Laser Ablation Inductively Coupled Plasma Mass Spectrometry Research Articles

The leaky chronometer: Evidence for systematic cryptic Pb loss in laser ablation U‐Pb dating of zircon relative to CA‐TIMS

AbstractU–Pb dating of zircon via laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) has become a primary method for determining the age of crystalline rocks and the provenance and maximum depositional age of (meta)sedimentary rocks. Although chemical abrasion has become a standard approach for mitigating Pb loss in zircon dated via high‐resolution thermal ionization mass spectrometry (CA‐TIMS), laser ablation dating is rarely accompanied by chemical abrasion. We evaluate the accuracy of U–Pb dates acquired via LA‐ICP‐MS relative to CA‐TIMS through analysis of a large database of paired analyses from the same zircon crystals. We show that laser ablation 206Pb/238U dates are systematically younger than their CA‐TIMS counterparts, with a greater shift in detrital zircon (−2.0%) versus igneous or metamorphic zircon (−0.9%). Although systematic biases related to “matrix effects” may be a contributing factor, our analysis suggests that unmitigated cryptic Pb loss is likely widespread in laser ablation U–Pb datasets.

Yampi Peninsula felsic Hart Dolerite: re-evaluating the Nellie Tonalite using evidence from whole rock, petrography and geochronology

The Nellie Tonalite forms a discontinuous 20 km elongate northwest-trending felsic intrusion at the far-western end of the Western Zone of the Lamboo Province, in the Wunaamin Miliwundi Orogen, Western Australia. This intrusion is poorly understood with previous interpretations assigning it to the ca 1860 Ma Paperbark Supersuite. We present the first geochronological results for the Nellie Tonalite, which have a weighted mean laser ablation, inductively coupled plasma, mass spectrometry (LA-ICP-MS) U–Pb zircon age of 1794 ± 4 Ma. This date is coincident with the age for felsic granophyres of the Hart Dolerite, which have previously been described from the Kimberley Basin overlying the Halls Creek Orogen and central parts of the Wunaamin Miliwundi Orogen. Other similarities of the Nellie Tonalite with the felsic Hart Dolerite are micrographic and granophyric intergrowths of quartz and K-feldspar, and a distinct geochemical depletion of V. This V depletion is interpreted to be the result of closed-system, in situ fractional crystallisation of titanomagnetite from a basaltic composition. The fractional residue from this process can be found at several locations across the Halls Creek Orogen and Wunaamin Miliwundi Orogen and at Speewah Dome in the east Kimberley where magnetite gabbros within the Hart Dolerite also host a large Ti–V mineral resource. It is proposed that the Nellie Tonalite is a western correlate of the felsic Hart Dolerite. This demonstrates that the magmatic processes required for Speewah-style Ti–V mineralisation are extensive across the entire Lamboo Province. Additionally, the scale, constancy of the composition, texture and age of the felsic Hart Dolerite encompassing the entire inland margin of the Kimberley Region, and the rapid emplacement time of <3 m.y., support the interpretation of a mantle plume model for the emplacement of the Hart Dolerite.

Assessing spatial distribution of bioindicator elements in various cutaneous tumors using correlative imaging with laser-ablation-based analytical methods

Correlative imaging of cutaneous tumors provides additional information to the standard histopathologic examination. However, the joint progress in the establishment of analytical techniques, such as Laser-Induced Breakdown Spectroscopy (LIBS) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) in clinical practice is still limited. Their combination provides complementary information as it is also shown in our study in terms of major biotic (Ca, Mg, and P) and trace (Cu and Zn) elements. To elucidate changes in the elemental composition in tumors, we have compiled a set of malignant tumors (Squamous Cell Carcinoma, Basal Cell Carcinoma, Malignant Melanoma, and Epithelioid Angiosarcoma), one benign tumor (Pigmented Nevus) and one healthy-skin sample. The data processing was based on a methodological pipeline involving binary image registration and affine transformation. Thus, our paper brings a feasibility study of a practical methodological concept that enables us to compare LIBS and LA-ICP-MS results despite the mutual spatial distortion of original elemental images. Moreover, we also show that LIBS could be a sufficient pre-screening method even for a larger number of samples according to the speed and reproducibility of the analyses. Whereas LA-ICP-MS could serve as a ground truth and reference technique for preselected samples.

P-based referencing for correcting tissue artifacts in laser ablation-inductively coupled plasma-mass spectrometry imaging of cancer samples.

A referencing strategy based on the element P is presented to compensate for cryosectioning tissue artifacts in laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) data. The study examines how the gadolinium-based contrast agent Gadofosveset is distributed in murine cancer tissue, and illustrates how referenced images can compensate for tissue artifacts like folds, overlaps, and density variations. Compared to non-referenced images that provide information on the absolute distribution of the analyte, referenced images allow for the representation of the analyte distribution relative to the amount of material introduced into the instrument, which in this case is correlated to the P signal. Tissue artifacts were corrected in referenced images for both Gadofosveset and endogenous elements, such as Fe and Zn. Additionally, the referencing approach provides valuable information on the Gd uptake relative to the tissue density in necrotic compared to vital tumor areas, which is not obtained from in vivo magnetic resonance imaging (MRI) data. However, validation of in vivo MRI and ex vivo LA-ICP-MS methods was possible by establishing a mean ratio of necrotic to vital tumor areas in the T1-weighted image post Gadofosveset injection and the non-referenced LA-ICP-MS image of Gd. In summary, P-based correction of LA-ICP-MS imaging data allows for a more accurate spatial representation of certain elements, including endogenous and exogenous elements such as injected contrast agents.

Xenolith Petrochronology (San Luis Potosi, Mexico) Constrains Heat Sources for Cenozoic Ultrahigh‐Temperature Metamorphism in the Lower Crust

AbstractUltrahigh‐temperature (UHT; &gt;900°C) metamorphism drives crustal differentiation and is widely recognized in the rock record, but its geodynamic causes are debated. Previous work on granulite‐facies metapelite xenoliths from San Luis Potosí, Mexico suggests the lower crust experienced a protracted UHT metamorphic event that coincided with the onset of regional extension. To determine the duration, conditions, and heat sources of UHT metamorphism recorded by these xenoliths, this study characterizes the major‐element, trace‐element, and U‐Pb isotopic systematics of quartz, rutile, feldspar, garnet, and zircon by in situ electron microprobe (EPMA) and laser‐ablation inductively coupled‐plasma mass spectrometry (LA‐ICP‐MS), and augments these data with detailed petrography, thermobarometry, phase equilibria modeling, and diffusion modeling. Thermobarometry and phase equilibria modeling suggest peak metamorphic conditions exceeded 0.7 GPa and 900°C. Zircon petrochronology confirms &gt;15 Myr of UHT conditions since its onset at ∼30 Ma. A small population of zircon record elevated temperatures following transition from backarc compression to extension during the waning stages of orogenesis (60–37 Ma). Garnet preserves trace‐element zoning and mineral inclusions consistent with suprasolidus garnet growth and subsequent compositional modification by intracrystalline rare‐earth element diffusion during protracted heating, with diffusion chronometry timescales in agreement with zircon data, followed by fluid‐driven remobilization of trace elements along now‐healed fractures within ∼1 Myr of eruption. In sum, these data are most compatible with lithospheric mantle attenuation or removal as the dominant heat transport mechanism driving synextensional UHT metamorphism and crustal melting, which has bearing on models for crustal differentiation and formation of modern and ancient granulite terranes globally.

Detecting element migration from ore systems: an LA-ICP-MS method for the in situ measurement of element contents and 207 Pb/ 206 Pb values on rough fracture coatings

In situ elemental content and 207 Pb/ 206 Pb values in three rough fracture coatings within drill cores from the McArthur River unconformity-related uranium deposit, Athabasca Basin, Canada, were measured using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) image mapping. Fracture-coating samples were located proximal and distal to the ore deposit. Samples required minimal preparation in this method, with areas ( c . 500 × 500 μ m) targeted in a cell-spaced grid pattern using a 50 μ m spot, spaced 200 μ m on the x -axis with an offset of 100 μ m on the y -axis, to overcome sample surface topography. A 5 s acquisition time was applied to elemental content measurements and a 2 s acquisition time was applied to 207 Pb/ 206 Pb measurements. These parameters increased the spatial resolution and analytical sensitivity and minimized the contribution of the host rock underlying the fracture surface to the geochemical signal in comparison to extended acquisition times. In addition, laser ablation temporal profiles allow for the interpretation of the timing of element/isotope migration and fixation on the rough fracture coating. Rasterized maps generated in Iolite™ v.4 demonstrate the chemical distribution of elements and 207 Pb/ 206 Pb values on the rough fracture coatings, allowing for the identification of mineral phases hosting pathfinder elements, pathfinder element associations and the generation of bulk in situ or specific mineralogy geochemical values. Bulk in situ values calculated using an integration of the 2D image data and targeting the c . 500 × 500 μ m surface of the fracture coating compared to previous bulk geochemical methods obtained by sampling the fracture coating with a microdrill (i.e. modified aqua regia (HCl: HNO 3 : H 2 O) and weak acid leach (2% HNO 3 )) highlights that in situ analysis greatly improved detection of pathfinder elements on the fracture surface. This study is the first application of in situ LA-ICP-MS for measuring element contents and 207 Pb/ 206 Pb values on rough fracture coatings and demonstrates its importance as a new geochemical tool to the mining industry for future mineral exploration.

Tracking Childhood Lead Exposure in Early Industrial Romanians

Childhood lead exposure has been linked to severe adverse health outcomes throughout life. Measurements of lead in teeth have established that individuals living in contaminated environments show higher levels compared to individuals living further away, although less is known about when individuals are most susceptible to these exposures. We examined lead (Pb208) concentrations (ppm) in teeth over the first 2.5 years of life in 16 children born in the late 19th to early 20th century throughout Romania. This period of intense industrialization was characterized by increases in mining, coal burning, and oil refining—activities that contaminate air, water, and food with Pb. We hypothesized the distance from an operational mine or oil refinery, or being born in a city, would be positively associated with cumulative dentine Pb exposure (CDPE). We also predicted that Pb exposures would peak in the first six months of life when gastrointestinal (GI) absorption of Pb is likely highest. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) of sectioned tooth dentine followed by Bayesian statistical analyses revealed that living 30 km or more from a mine or oil refinery did not explain CDPE. However, being born in a city explained 42% of CDPE. All individuals showed maximum Pb exposures after six months of age, likely due to contaminated solid food and/or non-milk liquids. This research demonstrates how tooth formation can be coupled with comprehensive elemental mapping to analyse the context and timing of early-life neurotoxicant exposures, which may be extended to well-preserved teeth from clinical and historic populations.

LA-ICPMS for In Situ U-Th Dating of Holocene Stalagmites.

Here, we present an in situ U-Th dating approach of carbonate speleothems using laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) with a detection efficiency of 1-2%. By online addition of a 229Th-233U-236U isotope triple spike to the laser-generated aerosol, instrumental mass discrimination and U/Th elemental fractionation could be monitored and corrected. With this approach, the 234U/238U and 230Th/238U activity ratios of a flowstone sample in secular equilibrium could be accurately reproduced as unity with two-sigma uncertainties ±0.053 and ±0.050, respectively. The method was used for the determination of the formation ages of individual layers in natural stalagmites ranging between 210 and 1 thousand years ago (ka). The determined ages corresponded well with those obtained using conventional solution multi collector-ICPMS techniques after isotope separation. Particularly, Holocene stalagmites, as young as 1 ka, could be accurately dated with 2 standard error of ±76 years. This developed microdomain U-Th dating approach thus can be applicable for diverse research areas, such as paleoclimatology, oceanography, geomagnetism, and archeology.

Investigating the impact of paleoclimatic conditions and diagenesis on the genesis of Permian Continental Red Beds: A case study from the Bohemian Massif, Czechia

The processes responsible for reddening of Continental Red Beds (CRBs) and the relationship between color variation and paleoenvironmental conditions are presented focusing on a comprehensive multi-proxy study of Permian sediments in the Bohemian Massif, Czechia. The investigation incorporates facies analysis, quantitative color assessment using diffuse Vis-spectral reflectance (DRS), optical and electron microprobe microscopy, bulk-rock (XRF and XRD), and in-situ geochemistry (laser-ablation ICP-MS). Results indicate a progressive drying trend from the Cisuralian to Guadalupian series in studied continental red sediments. Different facies indicate the change of the sedimentary environment from a deep lacustrine environment (lower part of Rudník Member, Cisuralian) to a fluvial floodplain and eolian environment (Trutnov Formation, Guadalupian). Examination of the three major categories (white, gray–green and red sediments) identified in the studied continental red beds indicates that diagenetic alteration of clay minerals and biotite was the main source of iron fueling the growth of hematite responsible for their red color. Early diagenetic processes and paleoenvironmental conditions, particularly the oxidizing or reducing conditions play a key role in the red sediment formation. It is suggested that later diagenetic stages are incapable of coloring non-red, iron-rich sediments formed in deep anoxic lacustrine environments. Microbial activities and reducing fluids have been identified as the main factors in the formation of gray–green sediments forming distinct reduction zones. The reduction spots formed during the early stages of diagenesis (eodiagenesis), and they were likely never red. In contrast, reduction strips, initially exhibiting a red hue, underwent a color change during more advanced stages of diagenesis (mesodiagenesis).

Association of rare earth elements with secondary mineral phases formed during alkalinization of acid mine drainage

Rare Earth Elements (REE) are present in acid mine drainage (AMD) in micromolar concentrations and AMD discharge may lead to an environmental risk. Alkaline Passive Treatment Systems (PTS) are often used to treat AMD and trap toxic trace elements. This study was set up to identify mechanisms by which REE are trapped in or on secondary phases formed in a PTS. Batch alkalinization experiments were performed to simulate PTS by sequentially increasing the pH of AMD collected from the Tharsis mining area inside the Iberian Pyrite Belt and synthetic AMD water samples via CaCO3 addition. The solids that precipitated up to pH ~4 and between pH 4–6 were collected and characterized by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) in combination with Scanning Electron Microscope/Energy Dispersive X-ray spectroscopy (SEM/EDX) and synchrotron-based X-ray Absorption Spectroscopy (XAS) and synchrotron-based Micro-X-ray Fluorescence (μ-XRF). Results reveal that REE are mostly scavenged between pH 4–6 in association with Al and Fe phases, whereas a smaller fraction is scavenged at pH ~4 by association with gypsum. Synchrotron-based analysis evidences the incorporation of La3+ into the gypsum structure by substituting Ca2+, indicating a co-precipitation mechanism with gypsum occurring mainly at low pH. Results from parallel adsorption and co-precipitation tests suggest that the REE scavenging between pH 4–6 could be due to a combination of adsorption and co-precipitation on Al(OH)3 and ferrihydrite. This implies that in PTS, REE would be mainly found in Al- (and Fe-) oxyhydroxides occurring in deeper layers of the PTS, i.e., where higher pH-values occur, though a small fraction, especially the light REE, could also be found incorporated into gypsum in the upper layers.

Stable isotopes (O, H) and quartz geochemistry provide insight to melt source and subsolidus fluid:rock interaction in the Cretaceous Little Nahanni LCT Pegmatites (NWT, Canada)

Previous studies of the mid-Cretaceous (ca. 85 Ma) LCT-type Little Nahanni Pegmatite Group (LNPG; Northwest Territories, Canada) document disequilibrium textures and pervasive metasomatism associated with rare-metal (e.g., Ta, Nb, Sn) mineralization. As in other pegmatite settings, the source of the melts and the nature and origin of pervasive metasomatism remain enigmatic. To resolve these latter issues, an integrated study of bulk O and H isotope analysis of mineral separates (quartz, K-feldspar, albite, muscovite, garnet), in situ Secondary Ion Mass Spectrometry (SIMS) isotopic (O) analysis of quartz and albite, and in situ Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) trace element analysis of quartz was done in concert with cathodoluminescence (CL) imaging and petrographic observations. Quartz with elevated δ18O values (δ18Oquartz = 10 to 16.3‰) also have high Ti-in-quartz temperatures (551 ± 17 °C to 603 ± 16 °C). These data along with their pristine nature from CL imaging suggest some localized melt-wall rock (WR) exchange occurred at the time of pegmatite melt emplacement. Furthermore, the elevated δ18O values indicate a crustal source (i.e., S-type granite) for the LNPG parental melt, which also overlaps with δ18Oquartz data for granitoids of the mid- to Late-Cretaceous Selwyn Plutonic Suite of this area. In contrast, the large range for δ18O values for metasomatic minerals, such as albite (−3.0 to +18.3‰) indicate a complex evolution involving multiple oxygen isotopic reservoirs, in particular incursion of meteoric water previously equilibrated with metasedimentary wall rocks. Finally, the large range for mineral pairs (e.g., Δquartz-albite = −5.1 to +14.3‰) and abundance of dissolution features in late-stage assemblages unequivocally indicates that sub-solidus fluid:rock interaction was responsible for such large spreads in δ18O and values δD values, although other processes (e.g., disequilibrium crystallization, thermal gradients, rapid cooling) might have also contributed, but to lesser extents.

Apatite Fission-Track Dating: A Comparative Study of Ages Obtained by the Automated Counting LA-ICP-MS and External Detector Methodologies

Abstract Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) in combination with developments in digital microscopy, image analysis, and computer software has allowed the implementation of an automated counting approach for the apatite fission-track (AFT) analysis. We refer to this approach as the “automated counting-LA-ICP-MS” (ACLA) method. Two major components comprise the ACLA method: (i) the digital counting of spontaneous tracks performed on high-resolution images captured from apatite grains and (ii) the measurement of 238U content in apatite by LA-ICP-MS. This study includes ACLA analyses from Fish Canyon Tuff (FCT) and Durango apatite standard crystals. Furthermore, a comparative age study between the ACLA and conventional external detector method (EDM) strategies was performed on a set of thirteen granitoid samples from northwestern Mexico and four granitic samples from the eastern Dharwar craton (EDC), India. ACLA analyses on FCT yielded an AFT age of 28.1 ± 0.6 (1σ) and 28.8 ± 1.1 (1σ) Ma for Durango apatite, whereas reported EDM ages are 27.5 ± 0.5 and 31.4 ± 0.5 Ma, respectively. Calculated AFT ages using the ACLA method from northwestern Mexico samples range from 11.1 ± 1.1 to 42.0 ± 3.6 Ma (EDM ages range from 10.0 ± 0.8 to 54.0 ± 3.0 Ma), whereas AFT ages from the EDC samples range from 147 ± 3.1 to 220.5 ± 12.5 Ma (EDM ages range from 120.9 ± 4.5 to 197.1 ± 19.4 Ma). Based on a statistical comparison with ages previously determined by the conventional EDM on the same samples and considering their 2σ uncertainties, these ages are in good agreement.

GOLD ENRICHMENT MECHANISM IN MID-OCEAN RIDGE HYDROTHERMAL SYSTEMS: AN EXAMPLE FROM THE LONGQI HYDROTHERMAL FIELD ON THE ULTRASLOW-SPREADING SOUTHWEST INDIAN RIDGE

Abstract In mid-ocean ridge (MOR) hydrothermal systems, the gold grade of sea-floor massive sulfides (SMSs) is negatively correlated with the spreading rate of the ridge. Previous investigations have addressed the distribution of gold in sulfides from hydrothermal fields hosted by ultramafic rocks. In contrast, the gold enrichment mechanisms in sulfides from hydrothermal fields hosted by mafic rocks in ultraslow-spreading ridge environments are less well constrained. The basalt-hosted Longqi hydrothermal field, located on the classic ultraslow-spreading Southwest Indian Ridge, provides an opportunity to examine gold enrichment mechanisms in such an environment. Two ore-forming stages are identified in chimney fragments: anhydrite + barite + colloidal/porous pyrite (Py1) + marcasite + fine-grained sphalerite (stage 1); euhedral-subhedral pyrite (Py2) + coarse-grained sphalerite + chalcopyrite + isocubanite (stage 2). Py1 is usually overgrown by marcasite, which is in turn enclosed by Py2. Py2 coexists with coarse-grained sphalerite and chalcopyrite. Abundant native gold nanoparticles occur in Py1 or at the transition zone between Py1 and Py2. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis suggests that Py1 contains higher Mo, V, Sn, and Pb and lower As, Co/Ni, and Se/Tl values compared to Py2. In situ LA-multicollector (MC)-ICP-MS analyses show that Py1 has a higher mean δ34S (+7.1‰) value than Py2 (+6.6‰). Sulfur primarily derives from MORB and seawater sulfate, of which the proportion of sulfur from seawater sulfate is between 20.5 and 47.6%. Textures, mineral assemblages, and trace element contents of sulfides indicate that the degree of mixing between hydrothermal fluids and seawater decreases as the chimney grows and is accompanied by a gradual increase in temperature. Based on data compiled from 41 hydrothermal fields hosted by basalt, the large range of sulfide δ34S from slow- and ultraslow-spreading MORs may be attributed to the wide range of sulfur sources (e.g., leaching from MOR basalt, thermochemical reduction of seawater sulfate, magma degassing, and bacterial activity), fluid-basalt interaction, and redox state (CH4/CO2 ratios). Prolonged fluid-basalt interaction and the type of chimneys, such as beehive chimneys, may lead to higher gold grades in hydrothermal fields. Moreover, low H2S content may be an important contributor to gold enrichment in basalt-hosted SMS deposits in ultraslow-spreading MOR environments.

Mytilus galloprovincialis shell growth – Insights from shell geochemistry

Despite the wide geographic distribution of mussels and their importance in fisheries and aquaculture, understanding of temporal and spatial variations of their growth is still limited. This can be, at least partly, attributed to the lack of distinct growth lines in their shells. Our study uses geochemical properties of shells, particularly oxygen (δ18Oshell) and carbon (δ13Cshell) stable isotope values, to reconstruct mussel growth. Mytilus galloprovincialis specimens were collected from two of the most important bivalve aquaculture sites in the eastern Adriatic - Krka River estuary and Mali Ston Bay. The first site has variable environmental conditions, influenced mainly by the Krka River, resulting in a strong temperature and salinity gradient along the estuary. In contrast, Mali Ston Bay is a relatively shallow enclosed bay with more stable conditions. Samples for δ18Oshell and δ13Cshell analysis were acquired by manual microdrilling cross-sectioned shells from three similar sized shells from each site. In addition, analysis of elemental profiles (Mg/Ca, Sr/Ca, and Ba/Ca) in shells from the Krka River estuary was conducted using laser ablation ICPMS. Temperature and salinity values were obtained for each site through research and monitoring projects and used to calculate predicted δ18Oshell values. By aligning the measured δ18Oshell data along the predicted δ18Oshell curve, it was possible to reconstruct the timing and rate of seasonal shell growth. Results show that M. galloprovincialis shell deposition slows down and/or ceases during high temperature and low salinity periods. Specimens from the Krka River estuary had faster shell growth rates and were characterised by higher δ13Cshell values. Mg/Ca profiles of M. galloprovincialis specimens from the Krka River estuary, confirm growth periodicity data obtained by δ18O analysis. Ba/Ca peaks were also discussed by comparison with δ13C time-series and environmental data. Results have potential applications in fisheries studies as well as in palaeoecology and palaeoceanography research.

Aerosol exposure at air-liquid-interface (AE-ALI) in vitro toxicity system characterisation: Particle deposition and the importance of air control responses

Experimental systems allowing aerosol exposure (AE) of cell cultures at the air-liquid-interface (ALI) are increasingly being used to assess the toxicity of inhaled contaminants as they are more biomimetic than standard methods using submerged cultures, however, they require detailed characterisation before use. An AE-ALI system combining aerosol generation with a CULTEX® exposure chamber was characterised with respect to particle deposition and the cellular effects of filtered air (typical control) exposures. The effect of system parameters (electrostatic precipitator voltage, air flowrate to cells and insert size) on deposition efficiency and spatial distribution were investigated using ICP-MS and laser ablation ICP-MS, for an aerosol of CeO2 nanoparticles. Deposition varied with conditions, but appropriate choice of operating parameters produced broadly uniform deposition at suitable levels. The impact of air exposure duration on alveolar cells (A549) and primary small airway epithelial cells (SAECs) was explored with respect to LDH release and expression of selected genes. Results indicated that air exposures could have a significant impact on cells (e.g., cytotoxicity and expression of genes, including CXCL1, HMOX1, and SPP1) at relatively short durations (from 10 mins) and that SAECs were more sensitive. These findings indicate that detailed system characterisation is essential to ensure meaningful results.

Using compositions of zircon to reveal fertile magmas for the formation of porphyry deposits in the Loei and Truong Son fold belts, northern Laos

The Loei and Truong Son fold belts are well known as being the most geologically important and highly mineralized magmatic arc-related terranes in mainland southeast Asia. Numerous studies have examined the geology, geochemistry, and geochronology but only a few metallogenic and detailed deposit characterizations have been undertaken. This study of zircon geochemical analyses uses laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to provide U-Pb ages and magmatic fertility of felsic to intermediate volcanic and plutonic rocks from ten prospects in the Loei and Truong Son fold belts, in the northwest Laos region. The geochemical and geochronological analyses suggest at least three episodes of magmatism occurred: Silurian-Devonian (434–411 Ma), Early to Middle Permian (299–277 Ma), and Late Permian to Middle Triassic (253–243 Ma). The variable ranges of ɛHf values (−12 to + 12) suggest that mantle-derived and crustal contamination signatures are related to the history of subduction and arc magmatism in this region. Key trace elements and ratios associated with oxygen fugacity of magmas (e.g., Eu/Eu*, Dy/Yb, Ce/Nd, ΔFMQ) imply that the Phu Kham and the west of Vientiane along the Mekong River are likely to be fertile for porphyry copper deposits. In contrast, the Pha Gnai and other suites are less fertile. Using zircon as a fertility indication can be a valuable tool to distinguish between fertile and barren magmatic suites in this area.

On the viability of detrital biotite Rb–Sr geochronology

Abstract. Re-examination of International Ocean Discovery Program (IODP) sediment samples collected from the Bay of Bengal via laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) Rb–Sr geochronology demonstrates the viability of the biotite Rb–Sr system for use as a detrital chronometer. The age population defined by the Rb–Sr dates essentially reproduces that previously published for detrital 40Ar/39Ar dates. The effect of unknown/assumed initial 87Sr/86Sr on the calculated population can be ameliorated by filtering for higher 87Rb/86Sr ratios. Such filtering, however, could introduce bias toward more radiogenic populations, especially in younger material that has not had time to accumulate radiogenic product (e.g. limiting the effect of initial 87Sr/86Sr to ∼ &lt;5 % requires filtering of 87Rb/86Sr &gt;500 at 250 Ma and 87Rb/86Sr &gt;50 at 2500 Ma). Finally, Ti-in-biotite temperatures calculated based on element concentration data collected during LA-ICP-MS overlap with those calculated for the same material based on electron probe microanalyzer data, demonstrating the potential for in situ biotite petrochronology based on the Rb–Sr system.

Mineralogical Characteristics of Color-Changing Garnet and the Effect of Light Path Length on Color

The color-changing garnet displays the “alexandrite effect”, changing from green in daylight to purplish-red under incandescent light. The mineralogical characteristics of color-changing garnet is analyzed using Raman spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, an electron probe, and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The color of garnets with different thicknesses was calculated using the International Commission on Illumination (CIE 1976) L*a*b* uniform color system. The results revealed the presence of rutile inclusions in color-changing garnet. Strong absorption in both the blue-violet zone and orange-yellow zone was the main cause for the color-changing effect of garnet. The distribution pattern of rare earth elements (REE) was left-leaning, showing the enrichment of heavy rare earth elements (HREE) and depletion of light rare earth elements (LREE). As the total Cr and V concentrations increased, the area of the 574 nm absorption peak in the UV-Vis spectrum also increased, leading to a more significant variation in color ΔE*ab. The light path length of the gemstone had a significant impact on the extent of the color-changing effect. The color difference reached a maximum and the color-changing effect was most visible when the thickness of the gemstone was 5 mm.

Magnetite geochemistry as a proxy for metallogenic processes: A study on sulfide-mineralized mafic–ultramafic intrusions peripheral to the Kunene Complex in Angola and Namibia

AbstractTrace element concentrations in magnetite are dictated by the petrogenetic environment and by the physico-chemical conditions during magmatic, hydrothermal, or sedimentary processes. This makes magnetite chemistry a useful tool in the exploration of ore-forming processes. We describe magnetite compositions from Ni-Cu-(PGE)-sulfide mineralized rocks from seven mafic–ultramafic intrusions peripheral to the Mesoproterozoic AMCG (anorthosite-mangerite-charnockite-granite) suite of the Kunene Complex of Angola and Namibia to investigate metallogenic processes through the geochemical characterization of Fe-oxides, which were analyzed in-situ via Electron Probe Microanalysis (EPMA), and Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS). We identified magmatic magnetite, segregated from both a silicate liquid and an immiscible sulfide liquid. Elements like Cr, Co and V suggest that the sulfide-related magnetite segregated from a relatively primitive Fe-rich monosulfide solid solution (MSS). Secondary Cr-rich magnetite appears in intrusions with abundant chromite or Cr-spinel. Two types of hydrothermal magnetite were identified, related to the pervasive replacement of sulfides and a late-stage, low-T fluid circulation event. Magnetite replacing sulfides is associated with serpentinized ultramafic rocks and is preferentially observed in the intrusions with the highest base and precious metal tenors. The high concentration of Ni, Co, Cu, Pd, As and Sb in these grains is corroborated by the identification of micron-size PGE mineral inclusions. We infer that serpentinization during hydrothermal fluid circulation was accompanied by desulphurization of sulfides with metal remobilization and reconcentration to generate magnetite carrying Pd microinclusions. We suggest that the highly serpentinized ultramafic rocks in the Kunene Complex region may become a possible target for economic Ni-Cu-(PGE) mineralization.

Persistent Luminescence Nanoplatform for Autofluorescence-Free Tracking of Submicrometer Plastic Particles in Plant.

The uptake of plastic particles by plants and their transport through the food chain make great risks to biota and human health. Therefore, it is important to trace plastic particles in the plant. Traditional fluorescence imaging in plants usually suffers significant autofluorescence background. Here, we report a persistent luminescence nanoplatform for autofluorescence-free imaging and quantitation of submicrometer plastic particles in plant. The nanoplatform was fabricated by doping persistent luminescence nanoparticles (PLNPs) onto polystyrene (PS) nanoparticles. Cr3+-doped zinc gallate PLNP was employed as the dopant for autofluorescence-free imaging due to its persistent luminescence nature. In addition, the Ga element in PLNP was used as a proxy to quantify the PS in the plant by inductively coupled plasma mass spectrometry (ICP-MS). Thus, the developed nanoplatform allows not only dual-mode autofluorescence-free imaging (persistent luminescence and laser-ablation ICP-MS) but also ICP-MS quantitation for tracking PS in plant. Application of this nanoplatform in a typical plant model Arabidopsis thaliana revealed that PS mainly distributed in the root (>99.45%) and translocated very limited (<0.55%) to the shoot. The developed nanoplatform has great potential for quantitative tracing of submicrometer plastic particles to investigate the environmental process and impact of plastic particles.