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Academic literature on the topic 'Nd isotopes'

Author: Grafiati

Published: 4 June 2021

Last updated: 25 May 2024

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Journal articles on the topic "Nd isotopes"

1

Wu, Li, Ling, et al. "Further Characterization of the RW-1 Monazite: A New Working Reference Material for Oxygen and Neodymium Isotopic Microanalysis." Minerals 9, no. 10 (2019): 583. http://dx.doi.org/10.3390/min9100583.

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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–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–Nd isotopes. Here, we report on the RW-1 monazite as a potential new working reference material for microbeam analysis of O–Nd isotopes. Microbeam measurements by electron probe microanalysis (EPMA), SIMS, and LA-MC-ICPMS at 10–24 µm scales have confirmed that it is homogeneous in both elemental and O–Nd isotopic compositions. SIMS measurements yield δ18O 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 δ18O = 6.30‰ ± 0.16‰ (2SD) and 143Nd/144Nd = 0.512282 ± 0.000011 (2SD) as being the reference values for the RW-1 monazite.

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2

Vezinet, Adrien, Emilie Thomassot, Yan Luo, Chiranjeeb Sarkar, and D. Graham Pearson. "Diachronous Redistribution of Hf and Nd Isotopes at the Crystal Scale—Consequences for the Isotopic Evolution of a Poly-Metamorphic Crustal Terrane." Geosciences 12, no. 1 (2022): 36. http://dx.doi.org/10.3390/geosciences12010036.

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In metamorphic rocks, mineral species react over a range of pressure–temperature conditions that do not necessarily overlap. Mineral equilibration can occur at varied points along the metamorphic pressure–temperature (PT) path, and thus at different times. The sole or dominant use of zircon isotopic compositions to constrain the evolution of metamorphic rocks might then inadvertently skew geological interpretations towards one aspect or one moment of a rock’s history. Here, we present in-situ U–Pb/Sm–Nd isotope analyses of the apatite crystals extracted from two meta-igneous rocks exposed in the Saglek Block (North Atlantic craton, Canada), an Archean metamorphic terrane, with the aim of examining the various signatures and events that they record. The data are combined with published U–Pb/Hf/O isotope compositions of zircon extracted from the same hand-specimens. We found an offset of nearly ca. 1.5 Gyr between U-Pb ages derived from the oldest zircon cores and apatite U–Pb/Sm–Nd isotopic ages, and an offset of ca. 200 Ma between the youngest zircon metamorphic overgrowths and apatite. These differences in metamorphic ages recorded by zircon and apatite mean that the redistribution of Hf isotopes (largely hosted in zircon) and Nd isotopes (largely hosted in apatite within these rocks), were not synchronous at the hand-specimen scale (≤~0.001 m3). We propose that the diachronous redistribution of Hf and Nd isotopes and their parent isotopes was caused by the different PT conditions of growth equilibration between zircon and apatite during metamorphism. These findings document the latest metamorphic evolution of the Saglek Block, highlighting the role played by intra-crustal reworking during the late-Archean regional metamorphic event.

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3

van de Flierdt, Tina, Alexander M. Griffiths, Myriam Lambelet, Susan H. Little, Torben Stichel, and David J. Wilson. "Neodymium in the oceans: a global database, a regional comparison and implications for palaeoceanographic research." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 374, no. 2081 (2016): 20150293. http://dx.doi.org/10.1098/rsta.2015.0293.

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The neodymium (Nd) isotopic composition of seawater has been used extensively to reconstruct ocean circulation on a variety of time scales. However, dissolved neodymium concentrations and isotopes do not always behave conservatively, and quantitative deconvolution of this non-conservative component can be used to detect trace metal inputs and isotopic exchange at ocean–sediment interfaces. In order to facilitate such comparisons for historical datasets, we here provide an extended global database for Nd isotopes and concentrations in the context of hydrography and nutrients. Since 2010, combined datasets for a large range of trace elements and isotopes are collected on international GEOTRACES section cruises, alongside classical nutrient and hydrography measurements. Here, we take a first step towards exploiting these datasets by comparing high-resolution Nd sections for the western and eastern North Atlantic in the context of hydrography, nutrients and aluminium (Al) concentrations. Evaluating those data in tracer–tracer space reveals that North Atlantic seawater Nd isotopes and concentrations generally follow the patterns of advection, as do Al concentrations. Deviations from water mass mixing are observed locally, associated with the addition or removal of trace metals in benthic nepheloid layers, exchange with ocean margins (i.e. boundary exchange) and/or exchange with particulate phases (i.e. reversible scavenging). We emphasize that the complexity of some of the new datasets cautions against a quantitative interpretation of individual palaeo Nd isotope records, and indicates the importance of spatial reconstructions for a more balanced approach to deciphering past ocean changes. This article is part of the themed issue ‘Biological and climatic impacts of ocean trace element chemistry’.

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4

Jo, Hui Je, Hyo Min Lee, Go-Eun Kim, Won Myung Choi, and Taehoon Kim. "Determination of Sr–Nd–Pb Isotopic Ratios of Rock Reference Materials Using Column Separation Techniques and TIMS." Separations 8, no. 11 (2021): 213. http://dx.doi.org/10.3390/separations8110213.

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Thermal ionization mass spectrometry (TIMS) can provide highly accurate strontium (Sr), neodymium (Nd), and lead (Pb) isotope measurements for geological and environmental samples. Traces of these isotopes are useful for understanding crustal reworking and growth. In this study, we conducted a sequential separation of Sr, Nd, and Pb and subsequently measured the 87Sr/86Sr, 143Nd/144Nd, 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios of 13 widely used rock certified reference materials (CRMs), namely BCR-2, BHVO-2, GSP-2, JG-1a, HISS-1, JLk-1, JSd-1, JSd-2, JSd-3, LKSD-1, MAG-1, SGR-1, and 4353A, using TIMS. In particular, we reported the first isotopic ratios of Sr, Nd, and Pb in 4353A, Sr and Nd in HISS-1 and SGR-1, and Sr in JLk-1, JSd-2, JSd-3, and LKSD-1. The Sr–Nd–Pb isotopic compositions of most in-house CRMs were indistinguishable from previously reported values, although the Sr and Pb isotopic ratios of GSP-2, JSd-2, JSd-3, and LKSD-1 obtained in different aliquots and/or batches varied slightly. Hence, these rock reference materials can be used for monitoring the sample accuracy and assessing the quality of Sr–Nd–Pb isotope analyses.

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5

Viehmann, Sebastian. "Hf-Nd Isotopes in Archean Marine Chemical Sediments: Implications for the Geodynamical History of Early Earth and Its Impact on Earliest Marine Habitats." Geosciences 8, no. 7 (2018): 263. http://dx.doi.org/10.3390/geosciences8070263.

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The Hf-Nd isotope systems are coupled in magmatic systems, but incongruent Hf weathering (‘zircon effect’) of the continental crust leads to a decoupling of the Hf-Nd isotope systems in low-temperature environments during weathering and erosion processes. The Hf-Nd isotope record was recently dated back from the Cenozoic oceans until the Archean, showing that both isotope systems were already decoupled in seawater 2.7 Ga ago and potentially 3.4 Ga and 3.7 Ga ago. While there might have existed a hydrothermal pathway for Hf into Archean seawater, incongruent Hf weathering of more evolved, zircon-bearing uppermost continental crust that was emerged and available for subaerial weathering accounts for a significant decoupling of Hf-Nd isotopes in the dissolved (<0.2 µm) and suspended (>0.2 µm) fractions of Early Earth’s seawater. These findings contradict the consensus that uppermost Archean continental crust was (ultra)mafic in composition and predominantly submerged. Hence, Hf-Nd isotopes in Archean marine chemical sediments provide the unique potential for future research to trace the emergence of evolved continental crust, which in turn has major implications for the geodynamical evolution of Early Earth and the nutrient flux into the earliest marine habitats on Earth.

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6

Abbott, April N., Brian A. Haley, Aradhna K. Tripati, and Martin Frank. "Constraints on ocean circulation at the Paleocene–Eocene Thermal Maximum from neodymium isotopes." Climate of the Past 12, no. 4 (2016): 837–47. http://dx.doi.org/10.5194/cp-12-837-2016.

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Abstract. Global warming during the Paleocene–Eocene Thermal Maximum (PETM) ∼ 55 million years ago (Ma) coincided with a massive release of carbon to the ocean–atmosphere system, as indicated by carbon isotopic data. Previous studies have argued for a role of changing ocean circulation, possibly as a trigger or response to climatic changes. We use neodymium (Nd) isotopic data to reconstruct short high-resolution records of deep-water circulation across the PETM. These records are derived by reductively leaching sediments from seven globally distributed sites to reconstruct past deep-ocean circulation across the PETM. The Nd data for the leachates are interpreted to be consistent with previous studies that have used fish teeth Nd isotopes and benthic foraminiferal δ13C to constrain regions of convection. There is some evidence from combining Nd isotope and δ13C records that the three major ocean basins may not have had substantial exchanges of deep waters. If the isotopic data are interpreted within this framework, then the observed pattern may be explained if the strength of overturning in each basin varied distinctly over the PETM, resulting in differences in deep-water aging gradients between basins. Results are consistent with published interpretations from proxy data and model simulations that suggest modulation of overturning circulation had an important role for initiation and recovery of the ocean–atmosphere system associated with the PETM.

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PE-PIPER, GEORGIA, and DAVID J. W. PIPER. "Late Cenozoic, post-collisional Aegean igneous rocks: Nd, Pb and Sr isotopic constraints on petrogenetic and tectonic models." Geological Magazine 138, no. 6 (2001): 653–68. http://dx.doi.org/10.1017/s0016756801005957.

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Nd isotopic composition has been determined for 16 igneous rocks, representing the wide geochemical, spatial and temporal range of post-collisional, late Cenozoic magmas in the Aegean area. Nd isotopes are used to further interpret previously published Pb and Sr isotope data. The overall pattern of late Cenozoic volcanism resulted from rapid extension, with thermal effects causing melting of hydrated, enriched, subcontinental lithosphere to produce widespread K-rich magmas. Slab break-off and intrusion of hot asthenosphere caused partial melting of rift-related continental margin basalts at the detachment point to generate adakitic magmas. Further outboard, mafic magma from enriched lithospheric mantle melted thickened lower crust to produce the granitoid plutons of the Cyclades. Nd isotopic variation in these varied rock types correlates with pre-Cenozoic palaeo-geography. Proterozoic subduction-related enrichment in Th and U, together with other large-ion lithophile elements, produced distinctive Pb isotope composition. This was later modified where Mesozoic subduction of terrigenous sediment was important, whereas subduction of oceanic carbonate sediments produced enrichment in radiogenic Sr and low Ce/Sr ratios. Late Cenozoic magmas sourced in eastern Pelagonian zone sub-continental lithospheric mantle have Nd model ages of about 1.0 Ga, and generally high 87Sr/86Sr and high 207Pb/204Pb (∼ 15.68) and 208Pb/204Pb (∼ 39.0) for low 206Pb/204Pb (∼ 18.6), but rocks to the west have more radiogenic Pb and higher Ce/Sr as a result of greater subduction of terrigenous sediment from the northern Pindos ocean. Magmas sourced from sub-continental lithosphere beneath the Apulian continental block were strongly influenced by subduction of oceanic crust and sediments north of the passive margin of north Africa. Subduction of Nile-derived terrigenous sediment in the east resulted in Nd model ages of 0.7 to 0.8 Ga and radiogenic Pb isotopes. Greater subduction of oceanic carbonate in the west resulted in magmas with higher 87Sr/86Sr and lower Ce/Sr. The strongly negative εNd for adakites in the central Aegean rules out a source from subducted oceanic basalt, and the adakite magma was probably derived from melting of hydrated Triassic sub-alkaline basalt of continental origin. Where trachytic rocks are succeeded by nepheline-normative basalts (e.g. Samos), Nd isotope data imply that early partial melting of the enriched subcontinental lithospheric mantle involved hydrous amphibole and phlogopite, but once these minerals were consumed, younger magmas were produced by partial melting dominated by olivine and orthopyroxene.

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8

Zhang, Bang-Lu, Zhi-Cheng Lv, Zhi-Guo Dong, et al. "Source Characteristics of the Carboniferous Ortokarnash Manganese Deposit in the Western Kunlun Mountains." Minerals 12, no. 7 (2022): 786. http://dx.doi.org/10.3390/min12070786.

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The specific source of ancient sedimentary manganese (Mn) deposits is commonly complex. Here we use systematic major and trace element data with strontium (Sr) and neodymium (Nd) isotopic analyses of the Ortokarnash Mn(II) carbonate ores and associated carbonate rocks from the Upper Carboniferous Kalaatehe Formation (ca. 320 Ma) in order to constrain the Mn source. This formation consists of three members: the first member is a volcanic breccia limestone, the second member is a sandy limestone, and the third member is a black marlstone with the Mn(II) carbonate interlayers. Petrographic observations in combination with low Al2O3 (<3.0 wt%) and Hf (<0.40 ppm) contents and the lack of correlations between the Al2O3 and 87Sr/86Sr ratios as well as εNd(t) values demonstrate a negligible influence of terrigenous detrital contamination on both Sr and Nd isotopic compositions of the Mn(II) carbonate ores. The Sr isotopes of Mn(II) carbonate ores are most likely affected by post-depositional alteration, while Nd isotopes remain unaltered. The initial 87Sr/86Sr ratios in the associated carbonate rocks are likely the result of a mixture of the chemical components (i.e., seawater) and the Al-rich components (e.g., volcanoclastic material), while the detrital effects on Nd isotopes are negligible. In addition, both Sr and Nd isotopes in these non-mineralized wall rocks remained unchanged during post-depositional processes. The relatively low Th/Sc ratios and positive εNd(t) values suggest that the aluminosilicate fraction in the calcarenite and sandy limestone was mainly derived from the weathering of a depleted mafic source, representing the riverine input into the seawater. Given that the Mn(II) carbonate ores are characterized by negative εNd(t) values, these suggest that seafloor-vented hydrothermal fluids derived from interaction with the underlying old continental crust mainly contribute to the source of the Mn(II) carbonates.

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9

Qasim, Hussein N., and Falih H. Al-Khudair. "Structure of the low-lying positive and negative parity states in even–even 144−154Nd isotopes." International Journal of Modern Physics E 28, no. 12 (2019): 1950107. http://dx.doi.org/10.1142/s0218301319501076.

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The low-lying positive and negative parity states of even–even [Formula: see text]Nd isotopes are studied using the interacting boson model (IBM). The negative parity states are involved within the IBM model by adding a single angular momentum ([Formula: see text]) boson with intrinsic negative parity [Formula: see text]-boson to [Formula: see text] and [Formula: see text]-bosons model space. For these nuclei, the potential energy surfaces [Formula: see text], transition probability [Formula: see text], [Formula: see text] and [Formula: see text] are calculated. Phase transition from the [Formula: see text] limit to the [Formula: see text] limit is observed in the chain and the critical point has been determined for [Formula: see text]Nd isotope. It is found that the calculated positive and negative parity energy spectra of Nd-isotopes agree well with the experimental data.

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10

Robinson, Suzanne, Ruza F. Ivanovic, Lauren J. Gregoire, et al. "Simulating marine neodymium isotope distributions using Nd v1.0 coupled to the ocean component of the FAMOUS–MOSES1 climate model: sensitivities to reversible scavenging efficiency and benthic source distributions." Geoscientific Model Development 16, no. 4 (2023): 1231–64. http://dx.doi.org/10.5194/gmd-16-1231-2023.

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Abstract. The neodymium (Nd) isotopic composition of seawater is a widely used ocean circulation tracer. However, uncertainty in quantifying the global ocean Nd budget, particularly constraining elusive non-conservative processes, remains a major challenge. A substantial increase in modern seawater Nd measurements from the GEOTRACES programme, coupled with recent hypotheses that a seafloor-wide benthic Nd flux to the ocean may govern global Nd isotope distributions (εNd), presents an opportunity to develop a new scheme specifically designed to test these paradigms. Here, we present the implementation of Nd isotopes (143Nd and 144Nd) into the ocean component of the FAMOUS coupled atmosphere–ocean general circulation model (Nd v1.0), a tool which can be widely used for simulating complex feedbacks between different Earth system processes on decadal to multi-millennial timescales. Using an equilibrium pre-industrial simulation tuned to represent the large-scale Atlantic Ocean circulation, we perform a series of sensitivity tests evaluating the new Nd isotope scheme. We investigate how Nd source and sink and cycling parameters govern global marine εNd distributions and provide an updated compilation of 6048 Nd concentrations and 3278 εNd measurements to assess model performance. Our findings support the notions that reversible scavenging is a key process for enhancing the Atlantic–Pacific basinal εNd gradient and is capable of driving the observed increase in Nd concentration along the global circulation pathway. A benthic flux represents a major source of Nd to the deep ocean. However, model–data disparities in the North Pacific highlight that under a uniform benthic flux, the source of εNd from seafloor sediments is too non-radiogenic in our model to be able to accurately represent seawater measurements. Additionally, model–data mismatch in the northern North Atlantic alludes to the possibility of preferential contributions from “reactive” non-radiogenic detrital sediments. The new Nd isotope scheme forms an excellent tool for exploring global marine Nd cycling and the interplay between climatic and oceanographic conditions under both modern and palaeoceanographic contexts.

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Dissertations / Theses on the topic "Nd isotopes"

1

Chen, Tianyu [Verfasser]. "The geochemical cycling and paleoceanographic application of combined oceanic Nd-Hf isotopes / Tianyu Chen." Kiel : Universitätsbibliothek Kiel, 2013. http://d-nb.info/1044891807/34.

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2

Simien, Frédéric. "Croissance crustale et contraintes paléogéographiques apportées par les isotopes du Nd dans les sédiments." Paris, Institut de physique du globe, 1998. http://www.theses.fr/1998GLOB0005.

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Il n'existe pas de consensus pour savoir si la masse continentale a été extraite du manteau très tôt dans l'Histoire de la Terre ou bien si elle a été différenciée au cours du temps. Les études en Sm-Nd apportent des contraintes à ce problème car l'isotope père et l'isotope fils sont presque exclusivement fractionnés lors d'un épisode de différenciation crustale. Il est donc possible de dater depuis quand les matériaux font partie de la croûte. L'application de ce couple aux shales permet une approche à grande échelle car ils représentent une moyenne de la croûte continentale. Les évolutions des compositions isotopiques en Nd des séries paléozoïques en Europe de l'ouest et dans l'est du Canada indiquent qu'il n'y a pas eu de grand apports de matériaux juvéniles dans la masse sédimentaire au cours du Paléozoïque, même durant les orogenèses. Les informations apportées par cette méthode peuvent contraindre les reconstructions paléogéographiques. En accord avec les données stratigraphiques et paléontologiques, nous proposons qu'il faille reconsidérer les modèles d'évolution géodynamique dans lesquels un océan Sud Armorcain séparait la Bretagne de l'Espagne au cours du Paléozoïque. Les données canadiennes nous permettent de proposer un modèle d'évolution pour les zones exotiques des Appalaches. Nous pensons que la zone Avalon se situait à proximité de l'Amérique du Sud à l'aube du Paléozoïque, puis qu'elle a été accolée au continent nord Américain vers l'Ordovicien moyen (450 Ma). Pour la zone Méguma, nous pensons qu'elle devrait être rattachée à l'Afrique de l'ouest au Protérozoïque supérieur puis qu'elle est entrée en collision avecle continent Nord américain au Carbonifère (300 Ma). Dans la dernière partie, la compilation des données isotopiques en Sm-Nd dans les sédiments détritiques à grain fin permet d'avoir une idée de l'évolution de la croûte à l'échelle globale depuis presque 4 Ga. Malheureusement, pour pouvoir déterminer la courbe de croissance crustale, il nous faudrait connaître le volume de sédiments injectés dans le manteau au cours du temps et la taille du réservoir de type manteau appauvri dans les temps très anciens.

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Partey, Frederick Kenneh. "SOURCE OF FLUORINE AND PETROGENESIS OF THE RIO GRANDE RIFT TYPE BARITE-FLUORITE-GALENA DEPOSITS." Miami University / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=miami1092262697.

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4

Bayon, Germain. "An investigation into ND and SR isotopes in marine sediments and their application to paleoceanography." Thesis, University of Southampton, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250079.

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Wilson, David James. "Investigating Nd and Pb isotopes as paleoceanographic proxies in the Indian Ocean : influences of water mass sourcing and boundary exchange." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610292.

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Wei, Ran [Verfasser]. "Application of Sr-Nd-Pb isotopes to the late quaternary paleoceanography of the Atlantic Ocean / Ran Wei." Mainz : Universitätsbibliothek Mainz, 2016. http://d-nb.info/1120442559/34.

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Moragues, Quiroga Cristina. "Water mixing processes in the critical zone : evidence from trace elements and Sr-Nd-Pb-U isotopes." Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAH002.

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Les fonctions hydrologiques de captage, stockage et rejet d’eau ont des signatures géochimiques dans les cours d'eau reflétant énormément celles trouvées dans les compartiments de la zone critique. Ces signatures sont fortement contrôlées par des processus bio-géophysico-chimiques produits dans l'interface régolite-plante. Jusqu'à présent, les recherches sur régolithes et processus hydrologiques sont restées largement découplées - conduisant à une utilisation généralisée de traceurs non conservateurs d'origines multiples, bloquant ainsi notre capacité à identifier les sources et les voies d'écoulement d’eau. Nous étudions ici le mélange d'eau dans la subsurface à travers un portefeuille unique de traceurs (éléments traces et isotopes O-H-Sr-Nd-Pb-U) permettant d'étudier les processus d'évolution du régolithe et le transport des solutés dans la zone critique. Nous signalons l'intérêt de cette approche pour renforcer la caractérisation des sources et voies d'écoulement d’eau<br>Catchment hydrological functions of water collection, storage and release have geochemical signatures in stream water largely mirroring those found in critical zone compartments. These signatures are strongly controlled by the different bio-geo-physico-chemical processes that occur within the regolith-plant interface. Until now, investigations into the critical zone’s regolith and hydrological processes research have largely remained uncoupled –leading to a widespread use of non-conservative tracers with multiple origins and thereby stymieing our capability for identifying water pools and flow paths. Here we study the mixing of water in the subsurface through a unique portfolio of complementary groups of tracers (trace elements O-Hand Sr-Nd-Pb-U isotopes) which enables investigating regolith evolution processes and solutes transport within the critical zone. We report the interest of this approach to strengthen water flowpaths and end-members characterization

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Munier, Thomas. "Évolution des conditions d’altération et des paléoclimats au cours de l'intervalle Albien-Santonien (113-83 Ma) : apports des minéraux argileux et de la géochimie." Electronic Thesis or Diss., Sorbonne université, 2023. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2023SORUS156.pdf.

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L’intervalle Albien-Santonien (~113-83 Ma) est une période charnière dans l’histoire du Crétacé. Cet intervalle est caractérisé par un fort taux de production de croûte océanique, associée à la dislocation de la Pangée et par une activité importante des provinces magmatiques. Ces conditions engendrent une augmentation notable de la pCO2 (Arthur et al., 1985) et une hausse progressive des températures océaniques jusqu’au maximum thermique mi-Crétacé, enregistré à la limite Cénomanien/Turonien (~94 Ma). Ce maximum thermique est suivi, dès la fin du Turonien, par une baisse des températures et de la pCO2 (Linnert et al., 2014). La diminution du volcanisme, une production carbonatée accrue et un stockage de carbone organique important lors de l’événement océanique anoxique OAE 2 à la limite Cénomanien-Turonien participent à la diminution du CO2. Néanmoins l’altération des silicates peut également jouer un rôle dans cette baisse. L’étude de nouveaux forages, réalisés dans le cadre de la mission IODP 369 sur les marges sud et sud-ouest de l’Australie, couplés à d’anciens forages, obtenus lors des missions ODP 122 et 123 sur la marges nord-ouest, nous a permis d’étudier l’évolution des conditions d’altération durant cet intervalle aux moyennes et hautes latitudes dans une zone peu étudiée jusqu’à présent. Une étude détaillée, basée sur la minéralogie des argiles a été réalisée sur six sites dans le bassin de la Grande Baie (site U1512), le bassin Mentelle (sites U1513 et U1516), le bassin Carvarnon (sites 763 et 766) et la plaine abyssale d’Argo (site 765). Sur trois des sites étudiés (U1512, U1513 et 763), des observations au MEB et au MET et des analyses géochimiques (isotopie du Sr et du Nd, concentrations en éléments majeurs et traces) ont complété cette étude. Ces nouvelles données ont été comparées aux nombreux travaux déjà réalisés dans l’océan Atlantique et le domaine péri-téthysien. Au cours de l’intervalle Albien-Turonien, les assemblages de minéraux argileux sont caractérisés par une augmentation des proportions de smectites, observée sur l’ensemble des régions étudiées. Cette augmentation résulte de la combinaison de paramètres globaux et locaux. La stabilisation tectonique des marges africaines et nord-américaines réduit l’altération physique, ce qui entraine une diminution des proportions d’illites et de chlorites, et permet la mise en place de processus pédogénétiques favorisant la formation de smectites. L’altération préférentielle des roches volcaniques dès la fin du Cénomanien, mise en évidence par les mesures isotopiques du Sr et du Nd sur certains sites au large de l’Australie (U1513), entraine également une augmentation des smectites. Enfin, la hausse du niveau marin, enregistrée de l’Albien au Turonien inférieur et associé à un enrichissement en smectites, témoigne de l’influence de la sédimentation différentielle sur les cortèges argileux. L’intervalle Cénomanien/Turonien, caractérisé par une augmentation des kaolinites aux basses et moyennes latitudes de l’hémisphère nord, est marqué par des conditions plus hydrolysantes. Ces kaolinites sont abondantes dans les secteurs soumis aux contraintes tectoniques à la fin du Crétacé inférieur (Aptien-Albien). Ainsi, malgré un climat favorable à leurs formations, l’absence de ces kaolinites dans l’hémisphère sud caractérise l’influence de la topographie et la nécessité de bonnes conditions de drainage pour former ces argiles. L’intervalle Albien-Santonien est ainsi caractérisé par une intensification de l’altération chimique qui culmine au moment du maximum thermique mi-Crétacé. Cette hausse des conditions d’hydrolyse, découplée de l’altération physique, parait néanmoins insuffisante pour faire diminuer la pCO2 lors de ce maximum thermique. Il apparait alors que, malgré un climat favorable à l’hydrolyse, le haut niveau marin et l’aplanissement des masses continentales inhibent l’altération chimique des silicates qui ne tient plus son rôle de puits de CO2<br>The Albian-Santonian interval (~113-83 Ma) is a key period in Cretaceous history. This interval is characterised by a high seafloor spreading rate, related to the breakup of Pangea, and by a significant activity of large igneous provinces, which generate an increase in pCO2 (Arthur et al., 1985). These conditions lead to a progressive temperature increase until the mid-Cretaceous thermal maximum, recorded at the Cenomanian/Turonian boundary (~94 Ma). This latter is followed from the late Turonian by a decline in temperature and pCO2 (Linnert et al., 2014; Wang et al., 2014). A decrease of volcanic activity, an increase of carbonate production, and an enhanced organic carbon storage during the anoxic oceanic event OAE 2 (Cenomanian-Turonian boundary) are frequently cited to explain the pCO2 decline. However, silicate weathering can also be involved as a triggered mechanism for this decrease. The analyse of new boreholes, drilled during the IODP Leg 369 on the southern and southwestern margins of Australia, coupled with some old boreholes of the ODP Legs 122 and 123 on the northwestern margin, allowed us to investigate the evolution of weathering conditions during this interval at the middle and high latitudes in a poorly studied sector. A detailed work, based on clay mineralogy, has been done on six sites located in the Great Bay Basin (Site U1512), in the Mentelle Basin (sites U1513 & U1516), in the Carnarvon Basin (sites 763 & 766) and the Argo Abyssal Plain (Site 765), respectively. For 3 sites (U1512, U1513 and 763), these studies have been completed by SEM and TEM observations and geochemical analyses (Sr and Nd isotopic ratios and concentrations of major & trace elements). These new data have been compared to the several studies, already done in the Atlantic Ocean and in the peri-Tethyan domain. During the Albian-Turonian interval, the clay mineral assemblages are characterised by an increase in smectite proportions, observed over all the studied regions. This increase results from a combination of global and local parameters. The tectonic stabilisation of the African and North American margins reduces the physical weathering, which leads to a decrease in illite and chlorite proportions, and permits the implementation of pedogenetic processes, which favours the formation of smectites. The preferential weathering of volcanic rocks from the end of the Cenomanian, highlighted by Sr and Nd isotopic measurements on some sites of Australia (U1513) or Africa (959) margins, also results in a relative increase of smectites. Finally, the sea level rise, recorded from the Albian to the Lower Turonian and associated with an enrichment in smectites, highlights the influence of the differential settling process on clay assemblages. The Cenomanian-Turonian interval, characterised by an increase in the proportions of kaolinites at the low and middle latitudes of the Northern Hemisphere, is interpreted as marked by more hydrolysing conditions. These kaolinites are present only in sectors, where tectonic was active at the end of the Early Cretaceous (Aptian-Albian). Thus, despite a climate favourable to their formation, the absence of kaolinites in favour of smectites in the Southern Hemisphere characterizes the influence of topography and good drainage conditions to form these minerals. The Albian-Santonian interval is thus characterised by an increase in chemical weathering that was maximal at the mid-Cretaceous thermal maximum. Nevertheless, this increase in hydrolysing conditions, associated to the denudation of the continental landmasses, seems to be insufficient to cause the pCO2 decrease during this thermal maximum. It appears then, despite a climate favourable for hydrolysis, high sea level and flattening of the continental masses prevent the chemical weathering of silicates which cannot regulate pCO2

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Lahd, Geagea Majdi. "Caractérisation chimique et isotopique des aérosols organiques/inorganiques et détermination de l'impact de la pollution atmosphérique sur l'environnement urbain." Université Louis Pasteur (Strasbourg) (1971-2008), 2007. http://www.theses.fr/2007STR1GE14.

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Des écorces d'arbres et des aérosols ont été analysés pour déterminer la pollution par les métaux dans l'environnement urbain en utilisant les isotopes. Cette étude s'est focalisée sur trois aspects: 1) La composition isotopique du fond "naturel" dans la vallée du Rhin, les montagnes des Vosges et les Alpes Centrales (Suisse). 2) Les caractéristiques des terres rares et des isotopes du Pb, Sr, Nd des émissions d'une aciérie. 3) Le traçage des émissions industrielles dans un environnement urbain en utilisant les isotopes de Pb, Sr et Nd. Les poussières provenant des principales sources de pollution (incinérateurs, centrale thermique, aciérie) et les suies provenant des voitures et des bateaux ont été analysées. Les sources industrielles montrent des valeurs en εNd et en 87Sr/86Sr bien variables. Les aérosols collectés dans le centre urbain de Strasbourg montrent l'influence des différentes sources industrielles et naturelles<br>The aim of this study was to determine the heavy metal pollution in the urban environment of Strasbourg and Kehl with help of isotopes. This study focused on three aspects: 1) The « natural » background isotopic composition in the Rhine Valley, Vosges Mountains and the Central Swiss Alps. 2) The REE characteristics and Pb, Sr and Nd isotopic compositions of steel plant emissions. 3) Tracing of industrial aerosol sources in an urban environment using Pb, Sr and Nd isotopes. Filter dust of the principal pollutant sources (waste incinerators, thermal power plant, and steel plant) and soot of car and ship exhaust have been analyzed. The industrial sources have variable εNd values and 87Sr/86Sr ratios. PM10 collected in the urban centre of Strasbourg show the influence of different industrial and natural sources

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Blair, Susanna Whitman. "Nd isotopes investigation of Cretaceous Ocean Anoxic Event 2 and a systematic study of Fe-Mn oxide coatings /." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0015647.

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Books on the topic "Nd isotopes"

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A, Ayuso Robert, De Vivo B, and Geological Survey (U.S.), eds. A geochemical and isotopic (Nd-Pb) comparison of volcanic rocks erupted during the last 3,550 yrs. B.P. of interplinian activity of Somma-Vesuvius volcano, southern Italy. U.S. Dept. of the Interior, U.S. Geological Survey, 1999.

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A, Ayuso Robert, De Vivo B, and Geological Survey (U.S.), eds. A geochemical and isotopic (Nd-Pb) comparison of volcanic rocks erupted during the last 3,550 yrs. B.P. of interplinian activity of Somma-Vesuvius volcano, southern Italy. U.S. Dept. of the Interior, U.S. Geological Survey, 1999.

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A, Ayuso Robert, De Vivo B, and Geological Survey (U.S.), eds. A geochemical and isotopic (Nd-Pb) comparison of volcanic rocks erupted during the last 3,550 yrs. B.P. of interplinian activity of Somma-Vesuvius volcano, southern Italy. U.S. Dept. of the Interior, U.S. Geological Survey, 1999.

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Vroon, Pieter Zeger. Subduction of continental material in the Banda Arc, eastern Indonesia: Sr-Nd-Pb isotope and trace-element evidence from volcanics and sediments. Faculteit Aardwetenschappen der Rijksuniversiteit Utrecht, 1992.

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Valbracht, Peter Jan. The origin of the continental crust of the Baltic shield, as seen through Nd and Sr isotopic variations in 1.89-1.85 Ga old rocks from western Bergslagen, Sweden. Drukkeru Elinkwuk, 1991.

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Survey, Ontario Geological. Geochronology Compilation Map For Ontario : Sheet 2: Southern Ontario: Grenville : Province and Environs : rb-sr, nd-sm, U-pb, and Other Isotopic Systems. s.n, 1986.

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Kwon, Sung-Tack. Pb-Sr-Nd isotope study of the 100 to 2700 Ma old alkalic rock-carbonatite complexes in the Canadian Shield: Inferences on the geochemical and structural evolution of the mantle. University Microfilms International, 1987.

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A geochemical and isotopic (Nd-Pb) comparison of volcanic rocks erupted during the last 3,550 yrs. B.P. of interplinian activity of Somma-Vesuvius volcano, southern Italy. U.S. Dept. of the Interior, U.S. Geological Survey, 1999.

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Book chapters on the topic "Nd isotopes"

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Champion, David C., and David L. Huston. "Applications of Neodymium Isotopes to Ore Deposits and Metallogenic Terranes; Using Regional Isotopic Maps and the Mineral Systems Concept." In Isotopes in Economic Geology, Metallogenesis and Exploration. Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-27897-6_5.

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AbstractAlthough radiogenic isotopes historically have been used in ore genesis studies for age dating and as tracers, here we document the use of regional- and continental-scale Sm–Nd isotope data and derived isotopic maps to assist with metallogenic interpretation, including the identification of metallogenic terranes. For the Sm–Nd system, calculated Nd model ages, which are time independent, are of most value for small-scale isotopic maps. Typically, one- or two-stage depleted mantle model ages (TDM, T2DM) are used to infer age when the isotope characteristics of the rock were in isotopic equilibrium with a modelled (mantle) reservoir. An additional advantage is that Nd model ages provide, with a number of assumptions, an estimate of the approximate age of continental crust in a region. Regional- and continental-scale Nd model age maps, constructed from rocks such as granites, which effectively sample the middle to lower crust, therefore, provide a proxy to constrain the nature of the crust within a region. They are of increasing use in metallogenic analysis, especially when combined with a mineral systems approach, which recognizes that mineral deposits are the result of geological processes, at a scales from the ore shoot to the craton. These maps can be used empirically and/or predictively to identify and target large parts of mineral systems that may be indicative, or form part of, metallogenic terranes. Examples presented here include observed spatial relationships between mineral provinces and isotopic domains; the identification of old and/or thick cratonic blocks; determination of tectonic regimes favorable for mineralization; identification of isotopically juvenile zones that may indicate rifts or primitive arcs; recognition of crustal breaks that define metallogenic terrane boundaries or delineate fluid pathways; and, as baseline maps. Of course, any analysis of Sm–Nd and similar isotopic maps are predicated on integration with geological, geochemical and geophysical information data. In the future, research in this area should focus on the spatial and temporal evolution of the whole lithosphere at the province- to global-scales to more effectively targeting mineral exploration. This must involve integration of radiogenic isotopic data with other data, in particular, geophysical data, which has the advantage of being able to directly image the crust and lithosphere and being of a more continuous nature as compared to invariably incomplete isotopic data sets.

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Huston, David L., and David C. Champion. "Applications of Lead Isotopes to Ore Geology, Metallogenesis and Exploration." In Isotopes in Economic Geology, Metallogenesis and Exploration. Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-27897-6_6.

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AbstractAlthough lead isotopes are most commonly used to date geological events, including mineralizing events, they also can provide information on many aspects of metallogeny and can be directly used in mineral exploration. Lead isotope data are generally reported as ratios of radiogenic isotopes normalized to the non-radiogenic isotope 204Pb (e.g. 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb). These ratios can be used in exploration to characterize the style of mineralization, metal (i.e. Pb) source and as vectors to ore. When combined with lead isotope evolution models, the data can be used to indicate the age and tectonic environment of mineralization. The raw ratios and evolution models enable calculation of derived parameters such as μ (238U/204Pb), κ (232Th/238U) and ω (232Th/204Pb), which provide more information about tectonic setting and can be contoured to identify crustal boundaries and metallogenic provinces. In some cases, tectonic boundaries, mapped using gradients in μ and other derived parameters, are fundamental controls on the distribution of certain deposit types in space and time. Moreover, crustal character, as determined by lead and other radiogenic isotopes (e.g. Nd) can be an indicator of province fertility for many deposit types. The development of cost effective analytical techniques and the assembly of large geo-located datasets for lead and other isotope data has enabled significant advances in understanding the genesis and localization of many deposit type, particularly when the isotopic data are integrated with other independent datasets such as potential field, magnetotelluric, passive seismic and geochemical data.

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Waltenberg, Kathryn. "Application of the Lu–Hf Isotopic System to Ore Geology, Metallogenesis and Mineral Exploration." In Isotopes in Economic Geology, Metallogenesis and Exploration. Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-27897-6_7.

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AbstractThe Lu-Hf isotopic system, much like the Sm-Nd isotopic system, can be used to understand crustal evolution and growth. Crustal differentiation processes yield reservoirs with differing initial Lu/Hf values, and radioactive decay of 176Lu results in diverging 176Hf/177Hf between reservoirs over time. This chapter outlines the fundamentals of the Lu-Hf isotopic system, and provides several case studies outlining the utility of this system to mineral exploration and understanding formation processes of ore deposits. The current, rapid, evolution of this field of isotope science means that breadth of applications of the Lu-Hf system are increasing, especially in situations where high-precision, detailed analyses are required.

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Sukhoruchkin, S. I., and Z. N. Soroko. "Graphs for Isotopes of 60-Nd(Neodymium)." In Nuclei with Z = 55 - 100. Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-540-70609-0_7686.

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DePaolo, Donald J. "Nd Isotopes as Tracers in Planetary Evolution." In Minerals and Rocks. Springer Berlin Heidelberg, 1988. http://dx.doi.org/10.1007/978-3-642-48916-7_3.

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Tripathy, Gyana Ranjan, Sunil Kumar Singh, and S. Krishnaswami. "Sr and Nd Isotopes as Tracers of Chemical and Physical Erosion." In Advances in Isotope Geochemistry. Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-10637-8_26.

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Okano, Osamu, and Mitsunobu Tatsumoto. "Petrogenesis of Ultramafic Xenoliths from Hawaii Inferred From Sr, Nd, and Pb Isotopes." In Earth Processes: Reading the Isotopic Code. American Geophysical Union, 2013. http://dx.doi.org/10.1029/gm095p0135.

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Grousset, F. E., and P. E. Biscaye. "Nd and Sr Isotopes as Tracers of Wind Transport: Atlantic Aerosols and Surface Sediments." In Paleoclimatology and Paleometeorology: Modern and Past Patterns of Global Atmospheric Transport. Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-0995-3_16.

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Huston, David L., David C. Champion, and Kevin F. Cassidy. "Tectonic controls on the endowment of Archean cratons in VHMS deposits: Evidence from PB and Nd isotopes." In Mineral Deposit Research: Meeting the Global Challenge. Springer Berlin Heidelberg, 2005. http://dx.doi.org/10.1007/3-540-27946-6_4.

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DePaolo, Donald J. "Overview of Nd Isotopic Variations." In Minerals and Rocks. Springer Berlin Heidelberg, 1988. http://dx.doi.org/10.1007/978-3-642-48916-7_5.

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Conference papers on the topic "Nd isotopes"

1

Ouhachi, M., M. R. Oudih, M. Fellah, and N. H. Allal. "Exotic decay investigation of Nd isotopes." In 1ST INTERNATIONAL CONFERENCE ON RADIATIONS AND APPLICATIONS (ICRA-2017). Author(s), 2018. http://dx.doi.org/10.1063/1.5048147.

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Asai, Shiho, Keisuke Okumura, Yukiko Hanzawa, et al. "Validation of Correlations Between Nd Isotopes and Difficult-to-Measure Nuclides Predicted With Burn-Up Calculation Code by Postirradiation Examination." In ASME 2011 14th International Conference on Environmental Remediation and Radioactive Waste Management. ASMEDC, 2011. http://dx.doi.org/10.1115/icem2011-59086.

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Correlations between Nd isotopes and difficult-to-measure (DTM) nuclides, such as Se-79, Tc-99, Sn-126, and Cs-135, predicted using a calculation code have been validated by postirradiation examination (PIE). The calculation was performed with a burnup calculation code, MVP-BURN, using the updated nuclear data library JENDL-4.0. An irradiated PWR fuel with a burnup of 44.9 GWd/t and a cooling time of 7458 days was used as a standard sample. The concentrations of Nd isotopes in the sample solutions were determined by inductively coupled plasma mass spectrometry (ICP-MS) after purification by two consecutive anion-exchange separations. The ratios of Se-79 and Cs-135 to Nd isotopes (Nd-145, Nd-146, and Nd-145+Nd-146) calculated using MVP-BURN were in good agreement with PIE values within the deviations of 8% and 6%, respectively. This indicates that these calculated ratios are applicable to the scaling factors of Se-79 and Cs-135. For Tc-99 and Sn-126, the calculated values were respectively about 50% and 20% higher than the PIE values. These overestimations were mainly caused by the lack of the contribution of an insoluble residue to the measured concentrations.

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Duggan, Brian Daniel. "HF-ND ISOTOPES OF EQUATORIAL PACIFIC OXYHYDROXIDE LEACHATES ACROSS THE EOT." In 65th Annual Southeastern GSA Section Meeting. Geological Society of America, 2016. http://dx.doi.org/10.1130/abs/2016se-273830.

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An, Emily, Ellen Martin, Kelly Deuerling, and Jonathan B. Martin. "IMPACT OF GLACIAL RETREAT AND WEATHERING ON NORTH ATLANTIC ND ISOTOPES." In GSA 2020 Connects Online. Geological Society of America, 2020. http://dx.doi.org/10.1130/abs/2020am-357831.

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Fisher, Chris, Jeffrey Vervoort, Ross Salerno, Da Wang, and Tony Kemp. "Early Earth decoupling of Hf-Nd isotopes: the accessory mineral perspective." In Goldschmidt2021. European Association of Geochemistry, 2021. http://dx.doi.org/10.7185/gold2021.7002.

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Batenburg, Sietske J., Alex J. Dickson, Benjamin S. Kelsey, et al. "OCEANOGRAPHY OF THE WESTERN INTERIOR SEAWAY DURING OAE 2 USING ND ISOTOPES." In GSA Annual Meeting in Indianapolis, Indiana, USA - 2018. Geological Society of America, 2018. http://dx.doi.org/10.1130/abs/2018am-322094.

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Yokoyama, Rin, Eiji Ideguchi, Gary Simpson, et al. "Role Of Hexadecupole Deformation In The Shape Evolution Of Neutron-rich Nd Isotopes." In The 26th International Nuclear Physics Conference. Sissa Medialab, 2017. http://dx.doi.org/10.22323/1.281.0015.

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Doucelance, Régis, Claudine Israel, Maud Boyet, Pierre Bonnand, Matthew G. Jackson, and Jane Barling. "A Ce-Nd-Hf Isotopes Perspective on the EMI-Emii End-Members Distinction." In Goldschmidt2020. Geochemical Society, 2020. http://dx.doi.org/10.46427/gold2020.607.

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Bayon, Germain, Kwangchul Jang, Nathalie Vigier, et al. "REE and Nd isotopes in sedimentary Fe oxides as proxies for shale weathering." In Goldschmidt2021. European Association of Geochemistry, 2021. http://dx.doi.org/10.7185/gold2021.6327.

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Bruand, Emilie, Mike Fowler, Craig Storey, Bruno Dhuime, and Régis Doucelance. "Mineral-whole rock isotope fidelity in granitoids? A comparative study of Hf-Nd-O isotopes in apatite, titanite and zircon." In Goldschmidt2023. European Association of Geochemistry, 2023. http://dx.doi.org/10.7185/gold2023.16888.

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Reports on the topic "Nd isotopes"

1

Ahmad, I., C. J. Lister, and L. R. Morss. Lifetimes in neutron-rich Nd isotopes measured by Doppler profile method. Office of Scientific and Technical Information (OSTI), 1995. http://dx.doi.org/10.2172/166329.

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KIM, H., M. HERMAN, S. F. MUGHABGHAB, P. OBLOZINSKY, D. ROCHMAN, and LEE. Y.-O. EVALUATION OF NEUTRON CROSS SECTIONS FOR A COMPLETE SET OF Nd ISOTOPES. Office of Scientific and Technical Information (OSTI), 2007. http://dx.doi.org/10.2172/921937.

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Berman, R. G., B. E. Taylor, W. J. Davis, M. Sanborn-Barrie, and J B Whalen. Crustal architecture and evolution of the central Thelon tectonic zone, Nunavut: insights from Sm-Nd and O isotope analysis, U-Pb zircon geochronology, and targeted bedrock mapping. Natural Resources Canada/CMSS/Information Management, 2024. http://dx.doi.org/10.4095/332497.

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New isotopic analyses (Sm-Nd, O, and U-Pb), targeted geological mapping, and previously published whole-rock geochemical data and high-resolution aeromagnetic surveys define ten crustal domains across the central Thelon tectonic zone. In the eastern Slave Craton, granitoid rocks in the Overby Lake domain are more isotopically evolved than in the Tinney Hills domain and include tonalite dated at 2.71 Ga. The 400 km long main leucogranite belt separates most early (ca. 2.07-1.95 Ga) Thelon tectonic zone plutonic belts from the Queen Maud Block. Oxygen isotopes support its formation via melting of a sedimentary source during peak metamorphism, which coincides with three, new 1.925-1.91 Ga leucogranite ages. Modelling of Nd-Sm isotopes indicates Neoarchean crust as basement to early Thelon tectonic zone plutonic belts. Detrital zircon geochronology suggests a 2.5 Ga basement component that is not recognized in exposed crustal domains, but is compatible with the Dharwar Craton, which can be paleomagnetically reconstructed adjacent to the Slave Craton at 2.2 Ga. Two tectonic models are discussed for the evolution of the Thelon tectonic zone in the convergent margin tectonic setting indicated by the whole-rock geochemistry and mantle-like oxygen isotopic compositions of plutonic rocks. In one model, ca. 2.1 Ga extension precedes east-dipping subduction, which leads to 1.97 Ga collision of the Slave Craton with a composite Thelon tectonic zone basement-Rae Craton, upper plate. The second model proposes a ca. 2.05 Ga Slave-microcontinent (Thelon tectonic zone basement) collision, followed by a polarity flip with west-dipping subduction, leading to ca. 1.95 Ga collision of the Rae Craton.

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Manor, M. J., and S. J. Piercey. Whole-rock lithogeochemistry, Nd-Hf isotopes, and in situ zircon geochemistry of VMS-related felsic rocks, Finlayson Lake VMS district, Yukon. Natural Resources Canada/CMSS/Information Management, 2021. http://dx.doi.org/10.4095/328992.

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The Finlayson Lake district in southeastern Yukon is composed of a Late Paleozoic arc-backarc system that consists of metamorphosed volcanic, plutonic, and sedimentary rocks of the Yukon-Tanana and Slide Mountain terranes. These rocks host &amp;gt;40 Mt of polymetallic resources in numerous occurrences and styles of volcanogenic massive sulphide (VMS) mineralization. Geochemical and isotopic data from these rocks support previous interpretations that volcanism and plutonism occurred in arc-marginal arc (e.g., Fire Lake formation) and continental back-arc basin environments (e.g., Kudz Ze Kayah formation, Wind Lake formation, and Wolverine Lake group) where felsic magmatism formed from varying mixtures of crust- and mantle-derived material. The rocks have elevated high field strength element (HFSE) and rare earth element (REE) concentrations, and evolved to chondritic isotopic signatures, in VMS-proximal stratigraphy relative to VMS-barren assemblages. These geochemical features reflect the petrogenetic conditions that generated felsic rocks and likely played a role in the localization of VMS mineralization in the district. Preliminary in situ zircon chemistry supports these arguments with Th/U and Hf isotopic fingerprinting, where it is interpreted that the VMS-bearing lithofacies formed via crustal melting and mixing with increased juvenile, mafic magmatism; rocks that were less prospective have predominantly crustal signatures. These observations are consistent with the formation of VMS-related felsic rocks by basaltic underplating, crustal melting, and basalt-crustal melt mixing within an extensional setting. This work offers a unique perspective on magmatic petrogenesis that underscores the importance of integrating whole-rock with mineral-scale geochemistry in the characterization of VMS-related stratigraphy.

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Macêdo Filho, Antomat Avelino, and Maria Helena Hollanda. The Effect of Alteration on Sr-Nd Isotopes of Mafic Rocks: Examples From Rio Ceará-Mirim Dyke Swarm, NE Brazil. Peeref, 2022. http://dx.doi.org/10.54985/peeref.2209p1380949.

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Tomlinson, K. Y., and J. A. Percival. Geochemistry and Nd isotopes of granitoid rocks in the Shikag-Garden lakes area, Ontario: recycled Mesoarchean crust in the central Wabigoon Subprovince. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 2000. http://dx.doi.org/10.4095/211618.

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Matte, S., M. Constantin, and R. Stevenson. Mineralogical and geochemical characterisation of the Kipawa syenite complex, Quebec: implications for rare-earth element deposits. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/329212.

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Abstract:

The Kipawa rare-earth element (REE) deposit is located in the Parautochton zone of the Grenville Province 55 km south of the boundary with the Superior Province. The deposit is part of the Kipawa syenite complex of peralkaline syenites, gneisses, and amphibolites that are intercalated with calc-silicate rocks and marbles overlain by a peralkaline gneissic granite. The REE deposit is principally composed of eudialyte, mosandrite and britholite, and less abundant minerals such as xenotime, monazite or euxenite. The Kipawa Complex outcrops as a series of thin, folded sheet imbricates located between regional metasediments, suggesting a regional tectonic control. Several hypotheses for the origin of the complex have been suggested: crustal contamination of mantle-derived magmas, crustal melting, fluid alteration, metamorphism, and hydrothermal activity. Our objective is to characterize the mineralogical, geochemical, and isotopic composition of the Kipawa complex in order to improve our understanding of the formation and the post-formation processes, and the age of the complex. The complex has been deformed and metamorphosed with evidence of melting-recrystallization textures among REE and Zr rich magmatic and post magmatic minerals. Major and trace element geochemistry obtained by ICP-MS suggest that syenites, granites and monzonite of the complex have within-plate A2 type anorogenic signatures, and our analyses indicate a strong crustal signature based on TIMS whole rock Nd isotopes. We have analyzed zircon grains by SEM, EPMA, ICP-MS and MC-ICP-MS coupled with laser ablation (Lu-Hf). Initial isotopic results also support a strong crustal signature. Taken together, these results suggest that alkaline magmas of the Kipawa complex/deposit could have formed by partial melting of the mantle followed by strong crustal contamination or by melting of metasomatized continental crust. These processes and origins strongly differ compare to most alkaline complexes in the world. Additional TIMS and LA-MC-ICP-MS analyses are planned to investigate whether all lithologies share the same strong crustal signature.

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Scanlan, E. J., M. Leybourne, D. Layton-Matthews, A. Voinot, and N. van Wagoner. Alkaline magmatism in the Selwyn Basin, Yukon: relationship to SEDEX mineralization. Natural Resources Canada/CMSS/Information Management, 2021. http://dx.doi.org/10.4095/328994.

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Several sedimentary exhalative (SEDEX) deposits have alkaline magmatism that is temporally and spatially associated to mineralization. This report outlines interim data from a study of potential linkages between magmatism and SEDEX mineralization in the Selwyn Basin, Yukon. This region is an ideal study site due to the close spatial and temporal relationships between SEDEX deposits and magmatism, particularly in the MacMillan Pass, where volcanic rocks have been drilled with mineralization at the Boundary deposit. Alkaline volcanic samples were analysed from the Anvil District, MacMillan Pass, Keno-Mayo and the Misty Creek Embayment in the Selwyn Basin to characterise volcanism and examine the relationship to mineralization. Textural and field relationships indicate a volatile-rich explosive eruptive volcanic system in the MacMillan Pass region in comparison to the Anvil District, which is typically effusive in nature. High proportions of calcite and ankerite in comparison to other minerals are present in the MacMillan system. Cathodoluminescence imaging reveals zoning and carbonate that displays different luminescent colours within the same sample, likely indicating multiple generations of carbonate precipitation. Barium contents are enriched in volcanic rocks throughout the Selwyn Basin, which is predominately hosted by hyalophane with rare barite and barytocalcite. Thallium is positively correlated with Ba, Rb, Cs, Mo, As, Sb and the calcite-chlorite-pyrite index and is negatively correlated with Cu. Anvil District samples display a trend towards depleted mid-ocean ridge mantle on a plot of Ce/Tl versus Th/Rb. Hydrothermal alteration has likely led to the removal of Tl from volcanic rocks in the region. Ongoing research involves: i) the analysis of Sr, Nd, Pb and Tl isotopes of volcanic samples; ii) differentiating magmatic from hydrothermal carbonate using O, C and Sr isotopes; iii) examining sources of Ba in the Selwyn Basin; iv) and constraining age relationships through U-Th-Pb geochronology.

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Piercey, S. J., and J. L. Pilote. Nd-Hf isotope geochemistry and lithogeochemistry of the Rambler Rhyolite, Ming VMS deposit, Baie Verte Peninsula, Newfoundland: evidence for slab melting and implications for VMS localization. Natural Resources Canada/CMSS/Information Management, 2021. http://dx.doi.org/10.4095/328988.

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New high precision lithogeochemistry and Nd and Hf isotopic data were collected on felsic rocks of the Rambler Rhyolite formation from the Ming volcanogenic massive sulphide (VMS) deposit, Baie Verte Peninsula, Newfoundland. The Rambler Rhyolite formation consists of intermediate to felsic volcanic and volcaniclastic rocks with U-shaped primitive mantle normalized trace element patterns with negative Nb anomalies, light rare earth element-enrichment (high La/Sm), and distinctively positive Zr and Hf anomalies relative to surrounding middle rare earth elements (high Zr-Hf/Sm). The Rambler Rhyolite samples have epsilon-Ndt = -2.5 to -1.1 and epsilon-Hft = +3.6 to +6.6; depleted mantle model ages are TDM(Nd) = 1.3-1.5 Ga and TDM(Hf) = 0.9-1.1Ga. The decoupling of the Nd and Hf isotopic data is reflected in epsilon-Hft isotopic data that lies above the mantle array in epsilon-Ndt -epsilon-Hft space with positive ?epsilon-Hft values (+2.3 to +6.2). These Hf-Nd isotopic attributes, and high Zr-Hf/Sm and U-shaped trace element patterns, are consistent with these rocks having formed as slab melts, consistent with previous studies. The association of these slab melt rocks with Au-bearing VMS mineralization, and their FI-FII trace element signatures that are similar to rhyolites in Au-rich VMS deposits in other belts (e.g., Abitibi), suggests that assuming that FI-FII felsic rocks are less prospective is invalid and highlights the importance of having an integrated, full understanding of the tectono-magmatic history of a given belt before assigning whether or not it is prospective for VMS mineralization.

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Roddick, J. C., R. W. Sullivan, and F. O. Dudas. Precise Calibration of Tracer Compositions For Sm - Nd Isotopic Studies. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 1992. http://dx.doi.org/10.4095/132926.

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