Trace element and U isotope analysis of uraninite and ore concentrate: Applications for nuclear forensic investigations

The 20.000 km2 swamp of the Delta is organized into islands, flood plains and permanent and seasonal channels. Most of these islands display a surprising vegetation distribution composed of tree rings surrounding the islands and limiting an inner domain with scarce vegetation. Whereas the hydrology of the Okanvango wetlands is governed by a series of drivers such as, sedimentation, climate, tectonic and biological processes, the potential of the use of multi-chemical tracing has not been so far much investigated. The conducted study as part of a multidisciplinary project dedicated to the understanding of the functioning of the Delta, involved water samples collected both upstream and downsream the river, close to one of these islands and also recovered within the island as well. The main objective of this geochemical investigation was to better constrain the interactions prevailing in between these islands and the water chemical record. pH, conductivity (C), dissolved organic and inorganic carbon (DOC & DIC) concentrations were measured as well as those of major anion and cation and trace cation concentrations as well. Whichever the tracers are considered, two contrasted groups of samples were evidenced depending on their sampling positioning regarding the island. The samples recovered only within the island displayed pH around and over 9 and higher conductivities, whereas the other showed lower circumneutral pH values and conductivities as well. The high conductivities of the water samples fom the island also correspond to the highest DOC and DIC concentrations. The strong relationship linking the high DIC values and the high pH in the island samples records probably alkaline CO32- et HCO3- -rich waters resulting from water-rock interactions with carbonates. The marked DOC enrichment has mostly to be related to microbial or photo-degradation of plant-derived organic matter and/or hydrological condition variations promoting DOC release. Significant, Cl-, SO42-, NO2-enrichments as well as major cation ones were also evidenced in the same group of samples within the island. However, the most surprising results are sourced in the trace element fingerprinting. This latter includes huge enrichment in heavy, critical metals and metalloids as well (e.g. Cr, Pb, V, REE, U, Th or As). Beyond the only marked REE-spike, Upper Continental Crust-normalized REE patterns displayed markedly contrasted shapes exhibiting two types of waters with circumneutral pH ones with MREE-enrichment, whereas the alkaline waters evidenced a classical continuous enrichment throughout the whole series from LREE to HREE and a positive Ce anomaly. The use of such multi-tracing allowed an efficient fingerprinting of two distint types of waters to get clues to further constrain both the dynamics of such islands and the functioning of the water system. Still in progress, the study will be completed by (i) the stable isotope analysis, (ii) the modeling of the minerals possibly at equilibrium with the waters and of the organic matter-trace element interactions, (iii) the speciation analysis of some enriched elements, (iv) the comparison between water and solid samples analyses and (v) the understanding of the relations in between the concentrations and locations in the hydrological system.

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A preliminary assessment of the application of Sr, Nd, Pb, He and N isotope analysis to fluid inclusions in kimberlite olivine: A new approach to trace deep-mantle sources

10.5194/egusphere-egu2020-5267 ◽

2020 ◽

Author(s):

Andrea Giuliani ◽

Janne M. Koornneef ◽

Peter Barry ◽

Patrizia Will ◽

Henner Busemann ◽

...

Keyword(s):

Isotopic Composition ◽

Trace Element ◽

Mass Spectrometer ◽

Fluid Inclusions ◽

Noble Gas ◽

Isotope Analysis ◽

Helium Isotope ◽

New Approach ◽

Deep Mantle ◽

Mantle Sources

Kimberlites are the deepest melts that reach Earth&#8217;s surface and, therefore, can provide unique insights into the composition and evolution of the convective mantle through time. Application of isotope geochemistry to trace the composition of kimberlite sources has thus far been hindered by the ubiquitous alteration and incorporation of xenocrystic material in kimberlite rocks. Bulk-kimberlite analyses are typically considered reliable for Nd and Hf isotopes due to their overwhelmingly higher concentrations in kimberlite melts compared to common mantle and crustal contaminants. Conversely, Sr and Pb isotope compositions of bulk kimberlite samples are seldom considered representative of their parental melts thus requiring analysis of robust magmatic phases, primarily perovskite. Addressing the primary (i.e. magmatic) isotopic composition of volatile elements, such as N and noble gases, requires analyses of volatile-rich phases, and fluid inclusions in olivine represent a typical primary target in mantle-derived magmas. However, fluid inclusions in kimberlitic olivine are dominantly secondary in origin. Secondary inclusions can form at any time after crystallisation of their mineral host, which requires assessment of the origin of trapped fluids (i.e. pristine magmatic fluids, crustal fluids of external derivation, or combination thereof) before their isotopic composition can be used to make inferences about kimberlite mantle sources.Here we present trace-element and Sr-Nd-Pb-He-N isotopic compositions of multiple olivine aliquots representing two different magmatic units of the ~88 Ma Wesselton kimberlite (Kimberley, South Africa). The Sr and Nd isotopic composition of olivine analysed by isotope-dilution (ID) TIMS are within the narrow range of perovskite 87Sr/86Sr (0.7043-0.7046) and whole-rock 143Nd/144Nd (eNdi = 0.4&#8211;2.2) for the Kimberley kimberlites. These results indicate that the secondary fluid inclusions, which dominate the incompatible trace-element budget of olivine separates, have a pristine magmatic origin devoid of crustal contribution.Helium isotope compositions were measured by laser heating of 1.6 to 9.8 mg of olivine using an ultrahigh-sensitivity compressor-source noble gas mass spectrometer. 3He/4He ratios are between 1.6 RA and 3.7 RA (where RA indicates the atmospheric 3He/4He ratio), values more radiogenic than MORBs but comparable to HIMU OIBs. These results indicate a high time-integrated (U+Th)/He ratio in the source of the Kimberley kimberlites, which is consistent with the moderately high (i.e. HIMU-like) time-integrated U/Pb ratio implied by elevated initial 206Pb/204Pb in Wesselton olivine (19.1-19.5), Kimberley kimberlites (up to 19.9) and megacrysts in southern African Cretaceous kimberlites (up to 20.5). The combination of low 3He/4He, moderately radiogenic 87Sr/86Sr, and negative d34S values (-2.6&#8240; to -5.7&#8240;) require a contribution from subducted recycled material in the source of the Kimberley kimberlites. Conversely, a preliminary N isotope analysis of Wesselton olivine by in-vacuo crushing using a noble gas mass spectrometer returned a mantle-like d15N of -2.9&#8240;, which might suggest limited recycling of surface N (d15N >0&#8240;) in the source of these kimberlites. We conclude that the combination of Sr-Nd-Pb and He-N isotope tracing of fluid inclusions in olivine can provide a robust new approach to address the composition of kimberlite sources and, therefore, the evolution of the deep mantle through time.

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Boron isotope analysis of coral skeletons by laser ablation MC-ICP-MS: new insights into calcification and environmental reconstruction at high temporal resolution

10.5194/egusphere-egu2020-8202 ◽

2020 ◽

Author(s):

Gavin L. Foster ◽

Thomas B. Chalk ◽

Christopher D. Standish

Keyword(s):

Laser Ablation ◽

Trace Element ◽

Temporal Resolution ◽

Isotope Analysis ◽

Coral Skeleton ◽

Boron Isotope ◽

High Temporal Resolution ◽

Carbonate System ◽

Seawater Ph ◽

Icp Ms

Despite being some of the largest bio-constructions on the planet, coral reefs are made by many millions of cm- to mm-sized polyps of Scleractinian corals. Calcification occurs in a micron sized space sandwiched between the coral animal and the existing skeleton, known as the extra cellular medium (ECM). The coral animal has a tight control on the carbonate system in this space through deploying enzymatic pumps (e.g. Ca-ATPase) and secreting acidic-rich proteins. Tracking the state of the carbonate system in the ECM is therefore key to forming a mechanistic understanding of how environmental change, such as ocean acidification, influences skeletal formation and ultimately the growth and resilience of these important ecosystems.Traditional means to examine ECM composition is through the use of micro-electrodes. While these approaches have revealed many key insights they are, by their nature, invasive.&#160; They also only provide snap shots of information for corals grown in the laboratory. The boron isotopic composition of the coral skeleton and its boron content (expressed as B/Ca ratio) have recently emerged as a viable alternative approach to fully characterise the carbonate system in the ECM.&#160; However, most studies employ bulk sampling techniques which require averaging across both structural elements of the coral skeleton and many months to years of growth. Laser ablation MC-ICP-MS approaches are now available as an alternative sampling protocol (e.g. Standish et al. 2019), and along with B/Ca (and other trace element) measurements this not only allows a reconstruction of the full carbonate system of the ECM from an analysis of the skeleton of any coral (cultured or wild) at unprecedented spatial and temporal resolution, but it also allows an examination of the influence of the carbonate system in the ECM on trace element incorporation.&#160;Here we present boron isotope and trace element analyses of several tropical, reef-building, corals to examine the nature and magnitude of fine scale variation in ECM composition.&#160; By studying corals from locations where external seawater is well known we also gain insights into trace element incorporation and whether external seawater pH can be accurately reconstructed from the boron-based proxies at weekly (or better) resolution.&#160;&#160;Standish, C.D., Chalk, T.B., Babila, T.L., Milton, J.A., Palmer, M.R., Foster, G.L. (2019) The effect of matrix interferences in situ boron isotope analysis by laser ablation MC-ICP-MS, Rapid Communications in Mass Spectrometry 33: 959&#8211;968 https://doi.org/10.1002/rcm.8432

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Nuclear forensic investigations with a focus on plutonium

Journal of Alloys and Compounds ◽

10.1016/j.jallcom.2006.10.161 ◽

2007 ◽

Vol 444-445 ◽

pp. 57-62 ◽

Cited By ~ 45

Author(s):

Maria Wallenius ◽

Klaus Lützenkirchen ◽

Klaus Mayer ◽

Ian Ray ◽

Laura Aldave de las Heras ◽

...

Keyword(s):

Forensic Investigations ◽

Nuclear Forensic

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Extracting Reliable Paleo-Ocean Temperatures at Southern Mid-Latitudes During the Greenhouse to Icehouse Transition: a LA-ICP-MS Study of the Trace Element Chemistry of Eocene Foraminifera from New Zealand

10.26686/wgtn.17011562 ◽

2021 ◽

Author(s):

◽

John Benjamin Creech

Keyword(s):

New Zealand ◽

Trace Element ◽

Benthic Foraminifera ◽

Inductively Coupled Plasma ◽

Middle Eocene ◽

Isotope Analysis ◽

Time Interval ◽

Northern Margin ◽

Icp Ms ◽

Fe And Mn

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been used to measure in situ elemental (Mg, Al, Mn, Zn, Sr, Ba/Ca) ratios of 13 species of variably preserved early to middle Eocene planktonic and benthic foraminifera from the mid-Waipara River section, north Canterbury, New Zealand. The sediments from Waipara River were deposited at bathyal depths (ca. 1000 m) on the northern margin of the east-facing Canterbury Basin at a paleo-latitude of ca. 55 dgrees S. LA-ICP-MS analysis yields trace element depth profiles through foraminifera test walls that can be used to identify and exclude zones of surficial contamination and infilling material resulting from diagenetic coatings, mineralisation and detrital sediment. Screened Mg/Ca ratios are used to calculate sea temperatures from late early to early middle Eocene (ca. 51 to 46.5 Ma), a time interval that appears to span the termination of the Early Eocene Climatic Optimum (EECO). During this time, sea surface temperatures (SST) varied from 30 to 24 degrees C and bottom water temperatures (BWT) from 21 to 14 degrees C. Comparison of Mg/Ca sea temperatures with published delta superscript 18 O and TEX subscript 86 temperature data from the same samples (Hollis et al., 2009) shows close correspondence, indicating that LA-ICP-MS can provide reliable Mg/Ca sea temperatures even where foraminiferal test preservation is less than ideal. Agreement between the three proxies also implies that Mg/Ca - temperature calibrations for modern planktonic and benthic foraminifera can generally be applied to Eocene species, although some species (e.g., V. marshalli) show significant calibration differences. The Mg/Ca ratio of the Eocene ocean is constrained by our data to be 35-50% lower than the modern ocean depending on which TEX86 - temperature calibration is used to compare with the Mg/Ca sea temperatures (Kim et al., 2008; Liu et al., 2009). Sea temperatures derived from oxygen isotope analysis of foraminifera from mid-Waipara show amplified variability relative to the Mg/Ca and TEX86 derived temperatures. While this difference might be attributed to the oxygen isotopes being more susceptible to diagenetic effects, the data may be consistent with the growth and collapse of significant global ice sheets during cool periods in the Eocene on timescales of ca. 0.5 Myr. The timing of the termination of the EECO in the reconstructed climate record from mid-Waipara is consistent with other published climate records (Tripati et al., 2003, 2005; Zachos et al., 2008). A large decrease in foraminiferal Mn/Ca ratios up the mid-Waipara section is observed with the youngest samples having Mn/Ca ratios similar to modern foraminifera. This does not appear to be a diagenetic fingerprint as foraminiferal preservation is generally poorer up-section. Global cooling following the EECO may have led to enhanced biological productivity and uptake of Fe and Mn, thereafter producing an ocean with Mn concentrations more similar to the present ocean. This hypothesis is consistent with that proposed to explain changes in the thallium isotope ratios of Fe and Mn crusts observed at this time (Nielsen et al., 2009).

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