalen während der letzten 240,000 Jahre, sowie die Änderungen der Herkunftsgebiete der detritischen Partikel anhand ihrer Nd-, Pb- und Sr-Isotopensignaturen. Die Ergebnisse zeigen systematische Veränderungen der Meerwasser-Nd- und Pb-Isotopenzusammensetzungen, die den klimatischen Zyklen folgen, wobei ein geringerer Anteil zugemischten NADWs im Zirkumpolaren Tiefenwassser (CDW) während der Glazialzeiten angezeigt wird. Die zeitlichen Variationen waren relativ niedrig, was mit dem erwarteten geringeren Anteil von NADW im Südpazifik als Folge der erhöhten Verdünnung der Wassermassen aus dem Nordatlantik übereinstimmt. Eine stärkere Produktion von NPDW während Glazialzeiten konnte anhand der Lokation der Sedimentkerne nicht bewiesen werden, da diese unter dem Einfluss von CDW lagen. Die kombinierten Nd- und Sr-Isotopenzusammensetzungen der lithogenen Fraktion des Sediments der letzten 240 000 Jahre zeigen die Dominanz von lithogenem Material aus Südostaustralien und dem südlichen Neuseeland, wobei ein stärkerer Einfluss von Antarktischem Detritus während Glazialzeiten nachweisbar ist, was durch Suspension in ozeanische Strömungen transportiert wurde.

Combined oceanic hafnium (Hf) and neodymium (Nd) isotope compositions are a geochemical tool developed over the past 15 years to study the present and past ocean circulation and continental weathering regimes. Since it is a relatively new proxy in marine research, a number of issues regarding the geochemistry of oceanic Hf have previously not been investigated or are still controversial. This thesis presents Hf and Nd concentration/isotope data from a variety of archives, such as marine sediments, dust deposits, as well as seawater and river water in order to better understand the sources and cycling of oceanic Nd and Hf isotopes and to apply them in paleoceanographic studies.

In this study, the use of trace elements as a provenance indicator for Roman natron glass is evaluated. Suitable glass-making sand raw materials are analysed for their trace elemental composition and compared to glass from known production centres. It is shown that the combined use of Nd isotopic and trace element analysis can be efficient for the provenancing of Roman glass. Trace elements associated with (de)colourants of glass are only present in small concentrations in glass-making sands. Background levels introduced to the glass by the sand raw material are defined and a lower threshold for the concentrations influenced by recycling is determined. ispartof: Archaeometry vol:56 issue:SUPPLS1 pages:116-136 status: published

International audience; Three vertical profiles of rare earth element concentrations and Nd isotopic compositions have been measured in the remote southeast Pacific Ocean. The three stations represent contrasting environments: the oligotrophic center of the gyre (station GYR), the “transition zone” east of the South Tropical Front (station EGY), and the Peru-Chile upwelling marked by a pronounced oxygen minimum (station UPX). Rare earth concentrations display nutrient like vertical profiles except at UPX where surface waters are enriched. At this station Nd isotopic compositions are clearly more radiogenic than in the open ocean, suggesting that boundary exchange process is releasing lithogenic rare earth element from the volcanic Andes. Unexpected radiogenic values (eNd reaching –3.7) are also observed at 2000 m at station GYR in the Upper Circumpolar Deep Water that commonly have eNd values around –6. Exchange processes related to hydrothermal activity are suspected to produce this increase in eNd in the vicinity of the East Pacific Rise. These results provide some guidance for higher resolution studies planned in this region by the international GEOTRACES program.