Substitution Of Trace Elements Research Articles

Genesis of Cu-Sn Mineralization in the Shuangjianzishan Super-Large Silver Deposit, Inner Mongolia: Trace Element Constraints from Chalcopyrite and Cassiterite

The Shuangjianzishan silver polymetallic deposit is located in the copper–tin–lead–zinc–silver polymetallic metallogenic belt in the Southern Great Xing’an Range, with silver resources of more than 18,000 t, which is the largest silver polymetallic deposit in Asia. Early studies concluded that the Shuangjianzishan deposit is typically an epithermal Ag-Pb-Zn deposit that lacks a high-temperature mineralization stage. In recent years, with the deepening of research, a large amount of Cu-Sn mineralization has been found in the deep part of the Shuangjianzishan deposit, but it is less studied. The laser-ablation inductively coupled mass spectroscopy (LA-ICP-MS) technique is used to investigate the distribution and substitution of trace elements in chalcopyrite and cassiterite. In this paper, the trace element study of chalcopyrite and cassiterite from the Shuangjianzishan deposit reveals that Sn, In, As, Se, Sb, and Tl mainly exist in chalcopyrite in isomorphic form, while Pb, Bi, and Ni mainly exist in chalcopyrite in the form of mineral inclusions. The enrichment of the high-temperature elements Sn and Se in chalcopyrite, and the deficit of the middle- and low-temperature elements Ga, Sb, etc., reflect that the chalcopyrite in the Shuangjianzishan deposit was formed in a middle- and high-temperature environment, and it also indicates that the early ore-forming hydrothermal solution may be rich in Sn. Fe, In, Co, and Ni mainly exist in cassiterite in isomorphic form, and the content of W in cassiterite is high. There are two main forms, one is isomorphic and the other is wolframite inclusion. Cassiterite has Fe-rich and W-U-poor characteristics, indicating that cassiterite from the Shuangjianzishan deposit was formed under relatively oxidized conditions, and the relative enrichment of elements such as Fe, W, Zr, and Hf indicates that the temperature of cassiterite formation was high. The elemental content and inter-ionic coupling relationships suggest that the cassiterite from the Shuangjianzishan deposit may have an elemental replacement mechanism of W6+ + Fe2+ ↔ 2Sn4+ or Fe3+ + OH− ↔ Sn4+ + O2−. The trace elements in cassiterite of the Shuangjianzishan deposit are rich in Fe and Mn and depleted in Nb and Ta, according to the Fe-W diagram, and the tin mineralization of the Shuangjianzishan deposit belongs to cassiterite–sulfide-type tin mineralization. Chalcopyrite Co/Ni ratios >1 are consistent with the characteristics of chalcopyrite genesis in hydrothermal deposits.

Genesis of the newly discovered Pb–Zn vein of the Sucha giant fluorite deposit in Inner Mongolia: Constraints from LA-ICP-MS trace element of pyrite and sphalerite

The Sumochaganaobao (Sucha) deposit in Siziwang Banner, Inner Mongolia is considered to be the largest single fluorite deposit known in the world, and apart from a small amount of localized pyritization, no metal mineralization has been found for many years. In recent years larger scale Pb–Zn polymetallic veins have been uncovered which indicates the potential for large scale metal mineralization in this deposit in addition to fluorite ore. Laser-ablation inductively coupled mass spectroscopy (LA-ICPMS) technique is used to investigate the distribution and substitution of trace elements in sphalerite and pyrite. The confirming results show that sphalerite is mainly rich in Fe, Mn, Cd, Co, Ni, Cu, In and poor in Sb and Mo. Pyrite is mainly rich in Ni, As, Sb, Cr, Mn, Co, Cu, Sn, Pb, Tl, Se and poor in Cd, Au, Ga, In, Bi. Iron, Mn, Cd, In, Co, Ni, Cr, Bi and Cu in sphalerite and Ni, As, Sb, Mn, Co, Cu, Ni, As, Pb, Tl, and Se in pyrite are generally lattice-bounded, while Pb and Cd present both in solid solution and/or discrete micro/nano-inclusions. The elemental contents of Fe, Mn and In and elemental ratios of Ga/In, Zn/Cd and In/Ge illustrate the trace elemental characteristics of medium temperature sphalerite. The trace elements in pyrite are diverse along with both relatively high-temperature elements (e.g. Ni, Co, Sn, Cu, etc.) and relatively low-temperature elements (e.g. As, Sb, Pb, etc.). The Co/Ni ratios indicate that the pyrite formed under a low-temperature condition. The crystallisation from sphalerite to pyrite may have undergone a relatively rapid cooling process from medium to low temperature. The characteristics of sphalerite and trace elements indicate that the genesis of this deposit is closest to that of SEDEX type deposit. Considering the marine sedimentation or marine volcanic eruption, jasperite development, clastic rock hosting, layered ore-body, and the geochemical characteristics of trace elements of this deposit, the newly discovered Pb–Zn vein should belong to the SEDEX type.

Hide and Seek—Trace Element Incorporation and Diffusion in Olivine

Olivine, once overlooked as a host of trace elements, is becoming increasingly important for our understanding of the kinetic and equilibrium behaviour of these elements. Much of our understanding of trace element substitution and diffusion in geological materials comes as a result of experimental and petrological studies of olivine. Here, we consider trace element concentrations and incorporation mechanisms, and how these relate to diffusive behaviour. If we understand trace element behaviour in olivine, we have a powerful tool kit that can be directly applied to address many problems in petrology and volcanology. Perhaps more importantly, what we have learned from olivine can be applied to other minerals and aid us in addressing other far-reaching questions from across the Earth sciences.

Laboratory and calorimetric monitoring of medical nutrition therapy in intensive and intermediate care units : Second position paper of the Section Metabolism and Nutrition of the German Interdisciplinary Association for Intensive Care and Emergency Medicine (DIVI)

This second position paper of the Section Metabolism and Nutrition of the German Interdisciplinary Association for Intensive Care and Emergency Medicine (DIVI) provides recommendations on the laboratory monitoring of macro- and micronutrient intake as well as the use of indirect calorimetry in the context of medical nutrition therapy of critically ill adult patients. In addition, recommendations are given for disease-related or individual (level determination) substitution and (high-dose) pharmacotherapy of vitamins and trace elements.

A novel strategy to reduce trace element supplementation in the semi-solid anaerobic digestion with gradient ammonia concentration: the role of biochar

Solid anaerobic digestion of chicken manure is prone to the accumulation of volatile fatty acids (VFAs). Addition of trace elements (TEs) is an effective way to stabilize the digestion system. However, excessive supplementation of TEs may eventually cause environmental pollution. Therefore, it is necessary to develop an environmentally friendly method to reduce the addition for TEs. In this study, we explored the possibility of reducing the supplement for TEs with the assistance of biochar. The results showed that addition of biochar resulted in a 50 % decrease in the need for TE supplementation when the organic loading rate (OLR) was 5 g TS−1 d−1. Biochar increased the relative (+0.67–8.5 folds) and absolute amounts (0.1–104.6 mg kg−1 total solid (TS)) of the highly-bioavailable fraction of TEs (exchangeable fraction (F2)) by chemical adsorption. The conductivity of biochar increased from 4.2 to 38.4 mS m−1 after adsorbing TEs, which might explain the enrichment of conductive microorganisms (+16 folds) in the digestion system, such as Geobacter (34-fold increase). Substitution of TEs with biochar increased the absolute amounts of Methanosaeta, Mathanosarcina, Methanoculleus, and Methanospirillum by 72.7 %, 5.7 %, 46.1 % and 2.7 %, respectively, and propionate and butyrate oxidizing bacteria (Syntrophomonas, Syntrophobacter, and Smithella) had the highest abundance. In summary, beneficial interactions between biochar and TEs makes biochar an ideal material for reducing the amounts of TEs needed to stabilize the semi-solid anaerobic digestion (SSAD) system.

Mineralogical and Geochemical Characteristics of the H-Pit of the Chatree Gold Deposit, Central Thailand: A Case Study for Assessment of Acid Rock Drainage and Heavy Metal Sources

H-pit is one of the significant ore lenses of the Chatree mine in Thailand. Au-Ag mineralization mainly occurs as veins, stockworks, and minor breccias hosted by volcanic and volcaniclastic rocks. Disseminated pyrites are commonly present near mineralized veins in the hanging wall zone. This study aims to assess the acid rock drainage (ARD) potential and heavy metal content from the H-pit area. The results indicate that hanging wall rock is a potential acid-forming (PAF) material related to disseminated pyrite formed by hydrothermal alteration. In contrast, the footwall and ore zone materials are classified as non-acid forming (NAF). Because the ore zone has calcite in the veins, it may help buffer the material’s acidity. The results of heavy metal analysis reveal that the ore zone has significantly higher contents of As, Cd, Cu, Pb, and Zn than those in the hanging wall and footwall zones. Moreover, the hanging wall and footwall materials have exceeding values for As, Cd, and Zn compared to those in typical igneous rocks. These heavy metals are interpreted to be sourced from (1) the primary composition in base metal sulfides (e.g., Cu, Pb, and Zn), (2) the substitution of trace elements in sulfides (e.g., As and Cd), and (3) the substitution of trace elements in calcite (e.g., Mn), as evidenced in the EPMA results. In conclusion, the hanging wall rocks in this study containing high sulfur in proximity to the ore zone are a PAF material with heavy metal contaminant sources, whereas the footwall and ore zone materials have a lower potential to be such sources at the Chatree mine.

Shortwave infrared hyperspectral imaging as a novel method to elucidate multi-phase dolomitization, recrystallization, and cementation in carbonate sedimentary rocks

Carbonate rocks undergo low-temperature, post-depositional changes, including mineral precipitation, dissolution, or recrystallisation (diagenesis). Unravelling the sequence of these events is time-consuming, expensive, and relies on destructive analytical techniques, yet such characterization is essential to understand their post-depositional history for mineral and energy exploitation and carbon storage. Conversely, hyperspectral imaging offers a rapid, non-destructive method to determine mineralogy, while also providing compositional and textural information. It is commonly employed to differentiate lithology, but it has never been used to discern complex diagenetic phases in a largely monomineralic succession. Using spatial-spectral endmember extraction, we explore the efficacy and limitations of hyperspectral imaging to elucidate multi-phase dolomitization and cementation in the Cathedral Formation (Western Canadian Sedimentary Basin). Spectral endmembers include limestone, two replacement dolomite phases, and three saddle dolomite phases. Endmember distributions were mapped using Spectral Angle Mapper, then sampled and analyzed to investigate the controls on their spectral signatures. The absorption-band position of each phase reveals changes in %Ca (molar Ca/(Ca + Mg)) and trace element substitution, whereas the spectral contrast correlates with texture. The ensuing mineral distribution maps provide meter-scale spatial information on the diagenetic history of the succession that can be used independently and to design a rigorous sampling protocol.

U–Pb geochronology of apatite and zircon from the Brent impact structure, Canada: a Late Ordovician Sandbian–Katian boundary event associated with L-Chondrite parent body disruption

In situ LA-ICP-MS U–Pb geochronology has been performed on apatite and zircon within thermally recrystallized clast-laden and clast-poor impact melt rocks from the Brent impact structure. A total of 377 laser analyses on 120 impact melt-grown (n = 9) and impact-recrystallized zircon grains (n = 111) were obtained, from which a concordia age of 452.8 ± 2.7 Ma (MSWD 0.57, n = 11), and a weighted average mean 206Pb/238U age of 453.2 ± 2.9 Ma (MSWD 0.60) (n = 11) are calculated. A total of 300 laser analyses from 100 relict apatite grains were obtained, with an unanchored regression through all data yielding a lower intercept age of 453.2 ± 6.0 Ma (MSWD 5.8, n = 300), that overlaps within error of zircon. 207Pb/206Pb ratios obtained from feldspar clasts within clast-laden impact melt retain the same initial Pb composition as the target rocks from which they are derived, while feldspars that crystallized from impact melt have 207Pb/206Pb ratios indicative of isotopic re-equilibration between basement lithologies of two different ages. A similar variability in 207Pb/206Pb is recorded by apatite. This provides evidence for the involvement of Neoproterozoic Lake Nipissing alkaline suite, as well as Mesoproterozoic Grenville gneisses in the production of impact melt at Brent. Recrystallized apatite grains exhibit enrichments in light rare earth elements (LREEs) along neoblast grain boundaries, indicative of trace element substitution and phase precipitation during impact-induced recrystallization. An age of 452.8 ± 2.7 Ma from zircon and 453.2 ± 6.0 Ma from apatite places the impact event in the Late Ordovician, at or near the Sandbian–Katian boundary, confirming Brent’s involvement in the Middle to Late Ordovician crater cluster event—a period of enhanced impactor flux to Earth related to the L-Chondrite parent body disruption.

Infrared microthermometry of fluid inclusions in transparent to opaque minerals: challenges and new insights

Infrared (IR) studies of fluid inclusions in opaque minerals provide direct insights into the ore-forming fluids. However, the challenge posed by the “warming effect” of IR light during microthermometry remains unresolved. Here we address this problem and show that the deviation in temperature of phase changes within fluid inclusions caused by IR light is more common than what was thought before. Our results reveal that transparent to translucent minerals (e.g., quartz, sphalerite) also absorb IR energy. Since IR absorption is influenced by the host mineral, the fluid inclusions hosted by different minerals exhibit different degrees of deviation in temperature during microthermometry. The Fourier transform infrared (FTIR) spectra do not display a consistent correlation between the band gap energy of a mineral and its absorption of IR energy. Minerals with low band gap energy, such as pyrite, absorb limited IR energy, resulting in small deviations of fluid inclusion data. In contrast, this deviation could be significant for fluid inclusions hosted in minerals with a relatively high band gap energy, such as iron-rich sphalerite and wolframite. Substitution of iron increases the absorption of IR energy in these minerals. The substitution of trace elements may also play a role. Our quantitative analyses confirm that using the lowest possible IR light intensity with the smallest diaphragm minimizes the “warming effect” of IR light. We also propose an improved cycling method as a better option where high IR light intensity is required.

Apatite trace element geochemistry and cathodoluminescent textures—A comparison between regional magmatism and the Pea Ridge IOAREE and Boss IOCG deposits, southeastern Missouri iron metallogenic province, USA

The southeast Missouri iron metallogenic province contains a remarkable wealth of historically important Fe, Cu, Au, and rare earth element (REE) deposits including the Pea Ridge iron oxide-apatite-rare earth element (IOA-REE) deposit and the Boss iron oxide-copper–gold (IOCG) deposit. These deposits are coeval with silicic and intermediate composition magmatism in the St. Francois Mountains terrane. Magmatism, iron-oxide (±Cu, Au, Co) and apatite formation, and REE mineralization overlapped in space and time, but the specific role of regional magmatism in the metallogenesis of these deposits remains unclear and basic petrogenetic models are still debated.We report results from high-spatial resolution textural and geochemical analyses of apatite from regional igneous and ore rocks to elucidate their petrogenetic histories and evaluate deposit models. Backscattered electron and spectral cathodoluminescence imaging of apatite reveal no primary igneous zoning, but show different domains with intricate rims and dissolution/reprecipitation textures, each with distinctive REE patterns in many samples. Apatite from all samples are nearly endmember fluorapatite containing up to ∼1.3 wt% Cl and F/Cl ratios span nearly three orders of magnitude. Fresh igneous fluorapatite contain low Na2O (≤0.15 wt%) while most Pea Ridge ore samples contain higher Na2O (up to ∼0.45 wt%), and concentrations of sulfur in fluorapatite of all types are generally moderate to low (≤0.3 wt% SO3). Significant amounts of Fe (≤60,000 ppm), Mg (≤30,000 ppm), Mn (≤7000 ppm), and Sr (≤12,000 ppm) are contained in fluorapatite of all sample types, and they also have moderate amounts of As (≤4000 ppm), Ba (≤2000 ppm), Th (≤400 ppm), and U (≤80 ppm). Fluorapatite show an extraordinarily large range of ΣREE (∼0.1–2.0 wt%) and Y (∼100–7000 ppm) concentrations. While fresh igneous fluorapatite share many geochemical features with metasomatized igneous fluorapatite and ore-stage fluorapatite from the Pea Ridge IOA and Boss IOCG ore zones, they also have distinct geochemical signatures that are indicative of unique trace element partitioning and substitution mechanisms. These distinguishing textural and geochemical signatures preclude ore-zone fluorapatite genesis directly from a magma (i.e., crystallization directly from a silicate melt) but are permissive of ore-zone fluorapatite formation by magmatic-hydrothermal fluids derived from the regional magmas. Basinal brines may play an important role in the formation of fluorapatite, especially from the Pea Ridge hematite and Boss magnetite-rich zones. Fluorapatite from different ore zones likely formed by crystallization during pulses of hydrothermal fluids with varying Cl-, Na-, and F-contents, which fundamentally controlled the carrying capacity and solubility of ΣREE + Y and generated geochemically distinctive generations of fluorapatite.Exploration geologists using fluorapatite trace element geochemistry to identify IOA and IOCG deposits should proceed with caution, as more high-quality data from these deposits are needed to improve multivariate discrimination analysis. Fluorapatite from IOA/IOCG deposits can be reasonably discriminated from that of other mineral deposit types (e.g., porphyry/epithermal, skarn, orogenic), but no criteria successfully discriminate yet between IOA and IOCG deposits.

Selenium-substituted hydroxyapatite particles with regulated microstructures for osteogenic differentiation and anti-tumor effects

Abstract Selenium-substituted HA (Se/HA) particles with special micro/nanohybrid morphologies were prepared hydrothermally. With increasing Se substitution, Se/HA transitioned from a ribbon-like morphology, to a radical form, and further to microspheres (diameters: ∼10 μm) assembled from nanosheets (thickness: 2–5 μm; length and width: ∼100 nm). Chemical analyses confirmed increasing incorporation of Se in Se/HA particles, with increasing Se/(Se + P) molar ratio of the raw materials for their synthesis. Rat calvarial osteoblasts (RCOBs) adhered and spread on the Se/HA particles with Se/(Se + P) ratios ranging 0–0.05. Particles synthesized at Se/(Se + P) = 0.05 showed increased alkaline phosphatase activity of bone marrow mesenchymal stem cells, likely due to their micro/nano-sized surface morphology. Se released from particles effectively inhibited human osteosarcoma cell growth by inducing apoptosis. Therefore, Se/HA prepared at Se/(Se + P) = 0.05 presented a potential material for bone defect repair after surgical tumor removal, offering safety, increased osteogenic differentiation of stem cells, and inhibition of tumor cell growth. These results also suggest that trace element substitution is an effective approach to simultaneously imparting desirable microstructures and biological functions to bio-ceramics.

The influence of melt composition on the partitioning of trace elements between anorthite and silicate melt

The effect of melt composition on the partitioning of trace elements between anorthite and silicate melts has been studied experimentally in five compositions in the system CaO–Al2O3–SiO2 (CAS) at ~ 1400 °C and four compositions in the system CaO–MgO–Al2O3–SiO2 (CMAS) at 1332 °C. Melt composition has a significant impact on the substitution of trace elements into anorthite, particularly if the trace-element substitution is aliovalent and requires a charge balance for substitution. Melt composition strongly influences the partitioning of the trivalent rare earth element (REE) cations into the large-cation site (M) of anorthite. Due to charge balance requirements, the activity of alumina in the melt is the most important compositional variable for the REE partitioning in anorthite. Scandium, another trivalent cation, is much more compatible than is predicted for trivalent cations partitioning on the M-site. Therefore, scandium is likely partitioning onto the tetrahedral site in place of aluminium, which requires no charge balance and therefore is not affected strongly by melt composition. Similarly, the partitioning of the small divalent cations (Be and Mg) show a stronger relationship with changing melt composition than the large divalent cations (Ca, Sr, and Ba) and therefore are likely to partition on the tetrahedral site (T) of plagioclase rather than the large-cation site (M). Detailed thermodynamic modelling of the effects of melt composition is required for an adequate parameterization of trace-element mineral/melt partition coefficients, in addition to models of the effects of mineral composition.

The dark side of zircon: textural, age, oxygen isotopic and trace element evidence of fluid saturation in the subvolcanic reservoir of the Island Park-Mount Jackson Rhyolite, Yellowstone (USA)

The Island Park-Mount Jackson series in the Yellowstone volcanic field, Wyoming (USA), is a suite of rhyolitic domes and lavas that erupted between the caldera-forming eruptions of the Mesa Fall Tuff (1.3 Ma) and the Lava Creek Tuff (0.6 Ma). Combined zircon U/Pb geochronology, Raman spectroscopy, oxygen isotopic and trace elemental compositions document storage conditions of these magmas between consecutive supereruptions. Based on comparison with co-erupted melt compositions and textural criteria, four zircon compositional groups are identified that record different stages along a continuous magmatic evolution from trace element-poor rhyolite at high temperatures to extremely fractionated rhyolite where zircon trace elements are highly enriched (e.g., > 1000 ppm U). These latter zircon domains are dark in cathodoluminescence images and show broadened Raman peaks relative to near-endmember zircon, indicating that substitution of non-stoichiometric trace elements into zircon leads to distortion of the crystal lattice. Some of these zircon domains contain inclusions of U-Th-REE-phases, likely originating from coupled dissolution–reprecipitation of metastable trace element-rich zircon in the presence of a fluid phase. Rhyolite-MELTS simulations indicate that at the conditions required to produce the observed enrichment in trace elements, a fluid phase is likely present. These findings illustrate that zircons can be assembled from a variety of co-existing magmatic environments in the same magma reservoir, including near-solidus volatile-rich melts close to the magmatic–hydrothermal transition.

DOUBLE FIT: Optimization procedure applied to lattice strain model

Modeling trace element partition coefficients using the lattice strain model is a powerful tool for understanding the effects of P-T conditions and mineral and melt compositions on partition coefficients, thus significantly advancing the geochemical studies of trace element distributions in nature. In this model, partition coefficients describe the strain caused by a volume change upon cation substitution in the crystal lattice. In some mantle minerals, divalent, trivalent, and tetravalent trace element cations are mainly substituted in one specific site. Lattice strain model parameters, for instance in olivine and plagioclase, are thus fit for one crystal site. However, trace element cations can be substituted in two sites in the cases of pyroxenes, garnets, amphiboles, micas, or epidote-group minerals.To thoroughly study element partitioning in those minerals, one must consider the lattice strain parameters of the two sites. In this paper, we present a user-friendly executable program, working on PC, Linux, and Macintosh, to fit a lattice strain model by an error-weighted differential-evolution-constrained algorithm (Storn, R., and Price, K. 1997. Differential evolution - A simple and efficient heuristic for global optimization over continuous spaces. Journal of Global Optimization 11, 341–359). This optimization procedure is called DOUBLE FIT and is available for download on http://celiadalou.wixsite.com/website/double-fit-program. DOUBLE FIT generates single or double parabolas fitting experimentally determined trace element partition coefficients using a very limited amount of data (at minimum six experimental data points) and accounting for data uncertainties. It is the fastest calculation available to obtain the best-fit lattice strain parameters while accounting for the elastic response of two different sites to trace element substitution in various minerals.

Trace elements and mineral chemistry of silicified wood from Thailand: colours and elemental distribution

ABSTRACTThai silicified woods were examined using electron probe microanalysis, yielding chemical data that characterised the samples into two groups: low and high silica contents (82—94 wt% and 94—98 wt%). The elements analysed in order of abundance include Si > Fe > Ca > Na > Al > Ti > K > Mg > Mn > Zr. Iron plays a major role in the colour range (red, orange, yellow, brown, grey and black) of the samples. Calcium is associated with Fe in the darker colours of the wood. Pseudo-crystallochemistry has been used for the substitution of trace elements for Si4+ in silica polymorphs. The atomic channels that run parallel to the c-axis of silica polymorphs or lattice defects, or even the charge balance for trivalent-ion substitution for Si4+, can accommodate monovalent ions (K+ and Na+). Vacant and atomic cavities, which are charged balanced by trivalent ions [Al3+ or Fe3+ substituting for Si4+], are commonly occupied by divalent ions (Ca2+, Mg2+ and Mn2+). Quadrivalent ions, Ti4+ and Zr4+ are non-structurally incorporated but form clusters of mineral inclusions in the samples. Several other trace-element contents are also in the form of mineral/fluid inclusions hosted in the woods.

An investigation of the laser-induced zircon ‘matrix effect’

This study aims to improve our understanding of the current limitations to high-precision U–Pb analysis of zircon by LA-ICP-MS by investigating the underlying causes of variation in ablation behaviour between different zircon matrices. Multiple factors such as: the degree of accumulated radiation damage; trace element composition; crystal colour; and crystallographic orientation are all systematically investigated. Due to the marked decrease in elastic moduli of natural zircon crystals with increasing radiation damage, the accumulation of this damage is the dominant factor controlling the rate of ablation for partially damaged to highly metamict zircon samples. There are slight differences, however, in ablation behaviour between highly crystalline matrices that cannot be attributed solely to differences in the degree of accumulated radiation damage. These differences are associated with structural weakening (i.e., decrease in elastic moduli and overall lower mechanical resistance) caused by an increasing degree of cation substitution in some of the zircon samples. Effects of crystallographic orientation and of crystal opacity (i.e., colour) on ablation behaviour are negligible compared to the combined influences of accumulated radiation damage and trace element substitution into the zircon structure. Experiments performed on natural and annealed zircon grains reveal that the reduction in ablation rates observed for the treated samples compared to the untreated grains is proportional to the degree of structural reconstitution achieved after annealing. Thermal annealing of natural zircon at temperatures >1000°C results in much more uniform ablation characteristics. This ‘homogenisation’ of ablation behaviour between zircon matrices produces a decrease in the laser-induced matrix effects and subsequent improvement in the accuracy of 206Pb/238U ratio determinations by LA-ICP-MS.

Diffusion kinetics of Cr in spinel: Experimental studies and implications for 53Mn–53Cr cosmochronology

The 53Mn–53Cr decay system, in which 53Mn decays to 53Cr (t1/2=3.7Ma) has been widely used to construct 53Cr/52Cr vs. 55Mn/52Cr isochrons and thus determine relative ages of early solar system objects or events, assuming that the initial Cr isotopic ratio, (53Cr/52Cr)o, equals (53Mn/52Cr)o. With the primary objective of interpretation of these ages within a diffusion kinetic framework, we have determined the tracer diffusion coefficient of Cr in natural spinels, which are very close to the MgAl2O4 end-member composition, as a function of temperature and oxygen fugacity (f(O2)). It is found that the diffusion coefficient of Cr, D(Cr), in two stocks of spinels (referred to as cut-gems and gem-gravels) with very similar major element chemistry is consistently different, but the data in each stock yield well defined Arrhenius relations that show a difference of logD of 0.6–1.0, depending on temperature, with the D(Cr) in gem-gravel being higher than that in the cut-gem stock. The D(Cr) was found to have a positive dependence on f(O2) in the range of f(O2) of around ±2 log units relative to that of the wüstite–magnetite buffer. The difference in the D(Cr) between the two stocks and the observed D(Cr) vs. f(O2) relation has been explained in terms of a change of point defect concentration resulting from heterovalent substitution of trace elements and equilibration with the imposed f(O2) conditions, respectively. Assuming a homogeneous semi-infinite matrix, the closure temperature (Tc) of Cr diffusion in spinel has been calculated as a function of grain size, cooling rate, peak temperature (To) and f(O2). Also the dependence of D(Cr) and Tc(Cr) on the Cr# (i.e. Cr/(Cr+Al) ratio) has been accounted for using available D(Cr) vs. Cr# data in Suzuki et al. (2008). We argue, on the basis of crystal chemical considerations and available diffusion kinetic data for minerals, that the Tc for Mn should be much lower than that for Cr in spinel, olivine and orthopyroxene, and discuss the potential implications of the anticipated disparity between Tc(Cr) and Tc(Mn) for the estimation of the (53Mn/55Mn)o ratio from an internal isochron defined by these minerals. Finally, we discuss the problem of determining the Tc for an internal isochron in relation to the individual Tc(Cr) for spinel, olivine and orthopyroxene.

Calcite and dolomite in intrusive carbonatites. II. Trace-element variations

The composition of calcite and dolomite from several carbonatite complexes (including a large set of petrographically diverse samples from the Aley complex in Canada) was studied by electron-microprobe analysis and laser-ablation inductively-coupled-plasma mass-spectrometry to identify the extent of substitution of rare-earth and other trace elements in these minerals and the effects of different igneous and postmagmatic processes on their composition. Analysis of the newly acquired and published data shows that the contents of rare-earth elements (REE) and certain REE ratios in magmatic calcite and dolomite are controlled by crystal fractionation of fluorapatite, monazite and, possibly, other minerals. Enrichment in REE observed in some samples (up to ~2000 ppm in calcite) cannot be accounted for by coupled substitutions involving Na, P or As. At Aley, the REE abundances and chondrite-normalized (La/Yb)cn ratios in carbonates decrease with progressive fractionation. Sequestration of heavy REE from carbonatitic magma by calcic garnet may be responsible for a steeply sloping “exponential” pattern and lowered Ce/Ce* ratios of calcite from Magnet Cove (USA) and other localities. Alternatively, the low levels of Ce and Mn in these samples could result from preferential removal of these elements by Ce4+- and Mn3+-bearing minerals (such as cerianite and spinels) at increasing f(O2) in the magma. The distribution of large-ion lithophile elements (LILE = Sr, Ba and Pb) in rock-forming carbonates also shows trends indicative of crystal fractionation effects (e.g., concomitant depletion in Ba + Pb at Aley, or Sr + Ba at Kerimasi), although the phases responsible for these variations cannot be identified unambiguously at present. Overall, element ratios sensitive to the redox state of the magma and its complexing characteristics (Eu/Eu*, Ce/Ce* and Y/Ho) are least variable and in both primary calcite and dolomite, approach the average chondritic values. In consanguineous rocks, calcite invariably has higher REE and LILE levels than dolomite. Hydrothermal reworking of carbonatites does not produce a unique geochemical fingerprint, leading instead to a variety of evolutionary trends that range from light-REE and LILE enrichment (Turiy Mys, Russia) to heavy-REE enrichment and LILE depletion (Bear Lodge, USA). These differences clearly attest to variations in the chemistry of carbonatitic fluids and, consequently, their ability to mobilize specific trace elements from earlier-crystallized minerals. An important telltale indicator of hydrothermal reworking is deviation from the primary, chondrite-like REE ratios (in particular, Y/Ho and Eu/Eu*), accompanied by a variety of other compositional changes depending on the redox state of the fluid (e.g., depletion of carbonates in Mn owing to its oxidation and sequestration by secondary oxides). The effect of supergene processes was studied on a single sample from Bear Lodge, which shows extreme depletion in Mn and Ce (both due to oxidation), coupled with enrichment in Pb and U, possibly reflecting an increased availability of Pb2+ and (UO2)2+ species in the system. On the basis of these findings, several avenues for future research can be outlined: (1) structural mechanisms of REE uptake by carbonates; (2) partitioning of REE and LILE between cogenetic calcite and dolomite; (3) the effects of fluorapatite, phlogopite and pyrochlore fractionation on the LILE budget of magmatic carbonates; (4) the cause(s) of coupled Mn-Ce depletion in some primary calcite; and (5) relations between fluid chemistry and compositional changes in hydrothermal carbonates.

Preparation, thermal stability and biocompatibility studies of gelatin-induced hydroxyapatite co-substituted with essential physiological trace elements

Gelatin-induced hydroxyapatite with combined substitution of essential physiological trace elements (G-FAP) was prepared by a precipitation method. Pure hydroxyapatite (HAP) and ion-substituted hydroxyapatite (FAP) were also prepared for comparison. The characteristics of the precipitated powders were determined using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), specific surface area measurement (SSA), X-ray fluorescence spectroscopy (XRF), and thermogravimetric (TG) analysis. The biocompatibility was also determined by an in vitro investigation with MC3T3-E1 cells. SEM and TEM results showed that the G-FAP powders were composed of dense aggregates of agglomerated whisker-like crystals of 200–300 nm in length and 10–20 nm in width. XRD and FT-IR analyses indicated the formation of pure apatite phase, and the substituted ions and gelatin did not change the diffraction pattern of the precipitated powders. The SSAs of the precipitated powder were 64.741, 72.492, and 107.745 m2/g, for HAP, FAP, and G-FAP, respectively. XRF analysis showed that Na+, Mg2+, and F− were substituted into the crystal lattice. TG results showed a reduced thermal stability of the precipitated G-FAP powders, with an advanced phase transformation beginning at 800 °C and a serious phase transformation from hexagonal apatite phase to rhombohedral β-TCP phase at 1,200 °C in comparison with HAP and FAP. In vitro biological tests showed non-cytotoxic effects for all powders. However, G-FAP stimulated the proliferation of MC3T3-E1 cells earlier than HAP and FAP. The present G-FAP will therefore be a promising primary biomaterial for bone regeneration, tooth filling, or as a coating for metal artificial limbs.

ESPEN endorsed recommendations: Nutritional therapy in major burns

Nutrition therapy is a cornerstone of burn care from the early resuscitation phase until the end of rehabilitation. While several aspects of nutrition therapy are similar in major burns and other critical care conditions, the patho-physiology of burn injury with its major endocrine, inflammatory, metabolic and immune alterations requires some specific nutritional interventions. The present text developed by the French speaking societies, is updated to provide evidenced-based recommendations for clinical practice. A group of burn specialists used the GRADE methodology (Grade of Recommendation, Assessment, Development and Evaluation) to evaluate human burn clinical trials between 1979 and 2011. The resulting recommendations, strong suggestions or suggestions were then rated by the non-burn specialized experts according to their agreement (strong, moderate or weak). Eight major recommendations were made. Strong recommendations were made regarding, 1) early enteral feeding, 2) the elevated protein requirements (1.5-2 g/kg in adults, 3 g/kg in children), 3) the limitation of glucose delivery to a maximum of 55% of energy and 5 mg/kg/h associated with moderate blood glucose (target ≤ 8 mmol/l) control by means of continuous infusion, 4) to associated trace element and vitamin substitution early on, and 5) to use non-nutritional strategies to attenuate hypermetabolism by pharmacological (propranolol, oxandrolone) and physical tools (early surgery and thermo-neutral room) during the first weeks after injury. Suggestion were made in absence of indirect calorimetry, to use of the Toronto equation (Schoffield in children) for energy requirement determination (risk of overfeeding), and to maintain fat administration ≤ 30% of total energy delivery. The nutritional therapy in major burns has evidence-based specificities that contribute to improve clinical outcome.