Mixing Curves Research Articles

Lead isotope variability in olivine-hosted melt inclusions from Iceland

The lead isotope and trace element compositions of a suite of olivine-hosted melt inclusions in primitive lava flows from the Reykjanes Peninsula in Iceland show extreme variability. Much of this variability is present in the composition of inclusions from one hand specimen of Háleyjabunga, a depleted picrite lava shield that erupted 13 ka. 208Pb/ 206Pb compositions in this sample span 50–90% of the total range found in Atlantic MORB, indicating that high-amplitude compositional heterogeneity is present in the mantle source of melts that aggregated to form a single eruption. The trace element and isotopic trends in the melt inclusions are coincident with those in whole rock samples from young lava flows of the Reykjanes Peninsula, and extend the total range of variation towards more depleted compositions. The incompatible trace element and lead isotope compositions of the inclusions are strongly coupled and lie close to binary mixing trends between the extreme melt inclusion compositions. These relationships indicate that the trace element variation in the melt inclusions reflects heterogeneity in the composition of the mantle source entering the melting region under the Reykjanes Peninsula. Large positive Sr concentration anomalies are present in three of the inclusions, but do not correlate with indicators of mantle melting or source variations and are likely to arise by reaction with plagioclase during crustal storage. Fractional melting of heterogeneous mantle is predicted to generate melts with a wide range of compositions, filling a large volume in trace element–isotope space. However, the compositional variations observed in the melt inclusions lie close to binary mixing curves. These observations may be accounted for by a two-stage model of melt mixing. The first stage occurs in porous channels that transport melt in the mantle and takes place before inclusion entrapment. This mixing stage generates a bimodal distribution of melt compositions that is supplied from the channels to sub-Moho and lower crustal magma lenses. The second stage of mixing occurs in these chambers, producing the binary mixing trends recorded in the inclusion compositions. The distribution of isotopic compositions observed in the melt inclusions and whole rock samples from the Reykjanes Peninsula is therefore controlled by melt mixing. These results have important implications for the interpretation of basalt composition in terms of distinct compositional entities within the upwelling solid mantle under mid-ocean ridges and ocean islands.

Reconciling Electrical Resistance Tomography (ERT) Measurements with a Fluid Mixing Model for Semi-Batch Operation of a Stirred Vessel

An electrical resistance tomography (ERT) system retrofitted to a 2.3 m3 vessel has been used to image the vessel volume for single feed semi-batch operation. Images reconstructed from the raw ERT measurements may be represented as time incremented 3-D iso-surface representations of the fluid mixing. ERT derived mixing curves have been evaluated against a network of zones (NOZ) mixing model, which is able to compute the time evolving concentration fields. Like the ERT system, the NOZ model is also able to visualise the evolving feed plume and has the power to predict the corresponding time-wise reaction behaviour in space for a simple A + B → products reaction. On a eu recours à un système de tomographie à résistance électrique (ERT) adapté à un réservoir de 2,3 m3 pour cartographier le volume du réservoir pour un fonctionnement semi-discontinu à alimentation unique. Les images reconstruites à partir de mesures d'ERT brutes peuvent être représentées sous forme d'une série chronologique d'iso-surface en 3-D du mélange de fluide. Les courbes de mélange établies par ERT sont évaluées par rapport à un modèle de mélange à réseau de zones (NOZ), qui est capable de calculer l'évolution du champ de concentration dans le temps. À l'instar du système ERT, le modèle NOZ est également capable de visualiser le panache d'alimentation en évolution et de prédire le comportement dans le temps et l'espace d'une réaction simple A+B → produit.

Role of rice and added wheat protein in the mixing properties of different rice flours

Structure and composition of wheat storage proteins and functional properties of wheat gluten are well studied; therefore several methods and instruments are available to determine these properties. The investigation of functional properties of rice proteins, depending on the different goal of utilisation, has not been well established, yet. In this study, the rheological properties of four varieties of rice flour were studied using a 50 g Farinograph demonstrating the mixing properties of rice flours and the alterations of these properties caused by the supplementation of wheat proteins. The considerable differences identified on the mixing curves of different rice flours indicate that the investigation of mixing properties can be one of the useful approaches for the characterisation of functional properties of rice dough. The large effects of the addition of wheat gluten on the mixing properties of rice flours demonstrate the possibility of using rice flour and dough as a wheat protein free model system for the in vitro investigation of the functional roles of wheat storage proteins.

Thermodynamic assessment of the Ca–Zn, Sr–Zn, Y–Zn and Ce–Zn systems

Published experimental thermodynamic and phase diagram data for the Ca–Zn, Sr–Zn, Y–Zn and Ce–Zn systems have been critically evaluated to provide assessed thermodynamic parameters for the different phases of the systems. The parameters allow all thermodynamic properties and phase boundaries for each system to be calculated within reasonable error limits. Because a strong compound-forming tendency and pronounced minimum in the enthalpy of mixing curve is observed for the liquid phase of all the systems, the Modified Quasichemical Model (MQM) in the pair approximation has been used throughout the assessment work to treat short-range ordering in the liquid.

Martian mantle mineralogy investigated by the 176Lu– 176Hf and 147Sm– 143Nd systematics of shergottites

Chemical heterogeneities in the Martian mantle are believed to result from the crystallization of a magma ocean in the first 100 million years of its history. Shergottite meteorites from Mars are thought to retain a compositional record of such early differentiation and the resulting mineralogy at different depths. The coupled 176Lu– 176Hf and 147Sm– 143Nd isotope systematics in 9 shergottites are used here to investigate these issues. Three compositional groups in the shergottites display distinct isotope systematics. One group, commonly termed as depleted, is characterized by positive ɛ 176Hf i from + 46.2 to + 50.4 and ɛ 143Nd i from + 36.2 to + 39.1. Another, termed as enriched, has negative ɛ 176Hf i = − 16.5 to − 13.2 and ɛ 143Nd i = − 7.0 to − 6.5. The third group is intermediate between the depleted and enriched groups with positive ɛ 176Hf i = + 30.0 to + 33.4 and ɛ 143Nd i = + 16.9. Together, they describe mixing curves between 176Hf/ 177Hf, 143Nd/ 144Nd, Lu/Hf, and Sm/Nd, implying that they sample two distinct sources in the Martian mantle. All shergottites are characterized by (Sm/Nd) source < (Sm/Nd) sample, but (Lu/Hf) source > (Lu/Hf) sample. This decoupling can be explained by two successive partial melting episodes in the depleted shergottite source and localized in the Martian upper mantle. The genesis of shergottites can be modeled using non-modal equilibrium partial melting in a source initially composed of 60% olivine, 21% clinopyroxene, 9% orthopyroxene, and 10% garnet, with degrees of partial melting of 8.8% and 3.9%, respectively, for the two successive events. The enriched end-member of the shergottite mixing curve is best modeled by late-stage quenched residual melt resulting from the crystallization of a magma ocean. The depleted shergottite source may be modeled as a mixture of cumulates and residual melt, as convection in the Martian magma ocean is expected to reduce the incompatible trace element heterogeneity in the final solidified layers. Consequently, equilibrium crystallization is preferred to model the crystallization of the Martian magma ocean. The models that best explain the shergottite data are those where the magma ocean is at a depth of at least 1350 km in Mars.

Modeling biogeochemical processes in subterranean estuaries: Effect of flow dynamics and redox conditions on submarine groundwater discharge of nutrients

A two‐dimensional density‐dependent reactive transport model, which couples groundwater flow and biogeochemical reactions, is used to investigate the fate of nutrients (NO3−, NH4+, and PO4) in idealized subterranean estuaries representing four end‐members of oxic/anoxic aquifer and seawater redox conditions. Results from the simplified model representations show that the prevalent flow characteristics and redox conditions in the freshwater‐seawater mixing zone determine the extent of nutrient removal and the input of nitrogen and phosphorus to coastal waters. At low to moderate groundwater velocities, simultaneous nitrification and denitrification can lead to a reversal in the depth of freshwater NO3− and NH4+‐PO4 plumes, compared to their original positions at the landward source. Model results suggest that autotrophic denitrification pathways with Fe2+ or FeS2 may provide an important, often overlooked link between nitrogen and phosphorus biogeochemistry through the precipitation of iron oxides and subsequent binding of phosphorus. Simulations also highlight that deviations of nutrient data from conservative mixing curves do not necessarily indicate nutrient removal.

Total depletion of Hg° in the upper troposphere–lower stratosphere

Our current understanding of atmospheric mercury lacks fundamental details. Gas phase elemental mercury (Hg°) was measured aboard the NASA DC‐8 research aircraft during the Intercontinental Chemical Transport Experiment‐Phase B (INTEX‐B) conducted in spring 2006 over the North Pacific. Our data confirm efficient chemical cycling of Hg° in the tropopause region and show that it is strongly anti‐correlated with O3 there, yielding a tropospheric‐stratospheric mixing curve of ∼−0.20 ppqv Hg°/ppbv O3. In addition, we found frequent total depletion of Hg° in upper tropospheric (8–12 km) air masses impacted by stratospheric influence. When O3 mixing ratios were &gt;300 ppbv, Hg° was rarely detected. It appears that in the tropopause and stratosphere Hg° is oxidized on the order of days followed by heterogeneous transformation to particulate mercury. These processes constitute an effective chemical sink for Hg° at the top of the troposphere, which may recycle mercury back to the gas phase as stratospheric aerosols are eventually dispersed into the troposphere.

Physicochemical properties of hull-less barley fibre-rich fractions varying in particle size and their potential as functional ingredients in two-layer flat bread

The performance of barley fibre-rich fractions (FRF), as high dietary fibre ingredients, in two-layer flat bread was investigated. In addition, the effects of particle size reduction by pin milling on functional properties of FRF were studied. FRF enriched in non-starch polysaccharides (β-glucans and arabinoxylans) were obtained by roller milling of hull-less barley. Pin milling (PM) of FRF significantly reduced their particle size, slightly increased the solubility of β-glucans and arabinoxylans, and increased the viscosity of water slurries containing FRF. The addition of 20% of barley FRF to wheat flour significantly increased dough water absorption and weakened the dough properties, as indicated by farinograph mixing curves, but the FRF-enriched doughs exhibited good handling characteristics at the dividing and sheeting stages. The appearance, diameter, layer separation, crumb, and aroma of the FRF-enriched flat breads were comparable to that of the control. The PM of FRF did not significantly affect the dough handling or the quality characteristics of flat breads. The addition of 20% of barley FRF to wheat flour flat bread provided substantial health benefits by significantly increasing the total and soluble dietary fibre contents and by decreasing starch digestibility.

Widespread elevated atmospheric SF 6 mixing ratios in the Northeastern United States: Implications for groundwater dating

SF 6 is a promising transient tracer for groundwater dating, but elevated levels of atmospheric SF 6 may limit application of this dating method in urban areas. To determine the magnitude of this limitation within the United States (US), this study derives average atmospheric SF 6 mixing ratios from soil air measurements from five major urban areas. All surveyed sites showed SF 6 elevated above Northern Hemisphere clean air levels. In many cases, SF 6 mixing ratios were highest within large cities, but significantly elevated levels persisted hundreds of kilometers beyond the urban centers. Estimated SF 6 emissions from New York city were anomalously large, resulting in average levels over 200% above remote atmosphere values. Emissions from other urban areas included in this study appear to be typical for large cities in the US and maximum observed elevations of SF 6, in these areas, were in the range of 50–100%. These findings imply that caution is needed in choosing an atmospheric input function when using SF 6 as a transient tracer within or near urbanized regions. Within the Northeast US, the assumption of remote atmospheric SF 6 may lead to significant errors in estimation of groundwater ages, especially in the case of an expected future flattening of the atmospheric mixing ratio curve.

Differential mixing action effects on functional properties and polymeric protein size distribution of wheat dough

A micro Z-arm mixer and a 2g-Mixograph were used to compare the effect of pin and Z-arm-type mixing actions on mixing properties of wheat flour dough. Although the two mixing curves obtained with pin- and Z-arm-type mixing action showed a very similar mixing trace, no significant correlation was found between the two mixers other than the number of revolutions required for optimal dough consistency (peak resistance). Mixing requirement was described by a rate-independent parameter, the number of revolutions to peak dough development and was found to be greater in a Z-arm mixer than in a pin mixer. Mixing requirement showed significant correlation with stability, which is therefore a dough strength parameter. The change in the polymeric structure of gluten proteins of dough as indicated by %UPP (unextractable polymeric protein percentage) was monitored and showed a smaller decrease with Z-arm mixing than with pin mixing. Therefore, pin-mixing action is more energetic than Z-arm mixing. At peak resistance, Z-arm mixing gives a larger quantity of polymeric protein content in the dough relative to pin mixing. The degree of dough development at maximum resistance in the different mixers was shown to be different. A new parameter, delta- UPP MZ (the difference between %UPP of dough obtained with pin vs Z-arm mixing actions) was identified and proposed to have some relationship to the stability of the polymeric proteins in the dough.

Lead isotopes by LA-MC-ICPMS: Tracking the emergence of mantle signatures in an evolving silicic magma system

At Long Valley (LV) model Sr isotope phenocryst ages and absolute U–Pb zircon ages from precaldera Glass Mountain (GM) and caldera-related Bishop Tuff (BT) rhyolites show that these crystals track >1 Myr of evolution of a voluminous rhyolite magmatic system. In detail, strong disparities between the different age populations complicate ideas for a unified model for rhyolite generation, differentiation, and storage. To better elucidate the age discrepancies a new in situ Pb isotope technique has been developed to measure the compositions of 113 individual LV feldspars (mainly sanidine) and their host glasses by UV laser ablation MC-ICPMS. Given sufficient signal the accuracy and precision of this technique approaches that of double-spike thermal ionization mass spectrometry. The utility of our technique for many geologic materials is, however, limited to determining Pb isotope ratios that include 206Pb, 207Pb, and 208Pb, but exclude 204Pb. New zircon 238U– 206Pb crystallization ages were also obtained for two older Glass Mountain domes. A >1.5‰ difference between the Pb isotope compositions of feldspars from older (1.7–2.2 Ma) precaldera Glass Mountain (GM) rhyolites and younger LV rhyolites, including the BT, is found. The Pb isotope data for feldspars and their host glasses lie along a regional trend line between young basalts and evolved crust compositions, spanning ∼15% of that isotopic difference, and show a secular change towards increasing mantle contribution. Most feldspars have Pb isotope compositions that are similar to their host glasses and, as such, there persists an apparent >100 k.y. difference between Sr model feldspar ages and zircon ages for some GM rhyolites. Collectively, the feldspars define a Sr–Pb isotope mixing curve. Evidence for mixing complicates the interpretation that the Sr isotope data solely reflect radiogenic ingrowth. Where isotopically heterogeneous feldspar populations occur, there is greater uncertainty about the veracity of the Sr model ages. Specifically, we find no Pb isotope evidence that BT feldspars grew from older GM-like magmas. The distinct Pb isotope signatures for individual rhyolites and their feldspars support evidence based on zircon dating that LV volcanism did not erupt from a single long-lived magma chamber but rather tapped a number of different magmas. Moreover, contrary to the conventional model of gradual build-up prior to cataclysmic eruption, secular changes in the U–Pb age constraints on magma residence times and the magmas’ distinct Pb isotopic compositions suggest that, at Long Valley, eruptive volumes increase with shorter magma residence time and correlate with greater mantle input. Evidently, the plumbing and therefore activity at Long Valley was influenced by the evolving interaction between source and crustal magma system.

Characterization of Mixing Patterns in a Coaxial Mixer

The hydrodynamics performance of a coaxial mixing system operating in the laminar regime has been experimentally studied by flow visualization. A Rushton turbine was used in combination with an anchor in both co- and counter-rotating modes to mix viscous Newtonian and non-Newtonian fluids. Image analysis of a discoloration reaction was used to quantify the mixing evolution in the tank. The mixing curves generated by this method were used to reveal the presence of flow compartmentalization and dead zones. It was shown that the co-rotating mode is better to avoid flow compartmentalization while the counter-rotating mode appears to be more efficient to break the segregated regions.

Dimensional analysis for planetary mixer: Mixing time and Reynolds numbers

Mixing time number is a convenient parameter to characterize mixing performance of stirred tanks. This dimensionless number is now well established for agitated vessels equipped with vertically and centrally mounted impeller for Newtonian as well as for non-Newtonian fluids. To our knowledge, there is more ambiguity concerning its definition for planetary mixers especially when they have dual motion (around two perpendicular axes) to achieve homogenization. In this study, dimensional analysis of mixing time and reliability of the modified Reynolds and mixing time numbers are proposed for such a planetary mixer particularly named as TRIAXE ® system. These two numbers are based on the maximum tip speed of mixer as the characteristic velocity. Modified dimensionless numbers are consistent with the definition of conventional Reynolds and mixing numbers (when only one revolving motion around the vertical axis of the mixing device occurs in the vessel). Mixing time experiments with TRIAXE ® mixer for highly viscous Newtonian fluids showed that the proposed modified Reynolds and mixing time numbers succeeded to obtain a unique mixing curve irrespective of the different speed ratio chosens. This agreement proves that the proposed modified dimensionless numbers can be well adapted for engineering purposes and they can be used to compare the mixing performance of planetary mixers.

Mixing of shallow and deep groundwater as indicated by the chemistry and age of karstic springs

Large karstic springs in east-central Florida, USA were studied using multi-tracer and geochemical modeling techniques to better understand groundwater flow paths and mixing of shallow and deep groundwater. Spring water types included Ca–HCO3 (six), Na–Cl (four), and mixed (one). The evolution of water chemistry for Ca–HCO3 spring waters was modeled by reactions of rainwater with soil organic matter, calcite, and dolomite under oxic conditions. The Na–Cl and mixed-type springs were modeled by reactions of either rainwater or Upper Floridan aquifer water with soil organic matter, calcite, and dolomite under oxic conditions and mixed with varying proportions of saline Lower Floridan aquifer water, which represented 4–53% of the total spring discharge. Multiple-tracer data—chlorofluorocarbon CFC-113, tritium (3H), helium-3 (3Hetrit), sulfur hexafluoride (SF6)—for four Ca–HCO3 spring waters were consistent with binary mixing curves representing water recharged during 1980 or 1990 mixing with an older (recharged before 1940) tracer-free component. Young-water mixing fractions ranged from 0.3 to 0.7. Tracer concentration data for two Na–Cl spring waters appear to be consistent with binary mixtures of 1990 water with older water recharged in 1965 or 1975. Nitrate-N concentrations are inversely related to apparent ages of spring waters, which indicated that elevated nitrate-N concentrations were likely contributed from recent recharge.

Comparison of Th, Sr, Nd and Pb isotopes in oceanic basalts: Implications for mantle heterogeneity and magma genesis

We report U–Th disequilibria data for a suite of 13 young basaltic samples from the Samoan Islands, which represent the end-member mantle component EM2, and 4 historic lavas from Mt. Erebus, typifying young HIMU. The Samoan samples have low 230Th/232Th and 238U/232Th, consistent with the enriched nature (EM2) of the Samoan mantle source, whereas the Mt. Erebus samples have high 206Pb/204Pb and intermediate (230Th/232Th) and (238U/232Th). When considered in the context of the global oceanic basalt database, the Samoan samples' low 230Th/232Th and 238U/232Th greatly extend the global correlations between 230Th/232Th and 238U/232Th with 87Sr/86Sr and 143Nd/144Nd and change the functional form of these correlations from linear to hyperbolic. Using a maximum likelihood non-linear inversion method, we show that these correlations of 230Th/232Th and 238U/232Th with 87Sr/86Sr and 143Nd/144Nd can be approximated by two-component mixing. However, the global oceanic basalt data also show considerable scatter about the best-fit mixing curves. This scatter is attributed to additional source components and melting processes influencing the lavas (230Th/232Th) and (238U/232Th). Additional source components are supported by the Pb isotope data, which clearly require more than two endmember mantle components. We also show that the extent and variability in (230Th/238U) decreases as a function of source enrichment, with “depleted” MORB showing the largest extents and greatest variability in (230Th/238U) and “enriched” OIB, like Samoa, showing smaller extents and less variability of (230Th/238U). We interpret this observation in terms of differences in the melting regimes beneath mid-ocean ridges and ocean islands.

New constraints on the petrogenesis of the Nuanetsi picrite basalts from Pb and Hf isotope data

Previous studies established strong linear correlations between 143Nd/ 144Nd and a variety of incompatible element abundances and inter-element ratios for a suite of picrite basalts from Nuanetsi in the Karoo CFB province. While a heterogeneous source was clearly indicated, the extent to which mantle heterogeneity exceeds that sampled by magmatism was unconstrained because the linear correlations can be extrapolated to extreme end-members well beyond the picrite basalt compositions. The Nuanetsi samples showed a small variation in Pb isotope composition and any coherent Pb–Nd isotope relationship was obscured by the likely analytical uncertainty. New Pb isotope data obtained by MC-ICP-MS reveal coherent Pb–Nd isotope arrays that are suggestive of hyperbolic mixing curves. New Hf isotope data reveal very similar Pb–Hf relationships. Least-squares hyperbolic fits are used to constrain the asymptotes of these putative mixing hyperbolae, thereby defining end-member isotopic compositions. The low ε Nd, low ε Hf end-member equates with the enriched lithospheric mantle component previously postulated, and it is now possible to define the Pb isotope characteristics of this end-member more precisely. The higher ε Nd and ε Hf end-member is constrained to have sub-chondritic 143Nd/ 144Nd and 176Hf/ 177Hf. These characteristics are not readily reconciled with an asthenospheric source because there are few oceanic basalts with sub-chondritic ε Nd and it seems unlikely that the Karoo would fortuitously have sampled an extreme asthenospheric composition. Either, the Nuanetsi picrite basalts are derived largely from lithospheric mantle, or they sample a more complex mixture of source materials than previously inferred.

Mixing of shallow and deep groundwater as indicated by the chemistry and age of karstic springs

Large karstic springs in east-central Florida, USA were studied using multi-tracer and geochemical modeling techniques to better understand groundwater flow paths and mixing of shallow and deep groundwater. Spring water types included Ca–HCO3 (six), Na–Cl (four), and mixed (one). The evolution of water chemistry for Ca–HCO3 spring waters was modeled by reactions of rainwater with soil organic matter, calcite, and dolomite under oxic conditions. The Na–Cl and mixed-type springs were modeled by reactions of either rainwater or Upper Floridan aquifer water with soil organic matter, calcite, and dolomite under oxic conditions and mixed with varying proportions of saline Lower Floridan aquifer water, which represented 4–53% of the total spring discharge. Multiple-tracer data—chlorofluorocarbon CFC-113, tritium (3H), helium-3 (3Hetrit), sulfur hexafluoride (SF6)—for four Ca–HCO3 spring waters were consistent with binary mixing curves representing water recharged during 1980 or 1990 mixing with an older (recharged before 1940) tracer-free component. Young-water mixing fractions ranged from 0.3 to 0.7. Tracer concentration data for two Na–Cl spring waters appear to be consistent with binary mixtures of 1990 water with older water recharged in 1965 or 1975. Nitrate-N concentrations are inversely related to apparent ages of spring waters, which indicated that elevated nitrate-N concentrations were likely contributed from recent recharge.

Experimental and CFD investigation on mixing by a jet in a semi-industrial stirred tank

Abstract This paper reports the results of a study on the flow generated and mixing time in a semi-industrial tank equipped with a side entry jet mixer. For this purpose, a three dimensional modeling is carried out using an in-house Computational Fluid Dynamics (CFD) code. In this study, the theoretical mixing curves predicted by the CFD were validated by experiments. The experimental mixing curves were obtained by monitoring of the homogenization progress of the dark blue Nigrosine solution inside the tank. A photometer equipped with an online detector was used for this purpose. The experiments were carried out for 0°, 22.5° and 45° jet angle setups. The results showed that the mixing time in the 45° jet layout is lower than other setups. The CFD code with the ability of simultaneous solving of the continuity, the Reynolds-averaged Navier–Stokes (RANS) equations and employing various types of turbulence models was used. The effect of the mesh size on the predicted results was investigated and the theoretical results obtained from various mesh sizes configuration were compared with the experiments. The results showed that the number of meshes is quite effective on the obtained theoretical results in a way that the predicted results for the largest mesh size were far away from the experiments. In addition, the two equation k – ɛ family models including: standard, RNG and realizable models were introduced to the code and the effect of these models on the predicted results was investigated. The results show that there are considerable differences between the predicted mixing progress using the three versions of the k – ɛ family models. The RNG k – ɛ model shows more convincing results in comparison with the other models.

Refining the noble gas record of the Réunion mantle plume source: Implications on mantle geochemistry

Abstract We report isotope analyses of helium, neon, argon, and xenon using different extraction techniques such as stepwise dynamic and static crushing, and high-resolution stepwise heating of three mantle xenoliths from Reunion Island. He and Ne isotopic compositions were similar to previously reported Reunion data, yielding a more radiogenic composition when compared to the Hawaiian or Icelandic mantle plume sources. We furthermore observed correlated 129 Xe/ 130 Xe and 136 Xe/ 130 Xe ratios following the mantle trend with maximum values of 6.93 ± 0.14 and 2.36 ± 0.06, respectively. High-resolution argon analyses resulted in maximum 40 Ar/ 36 Ar ratios of 9000–11,000, in agreement with maximum values obtained in previous studies. We observed a well-defined hyperbolic mixing curve between an atmospheric and a mantle component in a diagram of 40 Ar/ 36 Ar vs. 20 Ne/ 22 Ne. Using a mantle 20 Ne/ 22 Ne of 12.5 (Ne–B) a consistent 40 Ar/ 36 Ar value of 11,053 ± 220 in sample ILR 84-4 was obtained, whereas extrapolations to a higher mantle 20 Ne/ 22 Ne ratio of 13.8 (solar wind) would lead to a much higher 40 Ar/ 36 Ar ratio of 75,000, far above observed maximum values. This favours a mantle 20 Ne/ 22 Ne of about 12.5 considered to be equivalent to Ne–B. Extrapolated and estimated 40 Ar/ 36 Ar ratios of the Reunion, Iceland, Loihi, and MORB mantle sources, respectively, tend to be linearly correlated with air corrected 21 Ne/ 22 Ne and show the same systematic sequence of increasing relative contributions in radiogenic isotopes (Iceland–Loihi–Reunion–MORB) as observed for 4 He/ 3 He. In general, He–Ne–Ar isotope systematics of the oceanic mantle can be explained by following processes: (i) different degree of mixing between pure radiogenic and pure primordial isotopes generating the MORB and primitive plume (Loihi-type) endmembers; (ii) relatively recent fractionation of He relative to Ne and Ar, in one or both endmembers; (iii) after the primary fractionation event, different degrees of mixing between melts or fluids of MORB and primitive plume affinity generate the variety of observed OIB data, also on a local scale; (iv) very late-stage secondary fractionation during magma ascent and magma degassing leads to further strong variation in He/Ne and He/Ar ratios.

PIM of non-conventional particles

The use of particles with shape, mean particle size, particle size distribution and stability traditionally considered inappropriate for powder injection moulding (PIM) requires the use of feedstocks with high quality. A method that leads to an accurate value of critical powder volume concentration (CPVC) was developed. The present study, based on torque rheometry, led to the evaluation of optimal feedstock from selecting a raw material powder with non-conventional characteristics for PIM (lamellar morphology, d 50 = 10.5 μm, and 0.1 ≤ d ≤ 174.8 μm). The optimal value of solids loading was calculated as the highest value resulted from the intersections of the adjustment of linear functions of the mixing torque versus powder content curves. The final products of this feedstock presented, after sintering, high density and flexural strength values.