High Resolution SIMS Research Articles

High resolution SIMS U-Th-Pb geochronology of small size (< 5 μm) monazite: Constraints on the timing of Qiuling sediment-hosted gold deposit, South Qinling Orogen, central China

Abstract Accurately determining the timing of hydrothermal mineralization for the sediment-hosted disseminated gold (SHDG) deposits is difficult because of a lack of both suitable chronometers and in-situ techniques with the required spatial resolution and precision. The lack of precise age determinations on gold deposits has hindered understanding of their genesis and relation to the geodynamic setting. The Qinling orogen is one of the most important gold regions in China and contains numerous SHDG deposits. The Qiuling-Jinlongshan deposit is a typical SHDG deposit located in the eastern of the South Qinling Orogen (SQO), with 109 t Au at an average grade of 6.17 g/t. Devonian and Carboniferous metasedimentary rocks host structurally controlled gold mineralization, which is associated with silica-carbonate alteration. Pyrite, arsenopyrite, and arsenian pyrite are major gold carriers and gold also occurs as native gold grains and invisible gold in the sulfides. In this study, the well-defined hydrothermal overgrowth rims (~ 2 μm) of single monazite grains-associated with disseminated auriferous arsenian pyrite and arsenopyrite in low-grade metasedimentary rocks yield U-Pb age of 239 ± 13 Ma (2σ) by high spatial resolution secondary ion mass spectrometry (SIMS). The hydrothermal monazites are cogenetic to the primary gold mineralization where they are closely associated with gold-bearing sulfides. This new age implies that the early to middle Triassic mineralization event in the eastern SQO was related to the Triassic tectonic transition from compression to transpression in the Qinling Orogen after the closure of the Mianlue Ocean. This study highlights 2-μm high spatial resolution SIMS monazite U-Th-Pb dating method as a powerful tool for determining the timing of SHDG deposit worldwide elsewhere. It is crucial to examine monazite textures and its link to hydrothermal alteration before carrying out the isotopic dating of monazite.

A new Ion Microscope for high-resolution imaging and SIMS nano-analytics

A new Ion Microscope for high-resolution imaging and SIMS nano-analytics

High-resolution EBSD and SIMS U–Pb geochronology of zircon, titanite, and apatite: insights from the Lac La Moinerie impact structure, Canada

High-resolution EBSD and SIMS U–Pb geochronology of zircon, titanite, and apatite: insights from the Lac La Moinerie impact structure, Canada

Evolution of boron segregation during tempering in B doped 9%Cr ferritic steel

Boron segregation behavior during tempering at 600 and 790 °C was examined in a boron-doped 9Cr-steel by using high-resolution SIMS imaging (nano-SIMS). Boron segregation that developed at prior austenite grain boundaries (PAGBs) during austenitizing was found to decrease reduced during tempering because the equilibrium concentration of B segregation for austenite is larger than that for ferrite so that the segregated boron atoms diffused into block and packet boundaries. The size and the volume fraction of the carbide precipitates at PAGBs were smaller than those at packet boundaries, suggesting that boron segregation at PAGBs suppresses the carbide precipitation upon tempering.

The Neoarchean GT-34 Ni deposit, Carajás mineral Province, Brazil: An atypical IOCG-related Ni sulfide mineralization

The GT-34 deposit, located 12 km to the SW of the Sossego copper–gold mine in the Carajás Province, northern Brazil, represents an unusual Ni sulfide mineralization. The deposit occurs along a NE-SW-trending sub-vertical shear zone marked by progressive Mg-alkalic alteration zones, predominantly hosted in granitic and locally in granodioritic to tonalitic orthogneisses. Initial alteration zones result in unique scapolite-orthopyroxene assemblage, which is partially preserved within pervasive hornblende-chlorapatite ± plagioclase replacement zones. Nickel mineralization occurs mainly as matrix-supported breccias characterized by a pentlandite-pyrrhotite-rich matrix and rounded fragments chiefly of hornblende and chlorapatite. Irregular stockworks and net textured veins containing chalcopyrite-pentlandite are less common. Phlogopite ± talc ± actinolite alteration and late-stage veinlets crosscut the previous alteration zones and the mineralization. The phlogopite ± talc ± actinolite alteration occurs as irregular veins and chalcopyrite-pyrrhotite-magnetite are commonly observed where such alteration intersects the Ni mineralization. Late-stage veinlets are represented by K feldspar-epidote-chlorite-calcite and quartz-albite-chlorite-calcite-epidote veins, both containing minor amounts of millerite, pyrite and F-OH-apatite. High-resolution SIMS U-Pb zircon geochronology obtained for the GT-34 deposit revealed an age of 2828 ± 4 Ma for zircon grains inherited from the host orthogneisses. The timing of the mineralization altered zircon grains from the scapolite-orthopyroxene and phlogopite ± talc ± actinolite alteration zones, is attributed to an age interval between 2751 and 2720 Ma. Although poorly constrained, the geochronological data corroborate a Neoarchean age for the GT-34 Ni mineralization, similar to that of other IOCG deposits in the Carajás Province and coeval with the bimodal magmatism in the area. The atypical orthopyroxene-marialite mineral chemistry support a metasomatic crystallization at high temperatures (>700 °C), low aH2O (<0.5) and pressures between 5 and 7 kbar. Hypersaline fluids, as the ones described for the IOCG deposits in Carajás at such PxT conditions, would enable the orthopyroxene-marialite crystallization, as supported by experimental studies available in the literature. Mineralogical and geochemical considerations on the nature of the Ni sulfide mineralization points toward a metasomatic origin, feasible with the predicted P-T-fluid scenario for the hydrothermal alteration. Such conditions raise the initial temperature and pressure estimates of the IOCG metasomatic alteration by at least 200 °C and pressure up to 7 kbar, making it the hottest and probably deepest IOCG-related metasomatic alteration known to date for Carajás.

Characterisation of deuterium distributions in corroded zirconium alloys using high-resolution SIMS imaging

Hydrogen diffusion through the oxide grown on Zr alloys by aqueous corrosion processes plays a critical role in determining the rate of hydrogen pickup (HPU) which can result in embrittlement of fuel cladding and limit the burnup of the nuclear fuel it encapsulates. Mapping the hydrogen/deuterium distributions in these oxide layers, especially in the barrier layer close to the metal/oxide interface, is a powerful way to understand the mechanism of both oxidation and hydrogen pickup. Here we have characterised by high-resolution SIMS analysis the deuterium distribution in oxide layers on a series of Zr alloys, including autoclave-oxidised Zircaloy-4, Zr-1Nb and Zr-2.5Nb alloys, and in-flux and out-of-flux corroded Zr-2.5Nb samples. Pre-transition Zircaloy-4 samples show a high deuterium trapping ratio in the oxide and a higher diffusion coefficient than in oxides on the Nb-containing samples. Neutron irradiation increases the deuterium diffusion coefficient, the deuterium concentration in the oxide and the pickup fraction in Zr-2.5 Nb samples. Comparative NanoSIMS and EDX/SEM analysis demonstrates that the deuterium is not preferentially trapped at second phase particles in the oxides on any of the alloys studied, but there is direct evidence for trapping at the surfaces of small oxide cracks especially in Zircaloy-4 samples. The high resolution mapping of these hot-spots in 3D can provide unique information on the mechanisms of hydrogen uptake, and suggests that the development of interconnected porosity in the oxide may be the critical rate-determining mechanism that controls HPU in the aqueous corrosion of zirconium alloys in water-cooled reactors.

Characterisation of Deuterium Distributions in Corroded Zirconium Alloys Using High-Resolution SIMS

Hydrogen diffusion through the oxide grown on Zr alloys by aqueous corrosion processes plays a critical role in determining the rate of hydrogen pickup which can result in embrittlement of fuel cladding and limit the burnup of the nuclear fuel it encapsulates. Mapping the hydrogen/deuterium distributions in these oxide layers, especially in the barrier layer close to the metal/oxide interface, is a powerful way to understand the mechanism of both oxidation and hydrogen pickup. Here we have characterised by high-resolution SIMS analysis the deuterium distribution in oxide layers on a series of Zr alloys, including autoclave-oxidised Zircaloy-4, Zr-1Nb and Zr-2.5Nb alloys, and in-flux and out-of-flux corroded Zr-2.5Nb samples. Pre-transition Zircaloy-4 samples show a high deuterium trapping ratio in the oxide and a higher diffusion coefficient than in oxides on the Nb-containing samples. Neutron irradiation increases the deuterium diffusion coefficient, the deuterium concentration in the oxide and the pickup fraction in Zr-2.5 Nb samples. Comparative NanoSIMS and EDX/SEM analysis demonstrates that the deuterium is not preferentially trapped at SPPs in the oxides on any of the alloys studied, but there is direct evidence for trapping at the surfaces of small oxide cracks especially in Zircaloy-4 samples. The high resolution mapping of these hot-spots in 3D can provide unique information on the mechanisms of hydrogen uptake, and suggests that the development of interconnected porosity in the oxide may be the critical rate-determining mechanism that controls HPU in the aqueous corrosion of zirconium alloys in water-cooled reactors.

NanoSIMS Imaging and Analysis in Materials Science.

High-resolution SIMS analysis can be used to explore a wide range of problems in material science and engineering materials, especially when chemical imaging with good spatial resolution (50-100 nm) can be combined with efficient detection of light elements and precise separation of isotopes and isobaric species. Here, applications of the NanoSIMS instrument in the analysis of inorganic materials are reviewed, focusing on areas of current interest in the development of new materials and degradation mechanisms under service conditions. We have chosen examples illustrating NanoSIMS analysis of grain boundary segregation, chemical processes in cracking, and corrosion of nuclear components. An area where NanoSIMS analysis shows potential is in the localization of light elements, in particular, hydrogen and deuterium. Hydrogen embrittlement is a serious problem for industries where safety is critical, including aerospace, nuclear, and oil/gas, so it is imperative to know where in the microstructure hydrogen is located. By charging the metal with deuterium, to avoid uncertainty in the origin of the hydrogen, the microstructural features that can trap hydrogenic species, such as precipitates and grain and phase boundaries, can be determined by NanoSIMS analysis on a microstructurally relevant scale.

Understanding Microstructural Evolution in ZrC Inoculated Zr47.5Cu45.5Al5Co2 Via High Resolution SIMS

Understanding Microstructural Evolution in ZrC Inoculated Zr_47.5Cu_45.5Al₅Co₂ Via High Resolution SIMS

3D-characterization of deuterium distributions in zirconium oxide scale using high-resolution SIMS

In pressurised water reactors (PWRs), fuel rods are clad with zirconium alloy tubes chosen for their low neutron capture cross section and good oxidation resistance. Understanding cladding-water corrosion reactions at 280–350 °C and the correlated hydrogen pickup into these Zr alloys is crucial to the safe operation of PWRs and to increasing the burnup of the fuel. Here we describe a method based on 3D mapping by high resolution SIMS to measure the distribution of deuterium in oxidised Zircaloy-4 alloy samples. Two analysis directions, depth-profiling and cross-sectional, were used to ensure we understand possible imaging artefacts during sputtering of the complex microstructure in these samples. The topography of the sputtering carter and sputtering rate have been calibrated by Focused Ion Beam (FIB)/Scanning Electron Microscopy (SEM) analysis. The deuterium diffusion coefficients at 360 °C is calculated suing the depth profile in both samples. The results show that the 3D deuterium distribution can be successfully measured in isotopically spiked samples, but that care has to be taken to understand the effect of deuterium outgassing and surface diffusion during Cs+ primary ion bombardment, which results in a degraded lateral resolution, which distorts the apparent deuterium distribution. The detection method in this paper can be a useful tool in the analysis of the distribution of hydrogenic species in zirconium fuel cladding materials in service, and can also provide other engineering materials.

Gas Cluster Ion Beam Time-of-Flight Secondary Ion Mass Spectrometry High-Resolution Imaging of Cardiolipin Speciation in the Brain: Identification of Molecular Losses after Traumatic Injury.

Gas cluster ion beam-secondary ion mass spectrometry (GCIB-SIMS) has shown the full potential of mapping intact lipids in biological systems with better than 10 μm lateral resolution. This study investigated further the capability of GCIB-SIMS in imaging high-mass signals from intact cardiolipin (CL) and gangliosides in normal brain and the effect of a controlled cortical impact model (CCI) of traumatic brain injury (TBI) on their distribution. A combination of enzymatic and chemical treatments was employed to suppress the signals from the most abundant phospholipids (phosphatidylcholine (PC) and phosphatidylethanolamine (PE)) and enhance the signals from the low-abundance CLs and gangliosides to allow their GCIB-SIMS detection at 8 and 16 μm spatial resolution. Brain CLs have not been observed previously using other contemporary imaging mass spectrometry techniques at better than 50 μm spatial resolution. High-resolution images of naive and injured brain tissue facilitated the comparison of CL species across three multicell layers in the CA1, CA3, and DG regions of the hippocampus. GCIB-SIMS also reliably mapped losses of oxidizable polyunsaturated CL species (but not the oxidation-resistant saturated and monounsaturated gangliosides) to regions including the CA1 and CA3 of the hippocampus after CCI. This work extends the detection range for SIMS measurements of intact lipids to above m/z 2000, bridging the mass range gap compared with MALDI. Further advances in high-resolution SIMS of CLs, with the potential for single cell or supra-cellular imaging, will be essential for the understanding of CL's functional and structural organization in normal and injured brain.

Primary multiple sulfur isotopic compositions of pyrite in 2.7 Ga shales from the Joy Lake sequence (Superior Province) show felsic volcanic array-like signature

Multiple sulfur isotopes provide a powerful tool to study photochemical and biological processes controlling the Archean sulfur cycle and infer related atmospheric and marine environments. However, our understanding of early Earth’s environment remains limited by the availability of well-preserved geological samples, as most Archean sedimentary rocks have experienced some degree of metamorphic alteration. To evaluate sulfur isotopic behavior during post-depositional processes and elucidate the sulfur cycle at 2.7Ga, we use high-resolution in situ analytical techniques (EPMA and SIMS) to determine elemental compositions and multiple sulfur isotopic compositions of large diagenetic pyrite nodules and fine-grained secondary pyrite disseminated in quartz veins (formed during a lower greenschist metamorphic event) in shales from the 2.7Ga Joy Lake sequence in the southwest Superior Province. Results show that trace metals and sulfur in the secondary pyrite were derived from both metamorphic fluid and pre-existing diagenetic pyrite. Diagenetic pyrite nodules could have been partially dissolved by metamorphic fluid. But the surviving nodules show elemental and isotopic features different from those of the deduced metamorphic fluid endmember, suggesting the nodules were not geochemically altered by metamorphism, and thus preserve primary isotopic signatures acquired during diagenesis. The sulfur isotopic ratios of pyrite nodules show strong variations, with decreasing δ34S values and increasing Δ33S values from cores to rims. This negative Δ33S–δ34S relationship is different from the commonly observed ‘Archean reference line’ defined by most Archean pyrite data, but similar to the ‘felsic volcanic array’. Our observation provides a first possible case from 2.7Ga, the age of peak crustal growth in the Archean, to support the hypothesis that photochemical pathways could be different under conditions of intense volcanic emission. This study also shows that high-resolution SIMS and EPMA analyses are a robust method for distinguishing primary geochemical signatures from post-depositional alteration, and thus may be used to evaluate the sulfur cycle in Archean sedimentary rocks with low-grade metamorphic overprints.

Metamorphic P–T–t paths of pelitic granulites of the Taihua metamorphic complex in the Mts. Huashan area and tectonothermal implications for the Palaeoproterozoic Trans-North China Orogen

Metamorphic evolution and geochronology of pelitic granulites were reported for the first time in the Taihua metamorphic complex, Mts. Huashan area, southern segment of the trans-North China Orogen (TNCO). Three generations of metamorphic mineral assemblages are recognized: (1) the prograde metamorphic mineral assemblages (M1) are represented by mineral inclusions within the garnet porphyroblasts; (2) the metamorphic peak assemblage (M2) are the garnet porphyroblasts and minerals in the matrix (biotite+orthopyroxene+plagioclase+quartz+K-feldspar+ilmenite+zircon+magnetite); and (3) the retrograde metamorphic mineral assemblages (M3) are represented by the symplectic assemblages around the garnet porphyroblasts, resulted from decomposition reactions between garnet rims and neighboring minerals in the matrix. Calculated by both conventional thermobarometry and pseudosection modeling in the NCKFMASHT system using the Perple_X technique, the P–T conditions of these three metamorphic stages are constrained to be of 4–5kbar/520–530°C for the M1 stage, 6.8–8.6kbar/730–810°C for the M2 stage and 4.1–6.4kbar/570–740°C for the M3 stage, respectively. The derived clockwise P–T paths imply that the Mts. Huashan terrane involved in the subduction and subsequent collision between the Eastern and Western Blocks of the North China Craton (NCC) along the Palaeoproterozoic Trans-North China Orogen (TNCO). High resolution SIMS U–Pb dating of metamorphic zircons reveals the metamorphic ages of 1.85–1.82Ga. Combined with geochronological data from the literature, it is concluded that the tectonothermal evolution between the Eastern and Western Blocks started as early as ∼1.97Ga and lasted as late as 1.80Ga. Furthermore, the eastern Taihua complex records older metamorphic ages and higher peak metamorphic pressures than those of the western Taihua complex, possibly suggesting an eastward subduction model for the TNCO.

Metamorphic P–T–t path retrieved from metapelites in the southeastern Taihua metamorphic complex, and the Paleoproterozoic tectonic evolution of the southern North China Craton

The Taihua metamorphic complex in the southern part of the North China Craton is composed of tonalite-trondhjemite-granodiorite (TTG) gneisses, amphibolites, metapelitic gneisses, marbles, quartzites, and banded iron formations (BIFs). The protoliths of the complex have ages ranging from ∼2.1 to ∼2.9Ga and was metamorphosed under the upper amphibolite to granulite facies conditions with NWW-SEE-striking gneissosity. Metapelitites from the Wugang area have three stages of metamorphic mineral assemblages. The prograde metamorphic mineral assemblage (M1) includes biotite+plagioclase+quartz+ilmenite preserved as inclusions in garnet porphyroblasts. The peak mineral assemblage (M2) consists of garnet porphyroblasts and matrix minerals of sillimanite+biotite+plagioclase+quartz+K-feldspar+ilmenite+rutile+pyrite. The retrograde mineral assemblage (M3), biotite+plagioclase+quartz, occurs as symplectic assemblages surrounding embayed garnet porphyroblasts. Garnet porphyroblasts are chemically zoned. Pseudosection calculated in the NCKFMASHTO model system suggests that mantles of garnet porphyroblasts define high-pressure granulites facies P–T conditions of 12.2kbar and 830°C, whereas garnet rims record P–T conditions of 10.2kbar and 840°C. Integrating the prograde mineral assemblages, zoning of garnet porphyroblasts with symplectic assemblages, a clockwise metamorphic P–T path can be retrieved. High resolution SIMS U−Pb dating and LA−ICP−MS trace element measurements of the metamorphic zircons demonstrate that metapelites in Wugang possibly record the peak or near peak metamorphic ages of ∼1.92Ga. Furthermore, 40Ar/39Ar dating of biotite in metapelites suggests that the cooling of the Taihua complex may have lasted until ∼1.83Ga. Therefore, a long-lived Palaeoproterozoic metamorphic event may define a slow exhumation process. Field relationship and new metamorphic data for the Taihua metamorphic complex does not support the previous model in which the Tran-North China Craton (TNCO) was formed through the collision between the East and West blocks.

Carbon isotopes of eclogite-hosted diamonds from the Nyurbinskaya kimberlite pipe, Yakutia: The metasomatic origin of diamonds

Carbon isotope compositions and the distribution of nitrogen and hydrogen in diamonds from 18 eclogites from Nurbinskaya kimberlites were studied in situ in polished plates. Cathodoluminescence images show that most of the diamonds have complex growth structures with distinctive core, intermediate and rim zones. In some diamonds the cores display dissolution features, and intermediate growth zones are separated from the cores by narrow rounded oscillatory zones. At least three crystals show interrupted multistage diamond growth; variations in δ13C of 2–3‰ occur across the contacts between distinct zones. Generally, δ13C within the diamond cores varies only by 1–2‰, in rare cases up to 3.3‰. δ13C values are usually lower in the intermediate zones and drop further towards the rims by up to 3‰. High-resolution SIMS profiles show that variations in δ13C across the diamond growth zones are sharp with no evidence of diffusive relaxation.Diamonds with predominantly tangential octahedral growth have a wide range in δ13C from −15.2‰ up to 9.0‰ (±0.4‰), and their nitrogen (N) contents vary between 30 and 1500at.ppm. Six diamonds show little internal variation along the isotopic profiles with changes in δ13C of only 0.3–0.9‰ around mean values ranging from −6‰ to −3‰. Five crystals are isotopically heavy, with relatively homogeneous δ13C up to 9‰. FTIR data show markedly different N concentrations and nitrogen aggregation states between major growth zones. This implies that the diamonds in eclogitic xenoliths from Nyurbinskaya pipe grew in multiple and interrupted growth events, probably from fluids enriched in K and H.The wide variations of δ13C in the studied eclogitic diamonds and identification of their anomalously positive δ13C values, combined with the wide range of high δ18O in garnets from the diamondiferous xenoliths of the Nyurbinskaya pipe, which are mostly outside of the mantle range, suggest a crustal contribution to the parental mantle-related fluids forming diamonds in these xenoliths and indicate the complex metasomatic evolution of the lithospheric mantle beneath the Nakynsky kimberlite field.

High-resolution SIMS oxygen isotope analysis on conodont apatite from South China and implications for the end-Permian mass extinction

Understanding the interplay of climatic and biological events in deep time requires resolving the precise timing and pattern of paleotemperature changes and their temporal relationship with carbon cycle variations and biodiversity fluctuations. In situ oxygen isotope analyses of conodont apatite from South China enables us to reconstruct high-resolution seawater temperature records across the Permian–Triassic boundary (PTB) intervals in the upper slope (Meishan), lower slope (Shangsi), and carbonate platform (Daijiagou and Liangfengya) settings. Constrained by the latest high-precision geochronological dates and high-resolution conodont biozones, we can establish the temporal and spatial patterns of seawater temperature changes and assess their potential connections with the carbon cycle disruption and biodiversity decline. We find a rapid warming of ~10°C during the latest Permian–earliest Triassic that postdated the onset of the negative shift in δ13Ccarb by ~81kyr (thousand years), the abrupt decline in δ13Ccarb by ~32kyr and the onset of mass extinction by ~23kyr, which contradicts previous claims that the extreme temperature rise started immediately before or coincided with the onset of mass extinction. Our new evidence indicates that climate warming was most likely not a direct cause for the main pulse of the end-Permian mass extinction (EPME), but rather a later participant or a catalyst that increased the pace of the biodiversity decline. In addition, a prominent cooling is recorded in the earliest Changhsingian, with the main phase (a drop of ~8°C in ~0.2Ma) confined to the lower part of the Clarkina wangi zone and synchronous with the positive limb of the carbon isotope excursion (CIE) around the Wuchiapingian–Changhsingian boundary (WCB) in Meishan and Shangsi. Further long-term and high-resolution studies from other sections are needed to confirm the full contexts and underlying dynamics of the WCB “cooling event”.

Portrait of a reference material: Zircon production in the Middledale Gabbroic Diorite, Australia, and its implications for the TEMORA standard

The Middledale Gabbroic Diorite (MGD) in New South Wales, Australia, is host to the internationally distributed TEMORA 2 zircon reference material and its prototype, TEMORA 1. The original characterisation of the source of the reference zircons revealed that the more altered TEMORA 2 host rock contains an order of magnitude more zircon than the TEMORA 1 host, despite similar bulk-rock Zr concentrations. Although TEMORA 1 and 2 preserve the same U–Pb age, they are variable in oxygen isotope composition.In this study, petrographic observations in concert with bulk-rock and mineral geochemistry and zircon U–Pb geochronology have been applied to new samples of the MGD to investigate the link between alteration and zircon abundance. Trace element maps reveal that the products of late-stage, deuteric alteration (particularly actinolite after hornblende) are depleted in Zr, and many other trace elements, relative to the unaltered mafic, magmatic phases. It is posited that the conversion of hornblende to secondary amphiboles in the latter stages of magma solidification liberated Zr, permitting the crystallisation of additional zircon.New high resolution SIMS U–Pb determinations on four samples confirm the age homogeneity of the zircon across the pluton and reaffirm the value of TEMORA 2 as a valuable geochronological reference material. Zircon oxygen isotope data have been acquired for these same samples and the mean δ18O values encompass the accepted values for TEMORA 1 and 2. Likewise, the Hf-isotope determinations are similar to the accepted TEMORA 2 composition. Together with petrographic observations, these data reveal the TEMORA 2 zircon and its host to be broadly reflective of the relatively coarse-grained portions of the MGD, and that the isotopically less evolved compositions (i.e. the lower δ18O of TEMORA 1 and low δ18O, high 176Hf/177Hf of one sample from this study) are associated with a relatively fine-grained, marginal lithology. Given δ18O values greater than typical mantle-derived zircon and the broad correlation between O- and Hf-isotopic compositions, the data imply the pluton evolved by crustal contamination of a primitive magma.

Understanding Elemental Uptake in Plants Using High Resolution SIMS and Complementary Techniques

Understanding Elemental Uptake in Plants Using High Resolution SIMS and Complementary Techniques

High resolution metabolite imaging in the hippocampus following neonatal exposure to the environmental toxin BMAA using ToF-SIMS.

The environmental neurotoxin β-N-methylamino-L-alanine (BMAA) is suggested to be linked with neurodegenerative disease. In a rat model, neonatal exposure to BMAA induced selective uptake in the hippocampus and caused cell loss, mineralization and astrogliosis as well as learning and memory impairments in adulthood. Moreover, neonatal exposure resulted in increased protein ubiquitination in the cornus ammonis 1 (CA1) region of the adult hippocampus indicating that BMAA may induce protein aggregation. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) based imaging is a powerful technology for spatial profiling of small molecular weight compounds in biological tissues with high chemical specificity and high spatial resolution. The aim of this study was to characterize neurochemical changes in the hippocampus of six month-old rats treated neonatally (postnatal days 9-10) with BMAA. Multivariate data analysis of whole section ToF-SIMS scans was performed to delineate anatomical regions of interest based on their chemical distribution pattern. Further analysis of spectral data obtained from the outlined anatomical regions, including CA1 and dentate gyrus (DG) revealed BMAA-induced long-term changes. Increased levels of phospholipids and protein fragments in the histopathologically altered CA1 region as well as phosphate depletion in the DG were observed. Moreover, high resolution SIMS imaging revealed a specific localization of phosphatidylcholine lipids, protein signals and potassium in the histopathologically altered CA1. These findings demonstrate that ToF-SIMS based imaging is a powerful approach for probing biochemical changes in situ and might serve as promising technique for investigating neurotoxin-induced brain pathology.

Members of the uncultured bacterial candidate division WWE 1 are implicated in anaerobic digestion of cellulose

Clones of the WWE1 (Waste Water of Evry 1) candidate division were retrieved during the exploration of the bacterial diversity of an anaerobic mesophilic (35 ± 0.5°C) digester. In order to investigate the metabolic function of WWE1 members, a 16S rRNA gene-based stable isotope probing (SIP) method was used. Eighty-seven percent of 16S r rRNA gene sequences affiliated to WWE1 candidate division were retrieved in a clone library obtained after polymerase chain reaction (PCR) amplification of enriched DNA fraction from anaerobic municipal solid waste samples incubated with 13C-cellulose, at the end of the incubation (day 63) using a Pla46F-1390R primer pair. The design of a specific WWE1 probe associated with the fluorescence in situ hybridization (FISH) technique corroborated the abundant representation of WWE1 members in our 13C-cellulose incubations. Secondary ion mass spectrometry–in situ hybridization (SIMSISH) using an iodine-labeled oligonucleotide probe combined with high-resolution nanometer-scale SIMS (NanoSIMS) observation confirmed the isotopic enrichment of members of WWE1 candidate division. The 13C apparent isotopic composition of hybridized WWE1 cells reached the value of about 40% early during the cellulose degradation process, suggesting that these bacteria play a role either in an extracellular cellulose hydrolysis process and/or in the uptake fermentation products.