Biominerals, such as nacreous bivalve shells, are important archives of environmental information. Most marine calcifiers form their shells from amorphous calcium carbonate, hypothesised to occur via particle attachment and stepwise crystallisation of metastable precursor phases. However, the mechanism of this transformation, including the incorporation of trace elements used for environmental reconstructions, are poorly constrained. Here, using shells of the Mediterranean mussel, we explore the formation of nacre from the meso- to the atomic scale. We use a combination of strontium pulse-chase labelling experiments in aquaculture and correlated micro- to sub-nanoscale analysis to show that nacre grows in a dynamic two-step process with extensional and space-filling growth components. Furthermore, we show that nacre crystallizes via localised dissolution and reprecipitation within nanogranules. Our findings elucidate how stepwise crystallization pathways affect trace element incorporation in natural biominerals, while preserving their intricate hierarchical ultrastructure.

Journal Article Wide Field of View Versus High Spatial Resolution and High Sensitivity – the Advantage of Correlative Microscopies (APT, SIMS, EBSD, μXRF) for the Analysis of Minerals Get access Robert Ulfig, Robert Ulfig CAMECA Instruments Inc., Madison, WI, United States Corresponding author: Robert.Ulfig@ametek.com Search for other works by this author on: Oxford Academic Google Scholar Steven Reddy, Steven Reddy Geoscience Atom Probe Facility, John de Laeter Centre, School of Earth and Planetary Sciences, Curtin University, Perth, Australia Search for other works by this author on: Oxford Academic Google Scholar David Saxey, David Saxey Geoscience Atom Probe Facility, John de Laeter Centre, School of Earth and Planetary Sciences, Curtin University, Perth, Australia Search for other works by this author on: Oxford Academic Google Scholar Will Rickard, Will Rickard Geoscience Atom Probe Facility, John de Laeter Centre, School of Earth and Planetary Sciences, Curtin University, Perth, Australia Search for other works by this author on: Oxford Academic Google Scholar Denis Fougerouse, Denis Fougerouse Geoscience Atom Probe Facility, John de Laeter Centre, School of Earth and Planetary Sciences, Curtin University, Perth, Australia Search for other works by this author on: Oxford Academic Google Scholar Mark Pearce, Mark Pearce CSIRO, Kensington, Perth, Australia Search for other works by this author on: Oxford Academic Google Scholar Louise Fisher, Louise Fisher CSIRO, Kensington, Perth, Australia Search for other works by this author on: Oxford Academic Google Scholar Matt Kilburn, Matt Kilburn Centre for Microscopy, Characterization and Analysis, University of Western Australia, Perth, Australia Search for other works by this author on: Oxford Academic Google Scholar Paul Gagliardo, Paul Gagliardo Centre for Microscopy, Characterization and Analysis, University of Western Australia, Perth, Australia Search for other works by this author on: Oxford Academic Google Scholar Peter H Clifton, Peter H Clifton CAMECA Instruments Inc., Madison, WI, United States Search for other works by this author on: Oxford Academic Google Scholar ... Show more David A Reinhard, David A Reinhard CAMECA Instruments Inc., Madison, WI, United States Search for other works by this author on: Oxford Academic Google Scholar David J Larson David J Larson CAMECA Instruments Inc., Madison, WI, United States Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 29, Issue Supplement_1, 1 August 2023, Pages 790–791, https://doi.org/10.1093/micmic/ozad067.393 Published: 22 July 2023

The Paleoproterozoic hydrothermal system in the southern McArthur Basin, northern Australia, played a key role in the formation of the world-class clastic-dominant (CD)-type McArthur River Zn-Pb deposit, as well as several small-sized deposits nearby in this basin. However, the spatial scale of this hydrothermal system and its role in controlling mineralisation are uncertain. Such understanding is crucial for improving mineral exploration efficiency. In this study, we characterised the geochemistry of the fine-grained (<10 mu m) pyrite and the co-existing solid bitumen in the non-mineralised Paleoproterozoic Barney Creek Formation (BCF) intersected by the drillhole Lamont Pass 3, with a novel combination of Raman spectroscopy and nanoscale secondary ion mass spectrometry (Nano-SIMS), to underpin any potential hydrothermal activities distal (-50 km) to the McArthur River deposit. In the studied samples, fine-grained pyrites display sub-rounded, elongated and ultrafine-grained morphologies and occur as grain clusters spatially closely-associated with solid bitumen. Elemental maps obtained from Nano-SIMS reveal that some pyrites are enriched in trace elements, such as Pb, Tl, Ni, Co, and Cu, occurring as individual grains or overgrowth over the trace element-depleted pyrites. Fine-grained pyrites in the studied samples show similar trace element enrichment patterns to those often observed in the McArthur River deposit. The trace element-rich and -poor pyrites are interpreted to form as a result of hydrothermal and diagenetic processes, respectively. Formation temperatures of solid bitumen were estimated as - 170 celcius based on Raman spectral and reflectance data, approximating temperatures of hydrothermal fluids responsible for the McArthur River deposit. It is interpreted that solid bitumen may be either formed syngenetically with diagenetic pyrites and thermally reworked by hydrothermal fluids or formed contemporaneously with hydrothermal pyrite. The in-situ analysis of fine-grained pyrite and spatially-associated solid bitumen indicates that hydrothermal activity in the study area is consistent with the fluids responsible for the McArthur River deposit with respect to the trace element composition and fluid temperature. Hydrothermal fluid flow in the study area was likely a farfield effect of the McArthur River mineralisation extending along the Emu Fault. The widespread hydrothermal activity in the Barney Creek Formation strongly suggests that other factors, such as the fluid migration conduits (e.g. large-scale faults), are important controls for mineralization in this region.

Some iron oxide-copper-gold (IOCG) deposits contain variable amounts of uranium. Developing mineral deportment models for the radiogenic isotopes resulting from decay of U-238 presents a singular technical challenge, as concentrations of Ra-226, Pb-210, and Po-210 fall far below the detection limits achievable for most in situ analytical methodologies. The nanoscale secondary ion mass spectrometry (nanoSIMS) platform combines low detection limits with sub-micron resolution, revealing previously unseen spatial distribution patterns of radionuclides (RNs) in (and on) particles of copper sulphide concentrates. Many potential host minerals for these radionuclides can be readily predicted based on chemical behaviour, periodic table trends, and published studies documenting likely host minerals. Using nanoSIMS data for ores and metallurgical products from the Olympic Dam IOCG deposit and associated processing facilities, we present compelling evidence for the ability of certain minerals within the copper concentrates to host daughter radionuclides derived from uranium decay. Many of these minerals had not traditionally been considered or previously documented as such. These include high abundance minerals hosting low concentrations of radionuclides, and several relatively low abundance minerals exhibiting remarkable radionuclide enrichment. Rutile, fluorapatite, fluorite, hematite, zircon, covellite, and molybdenite are all proven to be minor hosts of at least some members of the U-238 decay chain, and are, collectively, important for establishing the overall RN budget. Surface effects are found to play a significant role, with elevated levels of Ra-226 and Pb-210 found on most available surfaces, irrespective of mineral, in acid-leached concentrate. Some rRNs, particularly Ra-226 and Pb-210 liberated from uranium minerals during sulphuric acid leaching, can become extensively redistributed throughout the concentrate, creating newly-formed RN hosts. This new mineralogical deportment information can be used in developing new flowsheets to enhance radionuclide removal without a corresponding loss of Cu. NanoSIMS has proven invaluable for elucidating the mineral-scale deportment of ultra-trace radionuclides throughout the processing circuit at Olympic Darn.

Trace elements and isotopic signatures are continuously recorded in growing shells and are empirically applied to monitor or reconstruct past environmental and climatic conditions. However, the precondition to correctly apply these proxy records is our understanding how trace elements are incorporated into growing biominerals. Although this understanding is still limited, we know today that bivalve shells form via non-classical crystallization pathways involving amorphous calcium carbonate (ACC) nanoparticles that transform to stable polymorphs aragonite calcite applications general understanding of the nano-scale properties of nacre is still limited. aim to understand trace element incorporation and mechanics of bivalve shell nacre at the nano-scale.

Zinc (as an essential phytonutrient) and cadmium (as a toxic but readily bioavailable nonessential metal for plants) share similar routes for crossing plant biomembranes, although with a substantially different potential for translocation into above-ground tissues. The in situ distribution of these metals in plant cells and tissues (particularly intensively-dividing and fast-growing areas) is poorly understood. In this study, 17-day-old radish (Raphanus sativus L.) plants grown in nutrient solution were subjected to short-term (24 h) equimolar contamination (2.2 µM of each 70Zn and Cd) to investigate their accumulation and distribution in the shoot apex (leaf primordia) and edible fleshy hypocotyl tissues. After 24-h exposure, radish hypocotyl had similar concentration (in µg/g dry weight) of 70Zn (12.1 ± 1.1) and total Cd (12.9 ± 0.8), with relatively limited translocation of both metals to shoots (concentrations lower by 2.5-fold for 70Zn and 4.8-fold for Cd) as determined by inductively-coupled plasma mass spectrometry (ICP-MS). The in situ Zn/Cd distribution maps created by high-resolution secondary ion mass spectrometry (NanoSIMS, Cameca, Gennevilliers, France) imaging corresponded well with the ICP-MS data, confirming a similar pattern and uniform distribution of 70Zn and Cd across the examined areas. Both applied techniques can be powerful tools for quantification (ICP-MS) and localisation and visualisation (NanoSIMS) of some ultra-trace isotopes in the intensively-dividing cells and fast-growing tissues of non-metalophytes even after short-term metal exposure. The results emphasise the importance of the quality of (agro)ecosystem resources (growing media, metal-contaminated soils/waters) in the public health risk, given that, even under low contamination and short-term exposure, some of the most toxic metallic ions (e.g., Cd) can relatively rapidly enter the human food chain.

Many analytical techniques for trace element analysis are available to the geochemist and geometallurgist to understand and, ideally, quantify the distribution of trace and minor components in a mineral deposit. Bulk trace element data are useful, but do not provide information regarding specific host minerals—or lack thereof, in cases of surface adherence or fracture fill—for each element. The CAMECA nanoscale secondary ion mass spectrometer (nanoSIMS) 50 and 50L instruments feature ultra-low minimum detection limits (to parts-per-billion) and sub-micron spatial resolution, a combination not found in any other analytical platform. Using ore and copper concentrate samples from the Olympic Dam mining-processing operation, South Australia, we demonstrate the application of nanoSIMS to understand the mineralogical distribution of potential by-product and detrimental elements. Results show previously undetected mineral host assemblages and elemental associations, providing geochemists with insight into mineral formation and elemental remobilization—and metallurgists with critical information necessary for optimizing ore processing techniques. Gold and Te may be seen associated with brannerite, and Ag prefers chalcocite over bornite. Rare earth elements may be found in trace quantities in fluorapatite and fluorite, which may report to final concentrates as entrained liberated or gangue-sulfide composite particles. Selenium, As, and Te reside in sulfides, commonly in association with Pb, Bi, Ag, and Au. Radionuclide daughters of the 238U decay chain may be located using nanoSIMS, providing critical information on these trace components that is unavailable using other microanalytical techniques. These radionuclides are observed in many minerals but seem particularly enriched in uranium minerals, some phosphates and sulfates, and within high surface area minerals. The nanoSIMS has proven a valuable tool in determining the spatial distribution of trace elements and isotopes in fine-grained copper ore, providing researchers with crucial evidence needed to answer questions of ore formation, ore alteration, and ore processing.

Olympic Dam hosts > 80 million tonnes of copper, as copper-iron sulphides, within hematite-dominant gangue. Processing of the relatively fine-grained copper ore is complicated by the presence of by-product uranium and its radiogenic isotopes, in particular Ra-226, Pb-210 and Po-210, which partially recover to the final copper sulphide concentrates. Although the majority (similar to 85%) of the U-bearing minerals (uraninite, coffinite, brannerite, thorianite, thorite) are recovered to flotation tailings, the remaining similar to 15% occurs in copper concentrates as sulphide-gangue composite particles and micron- to nanoscale grains occluded within sulphide minerals. Sulphuric acid leaching of copper concentrates significantly reduces the concentration of U but has only a minor impact on the daughter isotopes. Further reduction of these isotopes may be achieved through selective targeting and removal of specific minerals known to be radionuclide (RN) hosts, but fine-grained, micro- to nanoscale ore textures preclude easy direct identification of these RN host phases. Nanoscale secondary ion mass spectrometry (nanoSIMS) has proven to be an excellent platform for in situ mapping of ultra-trace RN distributions, with sub-micron spatial resolution, in individual mineral grains. Uranium and thorium minerals are, as expected, the major hosts and display significant concentrations of the entire U-238 decay chain. Although the majority of these minerals are removed via acid leaching of copper concentrate, sufficient RNs remain in the concentrate as micron- to nanoscale grains within sulphides and gangue minerals or along particle microfractures. Results show that brannerite, potentially more problematic due to its lower solubility in sulphuric acid than uraninite, does not appear to contain appreciable amounts of daughter isotopes. The insolubility of ThPO4 produces the potential for sequestration of Th-232 and Th-233 in rare earth phosphates such as xenotime, which then retain the respective decay chains. Likewise, the insolubility of certain sulphates (Sr, Ba, Pb, Ra) provides a mechanism for precipitation and entrapment of RNs. Baryte was shown to accumulate Ra and Pb naturally in the deposit, and it can upgrade its RN content substantially during sulphuric acid leaching through coupled dissolution-reprecipitation mechanisms involving Pb2+ and Ra2+ liberated from dissolved uranium minerals. Identification and prioritization of RN host minerals is crucial for the development of a more efficient processing flowsheet.

Marine sponges are set to become more abundant in many near-future oligotrophic environments, where they play crucial roles in nutrient cycling. Of high importance is their mass turnover of dissolved organic matter (DOM), a heterogeneous mixture that constitutes the largest fraction of organic matter in the ocean and is recycled primarily by bacterial mediation. Little is known, however, about the mechanism that enables sponges to incorporate large quantities of DOM in their nutrition, unlike most other invertebrates. Here, we examine the cellular capacity for direct processing of DOM, and the fate of the processed matter, inside a dinoflagellate-hosting bioeroding sponge that is prominent on Indo-Pacific coral reefs. Integrating transmission electron microscopy with nanoscale secondary ion mass spectrometry, we track 15N- and 13C-enriched DOM over time at the individual cell level of an intact sponge holobiont. We show initial high enrichment in the filter-feeding cells of the sponge, providing visual evidence of their capacity to process DOM through pinocytosis without mediation of resident bacteria. Subsequent enrichment of the endosymbiotic dinoflagellates also suggests sharing of host nitrogenous wastes. Our results shed light on the physiological mechanism behind the ecologically important ability of sponges to cycle DOM via the recently described sponge loop.

Production of radionuclide-free copper concentrates is dependent on understanding and controlling the deportment of daughter radionuclides (RNs) produced from 238 U decay, specifically 226 Ra, 210 Pb, and 210 Po. Sulfuric acid leaching is currently employed in the Olympic Dam processing plant (South Australia) to remove U and fluorine from copper concentrates prior to smelting but does not adequately remove the aforementioned RN. Due to chemical similarities between lead and alkaline earth metals (including Ra), two sets of experiments were designed to understand solution interactions between Sr, Ba, and Pb at various conditions. Nanoscale secondary ion mass spectrometry (NanoSIMS) isotopic spatial distribution maps and laser ablation inductively coupled-plasma mass spectrometry transects were performed on laboratory-grown crystals of baryte, celestite, and anglesite which had been exposed to different solutions under different pH and reaction time conditions. Analysis of experimental products reveals three uptake mechanisms: overgrowth of nearly pure SrSO 4 and PbSO 4 on baryte; incorporation of minor of Pb and Ba into celestite due to diffusion; and extensive replacement of Pb by Sr (and less extensive replacement of Pb by Ba) in anglesite via coupled dissolution-reprecipitation reactions. The presence of H 2 SO 4 either enhanced or inhibited these reactions. Kinetic modelling supports the experimental results, showing potential for extrapolating the (Sr, Ba, Pb)SO 4 system to encompass RaSO 4 . Direct observation of grain-scale element distributions by nanoSIMS aids understanding of the controlling conditions and mechanisms of replacement that may be critical steps for Pb and Ra removal from concentrates by allowing construction of a cationic replacement scenario targeting Pb or Ra, or ideally all insoluble sulfates. Experimental results provide a foundation for further investigation of RN uptake during minerals processing, especially during acid leaching. The new evidence enhances understanding of micro- to nanoscale chemical interactions and not only aids determination of where radionuclides reside during each processing stage but also guides development of flowsheets targeting their removal.

Rare garnet crystals from a peridotite xenolith from the Wesselton kimberlite, South Africa, have distinct zones related to two separate episodes of mantle metasomatism. The garnet cores were firstly depleted through melt extraction, then equilibrated during metasomatism by a potentially diamond-forming carbonate-bearing or proto-kimberlitic fluid at 1100-1300 degrees C and 4.5-5.5 GPa. The garnet rim chemistry, in contrast, is consistent with later overgrowth in equilibrium with a kimberlite at around 1025 +/- 25 degrees C and 4.2 +/- 0.5 GPa. This suggests that the rock was physically moved upwards by up to tens of kilometres between the two metasomatic episodes. Preserved high Ca, Al and Cr contents in orthopyroxenes suggest this uplift was tectonic, rather than magmatic. Diffusion profiles were measured over the transitions between garnet cores and rims using electron microprobe (Mg, Ca, Fe for modelling, plus Cr, Mn, Ti, Na, Al) and nano Secondary Ion Mass Spectrometry (NanoSIMS; (89)y, along with Na-23, Ca, Cr, Fe, Mn and Ti) analyses. The short profile lengths (generally <10 mu m) and low Y concentrations (0.2-60 ppm) make the NanoSIMS approach preferable. Diffusion profiles at the interface between the zones yield constraints on the timescale between the second metasomatic event and eruption of the kimberlite magma that brought the xenolith to the surface. The time taken to form the diffusion profiles is on the order of 25 days to 400 yr, primarily based on modelling of Y diffusion along with Ca, Fe and Mg (multicomponent diffusion) profiles. These timescales are too long to be produced by the interaction of the mantle xenolith with the host kimberlite magma during a single-stage ascent to the crust (hours to days). The samples offer a rare opportunity to study metasomatic processes associated with failed eruption attempts in the cratonic lithosphere. (C) 2017 Elsevier B.V. All rights reserved.

Gold and platinum-group-metals (PGM) are cycled through Earth’s environments by interwoven geological, physical, chemical and biological processes leading to the trans/neoformation of metallic particles in placers. The placer deposit at Corrego Bom Successo (CBS, Brazil) is one of the few localities worldwide containing secondary gold- and PGM-particles. Placer gold consists of detrital particles from nearby hydrothermal deposits that were transformed in the surface environment. Processes that have affected these particles include short-distance transport, chemical de-alloying of the primary gold‑silver, and (bio)geochemical dissolution/re-precipitation of gold leading to the formation of pure, secondary gold and the dispersion of gold nanoparticles. The latter processes are likely mediated by non-living organic matter (OM) and bacterial biofilms residing on the particles. The biofilms are largely composed of metallophillic β- and γ-Proteobacteria. Abundant mobile gold and platinum nanoparticles were detected in surface waters, suggesting similar mobilities of these metals. Earlier hydrothermal processes have led to the formation of coarsely-crystalline, arborescent dendritic potarite (PdHg). On potarite surfaces, biogeochemical processes have then led to the formation of platinum- and palladium-rich micro-crystalline layers, which make up the botryoidal platinum‑palladium aggregates. Subsequently potarite was dissolved from the core of many aggregates leaving voids now often filled by secondary anatase (TiO2) containing biophilic elements. The presence of fungal structures associated with the anatase suggests that fungi may have contributed to its formation. For the first time a primary magmatic PGM-particle comprising a mono-crystalline platinum‑palladium-alloy with platinum‑iridium‑osmium inclusions was described from this locality, finally defining a possible primary source for the PGM mineralisation. In conclusion, the formation of modern-day placer gold- and PGM-particles at CBS began 100s of millions of years ago by magmatic and hydrothermal processes. These provided the metal sources for more recent biogeochemical cycling of PGEs and gold that led to the trans/neoformation of gold- and PGM-particles.

The intertidal bivalve Katelysia rhytiphora, endemic to south Australia and Tasmania, is used here for pulsed Sr-labelling experiments in aquaculture experiments to visualize shell growth at the micro- to nanoscale. The ventral margin area of the outer shell layer composed of (i) an outermost outer shell layer (oOSL) with compound composite prismatic architecture with three hierarchical orders of prisms and (ii) an innermost outer shell layer (iOSL) with crossed-acicular architecture consisting of intersecting lamellae bundles. All structural orders in both layers are enveloped by an organic sheath and the smallest mineralized units are nano-granules. Electron backscatter diffraction reveals a strong preferred orientation of the aragonite c axes perpendicular to the growth layers, while the a and b axes are scattered within a plane normal to the local growth direction and >46 % twin grain boundaries are detected. The Young's modulus shows a girdle-like maximum of elastically stiffer orientations for the shell following the inner shell surface. For 6 d, the bivalves were subjected twice to seawater with an increased Sr concentration of 18× mean ocean water by dissolving 144 µg g−1 Sr (159.88 Sr∕Ca mmol ∕ mol) in seawater. The pulse labelling intervals in the shell are 17× (oOSL) and 12× (iOSL) enriched in Sr relative to the Sr-spiked seawater. All architectural units in the shell are transected by the Sr label, demonstrating shell growth to progress homogeneously instead of forming one individual architectural unit after the other. Distribution coefficients, DSr ∕ Ca, for labelled and unlabelled shells are similar to shell proportions formed in the wild (0.12 to 0.15). All DSr ∕ Ca values are lower than values for equilibrium partitioning of Sr in synthetic aragonite.

Zinc as a micronutrient and cadmium as a nonessential toxic element share similar pathways for entering plant tissues and thus may be antagonistic. In nutrient solution culture, 17-day-old radish (Raphanus sativus L) plants were exposed to short-term (24 h) equimolar metal contamination (2.2 µM of each 70Zn and total Cd) to investigate the in situ Zn/Cd distribution in the apical root tissues using high-resolution secondary ion mass spectrometry (NanoSIMS) imaging. Inductively-coupled plasma mass spectrometry analysis of bulk root tissue confirmed large root uptake of both metal elements. After 24-h exposure the total root concentration (in µg/g DW) of 70Zn was 180 ± 24 (mean±SE) and of total Cd 352 ± 11. NanoSIMS mapping was performed on the cross sections of the radish root apex as a crucial component in root growth and uptake of water and nutrients from soil. Elemental maps of 70Zn and 114Cd isotopes revealed greater enrichment of both metals in the outer epidermal root layer than in cortical tissues and especially stele, confirming the epidermal root cells as preferential sites of metal uptake, and indicating relatively slow and less-intensive metal transport into other parts (edible hypocotyl, shoot) of metal-sensitive radish. NanoSIMS has been confirmed as a powerful tool for spatial detection and visualisation of some ultra-trace metal isotopes (e.g. 70Zn) in the fast-growing root tips. However, precise (sub)cellular mapping of diffusible metallic ions (Cd, Zn) remains a technically-challenging task in plant specimens given an unavoidable compromise between optimising methodology for structural preservation vs. authentic in vivo ion localisation.

Photosynthesis in the seagrass Zostera muelleri remains poorly understood. We investigated the effect of reduced irradiance on the incorporation of 13C, gene expression of photosynthetic, photorespiratory and intermediates recycling genes as well as the enzymatic content and activity of Rubisco and PEPC within Z. muelleri. Following 48 h of reduced irradiance, we found that i) there was a ∼7 fold reduction in 13C incorporation in above ground tissue, ii) a significant down regulation of photosynthetic, photorespiratory and intermediates recycling genes and iii) no significant difference in enzyme activity and content. We propose that Z. muelleri is able to alter its physiology in order to reduce the amount of C lost through photorespiration to compensate for the reduced carbon assimilation as a result of reduced irradiance. In addition, the first estimated rate constant (Kcat) and maximum rates of carboxylation (Vcmax) of Rubisco is reported for the first time for Z. muelleri.

[This corrects the article on p. 214 in vol. 9, PMID: 29615919.].