Secondary Mass Spectrometer Research Articles

Does interfacial photochemistry play a role in the photolysis of pyruvic acid in water?

Pyruvic acid (PA) exists in fogs, aerosols and clouds. The photochemistry-driven reaction pathways of PA in the aqueous phase are more elusive than the gas phase. The PA photochemical process may occur in the bulk liquid phase and at the air-liquid interface in ambient conditions. We conducted two sample preparation methods to simulate two possible scenarios: the air-liquid interface and the bulk liquid phase under photolysis. Time-of-flight secondary ion mass spectrometer (ToF-SIMS) was used to analyze samples because of its high sensitivity and mass accuracy in surface analysis. Both negative and positive ion mode mass spectra provide complementary information of the products under different reaction conditions. Spectral principal component analysis (PCA) is used to determine similarities and differences among various samples. The air-liquid interface facilitates more radical reactions and form higher molecular weight compounds (HMWCs) more quickly than the bulk liquid phase, which mainly has non-radical reactions such as anhydride reactions and decarboxylation reactions. Our results show that interfacial chemistry plays an important role in atmospheric scenarios. Moreover, different types of secondary organic aerosols (SOAs) are formed, suggesting the strong influence of interfacial photochemistry has on the earth atmosphere.

Development of nanotwins in electroplated copper and its effect on shear strength of tin/copper joint

Cost-effective copper (Cu) electroplating is the primary technique used to fabricate wires/interconnects in microelectronics. Grain microstructure and impurity incorporation in electroplated Cu plays an important role in its mechanical, electrical, and thermal properties. In this study, a specific plating formula with a basic electrolyte and a suppressor, polyethylene glycol (PEG) and chloride ion (Cl−), is used to fabricate the Cu layers. An adjustment of plating current density dramatically alters the grain microstructure and impurity incorporation in the electroplated Cu. Scanning electron microscopy (SEM) and coincidence site lattice (CSL) analyses show that the Cu deposit plated at a low current density (<0.43 A/dm2) exhibits a lamellar nanotwinning structure with a large fraction of Σ3 (60° rotation at 〈111〉) twin boundary. Time-of-flight secondary ion mass spectrometer (TOF-SIMS) analysis shows that the impurity incorporation level in electroplated Cu is significantly reduced with the formation of twinning structure. The Sn/Cu joint benefits greatly from the formation of nanotwins in the electroplated Cu layer due to effective suppression of interfacial voids, which exhibits an improved shear strength as compared with that without the formation of nanotwins.

Corrosion behavior analyses of metallic membranes in hydrogen iodide environment for iodine-sulfur thermochemical cycle of hydrogen production

HI decomposition in Iodine-Sulfur (IS) thermochemical process for hydrogen production is one of the critical steps, which suffers from low equilibrium conversion as well as highly corrosive environment. Corrosion-resistant metal membrane reactor is proposed to be a process intensification tool, which can enable efficient HI decomposition by enhancing the equilibrium conversion value. Here we report corrosion resistance studies on tantalum, niobium and palladium membranes, along with their comparative evaluation. Thin layer each of tantalum, palladium and niobium was coated on tubular alumina support of length 250 mm and 10 mm OD using DC sputter deposition technique. Small pieces of the coated tubes were subject to immersion coupon tests in HI-water environment (57 wt% HI in water) at a temperature of 125–130 °C under reflux environment, and simulated HI decomposition environment at 450 °C. The unexposed and exposed cut pieces were analyzed using scanning electron microscope (SEM), energy dispersive X-ray (EDX) and secondary ion mass spectrometer (SIMS). The extent of leaching of metal into liquid HI was quantified using inductively coupled plasma-mass spectrometer (ICP-MS). Findings confirmed that tantalum is the most resistant membrane material in HI environment (liquid and gas) followed by niobium and palladium.

Searching for the Great Oxidation Event in North America: A Reappraisal of the Huronian Supergroup by SIMS Sulfur Four-Isotope Analysis.

Sedimentological observations from the Paleoproterozoic Huronian Supergroup are suggested to mark the rise in atmospheric oxygen at that time, which is commonly known as the Great Oxidation Event (GOE) and typically coupled with a transition from mass-independent fractionation (MIF) to mass-dependent fractionation (MDF) of sulfur isotopes. An early in situ study of S three-isotopes across the Huronian Supergroup by Papineau et al. ( 2007 ) identified a weak MIF-MDF transition. However, the interpretation and stratigraphic placement of this transition is ambiguous. In this study, all four S isotopes were analyzed for the first time in two Huronian drill cores by secondary ion mass spectrometer (SIMS), and both Δ33S and Δ36S were calculated. Based on improved precision and detailed petrography, we reinterpret the dominance of pyrrhotite in the studied sections, which was previously proposed as "early authigenic" in origin, as resulting from regional metamorphism. Small but analytically resolvable nonzero values of Δ33S (from -0.07‰ to +0.38‰) and Δ36S (from -4.1‰ to +1.0‰) persist throughout the lower Huronian Supergroup. Neither pronounced MIF-S signals nor a MIF-MDF transition are seen in this study. Four scenarios are proposed for the genesis of small nonzero Δ33S and Δ36S values in the Huronian: homogenization by regional metamorphism, recycling from older pyrite, dilution by magmatic fluids, and the occurrence of MDF. We argue that the precise location of the MIF-MDF transition in the Huronian remains unsolved. This putative transition may have been erased by postdepositional processes in the lower Huronian Supergroup, or may be located in the upper Huronian Supergroup. Our study highlights the importance of integrated scanning electron microscopy and secondary ion mass spectrometry techniques in deep-time studies and suggests that different analytical methods (bulk vs. SIMS) and diagenetic history (primary vs. metamorphic) among different basins may have caused inconsistent interpretations of S isotope profiles of the GOE successions at a global scale. Key Words: Great Oxidation Event (GOE)-Secondary ion mass spectrometer (SIMS)-Paleoproterozoic-Sulfur isotopes-Mass independent fractionation (MIF). Astrobiology 18, 519-538.

Productivity Contribution of Paleozoic Woodlands to the Formation of Shale‐Hosted Massive Sulfide Deposits in the Iberian Pyrite Belt (Tharsis, Spain)

AbstractThe geological materials produced during catastrophic and destructive events are an essential source of paleobiological knowledge. The paleobiological information recorded by such events can be rich in information on the size, diversity, and structure of paleocommunities. In this regard, the geobiological study of late Devonian organic matter sampled in Tharsis (Iberian Pyrite Belt) provided some new insights into a Paleozoic woodland community, which was recorded as massive sulfides and black shale deposits affected by a catastrophic event. Sample analysis using TOF‐SIMS (Time of Flight Secondary Ion Mass Spectrometer), and complemented by GC/MS (Gas Chromatrograph/Mass Spectrometer) identified organic compounds showing a very distinct distribution in the rock. While phytochemical compounds occur homogeneously in the sample matrix that is composed of black shale, the microbial‐derived organics are more abundant in the sulfide nodules. The cooccurrence of sulfur bacteria compounds and the overwhelming presence of phytochemicals provide support for the hypothesis that the formation of the massive sulfides resulted from a high rate of vegetal debris production and its oxidation through sulfate reduction under suboxic to anoxic conditions. A continuous supply of iron from hydrothermal activity coupled with microbial activity was strictly necessary to produce this massive orebody. A rough estimate of the woodland biomass was made possible by accounting for the microbial sulfur production activity recorded in the metallic sulfide. As a result, the biomass size of the late Devonian woodland community was comparable to modern woodlands like the Amazon or Congo rainforests.

High spatial resolution and high brightness ion beam probe for in-situ elemental and isotopic analysis

A high spatial resolution and high brightness ion beam from a cold cathode duoplasmatron source and primary ion optics are presented and applied to in-situ analysis of micro-scale geological material with complex structural and chemical features. The magnetic field in the source as well as the influence of relative permeability of magnetic materials on source performance was simulated using COMSOL to confirm the magnetic field strength of the source. Based on SIMION simulation, a high brightness and high spatial resolution negative ion optical system has been developed to achieve Critical (Gaussian) illumination mode. The ion source and primary column are installed on a new Time-of-Flight secondary ion mass spectrometer for analysis of geological samples. The diameter of the ion beam was measured by the knife-edge method and a scanning electron microscope (SEM). Results show that an O2- beam of ca. 5 µm diameter with a beam intensity of ∼5 nA and an O- beam of ca. 5 µm diameter with a beam intensity of ∼50 nA were obtained, respectively. This design will open new possibilities for in-situ elemental and isotopic analysis in geological studies.

Significance of variables for discrimination: Applied to the search of organic ions in mass spectra measured on cometary particles

AbstractThe instrument Cometary Secondary Ion Mass Analyzer (COSIMA) on board of the European Space Agency mission Rosetta to the comet 67P/Churyumov‐Gerasimenko is a secondary ion mass spectrometer with a time‐of‐flight mass analyzer. It collected near the comet several thousand particles, imaged them, and analyzed the elemental and chemical compositions of their surfaces. In this study, variables have been generated from the spectral data covering the mass ranges of potential C‐, H‐, N‐, and O‐containing ions. The variable importance in binary discriminations between spectra measured on cometary particles and those measured on the target background has been estimated by the univariate t test and the multivariate methods discriminant partial least squares, random forest, and a robust method based on the log ratios of all variable pairs. The results confirm the presence of organic substances in cometary matter—probably a complex macromolecular mixture.

Integration of paper-based microarray and time-of-flight secondary ion mass spectrometry (ToF-SIMS) for parallel detection and quantification of molecules in multiple samples automatically

With its low-cost fabrication and ease of modification, paper-based analytical devices have developed rapidly in recent years. Microarrays allow automatic analysis of multiple samples or multiple reactions with minimal sample consumption. While cellulose paper is generally used, its high backgrounds in spectrometry outside of the visible range has limited its application to be mostly colorimetric analysis. In this work, glass-microfiber paper is used as the substrate for a microarray. The glass-microfiber is essentially chemically inert SiOx, and the lower background from this inorganic microfiber can avoid interference from organic analytes in various spectrometers. However, generally used wax printing fails to wet glass microfibers to form hydrophobic barriers. Therefore, to prepare the hydrophobic-hydrophilic pattern, the glass-microfiber paper was first modified with an octadecyltrichlorosilane (OTS) self-assembled monolayer (SAM) to make the paper hydrophobic. A hydrophilic microarray was then prepared using a CO2 laser scriber that selectively removed the OTS layer with a designed pattern. One microliter of aqueous drops of peptides at various concentrations were then dispensed inside the round patterns where OTS SAM was removed while the surrounding area with OTS layer served as a barrier to separate each drop. The resulting specimen of multiple spots was automatically analyzed with a time-of-flight secondary ion mass spectrometer (ToF-SIMS), and all of the secondary ions were collected. Among the various cluster ions that have developed over the past decade, pulsed C60+ was selected as the primary ion because of its high secondary ion intensity in the high mass region, its minimal alteration of the surface when operating within the static-limit and spatial resolution at the ∼μm level. In the resulting spectra, parent ions of various peptides (in the forms [M+H]+ and [M+Na]+) were readily identified for parallel detection of molecules in a mixture. By normalizing the ion intensity of peptides with respect to the glass-microfiber matrix ([SiOH]+), a linear calibration curve for each peptide was generated to quantify these components in a mixture.

Mg lattice diffusion in iron-free olivine and implications to conductivity anomaly in the oceanic asthenosphere

Mg lattice diffusion coefficients in iron-free olivine aggregates were measured as a function of pressure from 1 to 13 GPa, temperature from 1100 to 1300 K, and bulk water content from less than 1 up to 350 wt. ppm using multi-anvil apparatus and secondary ion mass spectrometer in depth profiling mode. The water contents in the samples were analyzed by Fourier transmission infrared spectrometer. The results show that Mg lattice diffusion coefficient increase with increasing temperature and water content, and decrease with pressure. The activation energy, water content exponent, and activation volume are 250 ± 30 kJ/mol, 1.2 ± 0.2, and 4.3 ± 0.3 cm3/mol, respectively. Since Mg lattice diffusion controls the ionic conduction in olivine based on the Nernst–Einstein relation, the ionic conductivity in the upper mantle appears as a maximum at the top of oceanic asthenosphere due to the negative correction for pressure and positive correction for water content, which well explains the high conductivity anomaly observed at ∼70–120 km depth beneath young oceanic plates.

The Hyperion-II radio-frequency oxygen ion source on the UCLA ims1290 ion microprobe: Beam characterization and applications in geochemistry and cosmochemistry

A radio-frequency plasma ion source, the Hyperion-II, has been commissioned on a CAMECA ims1290, a high resolution/high transmission secondary ion mass spectrometer at UCLA. Performance characteristics (e.g., beam density, spot size, etc.) of the primary oxygen beam are documented and application to isotopic analyses requiring high lateral resolution with high secondary ion transmission are described. The Hyperion source delivers on average 10 times and 6 times the current density delivered by the CAMECA duoplasmatron for 16O− and 16O2− beams, respectively. This significantly enhanced current density allows for reduction of the analytical spot size by at least a factor of three while maintaining the beam intensity, making it possible to perform isotopic measurements at smaller scales without sacrificing analytical precision. In addition, the smaller Hyperion beam spot size also reduces the crossover size and spherical aberrations in the secondary ion optics, thereby improving secondary ion transmission at mass resolving power of 3000–12,000 by 25–80% compared to that achieved with a duoplasmatron.

Data Retention Characterization of Gate-Injected Gold-Nanoparticle Non-Volatile Memory with Low-Damage CF₄-Plasma-Treated Blocking Oxide Layer.

Gold-nanoparticle (Au-NP) non-volatile memories (NVMs) with low-damage CF4 plasma treatment on the blocking oxide (BO) layer have been investigated to present the gate injection of the holes. These holes, injected from the Al gate with the positive gate bias, were explained by the bandgap engineering of the gradually-fluorinated BO layer and the effective work function modulation of the Al gate. The Si–F complex in the BO layer was analyzed by X-ray photoelectron spectroscopy (XPS), while the depth of fluorine incorporation was verified using a secondary ion mass spectrometer (SIMS). In addition, the valence band modification of the fluorinated BO layer was examined by ultraviolet photoelectron spectroscopy (UPS) to support the bandgap engineering. The reactive power of the CF4 plasma treatment on the BO layer was modified to increase the electric field of the BO layer and raise the effective work function of the Al gate, leading to the hole-injection from the gate. The injected holes are trapped at the interface between the gold-nanoparticles (Au-NPs) and the tunneling oxide (TO) layer, resulting in superior data retention properties such as an extremely low charge loss of 5.7% at 104 s and a nearly negligible increase in charge loss at 85 °C of the CF4-plasma-treated Au-NP NVMs, which can be applied in highly reliable consumer electronics.

Ages and petrogenesis of Jurassic and Cretaceous intrusive rocks in the Matsu Islands: Implications for lower crust modification beneath southeastern China

Major and trace element, whole-rock Sr-, Nd- and Hf-isotope, zircon U-Pb age and Hf-O isotope data are reported for the intrusive rocks from the Matsu Islands in the coastal area of southeastern (SE) China, in order to study the ages, sources and petrogenesis of these rocks and evolution of the lower crust. The rocks include gneissic granite, massive granite, brecciated granite and diabase. Secondary ion mass spectrometer (SIMS) zircon U-Pb dating reveals that the rocks in the Matsu Islands were emplaced at ∼160 Ma, ∼130 Ma and ∼94 Ma. The Jurassic granites (∼160 Ma) have high SiO2 (74.1–74.5 wt%) and K2O+Na2O (8.32–8.33 wt%) contents and high Rb/Sr ratios of 0.6–1.2 and (La/Yb)CN ratios of 12.6–19.4. Their relatively high initial 87Sr/86Sr ratios (0.7074–0.7101), variable and negative εNd(t) values (−9.2 to −5.4), and variable zircon εHf(t) (−17.0 to +5.2) and δ18O (4.7–8.1‰) values indicate they were mainly derived from an ancient lower crustal source, but with involvement of high εHf(t) and low δ18O materials. The Early Cretaceous diabase (∼130 Ma) has SiO2 content of 56.5 wt%, relatively high MgO concentration, low initial 87Sr/86Sr ratio and negative εNd(t) value, similar to geochemical features of other Cretaceous mafic rocks in the coastal area of SE China. Zircons from the diabase have high εHf(t) values (−5.5 to +0.2) and relatively low δ18O values of 4.2–5.0‰. These characteristics indicate that the parental magma of the diabase was generated by partial melting of enriched lithospheric mantle, which have been metasomatised by altered oceanic crust-derived low-δ18O fluids. For the Cretaceous granitoids (∼130 Ma and 94 Ma), they have relatively low SiO2 (68.0–71.3 wt%) and K2O+Na2O (5.30–7.55 wt%) contents and low Rb/Sr ratios and (La/Yb)CN ratios of 5.8–7.1. They have low initial 87Sr/86Sr ratios (0.7071–0.7082), homogeneous εNd(t) (−4.3 to −4.5) and relatively high zircon εHf(t) values (−3.7 to +1.2) and low δ18O values (4.6–5.9‰). Their isotopic compositions are similar to those of the diabases in this study as well as other Cretaceous mafic rocks in the coastal area of SE China, suggesting that the sources of the Cretaceous granitoids might be the newly formed lower crust related to the underplated mafic rocks. Whole-rock geochemical, Sr-Nd and zircon Hf-O isotopic compositions indicate that the Jurassic granitoids are most likely generated by partial melting of relatively ancient basement rocks, whereas the Cretaceous granitoids were generated by partial melting of relatively young lower crustal rocks with addition of mantle-derived magma. This distinction implies that the pre-existing ancient lower crust beneath the coastal area of SE China has been modified by large-scale mafic magma underplating. Therefore, underplating of mantle-derived mafic magma would result in modification of the pre-existing ancient lower crust and formation of the relatively juvenile lower crust.

U-Pb geochronology of Martín García, Sola, and Dos Hermanas Islands (Argentina and Uruguay): Unveiling Rhyacian, Statherian, Ectasian, and Stenian of a forgotten area of the Río de la Plata Craton

The Río de la Plata Craton is one of the three major cratons of South America. The craton is largely covered by sedimentary basins where its most exposed area is Buenos Aires-Piedra Alta Province (Chernicoff et al., 2014). This province includes the Martín García Island in the confluence of Uruguay River and the Río de la Plata estuary. Despite to be a reference area for the craton the Martín García Island lacks modern geological investigation. We present U-Pb SIMS (secondary ion mass spectrometer) geochronological data on zircon and titanite, as well as Hf isotope determinations on zircon, from rocks of Martín García Island (Argentina), Sola and Dos Hermanas Islands (Uruguay) and from Paso Severino Formation (Uruguay). We investigated: 1) Rhyacian intermediate-to acidic plutonic, arc-type rocks of the Florida Belt dated between 2090 Ma and 2115 Ma, derived from juvenile Neoarchean crust (TDMHf: 2.52 Ga; average εHf: +3.62); 2) Rhyacian metadacite (San José metamorphic belt) of 2127 Ma; 3) Statherian metagabbros of 1724–1734 Ma, with Transplatense inheritance; 4) Early Ectasian metagabbro of 1392 Ma, with Rhyacian inheritance; and 5) Stenian metagabbros of 1193 Ma (TDMHf: 2.00 Ga, εHf: 0.1). Most of the dated orthogneisses show Brasilian-age (from 778 to 550 Ma) Pb loss in the zircons, interpreted to be caused by shearing or uplifting during Neoproterozoic. The results show that the area is not exclusively Rhyacian in age but encompasses Statherian, Ectasian, and Stenian gabbros. The last two are interpreted as distal intrusions associated to the Sunsás Orogen. All post-Transplatense metagabbros have geochemical signature of island arc basalt derived from primitive mantle with enrichment of LILE and depletion of HFSE. These characteristics point to the recurrence of magma chambers intermittently active during the Rhyacian, Statherian, Ectasian, and Stenian, all with a similar source. The term “Transplatense” is used to replace “Trans-Amazonian” events that occurred within the craton.

Lithium isotope fractionation by diffusion in minerals Part 2: Olivine

Recent experiments have shown that lithium isotopes can be significantly fractionated by diffusion in silicate liquids and in augite. Here we report new laboratory experiments that document similarly large lithium isotopic fractionation by diffusion in olivine. Two types of experiments were used. A powder-source method where lithium from finely ground spodumene (LiAlSi2O6) diffused into oriented San Carlos olivine, and piston cylinder annealing experiments where Kunlun clinopyroxene (∼30ppm lithium) and oriented San Carlos olivine (∼2ppm lithium) were juxtaposed. The lithium concentration along traverses across the run products was measured using both laser ablation asa source for a Varian 820-MS quadrupole mass spectrometer and a CAMECA 1270 secondary ion mass spectrometer. The CAMECA 1270 was also used to measure the lithium isotopic fractionation across olivine grains recovered from the experiments. The lithium isotopes were found to be fractionationed by many tens of permil in the diffusion boundary layer at the grain edges asa result of 6Li diffusing significantly faster than 7Li. The lithium concentration and isotopic fractionation data across the olivine recovered from the different experiments were modeled using calculations in which lithium was assumed to be of two distinct types – one being fast diffusing interstitial lithium, the other much less mobile lithium on a metal site. The two-site diffusion model involves a large number of independent parameters and we found that different choices of the parameters can produce very comparable fits to the lithium concentration profiles and associated isotopic fractionation. Because of this nonuniqueness we are able to determine only a range for the relative diffusivity of 6Li compared to 7Li. When the mass dependence of lithium diffusion is parameterized as D6Li/D7Li=(7/6)β, the isotope fractionation for diffusion along the a and c crystallographic direction of olivine can be fit by β=0.4±0.1 while the fractionation in the b direction appears to be somewhat lower. Model calculations were also used to fit the lithium concentration and isotopic fractionation across a natural olivine grain from a peridotite xenolith from the Eastern North China Craton. The isotopic data were fit using β values (0.3–0.36) similar to that of the laboratory experiments. This, along with the fact that the isotopic fractionation is restricted to that part of the mineral with a gradient in lithium concentration, is strong evidence that the lithium zoning of this mineral grain is the result of lithium loss by diffusion and thus that it can be used, as illustrated, to constrain the cooling history.

Intermineral oxygen three-isotope systematics of silicate minerals in equilibrated ordinary chondrites.

High precision oxygen three-isotope ratios were measured for four mineral phases (olivine, low-Ca and high-Ca pyroxene, and plagioclase) in equilibrated ordinary chondrites (EOC) using a secondary ion mass spectrometer. Eleven EOCs were studied that cover all groups (H, L, LL) and petrologic types (4, 5, 6), including S1-S4 shock stages, as well as unbrecciated and brecciated meteorites. SIMS analyses of multiple minerals were made in close proximity (mostly <100 μm) from several areas in each meteorite thin section, to evaluate isotope exchange among minerals. Oxygen isotope ratios in each mineral become more homogenized as petrologic type increases with the notable exception of brecciated samples. In type 4 chondrites, oxygen isotope ratios of olivine and low-Ca pyroxene are heterogeneous in both δ18O and Δ17O, showing similar systematics to those in type 3 chondrites. In types 5 and 6 chondrites, oxygen isotope ratios of the four mineral phases plot along mass dependent fractionation lines that are consistent with the bulk average Δ17O of each chondrite group. The δ18O of three minerals, low-Ca and high-Ca pyroxene and plagioclase, are consistent with equilibrium fractionation at temperatures of 700-1000°C. In most cases the δ18O values of olivine are higher than those expected from pyroxene and plagioclase, suggesting partial retention of premetamorphic values due to slower oxygen isotope diffusion in olivine than pyroxene during thermal metamorphism in ordinary chondrite parent bodies.

Dual Beam Depth Profiling and Imaging with Argon and Bismuth Clusters of Prenylated Stilbenes on Glandular Trichomes of Macaranga vedeliana.

Using a time-of-flight secondary ion mass spectrometer equipped with an argon cluster ion for sputtering and a bismuth liquid metal ion source for analysis, both surfaces of leaves and fruits of Macaranga vedeliana, an endemic New Caledonian species, have been for the first time analyzed by a dual beam depth profiling. To prevent in-vacuum evaporation of the liquid content of the small glandular trichomes covering fruits and leaves surfaces and also to be able to analyze their liquid content while preventing any sublimation of the latter, the samples were kept frozen during the whole experiment using a nitrogen cooled sample holder. Thus, it was possible to demonstrate that vedelianin, an active metabolite of the family of prenylated stilbenes named schweinfurthins, is only located in these glandular trichomes.

Damage threshold influenced by polishing imperfection distribution under 355-nm laser irradiation

A systematic interpretation of laser-induced damage in the nanosecond regime is realized with a defect distribution buried inside the redeposited layer arising from a polishing process. Under the 355-nm laser irradiation, the size dependence of the defect embedded in the fused silica can be illustrated through the thermal conduction model. Considering CeO2 as the major initiator, the size distribution with the power law model is determined from the damage probability statistics. To verify the accuracy of the size distribution, the ion output scaling with depth for the inclusion element is obtained with the secondary ion mass spectrometer. For CeO2 particulates in size of the depth interval with ion output satisfied in the negative exponential form, the corresponding density is consistent with that of the identical size in the calculated size distribution. This coincidence implies an alternative method for the density analysis of photoactive imperfections within optical components at the semi-quantitative level based on the laser damage tests.

Evidence of local sourcing of sulfur and gold in an Archaean sediment-hosted gold deposit

Determining the source of sulfur in an ore deposit is key to understanding the nature of the ore forming processes. The Neoarchaean Paulsens sediment-hosted gold deposit (∼1Moz @ 7.6g/t) located in the Pilbara Craton of Western Australia exhibits many of the characteristics of Phanerozoic shale hosted gold deposits (e.g. Huijiabao Trend, Northern Carlin Trend and Sukhoi Log), in that 1) black shales are the dominant host rock, 2) gold is hosted in pyrite as both free gold and dissolved gold in the lattice of the pyrite, and 3) multiple generations of pyrite have formed due to a variety of geological processes. In this contribution we utilised Secondary Ion Mass Spectrometer (SIMS) to measure the in-situ quadrupole (32S, 33S, 34S and 36S) sulfur isotope compositions of the different generations of pyrite. Our results indicate that the both diagenetic and hydrothermal pyrite generations display similar and anomalous Δ33S signatures (up to +0.4‰). Further, the Δ33S-Δ36S arrays in the hydrothermal pyrite generations lie on a slope which is similar to that of the diagenetic pyrite. These data support the hypothesis that the sulfur in the ore zones came from the host Hardey Formation black shales.We also performed trace element analyses of syn-sedimentary and early diagenetic pyrite from the Hardey Formaiton using Nano Secondary Ion Mass Spectrometry (NanoSIMS), Electron Probe Microanalysis (EPMA) and Laser Ablation-inductively coupled plasma-mass spectrometry (LA-ICPMS), all of which show that the syn-sedimentary and early diagenetic pyrite contain high concentrations of many trace elements (As, Ni, Co, Cu, Ag, Se, Te, Bi), including up to 1.5ppm Au. These metals contents are also abundant in the several generations of mineralised hydrothermal pyrite and form clear patterns of growth associated with couple dissolution reprecipitation reactions. These findings clearly indicate that the fluid that transported the Au must have also been enriched in the base and precious metals that are contained in the early, syn-diagenesis pyrite.Data from this study clearly support the hypothesis that in some sediment-hosted gold systems, all the sulfur and gold required to form the deposit are sourced from the local sedimentary package. By using the presence of anomalous mass independent sulfur isotope signatures as chemically conservative and indelible tracers, it is possible to fingerprint the source of sulfur in a wide range of mineral systems, thus enhancing predictive exploration strategies at the regional to camp scales.

Typical oxygen isotope profile of altered oceanic crust recorded in continental intraplate basalts

Recycled oceanic crust (ROC) has long been suggested to be a candidate introducing enriched geochemical signatures into the mantle source of intraplate basalts. The different parts of oceanic crust are characterized by variable oxygen isotope compositions (δ18O=3.7‰ to 13.6‰). To trace the signatures of ROC in the mantle source of intraplate basalts, we measured the δ18O values of clinopyroxene (cpx) phenocrysts in the Cenozoic basalts from the Shuangliao volcanic field, NE China using secondary ion mass spectrometer (SIMS). The δ18O values of the Shuangliao cpx phenocrysts in four basalts ranging from 4.10‰ to 6.73‰ (with average values 5.93‰±0.36‰, 5.95‰±0.30‰, 5.58‰±0.66‰, and 4.55‰± 0.38‰, respectively) apparently exceed those of normal mantle-derived cpx (5.6‰±0.2‰) and fall in the typical oxygen isotope range of altered oceanic crust. The δ18O values display the negative correlations with the Eu, Sr anomalies of whole rocks and erupted ages, demonstrating that (1) the ROC is the main enriched component in the mantle source of the Shuangliao basalts and (2) the contributions of ROC varied with time. The basalt with the lowest δ18O value is characterized by a significant K positive anomaly, highest H2O/Ce and Ba/Th ratios, suggesting that the mantle source of basalts with low δ18O can also include a water-rich sediment component that may be the trigger for partial melting. Considering the continuous subduction of the Pacific slab, the temporal heterogeneity of the source components is likely to be caused by the Pacific slab subduction.

Catalysis and chemical mechanisms of calcite dissolution in seawater

Near-equilibrium calcite dissolution in seawater contributes significantly to the regulation of atmospheric [Formula: see text] on 1,000-y timescales. Despite many studies on far-from-equilibrium dissolution, little is known about the detailed mechanisms responsible for calcite dissolution in seawater. In this paper, we dissolve 13C-labeled calcites in natural seawater. We show that the time-evolving enrichment of [Formula: see text] in solution is a direct measure of both dissolution and precipitation reactions across a large range of saturation states. Secondary Ion Mass Spectrometer profiles into the 13C-labeled solids confirm the presence of precipitated material even in undersaturated conditions. The close balance of precipitation and dissolution near equilibrium can alter the chemical composition of calcite deeper than one monolayer into the crystal. This balance of dissolution-precipitation shifts significantly toward a dissolution-dominated mechanism below about [Formula: see text] Finally, we show that the enzyme carbonic anhydrase (CA) increases the dissolution rate across all saturation states, and the effect is most pronounced close to equilibrium. This finding suggests that the rate of hydration of [Formula: see text] is a rate-limiting step for calcite dissolution in seawater. We then interpret our dissolution data in a framework that incorporates both solution chemistry and geometric constraints on the calcite solid. Near equilibrium, this framework demonstrates a lowered free energy barrier at the solid-solution interface in the presence of CA. This framework also indicates a significant change in dissolution mechanism at [Formula: see text], which we interpret as the onset of homogeneous etch pit nucleation.