Similar Trace Research Articles

Magma Evolution and Constraints on the Graphite Mineralization Hosted by the Huangyangshan Alkaline Granite Suite in the East Junggar of Xinjiang Province: Evidence from In Situ Analyses of Silicate Minerals

The Huangyangshan super-large graphite deposit, located in the East Junggar area of the Xinjiang Province, is hosted in and has closely temporal, spatial, and genetic relationships with the Huangyangshan alkaline granites. There are such silicate minerals as amphibole, biotite, pyroxene, and plagioclase occurring in the graphite-bearing granites. The integration of the electron microprobe analysis (EMPA) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) enabled us to reveal the physicochemical conditions and evolution process, as well as the relationship of alkaline magmatism with graphite mineralization. The results show that the amphiboles generally have low Al and high Ti, K, Si, and Fe contents, as well as similar rare-earth elements (REEs) patterns and trace element distribution patterns to granites with significantly negative Eu anomalies. In the analyzed samples, primary biotite belongs to Fe-biotite and has characteristics of high Si and Fe and low Al and Mg contents. In the graphite orbicules, the pyroxene phenocrysts develop multiple zonal structures and are characterized by high Si and low Ca and Fe contents. The dominant plagioclase phenocrysts in the graphite orbicules are oligoclase and andesine, with normal and occasionally oscillatory zoning. The calculated crystallization temperature of the pyroxene, amphibole, and primary biotite in graphite orbicules are 840–1012 °C, 681–761 °C, and 658–720 °C, respectively, corresponding with their crystallization order. The pressure and depth calculation results of the amphibole, representing those of the magmatism, are 157–220 Mpa and 5.95–8.32 km, respectively. Both amphibole and biotite crystallized in a reducing environment with extremely low oxygen fugacity. The elemental compositions of these silicates indicate that the Huangyangshan pluton experienced significant mixing of mafic mantle-derived magma and felsic crust-derived magma. The cores of graphite orbicules were formed in a relatively earlier magmatic stage, while the granites and their dioritic enclaves were formed in a later magmatic stage. During magmatism, the mixing of mantle-derived basic magma had an important influence on the evolution and differentiation of the melts. According to the coexisting sulfides with graphite and compositional difference of amphibole and biotite in the granites and graphite ores, the graphite mineralization might be triggered by a magma mixing process.

Geochemistry of meta‐mafic and meta‐tonalite‐trondhjemite intrusives from Jaintia and Karbi Anglong hills of Shillong Plateau, North East India: Implications on the evolution of the Proterozoic Shillong Basin

We present the whole‐rock and mineral chemical data of the Khasi meta‐mafic/basic‐trondhjemite intrusives (KMI) and meta‐tonalite‐trondhjemite (MTT) that coevally emplaced the Proterozoic Shillong Group (SG) of Shillong Plateau, northeast (NE) India and discuss their petrogenetic‐tectonic origin. The calc‐alkaline to tholeiite KMI are compositionally transitional between hornblende‐gabbro; hornblende‐diorite and minor‐hornblendite. They show Ta–Nb troughs and strong decoupling large‐ion lithophile/high field strength elements (HFSE) signature consistent with subduction zone‐related basic magmas. The calcic to calc‐alkaline, low‐Al2O3, and I‐type metaluminous Fe‐hedenbergite‐trondhjemite (KMT) exhibits similar trace and rare earth elements (REE) distribution to the KMI. The MTT on the other hand are depleted in trace elements and REE, and correspond with the I‐type granitoids, and are comparable to Proterozoic to Phanerozoic tonalite‐trondhjemite‐granodiorites. Gentle negative sloping of REE in KMI ([La/Lu]CN = 4.04 to 6.35) with moderate LREE, suggests partial melting or, fractional crystallization from a transitional source between garnet and spinel lherzolite. Although almost a flat pattern ([La/Lu]CN = 3.70 to 4.05) for MTT entails a high degree of partial melting from sources similar to Archaean Mafic Composite or Archaean Tholeiite. Trace elemental modellings ([Sr/Y] vs. Y and [La/Yb]N vs. YbN) for MTT infer low pressure (<15 kbar) and high degree partial melting of >50% in equilibrium with 10% garnet +90% amphibole residue. A relatively flat REE pattern with some elevated HREE of MTT compared to KMI suggests for depleted source. Bimodal plutonism and the prevalence of meta‐dacite‐rhyolite in SG invokes for tonalite‐trondhjemite‐dacite setting of a continental arc or, active continental margin tectonic setting. Emplacement of KMI initiated in a temporary relax‐extensional phase and MTT in a compressional regime. This is possibly caused by an over‐thickened crust later subjected to orogenic collapse, exhumation‐metamorphism, and decompressional melting. This event might have taken place between 1.0 to 0.5 Ga during the Pan‐African Orogenic crustal growth, linked to the amalgamation of Gondwana.

Trace element composition of silicate minerals in the porphyritic and nonporphyritic chondrules of Elenovka (L5) and Knyahinya (L/Ll5) meteorites

The results of SIMS and EPMA studies on the silicate minerals and bulk compositions (SEM-EDS) of porphyritic and nonporphyritic chondrules from Elenovka and Knyahinya meteorites are reported. The trace element composition of silicate minerals (olivine, low-Са pyroxene) in equilibrated ordinary chondrites (EOC) has not been affected considerably by thermal metamorphism on the chondritic parent bodies. Therefore, equilibrated chondrites can be used for chondrule-forming processes studies. Low-Са pyroxene in nonporphyritic chondrules contains higher REE, Ba, Sr concentrations than that in porphyritic chondrules at similar trace element concentrations in the olivine of chondrules. The data obtained indicate that the formation of non-porphyritic chondrules was triggered by an increase in the cooling rate of chondrules upon the formation of pyroxene, rather than a difference in the initial conditions of chondrule formation. Higher refractory incompatible element (Nb, LREE) concentrations in the olivine of chondrules than those in the olivine of the matrix and contrasting trace element (Zr, Sr, Cr, REE) concentrations in the low-Са pyroxene of the chondrules and the matrix suggest that the matrix and chondrules of the meteorites formed in one reservoir under different physico-chemical conditions (density, redox state, rotation speed, homogeneity, temperature, shocks, electrical discharge, etc.).

Trace element composition of base metal sulfides from the sediment-hosted Dolostone Ore Formation (DOF) Cu[sbnd]Co deposit in northwestern Namibia: Implications for ore genesis

The Dolostone Ore Formation (DOF) copper‑cobalt mineralization is a recently discovered sediment-hosted deposit in Neoproterozoic low-grade metamorphosed carbonates and fine-grained siliciclastics in the Pan-African Kaoko Belt in Namibia. Six mineralization styles have been identified in the DOF. They comprise both brittle and ductile (micro)textures and include sulfides occurring in disseminations, clusters, nodules, pressure shadows, veins and the locally termed “DOF event”.Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) in situ trace element analyses of base metal sulfides (sphalerite, chalcopyrite, pyrite and pyrrhotite) show distinct groupings of the mineralization styles. Sphalerite and chalcopyrite from the dissemination, cluster and nodule mineralization styles show similar trace element composition trends (e.g., Fe, Co, Ni, Se, Cd for sphalerite and Co, Ni, Se and Bi for chalcopyrite) that differ from vein and pressure shadow sphalerite and chalcopyrite which group together. Pyrite compositions in cluster and nodule types show a similar trace element grouping in elements such as Co, Ni, As, Se, Sb, Tl and Pb. In contrast, pyrites from pressure shadows and veins show a decoupling in elements such as Se, Sb, Tl and Pb, that grouped together in the aforementioned pyrite mineralization styles. GeGaInMnFe in sphalerite (GGIMFis) geothermometry indicates that the sphalerite (and associated sulfides) from all mineralization styles crystallized at temperatures at or above 310 ± 50 °C. This temperature range corresponds with the regional metamorphism induced by the Damaran orogeny. Thus, the DOF copper‑cobalt mineralization is related to, or at least strongly overprinted by, Damaran metamorphism and deformation.Trace element differences in the sphalerite-chalcopyrite groupings reveal that the vein and pressure shadows mineralization styles were formed at lower temperatures than the other ones but still above the GGIMFis closing temperature of 310 ± 50 °C. Evidence is vacant for a typical low-temperature, early sediment-hosted copper mineralization. This work demonstrates the strength of using trace elements for deducing the ore-forming system of polyphase sulfide deposits.

Petrological and geochemical characteristics of the mafic–ultramafic Americano do Brasil Complex, central Brazil, and the implications for its genesis

The Americano do Brasil Complex occurs in the Neoproterozoic Goias Magmatic Arc, central Brazil. It is composed of two mafic–ultramafic cumulate sequences, intruded into granodioritic gneisses. Although deformed and partially recrystallized by a regional metamorphic overprint, the complex still preserves relict igneous features, such as adcumulate to heteradcumulate textures. The Northern sequence is mostly composed of olivine and olivine-clinopyroxene cumulates, whereas the Southern consists mainly of two-pyroxene cumulate rocks, with plagioclase and olivine cumulates occurring in lesser amounts. The complex has three main orebodies, with textures that range from disseminated to massive sulfide breccias with durchbewegung texture. Thermodynamic modeling using a single picrite parental magma composition can predict cumulate rock compositions and mineral modes similar to all of the observed cumulate rock compositions of the Americano do Brasil Complex. Equilibrium crystallization of the liquid and assimilation-batch-crystallization involving up to 45 % of the host gneisses in the upper crust produces solids similar to the cumulates described in the Northern and Southern sequences, respectively. Modeled pressure–temperature emplacement conditions of the magma were c.a. 2.5 kbar and 1310 °C. Both sequences have similar incompatible trace element patterns which, together with the results of the modeling, imply a broadly comagmatic origin.

Volcanism at the end of continental rifting: The Cretaceous syn-rift to post-rift transition in the Songliao Basin (NE China)

The evolution of volcanism at the latest stages of continental rifting and its transition to the post-rift stage are poorly known. A Cretaceous rifting episode characterized the Songliao Basin (NE China) between 150 and 105–100 Ma. The transition to the post-rifting stage was marked by an increase in the subsidence rate due to thermal contraction. Here we present new major, trace element and Sr-Nd isotopic data on the volcanic rocks sampled in wells located in the Songliao Basin. These rocks are representative of two major eruptive cycles: K1yc1 (115–106 Ma, syn-rift stage) and K1yc3 (105–102 Ma, transition to the post-rift stage). The K1yc1 and K1yc3 rocks were erupted during the late phases of the Songliao rifting and have been found in the two members of the Yingcheng Formation. The K1yc1 rocks consist of trachybasalts, basaltic trachyandesites, and rhyolites. The K1yc3 rocks show a homogeneous rhyolitic composition. Both the K1yc1 and K1yc3 rocks display an alkaline, Within-Plate affinity. The trace element patterns and the isotopic composition of the K1yc1 mafic rocks indicate that they are the product of the fractional crystallization from a parent magma with an OIB signature. The felsic rocks from K1yc1 and K1yc3 have similar major and trace element patterns and originate from fractional crystallization of the K1yc1 trachybasalt and assimilation of upper crust material. The bimodal K1yc1 volcanism is related to fractionation processes producing low amounts of magmas with intermediate compositions. The lack of mafic eruption in K1yc3 is due to the reduction of porosity of the crustal rocks and a transition from ‘hot’ to ‘cold’ crust related to the thermal subsidence from syn-rift to post-rift stage. The late stage of the Songliao rifting volcanism coincides with a shift from a roll-backing phase of the Paleo-Pacific slab to its passive sinking in the asthenosphere.

Forgetting Details in Visual Long-Term Memory: Decay or Interference?

Two main explanations for memory loss have been proposed. On the one hand, decay theories consider that over time memory fades away. On the other hand, interference theories sustain that when similar memories are encoded, they become more prone to confusion. The interference is greater as the degree of similarity between memories increases, and as the number of similar traces increases too. To reduce interference, the pattern separation process allows the brain to separate similar memories and build detailed memory representations that are less easily confused. Nonetheless, with time, we tend to remember more general aspects of experiences, which also affects our ability to discriminate. We present the results of one experiment in which brain activity was recorded by EEG while two groups of healthy participants performed a visual memory discrimination task. This task assesses the ability to differentiate new but similar information from previously learned information and thus avoid interference. Unlike previous studies, we used a paradigm that was specifically designed to assess the impact of the number of items (2 or 6) of each category stored in memory, as well as the time elapsed after the study phase (20 min or 24 h), on recognition memory for objects. Behaviorally, our results suggest that mnemonic discrimination is not modulated by the passage of time, but by the number of stored events. ERP results show a reduced amplitude in posterior regions between 500 and 700 ms when comparing short and long delays. We also observe a more positive activity in a centro-posterior region in the 500–700 ms window at retrieval when participants store more items. Interestingly, amplitudes for old hits and similar false alarms were greater than amplitudes for correctly rejected new items between 500 and 700 ms. This finding indicates that a recollection-based process operates in both true and false recognition. We also found that the waveforms for correct rejections of similar lures and the waveforms for correct rejections of new items were comparable.

Geochemistry, U-Pb Zircon Ages and Hf Isotopes of Basement Rocks Beneath the Northeastern Margin of the Ordos Basin: Constraints on the Paleoproterozoic Evolution of the Western North China Craton

SHRIMP zircon ages, Hf-in-zircon isotopic compositions and whole rock geochemistry were analyzed on basement metamorphic rocks from drill cores collected from the northeastern margin of the Ordos Basin. Geochemical data from four metasedimentary rocks show large variations in major element compositions, but have similar REE patterns and trace element compositions, with ΣREE = 161.80 × 10−6~341.82 × 10−6, δEu = 0.26~0.63 and LaN/YbN = 3.44~25.38. SHRIMP zircon U-Pb dating of granitic gneiss yielded the magmatic zircon ages between 1856 ± 14 Ma and 2188 ± 11 Ma, with the upper intercept age of 2229 ± 88 Ma. The cores have εHf(t) values of −5.46 to +6.57, and Hf model ages vary from 2869 Ma to 2300 Ma. The analyses of metamorphic overgrowths on zircon grains yield an average metamorphic age of 1865 ± 17 Ma (MSWD = 3.5). The zircon cores have εHf(t) values of −3.98 to 1.95, and Hf model ages vary from 2782 to 2416 Ma. Combined with data from earlier studies, we draw the conclusion that the metamorphic rocks in the borehole were formed during middle Paleoproterozoic time and were involved in a major late Paleoproterozoic tectono-thermal event which might be attributable to the collision between the Western and Eastern Block along the TNCO (the Trans-North China Orogen). The basement rocks are petrologically, geochronologically and geochemically comparable with rocks from the Khondalite series. The fact that the material properties of basement rocks beneath the northeastern Ordos Basin are different from those of the Western Block indicates that the extent and exact boundaries of the Ordos Block need to be refined.

Foetal amplitude-integrated electroencephalography: proof of principle of a novel foetal monitoring technique in adult volunteers

Peripartum hypoxic neonatal brain injury cannot be accurately predicted with current foetal monitoring techniques. Neonatal brain monitoring through amplitude-integrated electroencephalography (aEEG) is utilised when brain injury is suspected. Intrapartum aEEG assessment may improve detection of foetal hypoxia, facilitating earlier intervention. Using different engineered configurations in adult volunteers (n = 18), we monitored aEEG through application of two foetal scalp electrodes (FSEs). This aided development of a novel signal splitter, our Foetal heart rate and aEEG Monitoring System (FEMS) to monitor aEEG intrapartum. We then compared FEMS with gold-standard EEG monitoring simultaneously in two adults. Average percentage of interpretable aEEG signal was 61.3%, with the FEMS obtaining 72.15%. EEG signal on the aEEG device consistently showed a similar trace to gold standard EEG. This study demonstrates feasibility of aEEG monitoring in adults with FEMS utilising FSE inputs. An intrapartum foetal study utilising FEMS is due to commence shortly. IMPACT STATEMENT What is already known on this subject? Cardiotography, the current gold standard in foetal monitoring, is not associated with a reduction in cerebral palsy or infant mortality rates. Neonatal amplitude-integrated electroencephalography (aEEG) is an established method of monitoring brain function to guide commencing cooling therapy in suspected hypoxic brain injury. Intrapartum animal studies have illustrated foetal EEG changes reflecting evolving hypoxia. What do the results of this study add? This study demonstrates aEEG monitoring in human adult volunteers through application of foetal scalp electrodes and use of a novel signal splitter. This Foetal heart rate and aEEG Monitoring System (FEMS) provided a good overall percentage of aEEG signal, consistently showing a similar trace to gold standard EEG. What the implications are of these findings for clinical practice and/or further research? This proof of principle study provides the first step in developing a novel intrapartum foetal monitoring technique to monitor foetal aEEG in labour. This provides an exciting prospect of transferring well established neonatal monitoring techniques to facilitate accurate brain function assessment intrapartum and early intervention to reduce hypoxic brain injury. An intrapartum foetal study of this technology is due to begin in the near future.

LocSeq: Automated Localization for Compiler Optimization Sequence Bugs of LLVM

Compiler bugs may be triggered when programs are optimized with optimization sequences. However, diagnosing compiler optimization sequence bugs is difficult due to limited debugging information. Although some techniques (e.g., DiWi and RecBi) have been proposed to automatically localize compiler bugs, no systematic work has been conducted to automatically localize compiler optimization sequence bugs. In this article, we propose LocSeq, a novel technique to automatically localize compiler optimization sequence bugs of LLVM. The core insight of LocSeq is based on the fact that the behaviors of optimizations may be influenced by each other, and thus, the innocent files may be excluded by constructing bug-free optimization sequences. First, given a buggy optimization sequence that triggers a compiler bug, in LocSeq, we transform the problem of the localization for a compiler optimization sequence bug to the problem of the construction for bug-free optimization sequences, which are helpful to localize buggy compiler files. Then, a constrained genetic algorithm is presented in LocSeq to generate a set of bug-free optimization sequences that share similar compiler execution traces with the buggy optimization sequence. Finally, LocSeq leverages a spectrum-based bug localization technique to localize the compiler optimization sequence bug by comparing the execution traces between bug-free optimization sequences and the buggy optimization sequence. To evaluate the effectiveness of LocSeq, we build a benchmark, including 60 optimization sequence bugs of LLVM, and compare LocSeq with the state-of-the-art techniques DiWi and RecBi. The experimental results show that LocSeq significantly outperforms DiWi and RecBi by up to 366.66%/72.27% and 250.00%/56.00% for localizing optimization sequence bugs within Top-1/5 files, respectively.

Geochemistry of granitoids from the Austroalpine Seckau Complex: a key for revealing the pre-Alpine evolution of the Eastern Alps

Recent studies revealed that the calc-alkaline metagranitoids of the Seckau Complex comprise both (1) a Late Cambrian to Early Ordovician and (2) a Late Devonian to Early Carboniferous (early Variscan) intrusive complex. The older rocks of the Hochreichart Plutonic Suite reflect I to S-type affinity and are peraluminous and characterized by a general decrease in TiO2, Al2O3, MgO, CaO, P2O5, FeOt and MnO with increasing SiO2. Chondrite-normalized rare earth element (REE) plots display a slight enrichment in light rare earth elements (LREE) relative to heavy rare earth elements (HREE) as well as negative Eu anomalies ((Eu/Eu*)N = 0.15- 0.77). The whole-rock initial 87Sr/86Sr ratios calculated back to the time of emplacement (~ 496 Ma) vary between 0.7056 to 0.7061. The early Variscan rocks of the Hintertal Plutonic Suite can be subdivided into (a) the meta- to peraluminous granodioritic suite of the Pletzen Pluton and (b) the peraluminous granitic suite of the Griessstein Pluton. The Pletzen Pluton shows typical magmatic fractionation trends for most of the major oxides and trace elements plotted against SiO2. On a chondrite-normalized diagram, metagranitoids are strongly enriched in LREE and show no significant negative Eu anomaly. Metagranitoids of the Griessstein Pluton have a more peraluminous character and similar major and trace element fractionation trends compared to the Pletzen Pluton. However, the contents in SiO2, major and trace elements clearly point towards a more evolved melt with generally lower TiO2, Al2O3, MgO and CaO values and higher K2O content. Metagranitoids of the Griessstein Pluton are additionally characterized by a slight negative Eu anomaly of about 0.81 on a chondrite-normalized REE plot. Initial 87Sr/86Sr values calculated back to the time of emplacement (~ 353 Ma) of the Pletzen Pluton and the Griessstein Pluton vary between 0.7051—0.7061 and 0.7054—0.7063, respectively, and suggest the same magmatic source for both units. Application of rhyolite-MELTS modelling to the Hintertal Plutonic Suite revealed that the Griessstein Pluton formed by fractional crystallization (~ 30%) from the more primitive Pletzen Pluton. Our geochemical data from the Hochreichart Suite granitoids suggest the existence of a Late Cambrian to Early Ordovician active margin with its remnants now exposed in the Seckau Complex. The early Variscan grainitoids of the Seckau Complex are inferred as part of a magmatic arc along the southern Bohemian active continental margin that was related to the subduction of differently termed oceanic domains (Galicia-Moldanubian Ocean or Paleotethys), prior to the final collision of Gondwana and Laurussia. The general paleogeographic position of the Seckau Complex during the Variscan orogeny is considered to be south to southeast of the Bohemian Massif, adjacent to the eastern Hohe Tauern, the Schladming Tauern, and the Western Carpathians.

Late Paleozoic Shoshonitic Magmatism in the Southwestern Middle Tianshan (Tajikistan) of the Southwestern Altaids: Implications for Slab Roll-Back With Extensional Arc-Related Basins After Flat Subduction

Paleozoic magmatic rocks are widespread in the western Middle Tianshan. Their petrogenesis can provide important insights into the geodynamic evolution of the southwestern Altaids. Here, we present an integrated study of U–Pb zircon geochronology and geochemical and Lu–Hf isotopic compositions for the Late Paleozoic shoshonitic Chorukhdairon pluton and genetically and spatially related quartz porphyry in the southern Chatkal–Kurama terrane, western Middle Tianshan. The Chorukhdairon pluton mainly comprises monzodiorite and quartz monzodiorite (first phase), quartz monzonite (second and main phase), monzogranite (third phase), and leucomonzogranite (fourth phase). LA–ICP–MS zircon dating yielded magma crystallization ages of 294–291 Ma and 286 Ma for the Chorukhdairon pluton and quartz porphyry, respectively. All the rocks possess high K2O content (3.29–5.90 wt.%) and show an affinity with shoshonite series rocks. They display similar trace element compositions characterized by the enrichment of large ion lithophile elements (e.g., Rb, Th, U, and K) and depletion of high-field strength elements (e.g., Nb, Ta, P, and Ti), compatible with typical arc magmatism. Combined with zircon Lu–Hf isotopic data, we suggest that the Chorukhdairon pluton was produced by partial melting of the enriched mantle, followed by fractional crystallization of pyroxenes, amphibole, plagioclase, biotite, and accessory Fe–Ti oxides, apatite, and zircon. The quartz porphyries are similar to highly fractionated I-type granitic rocks, and their parental magma could result from the mixing of different batches of mantle-derived magmas or magmas derived from the mantle and juvenile lower crust. Considering the continuousness of the Middle Carboniferous to Early Permian magmatism in the western Middle Tianshan and other regional geological data, we suggest that the Chorukhdairon pluton and related quartz porphyry probably formed in an oceanic subduction setting. Furthermore, the temporal and spatial evolution of the Paleozoic magmatism imply that the flat-slab subduction that was induced by the subduction/accretion of seamounts probably occurred beneath the Middle Tianshan during the Middle Devonian to Early Carboniferous, after which the southeastward slab roll-back occurred during the Middle Carboniferous to Early Permian. The late slab roll-back was responsible for the southeastward arc magmatism migration and magmatic flare-up in the Chatkal–Kurama terrane, western Tianshan, and led to the formation of arc-related extensional basins and significant crustal growth in the southwestern Altaids.

Photostability of benzodithiophene based polymer: effect of PC60BM and intermolecular interactions

Organic solar cells working under continuous light irradiation are prone to photo-induced degradation. Photostabilities of benzodithiophene-alt-2-decyltetradecyl substituted isoindigo (PBDTI-DT) copolymer in solution, and as pristine film, and a PBDTI-DT:PC60BM bulk hetero-junction (BHJ) film were investigated for more than 70 h under simulated AM 1.5 solar irradiation. The photodegradation kinetics studied in standalone polymer chains were found to be fast due to the absence of intermolecular interaction while the inter-chain interaction in the polymer films kept the backbone intact against light-induced degradation. Further addition of PC60BM in the polymer made the BHJ film more stable as PC60BM serves as photoprotective layer and radical scavenger. This conclusion was supported by the similar XRD traces of PBDTI-DT:PC60BM film during degradation while the traces of the pristine film indicated bleaching and shifted with increasing photon stress. In addition, the absorption of PBDTI-DT:PC60BM and pristine PBDTI-DT films were reduced to 80 and 56%, respectively, after 70 h of photo-degradation.

Non-linear and multi-domain modelling of a permanent magnet linear synchronous machine for free piston engine generators

• The motivations for continued FPE and LEM development are established. • A non-linear and multi-domain model of the PMLSM is presented. • Incorporation of the PMLSM in an FPEG multi-domain model is demonstrated. • Model validation with data captured from an experimental FPEG is conducted. • Simulation results indicate the model captures the dominant dynamics of the PMLSM. The Free Piston Engine (FPE) can be considered a viable and promising option in future low-carbon technology development. When coupled to the Linear Electric Machine (LEM) to produce electrical energy, its characteristic non-linear dynamics typically have been described as linear when considering a systems-level modelling approach. This paper presents a multi-domain model of a Permanent Magnet Linear Synchronous Machine (PMLSM) for Free Piston Engine Generators (FPEG) and offers a detailed non-linear mathematical description of the machine dynamics. The model was implemented in a free-piston expander system and validated against experimental data from a test rig that has identical parameters. The simulation results indicate a strong correlation to the experimental data, which captured the dominant dynamics of the PMLSM and prove the satisfactory accuracy and performance of the model, together with a similar voltage and current output trace, indicating a cyclic energy output error of approximately 10 %. This paper aims to extend the current knowledge and literature within FPEG PMLSM design by considering the inherent non-linearity and multi-directional nature of the system dynamics and its interactions with multi-physical domains.

Formation, remobilisation and alteration processes at inactive hydrothermal vents: insights from elemental analysis of Cu-(Fe-)S sulfides from TAG, Mid-Atlantic Ridge

Chalcopyrite is the main Cu mineral in mafic-hosted marine hydrothermal systems. Its trace element budget and that of its alteration products may hold valuable information on formation, remobilisation and alteration processes of the hydrothermal system. In this study, we analysed chalcopyrite from five inactive seafloor massive sulfide (SMS) sites from the TAG hydrothermal field on the Mid-Atlantic Ridge by electron probe microanalysis (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for 24 elements. Twelve of them are discussed in detail. In general, trace element concentrations range between sub-parts per million (ppm) to several hundreds of ppm. The elements Se and Co are incorporated into the lattice at high temperatures of > 300 °C, whereas As, Ge, Ga substitute into the structure at intermediate to low temperatures. Other elements, e.g. Zn, are either accommodated into the mineral lattice or form inclusions, whereas V and Mn, which originate from seawater, get adsorbed onto the mineral surface. Idaite, chalcocite, and covellite exhibit similar trace element patterns to those of the precursor chalcopyrite. However, the secondary copper minerals show enrichment of Ag and Mo. Factors controlling the incorporation are predominantly related to changes in physicochemical conditions with the host rock composition playing only a minor role.

Ore Genesis of the Baishitouwa Quartz–Wolframite Vein-Type Deposit in the Southern Great Xing’an Range W Belt, NE China: Constraints from Wolframite In-Situ Geochronology and Geochemistry Analyses

The Baishitouwa deposit is a medium-scale quartz–wolframite vein-type deposit in the southern Great Xing’an Range tungsten (W) belt. The W mineralization occurs mainly as veins and dissemination within the mica schist of the Mesoproterozoic Baiyunebo Group. The formation of the deposit can be divided into four stages. The wolframite yielded a lower intercept 206Pb/238U age of 221.0 ± 3.4 Ma (1σ, MSWD = 2.0), which records a late Triassic W mineralization event in the Baishitouwa deposit. In combination with previous geochronological data, we suggest that NE China may have an enormous potential for Triassic W mineralization and more attention should be given to the Triassic ore prospecting in the region. This work highlights that the chemical composition of wolframite is controlled by both the crystallochemical parameters and the composition of the primary ore-forming fluid. Trace-element compositions suggest that wolframite (I) was controlled by the substitution mechanism of 4A(Fe, Mn)2+ + 8BW6+ + B□ ↔ 3AM3+ + AN4+ + 7B(Nb, Ta)5+ + 2BN4+, whereas wolframite (II) was controlled by the substitution mechanism of A(Fe, Mn)2+ + A□ + 2BW6+ ↔ 2AM3+ + 2BN4+. Wolframite (I) contains higher concentrations of Nb, Ta, Sc, and heavy rare earth elements (HREEs), and lower Mn/(Mn + Fe) ratios than wolframite (II). Both wolframite (I) and (II) have similar trace elements and left-dipped REEN patterns, and analogical Nb/Ta ratios. They have similar Y/Ho ratios to Mesozoic highly fractionated W-mineralized granitoids in NE China. These data indicate that the W mineralization at Baishitouwa is genetically related to an underlying highly fractionated granite, and the compositional variation of fluids is likely driven by crystallization of wolframite during the processes of fluid evolution. A change of the ore-forming fluids from an oxidized to a relatively reduced state during the evolution occurred from stage 1 to 2.

Petrogenesis and geodynamic significance of Late Triassic mafic microgranular enclaves and its host granodiorite in the Shuanghu area, central Qiangtang

The genesis of Late Triassic granitoids in the central Qiangtang is significant for deducing the evolution of the Palaeo‐Tethys Ocean in Qiangtang Block. Herein, we present a comprehensive study of zircon U–Pb ages, whole‐rock geochemistry and zircon Lu–Hf isotopes for the mafic microgranular enclaves (MMEs) and host granodiorites from the Shuanghu area, in order to evaluate their petrogenesis and geodynamic implications. New zircon U–Pb dating show identical formation ages for host granodiorites (207.1 ± 2.2 Ma and 206.6 ± 3.8 Ma) and MMEs (205.4 ± 2.9 Ma and 209.2 ± 2.2 Ma). The Shuanghu granodiorites contain amphibole and biotite and are characterized by moderate SiO2 (64.74–66.40 wt%) and K2O contents (2.48–3.62 wt%) as well as low A/CNK (0.69–1.00), indicating I‐type granite affinity. Its enriched zircon Hf isotopes (εHf(t) = −12.04 to −5.09) indicate that they were derived from the ancient mafic lower crust. The MMEs have a similar mineral assemblage, emplacement ages, trace elemental and zircon Hf isotopic compositions with the host granodiorites, indicating the cognate origin. These MMEs represent autoliths captured by latter ascending host magmas in the middle‐upper magma chamber. The highly variable Mg# (37–53), Cr (16.9–190 ppm) and Ni (5.71–67.2 ppm) in the Shuanghu MMEs and host granodiorites indicate that the mantle‐derived magma provided not only the heat but also the mafic components. In combining with previous studies, we suggest that the Shuanghu granodiorites and MMEs were formed in the post‐collision stage, which were caused by the asthenosphere upwelling related to the slab breakoff.

Multiple Magma Storage Regions and Open System Processes Revealed by Chemistry and Textures of the Datong Tholeiitic Lavas, North China Craton

ABSTRACT The geochemistry of lavas combined with textural constraints can provide important information on magmatic processes occurring at inaccessible depths. Here we carry out a detailed textural and geochemical study on 0.23 Ma contemporaneous and adjacent Qiulin, Longbao, and Dayukou volcanoes in the intraplate Quaternary Datong volcanic field (DVF) in the North China Craton. Lavas from the three tholeiitic volcanoes have similar major and trace element compositions with their trace element patterns resembling enriched mid-ocean ridge basalts (E-MORB). However, distinct textures are observed between the samples from the three volcanoes. Samples from Qiulin are generally poorly-phyric (<10 vol. %) containing orthopyroxene, plagioclase, and olivine phenocrysts and monomineralic orthopyroxene glomerocrysts set in a groundmass of plagioclase, clinopyroxene, orthopyroxene, and Fe–Ti oxides. In contrast, samples from both Longbao and Dayukou are highly phyric (up to ~50 vol. %) and consist mainly of plagioclase, orthopyroxene, clinopyroxene, and olivine phenocrysts with mm- to cm-sized polymineralic glomerocrysts enclosed in a groundmass comprising plagioclase, clinopyroxene, olivine, and Fe–Ti oxides. Crystal types and proportions vary significantly between the glomerocrysts of Longbao and Dayukou even on a thin section scale. The phenocrysts and glomerocrysts at the two volcanoes commonly show resorbed and embayed margins and sieve textures. Moreover, pyroxenes present as phenocrysts and glomerocrysts are always characterised by corona textures containing orthopyroxene cores mantled by clinopyroxene. Notably, orthopyroxene is never observed in contact with groundmass. The relatively low Mg# (75–85) and Ca content in the cores indicate that the orthopyroxenes from all three volcanoes are crystallised early from the magma rather than being mantle xenocrysts. Thermobarometry and kernel density estimation indicate that orthopyroxenes in all three volcanoes initially crystallised at ~7 kbar (23 km depth), whereas clinopyroxenes crystallised at ~4 kbar (13 km) and the final crystallisation pressure is ~3 kbar (10 km). Thermodynamic modelling by COMAGMAT suggests early near-liquidus crystallisation of the orthopyroxene at high pressures, followed by partial dissolution likely associated with decompression. The relatively larger proportions of phenocrysts compared with glomerocrysts in Qiulin samples implies that the magma reservoir was only partially turned into mushes at the periphery. Magma ascending via the melt-rich interior of the magma reservoir formed the crystal-poor Qiulin lava. In contrast, those ascending through the mushes at the peripheries of the deeper reservoir and discrete shallower storage regions formed the highly phyric Longbao and Dayukou lavas. The pervasive occurrence of sieve textures and complex mineral composition profiles in both phenocrysts and glomerocrysts in Longbao and Dayukou samples belie complicated open system crystallisation histories of these magmas. We conclude that open system processes involving mush disaggregation and magma recharge in multi-level plumbing systems played an important role in the petrogenesis of these intracontinental tholeiites. Moreover, the important role of orthopyroxene in the petrogenesis of these tholeiites distinguishes them from many other tholeiite suites like MORB, as well as those erupted through thickened oceanic crust like in Iceland and the Shatsky Rise. This study highlights the importance of combining textural constraints with geochemical analyses.

Spatial Variations in Magmatic Volatile Influx and Fluid Boiling in the Submarine Hydrothermal Systems of Niuatahi Caldera, Tonga Rear‐Arc

AbstractSubmarine caldera volcanoes may host several hydrothermal systems along the caldera wall and related to volcanic cones. Fluid boiling and magmatic volatile influx are common processes in shallow (<2,000 mbsl) subduction zone‐related environments causing variations in the mineralogical and chemical composition of seafloor hydrothermal mineralizations that remain poorly constrained. The submarine caldera of Niuatahi volcano, Tonga rear‐arc, hosts four active vent sites discharging high temperature fluids (<334°C) with variable salinities (369–583 mM Cl) that are indicative of fluid boiling, recorded by distinct Te/As and Te/Au in pyrite, sphalerite, and chalcopyrite. High sulfidation mineral assemblages (e.g., enargite), stable S isotope data and similar trace element signatures in sulfides and native S condensates suggest a minor and/or infrequent contribution of magmatic SO2 to the hydrothermal systems located proximal to the caldera center causing a volatile element (e.g., Se, Bi, Te) enrichment. The hydrothermal system at the northern caldera wall is decoupled from the magmatic SO2 source, as revealed by radiogenic Pb isotopes. Instead, S isotope and trace element constraints propose a host rock‐dominated hydrothermal system, lacking a magmatic volatile influx. The observed hydrothermal fractionation processes (fluid boiling) and the distinct metal (loid) sources (magmatic volatiles vs. host rock) represent a continuum from magmatic volatile‐ to host rock‐dominated hydrothermal systems within the Niuatahi caldera. This leads to seafloor mineralizations with spatially selective trace element enrichments, like Te, Se, and Bi (±Au, Ag) in the caldera center compared to Au, Ag, Zn, Cd, and Pb at the northern caldera wall.

Isotopes track Tethyan seamount subduction beneath the Troodos spreading centre, Cyprus

Supra-subduction zone volcanoes record the chemical transfer of sedimentary and igneous material from the subducting plate to the overlying mantle and lithosphere. This transfer is thought to preferentially involve fluid-mobile elements, which swamp the signature of similar trace elements in the supra-subduction mantle. Using high-resolution isotope measurements of fluid-mobile Pb, we have traced the evolution and inputs beneath the supra-subduction spreading ridge that is now the Troodos Ophiolite, Cyprus. It is apparent that variable but significant amounts of Pb are actually derived from the mantle wedge, and substantial amounts of the fluid-immobile elements like Nb are introduced from the slab. Our study identifies a chemical transformation of the spreading crust, which reflects a spatial change in the Neo-Tethyan slab. The west was influenced by the subduction of pelagic/carbonate sediments overlying MORB, whereas the east and south also include a high 206Pb/204Pb component, similar to high-μ mantle plumes distributed around northern Africa. This chemo-tectonic switch is interpreted to represent the location of supra-subduction spreading relative to the path of a seamount chain colliding with and subducting beneath the Troodos trench. The Hecataeus Rise, located to the southeast of Cyprus, is a candidate to be a foundered relic of this seamount chain, locked in the subduction zone. We also demonstrate that the supra-subduction mantle wedge was of an Atlantic/Pacific-type composition, but the subducting Neo-Tethyan oceanic crust had an Indian Ocean signature. As such, this destructive plate boundary can be defined as the Cretaceous interface between the Atlantic and Indian mantle domains.