Composition Of Inclusions Research Articles

Research on the source of internal fault defects in 40Mn2 oil drill pipe

As an essential material in various industries, steel’s internal defects can seriously affect its performance and cause huge economic losses. To investigate the source of internal fault defects in oil drill pipes, this study used ultrasonic testing equipment to accurately locate internal fault defects in steel, and obtained the spatial coordinates of the defects as (2.15, 2.29, 0.77). Then, by dissecting layer by layer, the target defect was determined to be a large Al2O3 inclusion with a length of 1.609 mm and a width of 0.2 mm. Afterwards, based on the results of automatic scanning of inclusions, this study used extreme value statistical method to estimate the maximum size inclusions that may exist in steel, and found that the target defect size was much larger than the estimated value. Finally, to further determine the source of large inclusions, this study conducted sampling and analysis on immersion nozzles, refining slag, tundish slag, and mold flux. The study found that the matching degree between the composition of large inclusions and the composition of submerged nozzle nodules was the highest, indicating that the fault defect was caused by the peeling of nozzle nodules. This indicates the direction for process optimization.

Microstructural Characterisation of Ti and V-containing Synthetic Slags Mimicking the Chemical Composition of the Slag Inclusions of Ferrous Artefacts Produced in the Iron Factory of São João de Ipanema (XIX century, Brazil)

Microstructural Characterisation of Ti and V-containing Synthetic Slags Mimicking the Chemical Composition of the Slag Inclusions of Ferrous Artefacts Produced in the Iron Factory of São João de Ipanema (XIX century, Brazil)

Fluid flow, slag entrainment, and composition evolution of slag inclusions during vacuum degassing refining

A multiphase mathematical model was established to study the fluid flow, the open-eye formation, and the residence time of slag inclusions in a bottom argon-blowing ladle. The fluid flow was solved using the Eulerian-Lagrangian multiphase approach, and the interface between different phases was described using the Volume of Fluid (VOF) model. The motion of argon bubbles and slag inclusions was tracked with the method of the discrete phase model (DPM). Moreover, the composition transformation of slag inclusions was predicted by employing a kinetic model based on the coupled reactions model. Numerical results show that the flow of the molten steel and the open-eye of the molten slag were sensitive to the argon blowing rate. The larger argon blowing rate expanded the volume of the plume and the area of the open-eye. Slag droplets were considered to move with the steel to the region away from the open-eye and then entrained into the steel to form slag inclusions as there was barely any downward velocity around the open-eye. Most slag inclusions were able to be removed immediately after the entrainment, while there still were some slag inclusions retaining in the steel for as long as thousands of seconds. The composition of slag inclusions had an apparent transformation due to reactions with the steel. The content of SiO2 and MgO in slag inclusions had a decrease while that of Al2O3 rose remarkably. The variation of SiO2 content occurred in the early one minute and the MgO content reduced gradually from 7.34wt% to 1.12wt% in 10 min. The composition transformation of slag inclusions was basically completed within 10 min in the current case.

Transformation of inclusions in S32101 duplex stainless steel during continuous casting

In this study, the formation and characteristics of inclusions in S32101 duplex stainless steel (DSS) during continuous casting were investigated by analyzing inclusions in the tundish and continuous casting slabs. The composition of inclusions changed significantly during the continuous casting. The inclusion type in the tundish was primarily CaO-SiO2-Al2O3-MgO-MnO. There are two types of inclusions in the continuous casting slab: CaO-SiO2-Al2O3-MgO-MnO inclusions with dense Al2O3 and MnO, and Al2O3-MnO inclusions. TiN wraps the outer layers of both types of inclusions. The results obtained from thermodynamic calculations agreed with the experimental results. The weight percentage of Al2O3 and MnO in the inclusions increases significantly with the solidification process. In addition, the Al2O3-MnO inclusions were formed in the slab. TiN precipitates during the solidification of the S32101 DSS. The CaO-SiO2-Al2O3-MgO-MnO and Al2O3-MnO inclusions can be used as the nucleation sites of TiN.

ТИПОМОРФНЫЕ ПРИЗНАКИ САМОРОДНОГО ЗОЛОТА РОССЫПИ РЧ. ЛЕВЫЙ УЛАХАН ХАПТАСЫННААХ И ЕГО ВЕРОЯТНЫЕ КОРЕННЫЕ ИСТОЧНИКИ (АНАБАРСКИЙ ЩИТ)

The paper deals with studied typomorphic features of placer gold of the Left Ulakhan Haptasynnakh River, drainage rocks of the central Billakhskaya tectonofluid zone of the Anabar Shield, aimed at identifying its indicator signs and probable indigenous sources. The predominance of poorly rounded, mainly angular-cloddy individuals with rough pitted-lumpy surface, often with coatings of variable aluminosilicate composition, with small accretions of quartz and potassium feldspar, as well as a fraction >0.5 mm to 40% allowed the studied gold to be attributed to the autochthonous type. The study of nearby sulphidized rocks of the Haptasynnaakh zone showed that an ore mineralization is represented by a variety of mineral forms. The main ore mineral is pyrite. A wide range of telluride minerals was identified with predominance of silver and bismuth tellurides. For the first time, medium-high-grade gold of lamellar and rod-shaped forms was distinguished from crushed samples of mineralized rocks. Comparative analysis of the mineral inclusions composition in poorly rounded placer gold with a wide variation in gold fineness of the Left Ulakhan Haptasynnaakh and mineral parageneses of ores of the Haptasynnaakh ore zone allows researchers to assert that the zone ore manifestations are indigenous sources of the studied gold. The discovery of gold with an ore appearance of fraction >0.5 mm in the placer suggests the presence of mineralization of its coarser fractions in relatively deep horizons. This fact determines positive prospects for further study of the territory.

Effect of Mg treatment on inclusion behaviors in 430 ferritic stainless steel during solidification

To understand the effect of Mg treatment on the precipitation, growth, and transformation of inclusions in 430 ferritic stainless steel during solidification, slag refining and Mg treatment experiments with different cooling methods were conducted at 1873 K (1600 °C). Experimental results showed that the oxide inclusions in 430 stainless steel without Mg treatment were mainly Al2O3–SiO2–MnO (slag phase), Al2O3–Cr2O3–MnO (spinel phase), high-Al2O3 (corundum phase) and CaO–SiO2–Al2O3–MnO (slag phase), while all of the oxides except CaO–SiO2–Al2O3–MnO inclusions transformed to MgO–Al2O3–Cr2O3–MnO (spinel phase) after Mg treatment. With water quenching, the average inclusion diameters were about 1.4 μm in both of the Mg-free and Mg-bearing steels, while they increased to approximate 3.1 and 1.9 μm after furnace cooling, separately. With the decrease of cooling rate from 26.2 to 1.24 K s−1, in the Mg-free steel, the average Al2O3 and Cr2O3 contents in the inclusion increased from 19.6 to 42.6 mass% and from 12.22 to 19.44 mass%, respectively, and the average SiO2 content decreased from 43.5 to 17.1 mass%. However, the average composition of inclusions in Mg-bearing steel was relatively stable and independent of cooling rate. A kinetic model was established with the solute micro-segregation model to predict oxide inclusion growth during cooling and solidification. Without and with Mg treatment, under a cooling rate of 1 K s−1, the calculated final sizes of the most stable oxide inclusions were 3.27 and 1.88 μm, respectively. The predicted average compositions and diameters of oxide inclusions were generally consistent with the experimental results.

Stabilization Effect of Potato Starch on Characteristic Flavor Compounds in Onion Sauce

AbstractThe food industry is experiencing a substantial demand for transitioning to natural flavors. Nonetheless, the challenge lies in the inherent instability of most flavor molecules when removed from their original sources. Three representative flavor compounds, including dipropyl disulfide (DD), allyl mercaptan (AM), and dimethyl trisulfide (DT), are selected to form composites with potato starch (PS) to protect them from decomposition or transformation. Then, their physicochemical properties and microstructures are investigated using combined methods. PS can combine with these sulfides mainly through its amylose, and thioethers are more likely to interact with PS than mercaptan. All the composites have lower phase transition temperature and higher enthalpy values than PS, and PS‐AM exhibits the largest stability followed by PS‐DD and PS‐DT. The sulfides interact with PS by entering into the helical cavity of its amylose mainly through hydrophobic interaction and increase the long‐range ordered degree and short‐range ordered degree of the composites. DD, AM, and DT can form V‐type inclusion composites with PS, which reserves more DD and AM to delay flavor degradation and enhances the flavor stability of onion sauce. This study can provide valuable reference for the preservation of characteristic flavors of allium food products during thermal processing and storage.

Genesis of Pb-Zn deposits in northwestern Guizhou province of China: Constraints from the in situ analyses of fluid inclusions and sulfur isotopes

The northwestern Guizhou ore concentration area on the southwest margin of the Yangtze Block is an important part of the Sichuan-Yunnan-Guizhou Pb-Zn metallogenic province. Several large Pb-Zn deposits (e.g., Shanshulin, Shaojiwan, Yadu, and Tianqiao) are found in the area with similar mineral assemblages, ore-controlling structures, ore-hosting rocks, and genetic types. In this study, fluid inclusion microthermometry and in situ geochemical analysis were employed to determine the nature and compositions of the fluid inclusions trapped in calcite and sphalerite and the sulfur isotopic compositions of sphalerite and pyrite. Microthermometric results show that the ore-forming fluids are moderate to low temperature and salinity. The fluid inclusions in calcite and sphalerite share similar homogeneous temperatures (120 to 200 °C) and salinities (7–14 wt% NaCl equiv.). The in situ LA-ICP-MS analyses reveal that the fluid inclusions have high concentrations of elements such as Na, K, Mg, Ca, Rb, Sr, Ba, Cs, and Li. The ratios of K/Na, Rb/Na, Cs/Na, Ca/Na, and Ba/Na could be comparable to the basinal brines. The trend towards metamorphic water is possibly attributed to the involvement of basement-derived fluids. The in situ δ34S values of sphalerite and pyrite range from 11.3 to 20.2 ‰ and 12.0 to 18.9 ‰, respectively, which indicate that the reduced sulfur is most likely related to the thermochemical reduction of sulfate with multiple sources either from the ore-hosting strata or from Precambrian-Cambrian basement rocks which have high sulfur isotopic compositions. We propose that the fluid mixing is the main mechanism for the formation of Pb-Zn deposits in NW Guizhou.

Mechanism of carbonate assimilation by intraplate basaltic magma and liquid immiscibility: example of Wangtian’e volcano (Changbaishan volcanic area, NE China)

The balance of CO2 during abundant basaltic magma production is an important factor of volcanic hazards and climate. In particular, this can be explored based on CO2-rich mantle-derived magmas or carbonate assimilation by basaltic melts. To reconstruct the origin of Fe-rich carbonates hosted by Cenozoic basalts from Wangtian’e volcano (northeast China), we studied elemental compositions of melt, crystalline and fluid inclusions in magmatic minerals as well as the oxygen and carbon isotope compositions of the plagioclase and carbonates from basalts. The crystallization of basaltic magmas occurred in shallow chamber (∼4 km) at temperatures of 1,180°C–1,200°C and a pressure of 0.1 ± 0.01 GPa. Stable Fe-rich carbonates occur in the Wangtian’e tholeiite basalts as groundmass minerals, crystalline inclusions in plagioclase and globules in melt inclusions, which suggests that they crystallized from a ferrocarbonate melt. The values of δ18О and δ13С in the minerals analyzed by laser fluorination method are in line with the sedimentary source of Fe-rich carbonates, indicating assimilation and partial decomposition of carbonate phases. The parent ferrocarbonate melt could be produced during interactions between the basaltic magma and the crustal marbles. The phase diagram and thermodynamic calculations show that the ferrocarbonate melt is stable at a temperature of 1,200°C and a pressure of 0.1 GPa. Our thermodynamic calculations show that carbonate melt containing 73 wt% FeCO3, 24 wt% MgCO3 and 3 wt% CaCO3 is in thermodynamic equilibrium with silicate melt in agreement with our natural observations. The proposed mechanism is crustal carbonate sediment assimilation by the intraplate basaltic magma resulting in the melt immiscibility, production of the ferrocarbonate melt and the following Fe-rich carbonate mineral crystallization during magma residence and cooling.

Determination of the pressure and composition of wet gas fluid inclusions: An in situ Raman spectroscopic approach

Carbonaceous fluid within mineral-hosted inclusions provides important information for carbon cycle in deep Earth. In addition to CH4 and CO2, heavy hydrocarbons (e.g., C2H6 and C3H8) are frequently observed in carbonaceous fluid inclusions (i.e, wet gas inclusions with C1/∑Ci < 0.95). However, determination of the composition of such complex volatiles is difficult based on traditional microthermometric measurements. Here we carried out experimental calibrations on Raman spectroscopic measurements of the pressure (P) and composition of the CH4 ± C2H6 ± C3H8 ± H2S system at room temperature and 0.1–130 MPa. We confirmed that the C–H symmetric stretching vibration band of CH4 [ν1(CH4), ∼2917 cm−1] shifted to lower wavenumber with rising pressure, thus the P-ν1(CH4) relationship could be applied to calculate the pressure of wet gas. It should be noted that the presence of C2+ and/or H2S will shift the [ν1(CH4)] to lower wavenumber at constant pressure (with the order of C3H8 ≥ H2S > C2H6). Obviously, the P-ν1(CH4) relationship derived from pure CH4 system could not be simply applied to wet gas inclusion, otherwise the pressure would be overestimated. To avoid the overlap of the C–H vibrations of CH4, C2H6 and C3H8, the peak areas and peak heights of the overtone vibration of CH4 [2ν4(CH4), ∼2580 cm−1], C–C symmetric stretching vibrations of C2H6 [ν3(C2H6), ∼995 cm−1] and C3H8 [ν8(C3H8), ∼868 cm−1], and S–H symmetric stretching vibration of H2S [ν1(H2S), ∼2612 cm−1] were fitted using Gaussian + Lorentz functions. The obtained peak areas and peak heights were then used to calculate the Raman quantification factors (F factor and G factor, respectively) of C2H6, C3H8 and H2S relative to CH4, respectively. Both the F factor and G factor increased with rising pressure, whereas the FC2H6, FC3H8 and GH2S kept nearly constant at ∼5.69, 6.39 and 153.8, respectively in high pressure gas mixtures (e.g., >30 MPa). Therefore, for inclusions with higher internal pressure, the molar ratio of CH4, C2H6, C3H8 and H2S could be determined by the aforementioned F and G factors. This method was applied to the calcite-hosted single-phase gas inclusions in the Upper Permian Changxing Formation carbonate reservoir from the eastern Sichuan Basin (South China). Our results indicated that the trapping pressure would be obviously overestimated if the presence of heavy hydrocarbons was not taken into account.

An Assessment of Deep Borehole Disposal Post-Closure Safety

Around the world, deep borehole disposal is being evaluated for intermediate level-waste (ILW), high-level waste, and spent nuclear fuel. To facilitate a disposal concept options analysis for ILW in Australia, desktop and lab-based geoscientific investigations, together with generic post-closure safety assessments of deep borehole disposal of long-lived ILW, have been undertaken. This paper reports on geoscientific data obtained on crystalline rock and rock salt as model rocks for geological disposal. Petrophysical and mineralogical properties for these rocks have been investigated to provide realistic data for evaluation and input to post-closure safety assessments. For crystalline rock samples originating from depths between 700 to 1900 m, very low hydraulic conductivity (2 × 10−12 to 3 × 10−11 m/s) and very low porosity (0.02% to 1.2%) were obtained. The noble gas isotopic composition of fluid inclusions from the same depth interval confirmed the rock had been devoid of recent interaction with meteoric water, thus providing potentially suitable conditions for geological disposal. Rock salt from a 802-m (heterogeneous sample with 40% halite) and a 1100-m (sample with 98% halite) depth also had a low hydraulic conductivity (5 × 10−10 to 5 × 10−9 m/s at 802 m and 10−11 to 2 × 10−10 m/s at 1100 m) and very low porosity (~0.8% for the heterogenous sample and ~0.2% for the pure halite sample). Post-closure safety assessments based on numerical modeling provided bounding conditions around the thermal evolution of the disposal environment in crystalline rock for low heat generating ILW (50 W per 180-L vitrified waste canister), including exploring the sensitivity of temperature evolution within the borehole and rock environment to parameters such as heat load, borehole depth, geothermal gradients, and rock thermal conductivity. The coupling of heat transport with radionuclide migration to account for buoyancy-driven transport was shown to have a limited impact on radionuclide migration. For a disposal borehole in crystalline rock, the radionuclide concentrations and annual dose rates from key radionuclides (99Tc and 79Se) for a 500-m, 1000-m, or 3000-m deep borehole were negligible (i.e., many orders of magnitude smaller than the threshold dose the International Atomic Energy Agency considers insignificant for humans, 0.01 mSv/year). For disposal in rock salt, a suite of numerical model scenarios explored the effectiveness of the engineered barriers, including the glass matrix, primary package, and overpack, assuming diffusion-dominated transport. These scenarios illustrated that the performance of the disposal system was insensitive to the presence or absence of engineered barriers, as dose rates at late time (>105 years) were nearly identical for all scenarios. These results indicate that the natural barrier provided by the salt is very effective at containing radionuclides, while the engineered barriers serve mainly to delay the arrival of the peak dose. While the results are preliminary, the post-closure safety assessments, supported by measured data from crystalline rock and rock salt, give confidence that deep borehole disposal of long-lived ILW would result in dose rates considered insignificant for humans within a few meters from the borehole.

Investigation on the formation mechanism of composite inclusions by multi-scale characterization in high manganese steel with yttrium addition

The rare earth modification of inclusions is an effective method to solve the critical issue of brittle inclusions leading to the failure of high manganese steel railway frog as one of the most essential assemble units of the railway operating system. The high manganese steel with rare earth yttrium was produced using a vacuum induction furnace. The multi-dimensional structural analysis of composite inclusions in the high manganese steel was performed to clarify the composition, crystal structure, and interface structure of the composite inclusions at multi-scales ranging from micrometers and nanometers to atoms and electrons. The chemical composition and morphology of composite inclusions were characterized by scanning electron microscopy with energy dispersive X-ray spectroscopy. After modification with rare earth yttrium, the MnS-Al2O3 composite inclusions in the steel transform into Y2S3-Y2O2S composite inclusions with smaller dimensions and approximately spherical shapes. The interface structure and crystallographic orientation of the Y2S3-Y2O2S composite inclusions were revealed as Y2O2S (100) // Y2S3 (5 0 3) by the focused ion beams scanning electron microscopy and the high-resolution transmission electron microscopy analysis. Moreover, the first-principles calculations were performed to obtain the adsorption energies and electronic structures of Y and S atoms at various positions on different terminations of the three low-index surfaces ((1 0 0), (110), and (111)) of Y2O2S, which reveals the adsorption pathway of Y and S atoms and formation mechanism of enclosed phase Y2S3 on the core phase Y2O2S that the adsorbate Y and S atoms grew parallel to the Y2O2S (1 0 0) surface and formed specific hexagonal ring structures of Y2S3 crystal.

Micro FT-IR spectroscopic measurements of CH4: Experimental calibration with high-pressure and high temperature optical cell (HPOC)

Fourier transform infrared spectroscopy (FTIR) is a prevalent nondestructive in situ analytical technique widely employed for the qualitative characterization of natural fluid inclusions. Presently, the quantitative determination of the temperature, pressure, and composition of natural inclusions stands as a pivotal challenge in the geological application of laser spectroscopy. Through the integration of the capillary high-pressure optical cell (HPOC) technique and Fourier transform infrared spectroscopy, infrared quantitative models for the C–H symmetric stretching band (v3) in the vapor phase of CH4 under varying temperature (40–200 °C) and pressure (20–500 bar) conditions are established for the first time. This accomplishment is achieved through fitting and calculation of infrared spectra. A linear quantitative relationship and the dynamic evolution of infrared spectral parameters (peak area, full width at half maximum, peak height ratio, and peak shifts) concerning temperature, pressure, and density are meticulously investigated. The findings reveal that the peak area and full width at half maximum exhibit an upward trend with increasing pressure and density, and are inversely proportional to temperature. The height ratio (P band/Q band, R band/Q band) experiences an increase as density escalates. Moreover, the CH4v3 band position shows a higher wavenumber shift with increasing temperature, while its position correlates negatively with pressure and density. Thus, this method demonstrates its applicability in deducing the PVT-x properties of CH4-bearing systems, including CH4-rich fluid inclusions, CH4 content within hydrocarbon inclusions, and experimental fluid investigations. In contrast to the Raman quantitative approach, the infrared quantitative formula can be universally adopted in any infrared laboratory owing to the quantitative theory (Beer–Lambert law) governing infrared absorption spectra. By collecting Raman spectra and infrared spectra of pure methane fluid inclusions from the central region of the Alps and subsequently calculating the results using two distinct quantitative methods for fluid inclusions, we have demonstrated the feasibility of applying infrared spectroscopy in natural fluid inclusion studies.

Control of the Composition and Morphology of Non-Metallic Inclusions in Superduplex Stainless Steel

Duplex stainless steel is a unique material for cast products, the use of which is possible in various fields. With the same chemical composition, melting, casting and heat treatment technology, pitting and crevice corrosion were observed at the interphase boundaries of non-metallic inclusions and the steel matrix. To increase the cleanliness of steel, it is necessary to carefully select the technology for deoxidizing with titanium or aluminum, as the most common deoxidizers, and the technology for modifying with rare earth metals. In this work, a comprehensive analysis of the thermodynamic data in the literature on the behavior of oxides and sulfides in this highly alloyed system under consideration was performed. Based on this analysis, a thermodynamic model was developed to describe their behavior in liquid and solidified duplex stainless steels. The critical concentrations at which the existence of certain phases is possible during the deoxidation of DSS with titanium, aluminum and modification by rare earth metals, including the simultaneous contribution of lanthanum and cerium, was determined. Experimental ingots were produced, the cleanliness of experimental steels was assessed, and the key metric parameters of non-metallic inclusions were described. In steels deoxidized using titanium, clusters of inclusions with a diameter of 84 microns with a volume fraction of 0.066% were formed, the volume fraction of which was decreased to 0.01% with the subsequent addition of aluminum. The clusters completely disappeared when REMs were added. The reason for this behavior of inclusions was interpreted using thermodynamic modeling and explained by the difference in temperature at which specific types of NMIs begin to form. A comparison of experimental and calculated results showed that the proposed model adequately describes the process of formation of non-metallic inclusions in the steel under consideration and can be used for the development of industrial technology.

The oxidation state of titanium in silicate melts

Titanium occurs as Ti3+, in addition to the more usual Ti4+, in extraterrestrial materials such as Lunar basalts and chondritic meteorites. The proportion of Ti as Ti3+ was investigated by Ti K-edge X-ray absorption near edge structure (XANES) spectroscopy for five silicate glass compositions quenched from melts equilibrated at 1400 °C, atmospheric pressure, and oxygen fugacities (fO2) in log units relative to the fayalite-magnetite-quartz (FMQ) buffer from FMQ+3.3 to FMQ-10.2 (+6.6 to −6.9 log units relative to the iron-wüstite, IW, buffer). All spectra could be well fit using a linear combination of the spectra recorded from the most oxidised and reduced samples of the same composition, indicating that the samples only contain two Ti species. Ti3+/ΣTi (where ΣTi = Ti3+ + Ti4+) = 0 for the most oxidised samples but is unknown for the most reduced. Thus, the linear combination fit results were used in a regression model in which Ti3+/ΣTi of the reduced end-member was varied to give Ti3+/ΣTi values of the other samples that best fit the thermodynamically expected dependence of Ti3+/ΣTi on fO2. The most reduced samples were found to have Ti3+/ΣTi ∼ 0.6. The resulting modified equilibrium constants of the Ti oxidation reaction, logK', are linearly correlated with the optical basicity (Λ) parameterisation of melt composition, such that as Λ increases, Ti3+/ΣTi decreases, at constant fO2. This correlation allows Ti3+/ΣTi to be predicted for other compositions and, assuming that the temperature dependence of Ti3+/Ti4+ is parallel to FMQ, a general equation relating Ti3+/Ti4+ to fO2 was obtained: log(Ti3+/Ti4+) = −0.25ΔFMQ − 0.32(19) − 3.44(32)Λ. This equation was used to predict Ti3+/ΣTi as a function of fO2 for high-Ti Mare basalt, chondrule (CV and CM), and calcium aluminium inclusion (CAI; Type A and B) compositions. For melts of these compositions Ti3+ = Ti4+ at ∼ FMQ-10.8, −9.5, −9.3, −10.6, and −10.2 (∼IW-7.5, −6.2, −6.0, −7.3, and −6.9), respectively, independent of temperature.

Regional characteristics of iron manufacturing techniques and the related issue of the supply system on Han’s southern Frontiers: A metallurgical study of iron implements from Chenzhou, Hunan

Southern Hunan is known to be one of the few iron manufacturing regions in the Han period. The study of iron implements from this region should yield important evidence concerning the regional iron-making techniques used and the local iron industry. We provide a detailed account of the technological aspects of iron implements yielded from Chenzhou, a major node on the traffic routes entering the broader southern frontiers. Our analysis focuses on the metallographic features and chemical compositions of inclusions in the examined objects. The results reveal that cast iron and related annealing or decarburization techniques were commonly used. Most implements were made using solid-state decarburization of cast iron, along with malleable cast iron and fined iron. This technological profile is similar to other case studies in the literature, but also highlights regional characteristics such as the relatively sparse presence of fined iron. Based on this observation, we discuss various factors that could have contributed to this situation. In a broader context, the analysis of this collection can contribute to the further investigation of the regional characteristics of the Han period iron industry.

Subcretion of altered oceanic crust beneath the SW São Francisco Craton, Brazil – A stable isotope study on diamonds and their inclusions

The presence of diamonds of lherzolitic, eclogitic and websteritic paragenesis in proximal alluvial deposits on the southwestern edge of the São Francisco Craton documents the incorporation of subducted oceanic crust and associated metasomatism through slab dehydration fluids affecting the local SCLM. To better constrain the subduction-association of diamond substrates and metasomatic events, we conducted a combined study of the δ13C-δ15N-[N] characteristics of 81 diamonds and the δ18O values of four of their eclogitic garnet inclusions. Diamond carbon isotope compositions range from −25.5 to +0.5‰, with 13C-depleted diamonds (≤ −7‰) being exclusively of eclogitic/websteritic paragenesis while the 13C-enriched (≥ −2‰) tail of the distribution is related to diamonds with lherzolitic inclusions. Nitrogen isotope values range from −14.2 to +25.5‰, with about half of the values being positive. A general absence of coherent trends in δ13C-δ15N-[N] across growth zones implies that diamond formation did not occur under fluid-limited conditions. Instead, the observed heterogeneity in carbon and nitrogen isotope compositions reflects contributions of distinct source reservoirs hosted in both altered oceanic crust and Earth's mantle. Nitrogen contents peak around a δ15N value of −3.5‰, indicating that more N-rich fluids, presumably representing a primitive endmember composition, have a mantle-like δ15N signature. While positive and negative δ15N values occur equally near the δ13C mantle value (−5 ± 2‰), 13C-depleted diamonds have nitrogen isotope compositions skewed towards positive values.13C depletion and 15N enrichment is a signature of biogenic carbonates/organic matter and low-T clays in uppermost, basaltic sections of oceanic crust that experienced low-temperature seawater alteration prior to subduction. Correspondingly, the oxygen isotope compositions of eclogitic garnet inclusions fall in a restricted range between +5.5‰ to +7.0‰. For three of the four samples, the stable isotope signatures of inclusions and host diamonds display perfect agreement, with the intensity of seawater alteration signatures, in the form of garnet inclusion 18O enrichment and host diamond 13C depletion and 15N enrichment, increasing together. For the fourth sample, the δ18O signature of the garnet inclusion (+5.5‰) and δ13C-δ15N signatures of the diamond host (−25 and + 19‰, respectively) are decoupled. While the mantle-like δ18O signature indicates a diamond substrate derived from deeper levels in oceanic crust (e.g., deep sheeted dikes), the diamond-forming fluids must have originated from sources that originally resided near the sea water interface. A viable mode of mixing such disparate isotopic signatures is the interaction of diamond-forming fluids derived from shallow oceanic crust altered at low-temperatures with eclogitized substrates originally formed in deeper levels of oceanic crust. This process likely occurred during diamond formation in a tectonic subduction mélange, which juxtaposes deeper and shallower levels of oceanic crust. In the lithospheric mantle above the subcreted oceanic slab, the elevated carbon isotope and highly variable nitrogen isotope compositions of diamonds formed in lherzolitic substrates likely relate to devolatilization and/or melting of principally oceanic sediments containing marine carbonates and clays and subsequent mixing with mantle-derived volatile components. In combination, our diamond and inclusion stable isotope data provide insight into multiple processes that promote diamond formation both inside subducted slabs accreted to the São Francisco cratonic keel and in adjacent subcontinental lithospheric mantle.

The noble gas signature of the 2021 Tajogaite eruption (La Palma, Canary Islands)

Here, we characterize the temporal evolution of volatiles during the Tajogaite eruption by analyzing the elemental (He-Ar-CO2-N2) and isotopic (He-Ar-Ne) composition of fluid inclusions (FI) in phenocrysts (olivine+pyroxene) identified in erupted lavas. Our 2021 lava samples identify substantial temporal variations in volatile composition. We show that, during the 2021 Tajogaite eruption, the He-CO2-N2 concentrations in FI increased since October 15th; this increase was accompanied by increasing 40Ar/36Ar ratios (from ∼300 to >500), and paralleled a major shift in bulk lava chemistry, with increasing Mg contents (Mg#, from 47 to 52 to 55–59), CaO/Al2O3 (from 0.65 to 0.74 to 0.75–0.90), Ni and Cr, and decreasing TiO2, P2O5 and incompatible elements. The olivine core composition also became more forsteritic (from Mg# = 80–81 to Mg# = 84–86). Mineral thermobarometry and FI barometry results indicate that the eruption was sustained by magmas previously stored in at least two magma accumulation zones, at respectively ∼6–12 km and 15–30 km, corroborating previous seismic and FI evidence. We therefore propose that the compositional changes seen throughout the eruption can be explained by an increased contribution - since early/mid-October - of more primitive, less-degassed magma from the deeper (mantle) reservoir. Conversely, Rc/Ra values (3He/4He ratios corrected for atmospheric contamination) remained constant throughout the whole eruption at MORB-like values (7.38 ± 0.22 Ra, 1σ), suggesting an isotopically homogeneous magma feeding source. The Tajogaite He isotope signature is within the range of values observed for the 1677 San Antonio lavas (7.37 ± 0.17Ra, 1σ), but is more radiogenic than the 3He/4He values (>9 Rc/Ra) observed in the Caldera de Taburiente to the north. The 3He/4He ratios (6.75 ± 0.20 Ra, 1σ) measured in mantle xenoliths from the San Antonio volcano indicate a relatively radiogenic nature of the mantle beneath the Cumbre Vieja ridge. Based on these results and mixing modeling calculations, we propose that the homogeneous He isotopic signatures observed in volatiles from the Tajogaite/San Antonio lavas reflect three component mixing between a MORB-like source, a radiogenic component and small additions (6–15%) of a high 3He/4He reservoir-derived (>9Ra) fluid components. The simultaneous occurrence of high 3He/4He (>9Ra)- and MORB-like He signatures in northern and southern La Palma is interpreted to reflect small-scale heterogeneities in the local mantle, arising from spatially variable proportions of MORB, radiogenic, and high 3He/4He components.

HELIUM ISOTOPIC COMPOSITION IN ALKALINE INTRUSIONS OF THE HOVSGOL AREA, NORTHWESTERN MONGOLIA

The helium isotope composition of fluid inclusions has been studied in magnetite from alkaline and subalkaline intrusions of the Hovsgol area in NW Mongolia. The measured content of 4He is in the range from 6.6 × 10–7 to 114 × 10–7 см3/г. The 3He/4He isotopic ratio of most samples varies within 0.23–0.59 Ra and may indicate the presence of helium from different sources in the magmatogenic fluid. The largest amount of mantle He (2.51 Ra) is hosted by the magnetite of the subalkaline gabbro. During the generation of primary magma, which probably involved either SCLM-type material or a plume-like reservoir less enriched in 3He, the mantle component accounted for approximately 40–60%. In the evolution of foid and alkali-syenite melts, its share did not exceed ~10–15% due to mixing with crustal radiogenic He. We assume that the intrusions interacted with fragments of Precambrian accretionary-collisional complexes of the Tuva-Mongolian terrane. Such mixing of He isotopes in melts and fluids may be regarded as circumstantial evidence supporting the development of mantle magmatism at the active continental margin.

EVOLUTION OF THE VICTORIA PIPE ULTRAMAFIC ALKALINE MELT (ANABAR REGION, SIBERIAN CRATON): MELT INCLUSION WITHIN OLIVINE AND GROUNDMASS MINERALS

To provide new insights into evolution of the primary ultramafic alkaline melts, we present an investigation of the primary and secondary melt inclusions within olivine macrocrysts and groundmass minerals from the Victoria monticellite-nepheline damtjernite, Anabar diamondiferous province, Siberia craton. The primary melt inclusions within olivine macrocrysts shown that initial damtjernite melts were K–Na bearing carbonate-silicate melts by composition whereas the K and Na associated within only silicate phases like that phlogopite, nepheline, kalsilite. That distinguishes these inclusions from similar inclusions in olivines from aillikites and kimberlites and emphasizes a more alkaline character of the damtjernitic parental melts. Based on the composition of melt inclusions within spinel and monticellite from magmaclastic groundmass, under the further evolution of the damtjernitic melts, K and Na are not only included in silicate daughter phases, but they can also form alkaline phosphates, carbonates, sulfates, and halides. That led to form the alkaline carbonate and saline sulfate-phosphate-chloride-carbonate liquids. This composition of the evolved ultramafic alkaline melt is common for melt inclusions within different minerals from aillikite, kimberlite and some carbonatites highlighted uniform mechanism of evolution of alkaline-ultramafic melts. Further accumulation of the fluid phase led to its reaction interaction with olivine with the formation of monticellite and degassing processes.