Os Concentrations Research Articles

OH Radical Oxidation of Organosulfates in the Atmospheric Aqueous Phase.

Organosulfates (OS, ROSO3-), ubiquitous constituents of atmospheric particulate matter (PM), influence both the physicochemical and climatic properties of PM. Although the formation pathways of OS have been extensively researched, only a few studies have investigated the atmospheric fate of this class of compounds. Here, to better understand the reactivity and transformation of OS under cloudwater- and aerosol-relevant conditions, we investigate the hydroxyl radical (OH) oxidation bimolecular rate constants (kOS+OHII) and products of five atmospherically relevant OS as a function of pH and ionic strength: methyl sulfate (MeS), ethyl sulfate (EtS), propyl sulfate (PrS), hydroxyacetone sulfate (HaS) and phenyl sulfate (PhS). Our results show that OS are oxidized by OH with kOS+OHII between 108 - 109 M-1 s-1, which corresponds to atmospheric lifetimes of minutes in aqueous aerosol to days in cloudwater. We find that kOS+OHII increases with carbon chain length (MeS < EtS < PrS) and aromaticity (PrS < PhS), but does not depend on solution pH (2, 9). In addition, we find that whereas the OH reactivity of the aliphatic OS studied here decreases by ∼2× with increasing ionic strength (0-15 M), the reactivity of PhS decreases by ∼10×. The oxidation of EtS and PrS produced organic peroxides (ROOH) as first-generation oxidation products, which subsequently photolyzed; the oxidation of PhS resulted in hydroxylated aromatic products. These results highlight the need for inclusion of OS loss pathways in atmospheric models, and suggest caution in using ambient OS concentration measurements alone to estimate their production rates.

Rhenium–Os isotopic systematics of late Cenozoic intraplate basaltic rocks from Korea: Implications for recycled slab materials in their mantle source

We present, for the first time, comprehensive Re-Os isotopic data for 23 late Cenozoic intraplate basaltic rocks from seven locations (Mount Baekdu, Jeongok, Baengnyeong Island, Ganseong, Ullueng Island, Dok Island, and Jeju Island) on the Korean Peninsula. The Re-Os isotopic system serves as an important tracer of processes such as the reworking of old continental lithosphere or the deep crustal recycling. We use these data to investigate the role of the lithospheric mantle, which is currently debated as a source of the basaltic rocks, and to constrain the source lithology. The initial 187Os/188Os ratios of the Korean basalts range from 0.1321 to 0.6455, with γOs values of 4.0–408.3. The γOs values do not show a simple correlation with Sr-Nd-Hf-Pb isotope compositions. There are no significant correlations between MgO contents and 187Os/188Os ratios or Os contents and 187Os/188Os ratios, which demonstrate that crustal assimilation did not produce the supra-chondritic Os isotopic compositions. The γOs values of the Korean basalts are much higher than previously published γOs of spinel peridotite xenoliths (−9.1 to +1.2) hosted in the basalts, indicating the subcontinental lithospheric mantle was not the main source of the basaltic magmatism. The combination of the Os and Sr-Nd-Hf-Pb isotopic compositions suggests that recycled oceanic crust (potentially Pacific oceanic lithosphere), along with pelagic sediments, which possibly reside in the mantle transition zone, is the enriched component with the supra-chondritic Os isotopic composition in the mantle source of the Korean basalts.

Evidence for large-scale, long-term highly siderophile element heterogeneities in the Atlantic mantle from Leg 153 and 209 peridotites

Seafloor abyssal peridotites are products after partial melting and melt-rock interaction, providing constraints on upper mantle processes and heterogeneity. Despite extensive studies of ophiolitic peridotites and a burgeoning dataset for dredged abyssal peridotites, limited studies have been undertaken on abyssal peridotite drill core samples. This omission means a lack of comparison between modern ocean mantle lithosphere and that of ophiolites, where field context is possible in the latter, but not the former. Ocean Drilling Program (ODP) Leg 153 near the Kane fracture zone, and ODP Leg 209, near the Fifteen-Twenty fracture zone, both on the mid-Atlantic Ridge but ∼1000 km distant from one another, recovered serpentinized mantle peridotites. We report whole-rock major-, trace- and highly siderophile-element (HSE: Re, Pd, Pt, Ru, Ir, Os) abundances and 187Os/188Os ratios of peridotites from three cores (maximum depth of 200.8 m) from the two Legs to explore mantle heterogeneity within the Atlantic Ocean basin. Peridotites from ODP Leg 153 are relatively fertile, with Al2O3 contents ranging from 1.1 to 2.7 wt%. They are characterized by relatively radiogenic 187Os/188Os (0.1259 ± 0.0017; 2 S.D.) and uniform HSE abundances. The ODP Leg 209 peridotites are highly refractory, with Al2O3 contents ranging from 0.1 to 0.8 wt%, and imply that they record an extensively depleted mantle. They have 187Os/188Os of 0.1207 ± 0.0023 (2 S.D.) and fractionated HSE abundances, indicative of depletion occurring > 1 billion years ago. Marked heterogeneity both in the extent and timing of depletion are therefore evident along a large segment of the mid-Atlantic ridge that produces zero-age basalts. Measurement of Os isotopes in spatially associated mid-ocean ridge basalts (MORB) is challenging due to their sub ng/g Os contents. Instead, Nd isotopes of MORB are used to show that they are unlikely to have formed directly from abyssal peridotite-like sources. Abyssal peridotites therefore represent long-lived refractory residues during mantle upwelling with the sources of MORB being more enriched. Comparison between drilled abyssal peridotites and ophiolitic mantle reveals larger compositional variations in the latter. The overall higher melting extent in ophiolite mantle is likely reflective of a more complex life cycle than the modern oceanic lithosphere.

Colorimetric probe for the determination of osmium through a novel optical sensor in environmental samples

A novel optical probe has been successfully developed for the selective detection of Os(VIII) ions. This osmium-sensing platform was intricately designed by incorporating 4-(thiazol-2-yldiazenyl)benzene-1,3-diol (TDBD) as the ionophore within a plasticized PVC membrane, and tributylphosphate (TBP) serving as the plasticizer. Upon exposure to Os(VIII) ions in a 0.5 M HClO4 acid milieu, the sensing membrane undergoes a distinctive chromatic transition, shifting from a yellow to a pink hue. The preparation of the sensor and the methodology for Os(VIII) determination were meticulously refined to achieve optimal performance. Under these carefully optimized experimental conditions, the proposed optode demonstrated an impressive linear detection range spanning from 2.5 × 10−9 to 2.5 × 10−5 M for Os(VIII), alongside remarkable detection and quantification limits of 7.24 × 10−10 and 2.4 × 10−9 M, respectively. The sensor consistently delivered highly reproducible results, as evidenced by relative standard deviation (RSD) values of 1.45% and 1.30% for Os(VIII) concentrations at 7.5 × 10−7 and 2.5 × 10−6 M, respectively, underscoring its precision and reliability. Furthermore, the sensor exhibited a swift response time of 3.0 min, further emphasizing its efficiency. The incorporation of PIMs into the sensor architecture led to a remarkable eight-fold enhancement in its response compared to counterparts lacking PIMs, signifying a significant performance improvement. In assessing potential interference, an investigation into the influence of other ions on Os(III) determination revealed that the prepared sensor displayed exceptional selectivity for Os(VIII) ions, with negligible responses observed in the presence of common ions. Collectively, these experimental findings underscore the sensor's efficacy as an invaluable tool for the precise analysis of osmium content in water samples, aligning it with the rigorous standards of international scientific research.

An Extraterrestrial Pt Anomaly during the Late Glacial-Younger Dryas: Viso Massif (Italy and France)

Paleosol evidence supporting the Younger Dryas Impact Hypothesis (YDIH) on the Viso Massif of France and Italy is expanded by a Pt anomaly at all sites investigated, accompanied by elevated Os, Ir, Ru, and Rh concentrations at several sites, thus affirming a cosmic driver to the YD climatic shift at 12.8 ka. Original, thin Allerød soils prevalent at the end of the Late Glacial comprise sediments affected by an airburst from a hypothesized secondary daughter fragment or fragments of the main 2P/Encke progenitor comet train that intersected Earth’s land surface and its alpine-continental ice sheets. This event has been previously postulated to have breached Lake Agassiz and other proglacial lakes in North America, released meltwater into the Atlantic Ocean through the St. Lawrence and into the Arctic through the Mackenzie River system, after which cold surface water shut down the thermohaline circulation of the Gulf Stream in the North Atlantic. This thermohaline event is the traditional explanation for YD cooling, but was it fast enough to match the pollen evidence, which confirms rapid temperature reversal? Or was an “impact winter” involved? Cosmic signatures reported here include elevated Pt/Pd ratios, Os, Ir, Ru, and Rh concentrations with orders of magnitude (OM) for Ir used to establish the main center of conflagrations that helped trigger an impact winter. While most sections show variable distributions of PGEs, some are fully affected by concentrations entirely through the unweathered substrate or parent material horizons (called “Cu” horizons). Peak distributions of platinum group elements (PGEs) provide new information on the dispersal patterns of grains that add the Western European Alps to the intercontinental array of sites containing the Younger Dryas boundary (YDB) layer, also sometimes called the black mat (BM). Previously, most age determinations for the Alps were derived from relative dating determinations (RD), but here, we report an AMS C14 date from one LG paleosol (G11-Bw) yielding an age of 12,816 ±44 cal yr BP age, coeval with the average 12.8 ka age of the BM.

The Luna structure, India: A probable impact crater formed by an iron bolide

The Luna structure of India has been rumored to be an impact crater for more than a decade without any convincing evidence. This structure (1.5–1.8 km) is prominently visible in the low-lying Banni Plains of the tectonically active Kutch Basin as a circular morphological feature with a less-prominent rim. Luna area is strewn with melt-like rocks having high specific gravity and displaying wide range of magnetic properties. It contains minerals like wüstite, kirschsteinite, ulvöspinel, hercynite, and fayalite. The whole rock analysis denotes PGE enrichment, with notably higher average concentrations of Ru (19.02 ppb), Rh (5.68 ppb), Pd (8.64 ppb), Os (6.03 ppb), Ir (10.63 ppb) and Pt (18.31 ppb). The target is not exposed at Luna, owing to the overlying thick sequence of Quaternary sediments. The mineralogical and geochemical signatures points to an impact into a target, which is rich in clay with elevated calcium and silica (sand/silt) content. Geochemical data suggests an iron or stony-iron meteorite as the potential projectile at Luna. The silt layer containing plant remnants, underlying the strewn layer, yielded a radiocarbon age of 6905 years, making Luna the biggest crater to result from an iron bolide within the last 10,000 years.

High-precision simultaneous measurement of 187Os, 186Os, and 184Os using 1013 Ω amplifiers and CDDs on NTIMS

High-precision measurements of 184Os/188Os, 186Os/188Os, and 187Os/188Os ratios are significant in the fields of geochemistry and cosmochemistry. However, no high-precision measurement technique exists for simultaneously obtaining all three ratios using a static method for samples with an Os content of <1 ng or 186OsO3‾ and 187OsO3‾ ion-beam intensities of <150 mV. This greatly limits research on rare samples with small sample sizes or low Os contents, such as Lunar, Martian, or old Earth samples. This paper reports a static method, which could achieve the simultaneous measurement of 9 Faraday cups (FCs) with high-signal/noise ratio 1012 Ω amplifiers and 1013 Ω amplifiers and two compact discrete dynodes (CDDs). By analyzing two calibration solutions, a precision value of less than 3‰ (2RSD) could be achieved for 184Os/188Os ratios, even if the 184OsO3‾ intensity was as low as 1000 cps. The precision values for the 186Os/188Os and 187Os/188Os ratios were similar and could be better than 0.066‰ (2RSD) when the intensities of 186OsO3‾ and 187OsO3‾ were greater than 30 mV, which can be obtained with conventional 1011 Ω amplifiers only at signals larger than 150 mV. Three geological reference materials were used in this study. The precision values of 184Os/188Os, 186Os/188Os, and 187Os/188Os ratios reached 2, 0.061, and 0.050‰ (2RSD), respectively, when the maximum Os amount was approximately 12 ng, and 87, 15, and 10‰ (2RSD), respectively, when the maximum Os amount was as low as approximately 66 pg. Additionally, our results show that changes in the volume of oxygen added during measurement can cause significant variations in the oxygen isotope composition. This static measurement method not only avoids the nonlinear signal change of the instrument during the analysis process but also realizes the accurate removal of the oxygen isobaric interference in the run, which could improve the precision of 184Os/188Os, 186Os/188Os, and 187Os/188Os ratios for small-size/low-signal samples.

Behavior of palladium during fractionation of sulfide liquid: New constraints from the Kalatongke Cu-Ni sulfide-bearing intrusion in the central Asian orogenic belt, NW China

The distribution of platinum-group elements (PGE; Os, Ir, Ru, Rh, Pt, and Pd) in base metal sulfides (BMS) of magmatic Ni-Cu-(PGE) sulfide deposits has been extensively studied. However, the origin of Pd in pentlandite and the role of Te, As, Bi, Sb, and Se (TABS) in collecting PGE during fractionation of sulfide liquid have not yet been well constrained. Representative massive sulfide ores of the Kalatongke Cu-Ni sulfide-bearing mafic intrusion in the central Asian orogenic belt (CAOB) were selected to identify platinum-group minerals (PGM) using a scanning electron microscope (SEM) and to investigate the distribution of PGE and TABS in the BMS using in situ laser-ablation inductively coupled-plasma mass spectrometry (LA-ICP-MS). The results show that concentrations of Os, Ir, Ru, Rh, and Pt in the BMS are all below or close to the detection limits and only pentlandite contains 0.1 to 3.6 ppm Pd. Three generations of pentlandite are recognized in the massive sulfide ores; i.e., coarse-grained, granular pentlandite that crystallized earlier from monosulfide solid solution (MSS) prior to crystallization of pyrrhotite, loop-textured pentlandite around pyrrhotite that crystallized after pyrrhotite, and pentlandite that crystallized from evolved Fe-rich MSS and is associated with fine-grained myrmekitic magnetite. Granular pentlandite contains higher Pd (1.4 to 3.6 ppm) than that of loop-textured pentlandite (0.8 to 1.7 ppm Pd) and pentlandite associated with myrmekitic magnetite (0.1 to 0.5 ppm Pd). Given that Pd is incompatible to MSS during fractionation of sulfide liquid and is preferentially concentrated to residual sulfide liquid, we propose that the distribution of Pd in pentlandite may be attributed to rapid diffusion of Pd from the residual sulfide liquid into MSS/pentlandite on cooling and that Pd concentrations in the three generations were likely controlled by their crystallization sequence from MSS. In addition, LA-ICP-MS elemental mapping for BMS shows that TABS are not preferentially concentrated in chalcopyrite and euhedral Ni-merenskyite [(Pd,Pt)(Te,Bi)2] grains are mainly enclosed within pyrrhotite (n = 187) rather than chalcopyrite (n = 19). The random distribution of Ni-merenskyite in the BMS is supportive of an idea that Pt and a portion of Pd were likely stabilized by the presence of Te and Bi ligands in sulfide liquid and Te-Bi-Pd-Pt associations were then randomly distributed in MSS and intermediate solid solution (ISS) during fractionation of sulfide liquid. This study shows that the formation of TABS-bearing PGM in the massive sulfide ores of the Kalatongke intrusion was not controlled by fractionation of sulfide liquid, providing a new case that the behavior of PGE is mainly controlled by TABS rather than their partitioning coefficients in sulfide liquid.

Comparison of Interleukin-6 with Other Markers in Diagnosis of Ovarian Cancer.

The lack of specific symptoms in ovarian cancer delays onset of the diagnostic process. Hence, most cases are recognized in late stages of the disease. The aim of this study was to confirm the role of Il-6 compared to other markers in diagnosis and survival in ovarian cancer. The database was collected from 13 January 2021 to 15 February 2023. In total, 101 patients with pelvic tumors with a mean age of 57.86 ± 16.39 participated in the study. In every case, CA125, HE4, CEA, CA19-9, Il-6, C-reactive protein and procalcitonin measurements were taken. Patients with ovarian borderline tumor and metastatic ovarian tumors were excluded from further analysis. Statistically significant correlations were found between diagnosis of ovarian cancer and levels of CA125, HE4, CRP, PCT and Il-6. Comparison of Il-6 with other markers revealed that longer overall survival correlated with lower values of Il-6. In the case of a higher concentration of Il-6, OS and PFS were shorter. Sensitivity and specificity of Il-6 in diagnosis of ovarian cancer were 46.8% and 77.8%, respectively, while for CA125, CRP and PCT were 76.6% and 63%; 68% and 57.5%; 36% and 77%, respectively. More investigations are needed to identify the most specific and sensitive marker for ovarian cancer.

A new HNO3 digestion procedure for Re–Os isotope analysis and its implications for organic‐rich sedimentary rocks and mafic rocks

The precision of available Re–Os isotope analysis for organic‐rich sedimentary (ORS) rocks is influenced by the coexisting clastic and organic components and the considerable differences between Re and Os mass fractions in such rocks. Here, we present a new method to analyse Re–Os isotopes of organic‐rich sedimentary (ORS) rocks by thermal ionization mass spectrometry. Nitric acid (HNO3) was used as the single digestion medium, and this method mainly relies on HNO3 at the optimum digestion condition, which can both equilibrate Os isotope between spike and sample and prevent the dissolving of clastic particles as many as possible especially the non‐aqueous elements inside. After a series of condition experiments, our data demonstrate that digestion temperatures and durations play important roles not only on the equilibrium between sample and spike, but also on the dissolving‐out quantity of non‐aqueous Re and Os elements. The optimum condition of 24 h and 230°C (the obtained Re and Os concentrations for the oil shale reference material SGR‐1b, and the 187Os/188Os ratios are 33.44 ± 0.09 ng/g, 0.4452 ± 0.0107 ng/g and 1.7822 ± 0.0439, n = 3, 1SD) can produce the Re–Os isotopic ratios of ORS at a precise level, and restrain the liberation of clastic Re and Os. This method at the digestion condition of 24 h and 230°C, therefore, will increase the accuracy of Re–Os isotope analysis of ORS on the basis of low blank and high efficiency. When this method is used for olivine tholeiite reference materials (BIR‐1a), the result demonstrates that the Os isotopes of mafic rocks do not produce fractionation when the temperature is higher than 200°C during the HNO3 digestion.

Tuning resistive switching properties of WO3− x -memristors by oxygen vacancy engineering for neuromorphic and memory storage applications

High density memory storage capacity, in-memory computation and neuromorphic computing utilizing memristors are expected to solve the limitation of von-Neumann computing architecture. Controlling oxygen vacancy (V O) defects in metal oxide thin film based memristors holds the potential of designing resistive switching (RS) properties for memory storage and neuromorphic applications. Herein, we report on RS characteristics of complementary metal–oxide–semiconductor compatible WO3−x based memristors modulated by precisely controlled oxygen non-stoichiometry. Switchability of the resistance states has been found to depend strongly on the V Os concentration in the WO3−x layer. Depending on x, the memristors exhibited forming-free bipolar, forming-required bipolar, and non-formable characteristics. Devices with moderate V Os concentration (∼5.8 × 1020 cm−3) exhibited a large R off/R on ratio of ∼6500, and reset voltage-controlled multi-level resistance states. A forming-free, stable multi-level RS has been realized for a memristor possessing V Os concentration of ∼6.2 × 1020 cm−3. WO3−x -based memristors with higher V Os concentrations (∼8.9 × 1020 cm−3–1 × 1021 cm−3) exhibited lower initial resistance, low R off/R on ratios (∼15–63) and forming-free synaptic functions with reasonable conduction modulation linearity. Investigation of the conduction mechanism suggests that tailoring V Os concentration modifies the formation and dimension of the conducting filaments and the Schottky barrier height at the WO3−x /Pt interface, which paves the way for designing WO3−x -based memristors for memory storage and neuromorphic applications.

Mixing nitrogenous ligands in osmium(VI)ligand-polysaccharide complexes. Voltammetric sensing

• Electroinactive dextran was modified with complexes of Os(VI) and nitrogenous ligands. • Os(VI)ligand modified dextran is electroactive and yields several redox peaks. • Nitrogenous ligand type significantly influences interfacial properties of modified dextrans. • Ligand combination can improve dextran analysis comparing to one-ligand modification. Simple chemical modification of carbohydrates with complexes of sixvalent osmium and nitrogenous ligands (Os(VI)L) changes electro inactive carbohydrates to electroactive species. In this work we show that the type of the nitrogenous ligand (L) significantly influences adsorption of Os(VI)L-modified dextrans at a charged surface. Modification by mixture containing two ligands can improve electrochemical analysis in comparison to simple modification only with one ligand. For instance, modification with complexes of Os(VI) and mixture of N,N,Ń,Ń-tetramethylethylenediamine (temed) with 2,2́-bipyridine (bipy) allows to (i) determine the concentration of Os(VI)L modified dextran in one order higher range as in case of dextran modified only with Os(VI)temed and (ii) discriminate between various polysaccharides differing in building units and structures.

Meteoritic component in impact breccias of the Jeokjung-Chogye structure, South Korea: Evidence from the HSE abundances and Re[sbnd]Os isotopic systematics

Geochemical compositions, including highly siderophile element (HSE) abundances and Re-Os isotope compositions, of nine polymict impact breccias in two drill cores and three target rocks from the Jeokjung-Chogye structure, South Korea, have been investigated to test the impact origin of the structure, and to infer the potential projectile type for the formation of the crater. The impactites have around 5 times higher abundances of platinum-group elements (PGE) compared to target rocks, and two orders of magnitude higher Re abundances. The weighted mean for 187Os/188Os ratios of impactites is 0.806, which is lower than this value for the target rocks (1.049), suggesting the presence of a meteoritic component. The higher PGE abundances and a broad negative correlation between Os contents and 187Os/188Os ratios show that the impactites incorporated ∼0.05 wt% of a chondritic component. The endogenic or chondritic relative abundances of the HSE argue against iron meteorites as a potential impactor for the Jeokjung-Chogye structure. Yet, the present data do not allow to unambiguously identify the projectile type (i.e., chondrite class) present in the impactites because of the high proportion of the indigenous component.

Mantle source characteristics and magmatic processes during the 2021 La Palma eruption

The 2021 eruption of La Palma (September 19-December 13) was the first subaerial eruption in the Canary Islands in 50 years. Approximately 0.2 km3 of lava erupted from a newly formed, broadly basaltic composite volcanic edifice on the northwestern flank of the Cumbre Vieja volcanic ridge. Comprehensive sampling of the olivine- and clinopyroxene-phyric lavas over the eruption period reveals temporal changes in mineralogy and bulk rock geochemistry from tephrite to basanite. Initial tephrite lavas have low MgO (∼6 wt.%) and elevated TiO2 (∼4 wt.%) and contain amphibole crystals and gabbroic micro-xenoliths. In contrast, lavas with progressively more mafic compositions erupted to approximately day 20 of the eruption and thereafter remained as basanite (∼8 wt.% MgO; 3.7 wt.% TiO2) until eruption termination. Temporal changes in lava chemistry reflect initial eruption of fractionated magmas that crystallized 5-10% olivine and clinopyroxene, as well as minor spinel, sulfide, and magnetite, followed by later eruption of deeper-sourced and more primitive magma. Vanadium-in-olivine oxybarometry indicates parental magmas were oxidized (fO2 = +1.5 to +2 FMQ) with 8.2 ±0.8 wt.% MgO and were generated from between 2.5-3% partial melting of a mantle source potentially containing a pyroxenite component (Xpx = 0.31 ±0.12). Day 1-20 tephrites have more radiogenic 187Os/188Os (0.143-0.148) and lower Pd, Pt, Ir and Os contents than post day 20 basanites (187Os/188Os = 0.141-0.145). Combined with available seismic data, the lavas provide a high-resolution record of eruptive evolution. Initial fractionated tephrite magma was stored in the upper lithosphere up to four years prior to eruption, consistent with pre-cursor seismicity and the presence of partially reacted amphibole and micro-xenoliths. The later lavas of the eruption were fed by more primitive basanitic parental magmas that were likely sourced from the deeper portion of the magma storage system that is underplating the island. Precursor events to the 2021 La Palma eruption involved seismicity and magma emplacement, storage and differentiation, which was followed by mobilisation, eruption, and eventual exhaustion of stored magma and partial melts. This magmatic progression is similar to that documented from the 1949 and 1971 Cumbre Vieja eruptions. Ocean islands with limited basaltic magma supply show similarities to the magmatic evolution observed in large silicic systems, where initial magma emplacement and differentiation is followed by later magma remobilisation that induces volcanic activity.

Fractionation of trace and platinum-group elements during metamorphism of komatiitic chromites from the early Archean Gorumahishani greenstone belt, Singhbhum Craton (eastern India)

It is well established that the major and minor element contents of chromites are subject to change during greenschist to amphibolite facies metamorphism. During upper amphibolite facies metamorphism, chromite can be completely converted to chrome magnetite. However, not all elements are affected to the same degree, the concentrations of +2 ions (e.g. Zn, Co, Mn) being particularly vulnerable to modification. The degree to which trace elements, particularly the platinum-group elements (PGE), are affected has not been closely examined. The compositions and textures of chromites from komatiites of the Gorumahishani greenstone belt of the Singhbhum Craton (India) have experienced a range of metamorphic conditions from greenschist to amphibolite facies, providing the opportunity to study the changes of trace and platinum-group element composition with metamorphic grade. Five types of altered chromites are identified from the komatiitic suite of rocks in the ~120-km-long greenstone belt. The type-I chromites are non-porous and characterized by the least modified cores. These chromites are mostly present in the northern Maharajgunj-Tua Dungri section where rocks show metamorphism from greenschist to greenschist-amphibolite transition facies. The type-II and type-III chromites are porous and mostly found in the southern Kapili section of the greenstone belt where rocks show metamorphism up to the mid-amphibolite facies. Type-IV and type-V chromites are completely modified to ferritchromit and chrome magnetite, respectively, and are present in the komatiitic rocks from the entire greenstone belt. The central cores of the type-I and type-II grains have relatively higher concentrations of mobile trace elements (e.g. Zn, Co, and Mn) with higher Mg# [Mg/(Mg + Fe2+)], lower Cr# [Cr/(Cr + Al)], and lower Fe3+/R3+ (R3+ = Fe3+ + Cr3+ + Al3+) ratios than their respective rims. Significantly higher concentrations of the immobile trace elements (e.g. Ti and V) in the cores of the type-II grains relative to their chrome magnetite rims from the Kapili section and to the type-I varieties from other sections might be due to the metamorphism of the komatiitic rocks under higher-grade conditions (amphibolite facies). In situ LA-ICPMS analysis for PGE reveals a relatively higher concentration of Ru and Rh in the rims of the type-I chromites than in the cores which is due to the diffusion of these elements from the normal spinel structure of the cores towards the bivalent octahedral sites of the inverse spinel structure of the chrome magnetite rims during metamorphic processes. The lower concentrations of Os, Ir, Ru, and Rh in the cores of the type-II chromites from the Kapili section might be related to the metamorphism of the rocks under higher-grade conditions that facilitated the diffusion of these elements to associated sulphide or platinum-group mineral or alloy phases. The calculated partition coefficients of Sc, Ti, V, Mn, Ni, Ga, Os, Ir, Ru, and Rh from the least altered chromite cores assuming equilibrium with the parental komatiitic melt also suggest the variable effects of metamorphism when compared with global experimental and empirical values of the natural samples.

LIP volcanism (not anoxia) tracked by Cr isotopes during Ocean Anoxic Event 2 in the proto-North Atlantic region

Chromium is a redox sensitive element that exhibits a large range of isotopic compositions in Earth’s surface environments because of Cr(VI)-Cr(III) transformations. This property of Cr has been exploited as a tracer of Earth’s oxygenation history using marine sediments. However, paleoredox applications using Cr are difficult to implement due to its complicated cycling, which creates spatial variability in seawater δ53Cr values. Applications are further hindered by the potential for variability in the major inputs of Cr, such as submarine volcanism, to mask redox processes. Two previous reports of negative excursions in sedimentary δ53Cr values during the middle Cretaceous Ocean Anoxic Event 2 (OAE 2) demonstrate these complications. Observed negative shifts in marine sediments conflict with the positive shifts expected in response to the increased drawdown of isotopically light Cr(III) prompted by the expansion of anoxic depositional sinks. In this study, a marine carbonate succession cored from the Eagle Ford Formation in Texas, USA, in the southern part of the Western Interior Seaway, depicts the negative 1.5‰ δ53Cr excursion occurring in two steps, with the second step reaching peak minimum values indistinguishable from isotopically unfractionated igneous sources. In contrast to published δ53Cr records, each step stratigraphically matches proxy evidence for increased eruption frequency and/or intensity of volcanic activity using combined 187Os/188Os, 87Sr/86Sr and Os concentration proxies previously measured from the same core, supporting higher inputs of volcanically sourced Cr to the oceans as the driver for the negative Cr isotope excursion.

FrontMIND: A phase III, randomized, double-blind study of tafasitamab + lenalidomide + R-CHOP versus R-CHOP alone for newly diagnosed high-intermediate and high-risk diffuse large B-cell lymphoma.

TPS7590 Background: Up to 40% of patients relapse or are refractory (R/R) to R-CHOP, the current standard of care for diffuse large B-cell lymphoma (DLBCL), indicating an unmet need, particularly in patients with high-intermediate and high-risk disease (IPI 3–5). POLARIX (NCT03274492) evaluated a modified regimen substituting polatuzumab vedotin for vincristine (pola-R-CHP), demonstrating modest improvement in PFS with no OS benefit between treatment arms. The addition of lenalidomide (LEN) to R-CHOP improved both PFS and OS in the ECOG-ACRIN E1412 trial but not in the Phase III ROBUST study, in which a lower dose of LEN was used, despite a positive trend toward 2-year PFS in a subgroup analysis. The chemo-free immunotherapy tafasitamab + LEN has received accelerated approval in the United States (2020), and conditional marketing authorization in Europe and Canada (2021) in adult patients with R/R DLBCL ineligible for ASCT based on L-MIND (NCT02399085). The primary analysis of First-MIND (NCT04134936), a Phase Ib randomized safety study of R-CHOP + tafasitamab ± LEN in patients with previously untreated and newly diagnosed DLBCL, demonstrated that adding tafasitamab + LEN does not impair dosing and scheduling of R-CHOP, with toxicities similar to those expected with R-CHOP alone (ASH 2021; #3556). frontMIND (NCT04824092) will investigate the efficacy and safety of R-CHOP + tafasitamab + LEN vs R-CHOP alone in previously untreated patients with high-intermediate and high-risk DLBCL. Methods: frontMIND is a Phase III, multicenter, randomized, double-blind, placebo-controlled study. Approximately 880 patients are planned to be randomized at ̃350 centers in North and South America, Europe, and Asia-Pacific. Eligible patients aged 18‒80 years with previously untreated local biopsy-proven, CD20+ DLBCL with IPI score 3–5 (age-adjusted IPI 2–3 if ≤60 years), and ECOG PS 0–2 will be enrolled. Patients with transformed lymphoma (except double or triple hit lymphoma) are excluded. Patients will be randomized 1:1 to receive six 21-day (D) cycles of either R-CHOP + tafasitamab (12 mg/kg intravenously, D 1, 8, and 15) + LEN (25 mg orally, D1–10) or R-CHOP + tafasitamab and LEN placebos. Patients will be followed for up to 5 years after the end of treatment. The primary endpoint is investigator-assessed PFS. Secondary endpoints include investigator-assessed event-free survival, OS, safety, and tafasitamab serum concentration (trough and Cmax levels). Sensitivity and specificity of minimal residual disease for early detection of disease progression is an exploratory endpoint; further MRD parameters may also be investigated. The study is funded by MorphoSys AG and conducted with the scientific support of members of the Fondazione Italiana Linfomi and the German Lymphoma Alliance. Clinical trial information: NCT04824092.

Rhenium‐Osmium Isotope Constraints on the Origin of the Tianyu Cu‐Ni Deposit in the East Tianshan Orogenic Belt, Xinjiang, NW China

AbstractThe Tianyu Cu‐Ni sulfide deposit occurs in the north margin of the Central Tianshan Arc in East Tianshan orogenic belt, Xinjiang, NW China. The intrusions consist of gabbro, peridotite, and olivine pyroxenite. The peridotite and pyroxenite are the main host rock for the Cu‐Ni ores. Rhenium and osmium isotopic analyses of Ni‐ and Cu‐bearing sulfide minerals from the deposit have been used to determine the source of osmium, and by inference, the sources of ore metals. Sulfide ore samples have Os and Re concentrations varying in the ranges 1.85 to 4.58 ppb and 93.56 to 146.00 ppb, respectively. An initial 187Os/188Os ratio ranges from 0.86 to 1.23 for the ores and the γOs values from 592 to 2227. Osmium isotopic data suggest that the Tianyu intrusion and associated Cu‐Ni mineralization has derived from crustal‐contaminated mantle melts. The intrusions early show island‐arc geochemical signatures, which indicate that the Hulu mafic–ultramafic intrusions, along with the Cu‐Ni deposit, formed as a result of subduction of oceanic crust in the Early Permian.

Re-Os systematics and chronology of graphite

Natural graphite forms in a range of metamorphic and hydrothermal environments across timelines spanning from the birth of the solar system, to the evolution of early Precambrian life, and the development of contemporary geotectonic cycles. A precise timeline of these and other graphite-forming events, however, has hitherto been obscured by a lack of radiometric ages and as such, chronologies are inferred from host-rock or hydrothermal mineral ages. Herein we examine the Re-Os systematics and chronology of graphite formed in a suite of terrestrial and extraterrestrial environments (n = 17) with the principal aim of establishing the viability of Re-Os geochronology of natural graphite.Graphite Re and Os contents and isotopic ratios exhibit a wide range of values that extend up to 1520 ppb Re, 19,577 ppt Os, and 4101 and 42.18 for 187Re/188Os and 187Os/188Os ratios, respectively. These values are broadly comparable to those reported for crustal sulfides, organic-rich sedimentary rocks, and hydrocarbons. X-ray diffraction crystallinity data reveals that graphite Re abundances show a broadly inverse correlation with graphite formation temperature and crystallinity (d002 and Lc(002)) with interplanar spacing (d002) having the strongest anti-correlation with graphite Re contents.Graphite Re-Os geochronology is demonstrated with two independent case studies (Wollaston-Mudjatik Transition shear zones, Saskatchewan, Canada and Merelani Hills, Tanzania) yielding precise (<1%) Re-Os isochron dates of 1731.52 ± 7.43 Ma (2σ; MSWD = 1.3) and 586.89 ± 2.39 Ma (2σ; MSWD = 1.2) that are consistent, within uncertainty, to their mineralization ages constrained by other radiometric methods. These data confirm that graphite mineralization was synchronous with Trans-Hudsonian exhumation and tsavorite-tanzanite gemstone mineralization, respectively. Method accuracy, however, appears contingent on the analytical protocols used to isolate graphite, e.g. handpicking vs. heavy liquids (SPT) and water, with the latter perturbing graphite Re-Os systematics by as much as 20%. We, therefore, recommend handpicking paired with magnetic separation and grain mount examination.Our Re-Os age results are then coupled with new SIMS carbon isotope data (Wollaston-Mudjatik Transition graphite: δ13C = −21.64 to −15.28‰; Merelani Hills graphite: δ13C = −25.90 to −24.36‰) and 187Os/188Osi isotope data (Wollaston-Mudjatik Transition graphite = 0.3119 ± 0.0037; Merelani Hills graphite = 1.680 ± 0.038) to constrain graphitic carbon to sedimentary carbonate/organic (Wollaston-Mudjatik Transition graphite) and organic (Merelani Hills graphite) carbon sources. This unique pairing of isotope systems in graphite provides the first detailed chronology of localized carbon mobility in the Earth’s crust.Re-Os graphite geochronology likely has wide applications in ore-deposit and metamorphic geology with the potential to reshape our understanding of carbon cycling in the crust-mantle system, and for graphite exploration initiatives that are critical for a global transition to a green economy.

Re–Os geochemistry of hydrothermally altered dacitic rock in a submarine volcano at Site U1527, IODP Expedition 376: Implications for the Re cycle in intraoceanic arcs

Despite the widespread use of Re–Os isotopes in various geoscience fields, relatively little is known about the behavior of Re and Os during fluid-mediated hydrothermal alteration of igneous rocks in the (sub)seafloor, especially in an intraoceanic arc setting. Here, we provide a depth profile of Re–Os geochemistry at Site U1527, located on the NW caldera rim of the Brothers volcano hydrothermal field in the Kermadec arc and drilled during International Ocean Discovery Program (IODP) Expedition 376 in 2018. Volcaniclastic rocks from Hole U1527C that had experienced various degrees of high- and low-temperature hydrothermal alteration were analyzed for bulk chemical composition and Re–Os isotopes. The concentration of Re varied from 0.172 to 18.7 ppb, and that of Os from 9.7 to 147.1 ppt. Hydrothermal alteration usually resulted in Re uptake by rocks, but a part of Re was released into the ocean by later oxidative weathering. Compared with Re, Os mobility resulting from hydrothermal alteration was limited. The relatively homogenous 187Os/188Os values (0.13–0.14) of the original volcaniclastic rocks were altered, becoming slightly more radiogenic (up to 0.212), by the addition of seawater-derived radiogenic Os by (1) Os precipitation induced by seawater–hydrothermal fluid mixing, which was accompanied by enrichment with Ba (barite precipitation) as well as by the highest Re and Os concentrations in the profile, and (2) adsorption of seawater-derived radiogenic Os onto Fe hydroxide without any corresponding enrichment of Ba, Re, or Os. Compared with high temperature-altered zones of mid-ocean ridge basalt, the altered samples in this study showed intense Re enrichment, presumably reflecting abundant pyrite precipitation in a Re-rich magmatic–hydrothermal environment unique to the arc setting. The results at Hole U1527 may suggest that subseafloor high-temperature alteration can be a sink for Re degassed from magma. The altered rock may also be a source of Re in the ocean as a result of subsequent low-temperature alteration.