Homogenization Temperatures Research Articles

A novel flow channel design to achieve high temperature homogenization in solid oxide fuel cell

The thermal stress, which has a significant impact on the stable and prolonged operation of Solid Oxide Fuel Cells (SOFCs), can be further aggravated by the presence of local hot spots. Improving the distribution uniformity of physical quantities is of great significance to improving the internal temperature distribution of the SOFC. In this study, to improve the uniformity of temperature distribution, the thermal and flow distribution of three kinds of flow fields are investigated including Z, U, and L flow fields. The results show that the temperature distribution is dominated by the flow rate distribution. To optimize the physical quantity distribution of the designed flow channel, a novel, and easy-to-manufacture thermal management is proposed. This method is to adopt the extended ridge for controlling the flow rate into each flow channel. Moreover, a multi-population genetic algorithm is adopted to optimize the length of each extended ridge. The optimized results show that the temperature deviation in the Z, U, and L flow fields are reduced by about 64.20 %, 26.06 %, and 23.45 % respectively. This novel thermal management method enables more uniform temperature distribution and it is expected to be used in large-scale manufacturing due to its simple but subtle design.

Periods and Processes of Oil and Gas Accumulation in the HZ-A Structure Double Paleogene Field, Pearl River Mouth Basin

The source of oil and gas and the stages of oil and gas accumulation in the “double-Paleo” field of the HZ-A structure in the Pearl River Mouth Basin are analyzed, and the spatiotemporal coupling relationship of the key conditions of oil and gas accumulation are discussed to reconstruct the process of oil and gas accumulation. Based on previous research results, which are based the characteristics of biomarker compounds, the oil and gas in the HZ-A structure double Paleogene field came from the Paleogene Wenchang Formation hydrocarbon source rocks in the HZ26 sub-sag. By means of the casting thin section identification and inclusion homogenization temperature measurement, this paper reveals the three major hydrocarbon accumulation periods and corresponding fluid charging types in the “double-Paleo” field of the HZ-A structure in the Pearl River Mouth Basin. The results show that 13.8–10 Ma is the charging period of low mature crude oil, 10–5.3 Ma is the charging period of mature crude oil, and from 5.3 Ma is the natural gas charging period. Based on actual geological, drilling, logging, and seismic data, the key conditions for hydrocarbon accumulation in the HZ-A structure “double-Paleo” field are sorted out; that is, the source conditions are characterized by high-quality lacustrine source rocks generating early oil and late gas and a near-source continuous hydrocarbon supply. The reservoir conditions are characterized by weathering and superposition of a fracture zone that transforms into a reservoir, and a large-scale sandstone rock mass that transforms into a reservoir. The caprock conditions are characterized by the stacking of several thin mudstones that form a seal and the combination of multiple lithologies that block hydrocarbon migration. The trap conditions are characterized by multistage uplift structure traps and fracture-lithology combination control traps. The transport conditions are characterized by multi-stage cross-bed transport of source-connected faults and lateral differential transport of shallow sand in deep fractures. Finally, oil and gas accumulation models of the HZ-A structure double Paleogene field were established, and the accumulation process was reconstructed. The overall process involved three stages, with the first stage being the localized oil-displacing-water mode, the second being the large-scale oil-displacing-water mode, and the third being the late progressive gas-displacing-oil mode.

Mineralogy, fluid inclusion and stable isotope characteristics of the Inlice (Konya, Turkey) high sulfidation epithermal gold deposit: Implications for hydrothermal evolution and ore genesis

The Inlice high sulfidation epithermal gold deposit with 262,300 oz of gold ore is located in the Erenlerdağ-Alacadağ Volcanic Complex (EAVC) at the northern part of central Taurides. The volcanic succession of the study area is stratigraphically represented by andesite, block and ash flow, basaltic andesite lava flow and andesite lava flow. The deposit consists of seven neighboring mineralized veins termed Ana East, Ana West, West, Discovery, Güllü, Merkez and North Zone and is associated with an andesite (ca 8–9 Ma). Hydrothermal alteration from the innermost to the outermost parts of the deposit includes silicification, advanced argillic, intermediate argillic and propylitic. At the surface, quartz veins related to silicification are exposed as linear topographic relief trending mainly northwest-southeast and secondarily northeast-southwest and east-west. Deep drill core samples, including magnetite, quartz, biotite and anhydrite, imply the presence of potassic alteration in depth (50 to 970 m) possibly related to a porphyry Cu system. Ore assemblages are described as hypogene and supergene. The hypogene ore mainly includes pyrite (Py-I and Py-II) and enargite, and to a lesser extent chalcopyrite, sphalerite and marcasite. The supergene ore incorporates hematite and goethite, and minor covellite, chalcocite, malachite and native copper. Hypogene gold precipitation is associated with the mineral association of Py-II, chalcopyrite and enargite, while enargite mineral is a major host for gold (up to 600 ppm). Supergene oxidation resulted in the development of a secondary enrichment zone for gold (up to 14 g/t) extending to a depth of about 45 m.Microthermometric measurements show that the silicification associated with the mineralization was formed at homogenization temperatures ranging between 147 and 360 °C and salinities up to 6.5 wt% NaCl. This suggests that the fluid mixing and/or fluid dilution processes were important factors controlling the precipitation of gold. δ34S isotope compositions are between −0.9 and − 9 ‰, and further indicate a significant involvement of magmatic components into the hydrothermal fluids. Thus, it is concluded that at Inlice the hydrothermal fluids responsible for the alteration and mineralization processes were derived by relatively dilute fluids formed by the mixing of magmatic fluids with meteoric waters.

Source of quartz cement and its impact on reservoir quality in Jurassic Shaximiao Formation in central Sichuan Basin, China

Quartz cement is an essential authigenic mineral in the tight sandstones of the Shaximiao Formation in the Sichuan Basin, China. Accurately identifying its sources and investigating its impact on reservoir quality is important for understanding diagenetic fluid evolution and pore development in these reservoirs. To address this, we conducted a systematic analysis of the silicon sources in quartz cement employing mineralogical, fluid inclusion, and geochemical data. Quartz cement is characterized by two phases of quartz overgrowth and pore-filling authigenic quartz. Homogenization temperatures of fluid inclusions range from 60 to 150 °C, indicating that quartz cementation occurred from the early diagenetic phase (B stage) to the late mesodiagenetic phase. During the early diagenetic stage, volcanic material was dissolved by meteoric water, resulting in the formation of the earliest quartz cement and smectite. At temperatures of approximately 70–100 °C, smectite illitization, accompanied by K-feldspar consumption and SiO2 precipitation. In the mesodiagenetic stage (temperature approximately 100–130 °C), organic acids led to the dissolution of minerals like feldspar and laumontite, releasing SiO2. In the deep burial stage, clastic quartz grains experienced dissolution due to high stress, providing a limited source of SiO2. Smectite alteration and the dissolution of aluminosilicate minerals represent the primary sources of silicon for quartz cementation, while contributions from volcanic material hydrolysis and pressure solution are relatively minor. The presence of chlorite films inhibits the development of quartz overgrowths, and the limited precipitation of authigenic quartz within the primary porosity has a minimal impact on reservoir quality. Consequently, sandstones rich in chlorite films represent a favorable lithology for the development of high-quality reservoirs.

Multi-stage magmatic fluid recharge and fluid mixing developed the Gongdongchong intermediate-sulfidation type epithermal Pb-Zn deposit, North Huaiyang, China: Constraints from petrography, fluid inclusion and in situ geochemistry studies of sphalerite

The Gongdongchong (GDC) lead and zinc deposit is located in the North Huaiyang (NHY) metallogenic belt, northern part of the Dabie orogen. Its Pb-Zn orebodies are predominately in the breccia pipe hosted by the Early Paleozic Foziling Group. Three stages of mineralization could be divided according to replacement relationships and petrography, and the ore and gangue mineral assemblages at the main base metal stage were recognized as combination of Fe-poor sphalerite + galena + pyrite + chalcopyrite + tetrahedrite with quartz and calcite. Three successive generations of sphalerite were distinguished through detailed petrographic observation on crystal-scale, namely Spc (core), Spm (mantle), and Spr (rim). Fluid inclusion petrography result shows that two-phase liquid-rich fluid inclusions are the dominant type in sphalerite. Microthermometric results show the homogenization temperatures and salinities of Spc ranged from 233 °C to 268 °C and 6.6 to 10.4 wt% NaCl equiv. While fluid inclusions in the Spm display homogenization temperatures of 241 °C to 284 °C, with salinities of 8.7 to 11.3 wt% NaCl equiv. This increasing trend may imply a magmatic fluid recharging from core to mantle. However, fluid inclusions in the Spr have homogenization temperatures of 231–254 °C, with salinities of 6.3–9.1 wt% NaCl equiv. A trend of mixing with meteoric water is manifested by the decrease of temperatures with decreasing salinities from mantle to rim. It suggests the combination of the magmatic fluid recharging and mixing of meteoric water should be the key mechanism responsible for the sphalerite precipitation at the GDC deposit. Meanwhile, the GDC deposit shows a similar range of homogenization temperatures and salinities with typical intermediate-sulfidation epithermal deposits, and these homogenization temperatures also correspond well with the geological thermometer results acquired by trace element concentrations of sphalerite. In addition, the sphalerite geochemical results obtained from trace elements as Mn, Co, In and Ge illustrate that the GDC Pb-Zn deposit shares a good consistence with epithermal Pb-Zn deposit.Based on the evidences presented above, combined with the geological and geochemical features, the GDC deposit can be classified as an intermediate-sulfidation epithermal deposit. Intermediate-sulfidation epithermal deposits usually share spatial and genetic relationships with porphyry deposits. This may provide new implication for the mineral exploration of porphyry deposits at depth in the NHY metallogenic belt.

Temperature gradient enhances the solidification process and properties of a CoCrFeNi high-entropy alloy: Atomic insights from molecular dynamics simulations

Material properties are substantially affected by the process during fabrication. To what extent for high-entropy alloys (HEAs), however, is still an open question. Herein, we investigated the effect of a temperature gradient on the solidification of a CoCrFeNi HEA using molecular dynamic simulations. The nucleation and crystal growth under gradient temperatures significantly differ from those under homogeneous temperatures. The HEA solidified by a temperature gradient forms a single and uniform face-centered cubic (FCC) crystalline phase, and the residual stresses in the solidified tissue are optimized. During the homogeneous solidification process, in addition to the FCC phase, the hexagonal close-packed (HCP) phase and a small amount of body-centered cubic (BCC) phase were also formed. When the temperature gradient is 100 K, the stress distribution in the solidification microstructure is relatively low. Increasing the temperature gradient can enhance the crystallinity of the solidification microstructure. While, an increase in cooling rate will lead to a reduction in the crystallinity of the solidification microstructure and an increase in internal stresses within the solidification microstructure. A slight short-range order (SRO) phenomenon present in both solidified structures. Our atomistic insights might be helpful in the fundamental understanding and material design of HEAs.

Genetic relationship between skarn and porphyry mineralization at the Saibo copper deposit, West Tianshan, NW China: Constraints from fluid inclusions, H–O–C–S–Pb isotopes, and geochronology

The Saibo skarn–porphyry deposit, located in West Tianshan, NW China, is a large copper deposit discovered recently; however, information regarding the differences and connections between skarn and porphyry mineralization remains limited. Thus, this study aimed to investigate fluid inclusions (FIs), H–O–C–S–Pb isotopes, and U–Pb, and Re–Os geochronology to unravel the origin and evolution of the entire hydrothermal system. Skarn mineralization occurs as stratiform and lenticular in the contact zone between the granodiorite porphyry and Kusongmuqieke Group limestone. We identified four mineralization stages: prograde skarn stage (IS), retrograde skarn stage (IIS), quartz–pyrrhotite–chalcopyrite stage (IIIS), and calcite–quartz–pyrite stage (IVS), and four types of FIs: CH4-rich (C-type), halite-bearing (S-type), vapor-rich (V-type), and liquid-rich (L-type) FIs. The homogenization temperatures (Th) of FIs from stages IS, IIIS, and IVS were 366–419, 271–315, and 174–235 °C, respectively, with salinities of 1.7–46.0, 2.2–9.6, and 4.5–7.7 wt% NaCl eqv., respectively. Porphyry mineralization occurs as veinlet-disseminated ores in the granodiorite porphyry. We identified three mineralization stages: quartz–molybdenite–pyrite stage (IP), quartz–chalcopyrite–pyrite stage (IIP), and calcite–quartz–galena stage (IIIP). Unlike skarn mineralization, only the S-, V-, and L-type FIs were identified, with Th of 332–379, 263–315, and 169–233 °C from stages IP, IIP, and IIIP, respectively, and salinities of 1.9–42.3, 2.2–9.6, and 4.2–6.9 wt% NaCl eqv., respectively. The H–O isotope data indicate that the ore-forming fluids were initially derived from magmatic water and gradually diluted by meteoric water during fluid migration. According to C isotope data and the presence of C-type FIs, fluids from skarn mineralization contained more organic carbon than those from porphyry mineralization. The S–Pb isotope data of sulfides suggest that ore-forming materials are derived from both granodiorite porphyry and the Kusongmuqieke Group, although the latter contributed more to skarn mineralization. Pyrites from porphyry mineralization yielded a Re–Os isochron age of 376.0 ± 7.9 Ma, which was slightly younger than the chalcopyrite Re–Os ages of skarn mineralization (>379 Ma). The granodiorite porphyry, which is considered the ore-causative intrusion, yielded a U–Pb age of 380.8 ± 1.8 Ma. Our results indicate that two styles of mineralization were formed successively at different spatial locations during the emplacement of the granodiorite porphyry in a southward subduction setting of the North Tianshan Ocean. The proposed metallogenic model provides a better understanding of the Saibo skarn–porphyry metallogenic system and is expected to assist in the exploration of similar deposits in the West Tianshan orogenic belt.

Composition, formation conditions, distribution patterns and zoning of gold mineralization in the Stadukhinsky ore-placer region (Western Chukotka)

Gold deposits associated with granitoid intrusions have long been known. Recently, a class of deposits was identified among them, called intrusion-related granite systems, IRGS (gold-rare metal formation). The standards of the geological prospecting model for them are the deposits of the Tintin metallogenic belt (Alaska, Canada). In Russia, this type has been studied less; IRGS includes the Shkolnoye and Butarnoye (Magadan region) and Kekura (Chukotka) deposits. Based on field and laboratory studies, generalization of prospecting geological and geochemical data, the characteristics and localization features of gold mineralization associated with granitoids of a large igneous uplift in the South Anyui structural-formational zone (Western Chukotka) were determined. The mineral composition of ores, the sequence of their formation were studied, homogenization temperatures and salt concentrations in gas-liquid inclusions were determined. The geochemical and mineralogical zoning of the ore-magmatic system has been identified, and criteria have been developed for assessing erosion and predicting gold mineralization to depth.

The Influence of Homogenisation Parameters on the Microstructure and Hardness of AlMnFeMgSi(Zr) Wrought Alloys

The purpose of this investigation is to improve the mechanical properties of AlMnFeMgSi wrought alloys by forming a high number density of nano-scaled strengthening dispersoids during homogenisation annealing. The process chain for AlMnFeMgSi wrought alloys includes homogenisation annealing after continuous casting. In this step, inhomogeneities and segregations are dissolved and dispersoids are precipitated. The formed dispersoids hinder grain growth, but usually cannot increase the strength due to their coarse size of some 100 nm. Lower homogenisation temperatures should result in the precipitation of smaller dispersoids during homogenisation. The addition of Zr was investigated to increase this effect. Zr should form further dispersoids from the Al3Zr phase. This requires a fundamental understanding of the temperature-dependent kinetics and the nature of precipitation formation during homogenisation. For this purpose, the as-cast state is first characterised via differential scanning calorimetry. Subsequently, a large number of homogenisation parameters are investigated and quantified via hardness testing. The micro- and nanostructure are investigated for promising parameters and a particle analysis is performed. In the present study, it was possible to precipitate fine dispersoids of few 10 nm by reducing the homogenisation temperature, which resulted in a significant increase in hardness. Alloying with Zr enabled the precipitation of further dispersoids with a size of a few nm in a high number density, which further increased the strength.

Ore Mineralogy, Fluid Inclusion Geochemistry, and Zircon U-Pb Geochronology of the Nanmingshui Gold Deposit in East Junggar, Xinjiang, Northwest China: Implications for Ore Genesis

The Nanmingshui gold deposit, located in the eastern segment of the Kalamaili gold belt (KGB), is hosted by the sub-greenschist facies rocks of the Lower Carboniferous Jiangbasitao Formation. The genesis of this deposit, however, has been debated for decades because of controversial constraints on the P-T-X conditions and origins of hydrothermal fluid and mineralization age. In this study, we present gold-bearing sulfide compositions, fluid inclusions, H-O isotopes, and the results of hydrothermal zircon U-Pb dating to provide new insights into the genesis of the gold deposit. Three gold mineralization stages are recognized: quartz–pyrite–minor native gold veins (early), quartz–tourmaline–arsenopyrite–pyrite–gold–polymetallic sulfide veins (middle), and quartz–calcite veinlets (late). Gold predominantly occurs as native gold with high fineness ranging from 941 to 944 in sulfides and quartz, and some as solid solutions (Au+) within the lattice of pyrite and arsenopyrite. Three types of primary fluid inclusions are identified in hydrothermal quartz: CO2-H2O (C-type), aqueous (W-type), and pure CO2 (PC-type) inclusions. The early-stage quartz mainly contains C-type and minor W-type inclusions, with total homogenization temperatures (Th) of 220–339 °C, salinities of 0.4–3.7 wt.% NaCl eqv., and bulk densities of 0.66–1.01 g/cm3. All three types of inclusions are observed in the middle-stage quartz, of which the C- and W-type inclusions yield Th values of 190–361 °C, with salinities of 0.4–6.0 wt.% NaCl eqv. and bulk densities of 0.69–0.99 g/cm3. The late-stage quartz contains only W-type inclusions that have lower Th values of 172–287 °C, higher salinities of 1.4–6.9 wt.% NaCl eqv., and bulk densities of 0.79–0.95 g/cm3. Trapping pressures estimated from C-type inclusions in the early and middle stages cluster at 280–340 MPa and 220–310 MPa, respectively, corresponding to metallogenic depths of 10–13 km and 8–11 km. The H-O isotopic compositions (δ18Owater = 1.8–10.9‰, δD = −99 to −62.9‰) and microthermometric data indicate that the ore-forming fluids belong to medium–high-temperature, low-salinity, medium-density, and CO2-rich-H2O-NaCl ± CH4 ± N2 systems, probably originating from metamorphic water. Fluid immiscibility is a crucial mechanism for gold precipitation. Additionally, the U-Pb dating of hydrothermal zircons, from the auriferous quartz–tourmaline vein, yield a weighted mean 206Pb/238U age of 314.6 ± 9.6 Ma. Taking all of the above, the Nanmingshui deposit can be reasonably classed as a typical mesozonal orogenic gold deposit in the KGB, which was formed in a Late Carboniferous tectonic transition from syn-collision between the Jiangjunmiao accretionary complex and Yemaquan arc to post-collision in the East Junggar Orogen. Our results serve to better understand the gold mineralization and genesis of the Late Paleozoic orogenic system in the Kalamaili area, Xinjiang.

Origin of the Saibo-Lamasu Skarn Cu deposit, Western Tianshan, Xinjiang, NW China: Evidence from geology, mineral chemistry, fluid inclusions, stable isotopes, and organic geochemistry

The Saibo-Lamasu Cu deposit is the largest skarn Cu deposit in Western Tianshan, Xinjiang, NW China. The Cu orebodies are predominantly hosted in the contact zone between the oxidized granodiorite porphyry (lg fO2 = FMQ + 1.4 to 4.4) and reduced carbonaceous limestones (effective source rocks, TOC = 0.19 to 0.32 %). Three hydrothermal stages have been recognized: (1) The pre-ore stage skarn minerals in the proximal locations are dominated by andradite (And84Gro15Pyr1) and diopside (Di76-81Hd17-23Jo1-2), while that in the distal locations are mainly wollastonite, grossular (And15Gro83Pyr2), and hedenbergite (Di31-35Hd64-68Jo1-2). The coexistence of halite-bearing multiphase and vapor-rich fluid inclusions have similar total homogenization temperatures (Th) indicating that fluid boiling happened during this stage. (2) The syn-ore stage is typified by abundant sulfides and quartz. The coexistence of fluid inclusions representing trapped vapor (vapor-rich fluid inclusions) and liquid phases (liquid-rich fluid inclusions) showing similar Th implies the occurrence of a later boiling. (3) The non-boiling fluid inclusions in post-ore stage calcite are dominated by the liquid-rich fluid inclusions that have variable Th and relatively consistent salinities. The hydrothermal fluids are mainly magmatic water, the positive δ34S values of sulfides could reflect magmatic sulfur influenced by the interaction with wall rocks. The CH4 generated by the thermal pyrolysis of organic matter in carbonaceous limestones was dissolved in oxidized magmatic fluids that contributed to the change of skarn mineral assemblage and fluid characteristics on the temporal and spatial scales at the Saibo-Lamasu skarn Cu deposit.

Geological conditions and controls on accumulation of tight sandstone gas, deep part of the Shengbei sub-sag, Turpan-Hami basin, NW China

With the further exploration of the Jurassic strata in the Turpan-Hami Basin, the targets for hydrocarbon exploration have been gradually shifted from the tectonic belts around sags to the proximal lithological zones of deep sags. Based on the systematic coring of the first exploration well (well Qintan-1) in the center Shengbei sub-sag, this study conducted experiments of organic carbon, pyrolysis, gas chromatography (GC), nuclear magnetic resonance (NMR), and low-temperature nitrogen adsorption. Then, this study systematically analyzed the geological conditions and major controlling factors for the accumulation of tight sandstone gas in the deep part of the Shengbei sub-sag. The results show that: (1) Multiple sets of coal-measure source rocks have developed in the Jurassic strata in the center Shengbei sub-sag, providing plenty of gas sources for multilayered hydrocarbon accumulation; (2) Tight sandstones have poor physical properties and complex pore structures. However, high-permeability zones and anomalous zones of nano-scale pores have developed in the deep part, providing favorable spaces for the accumulation and preservation of tight oil and gas in the deep part; (3) Compaction and late carbonate cementation are key factors in reservoir densification. The microscopic storage space and connectivity of the tight sandstone reservoirs in the Shengbei sub-sag were improved due to the dissolution of fluids in coal measure strata. The occurrence of high-quality reservoirs in the Shengbei sub-sag is significantly controlled by source rocks, and both the former and the latter are characterized by adjacent sources and reservoirs and short-distance migration and accumulation. Furthermore, the special geological phenomena of chert cementation, abnormally high homogenization temperatures of fluid inclusions, and abnormal pyrolysis parameters confirm the presence of low-temperature hydrothermal activity in the deep part of the target strata. Therefore, the center Shengbei sub-sag has geological conditions for the large-scale accumulation of primary gas and, thus, is a key area for future hydrocarbon exploration.

The Effect of Soaking Time on Mechanical Properties of Roll-Bonded AA3003 and AA4045 Used for Heat Exchangers

Due to the rising need for energy saving, high-performing automotive heat exchangers, demand has significantly grown in recent years. As a result, effective fin-tube heat exchangers are becoming more popular. These tubes are typically made by rolling flat strips of AA3003 aluminum alloys that have either one or both sides coated with AA4xxx alloys. The AA3003 type of alloy is typically used as the core, which is then covered in either AA4045 or AA4343, which melts during the brazing process to adhere the fins to the tubes. To maintain the optimal size and distribution of manganese (Mn)-containing precipitates, preheating parameters are carefully controlled. Then, longer soaking times or higher soaking temperatures result in larger precipitates, which cause the final product to exhibit poor mechanical properties. Therefore, it is crucial to optimize the different manufacturing steps, such as homogenization, soaking time, and brazing in order to achieve a high quality product. Studies on the impact of homogenization temperature and time on the microstructure of AA3xxx aluminum alloys have been conducted. However, there has been little research on the impact of soaking (reheating) time on AA3003 cladded alloys. Hence, the effects of isothermal soaking time on the microstructure and mechanical properties of AA3003 cladded with AA4045 alloy were investigated in this work. Optical microscopy (OM) and scanning electron microscopy (SEM) were used to characterize the microstructure and identify intermetallic phases. The final microstructure in terms of grain structure at various homogenization times was characterized by electron backscattered diffraction (EBSD). After the hot-rolling and cold-rolling of the as-received material, large particles of intermetallic (mainly in the form of Chinese script morphology consisting of Fe-Mn-Si) were broken into smaller particles with an increased Fe, Mn, and Si content, indicating the formation of an α-Al(Fe,Mn)Si phase. The α-Al(Mn,Fe)Si was found to be a dominant dispersoid precipitate in the modified AA3003 core. Coarsening of the Al(Mn,Fe)Si dispersoids at 505 °C was only observed at a 45 h homogenization time. The hardness trend with homogenization time was found to be similar to that after homogenization, cold working, and annealing, with exception of an increase in hardness in the latter possibly due to strain hardening (from cold-rolling).

Effect of Homogenization Treatment on Microstructure and Eutectic Precipitates in Ce‐Containing 15Cr–22Ni–1Nb Austenitic Heat‐Resistant Stainless Steel

The effects of homogenization temperature and time on microstructure and eutectic precipitates in Ce‐containing heat‐resistant stainless steel are studied. The increase in the homogenization temperature and time promotes the diffusion of alloying elements and the transition from dendrite structure to austenitic grain. Laves phase particles are fully dissolved after the homogenization of the ingots regardless of the cerium contents and homogenization temperature and time, except for the case of the homogenization at 1130 °C for 4 h. Honeycomb Laves phases gradually dissolve and become clusters of small blocky during homogenization treatment. The amount of eutectic NbC dissolved into the matrix is increased with the increase in the homogenization temperature and time. The solubility of niobium and carbon in austenite is increased with increasing the cerium content, which is beneficial to the dissolution of eutectic NbC. The distribution homogeneity of alloying elements in the austenitic matrix is increased with the increase in the cerium content. The homogenization temperature for reaching full diffusion of alloying elements into austenitic matrix is decreased with increasing the homogenization time. The decrease in the secondary dendrite arm spacing by cerium addition is favorable to the homogenization of alloying elements during homogenization treatment.

Homogeneity and Trend Analysis of Climatic Variables in Cap-Bon Region of Tunisia

As a semi-arid Mediterranean country, Tunisia is affected by the impacts of climate change, particularly the coastal regions like the Cap-Bon. Irregular rainfall, rising temperatures and the recurrence of extreme events are all indicators that affect ecosystems and populations and make them more vulnerable to the influence of climatic variables. Therefore, an analysis of the trends of climate variables can contribute to facilitating the development of effective adaptation strategies. In this matter, this study was conducted to assess the homogeneity and trends of minimum and maximum air temperature (Tmin and Tmax) and precipitation (P) in the Cap-Bon region. Daily data were collected from the meteorological station of Nabeul for the period of 1982–2020. Pettitt and SNHT tests for homogeneity were applied to identify the breakpoints in multi-time scales of Tmax, Tmin and P data series. The Mann–Kendall (MK) test was used to detect the change in the time-series trend. A modified Mann–Kendall (mMK) test was used to remove the autocorrelation effect from the data series. Both the MK and mMK tests were used at the 5% significant level. The magnitude of the climatic trend was estimated using the non-parametric Sen’s slope estimator. Contrary to Tmin and P, the results of the homogeneity tests revealed the existence of significant breakpoints in the annual, seasonal and monthly Tmax time series. For most cases, the breakpoint occurred around the year 2000. For Tmin, significant breakpoints were recorded in March and April, while a significant shift in the P time series was detected in December. The Mann–Kendall results show a significant warming trend in annual Tmax, with magnitudes equal to 0.065 and 0.045 °C/year before and after the breakpoint, respectively. Nevertheless, non-significant tendencies were observed in the annual Tmin and P time series. On the monthly time scale, Tmax exhibited a significant upward trend in June and August, before the observed breakpoints, with Sen’s slope values equal to 0.065 and 0.045 °C/year, respectively. Regarding the Tmin data, a significant positive trend was observed in July at a rate of 0.033 °C/year.

Mineralogy and genesis of the Pb-Zn-Sb-Ag vein H32A in the Příbram uranium and base-metal district, Bohemian Massif, Czech Republic

A detailed paragenetic, electron microprobe, fluid inclusion and S,C,O-isotope study was conducted on Pb-Zn-Sb-Ag mineralization of the vein H32A, Háje deposit, Příbram uranium and base-metal district, Czech Republic. The vein is hosted by folded Neo-Proterozoic sandstones and siltstones of the Teplá-Barrandian unit in exo-contact of the Central Bohemian Plutonic Complex of the Variscan age (354–335 Ma). The ore zone is close to a crustal-scale tectonic zone dividing two distinctly different basement blocks of the Bohemian Massif. A rich mineral assemblage consisting of 44 mineral phases formed during two major mineralization stages (siderite-sulphidic and calcite-sulphidic) widespread in the Příbram area. A complex history of the vein is evidenced from the presence of seven mineralization sub-stages and widespread repeated metasomatic replacement and dissolution of older vein during younger mineralizing events. The vein is dominated by carbonates (especially siderite-rhodochrosite, less frequently dolomite-ankerite-kutnohorite, rarely calcite), minor constituents are quartz, illite-muscovite, and chamosite (locally with up to 1.52 apfu Sb, 0.53 apfu Zn and 0.38 apfu Pb). Ore minerals are dominated by Ag-poor galena. The Fe-poor sphalerite, pyrrhotite, löllingite, arsenopyrite, Pb-Sb, Pb-Sb-Ag and Cu-Ag-Sb sulphosalts are subordinate phases and dyscrasite, native antimony and native arsenic are accessories. The fluid inclusion study revealed the wide ranges of homogenization temperatures (210–<100 °C) and salinities (0.0–30.5 wt% NaCl eq.) of exclusively aqueous fluid inclusions. General decrease of both parameters occurred during evolution of the vein. Sulphur isotope disequilibrium was found between co-existing galenas and sphalerites. The calculated fluid δ13C values range between −9.0 and −12.3 ‰ V-PDB, implying for a well-mixed source of carbon, or its significant re-cycling during processes of dissolution-reprecipitation of vein carbonates. The calculated fluid δ18O values are highly positive for early siderite (+7.2 to +9.6 ‰ V-SMOW), and near-zero for later dolomites and calcites (−2.9 to +3.2 ‰ V-SMOW). The siderite fluids likely represent deeply circulated waters, which underwent a significant isotope exchange with hot crustal rocks. Late low-salinity fluids were likely sourced from the Permian partly evaporated freshwater piedmont basins. The high-salinity Ca-Na-Cl brines rarely recorded in secondary fluid inclusions hosted by late calcite likely represent either local “shield brines” or basinal brines of marine provenance. The study site covers a metallogenetically significant portion of the Late Variscan fluid history within an active crust-scale tectonic zone hosted by basement of the Bohemian Massif. A pronounced Ag enrichment of this vein is mainly caused by widespread occurrence of inclusions of late-stage Ag minerals (dyscrasite) in the vein, which form rich concentrations in the shallower parts of the Háje deposit.

Two-Stage Superimposed Gold Mineralization in the Xiejiagou Gold Deposit, Shandong Province: Insights from Fluid Inclusions, H-O-S Isotopes, and Trace Elements

The Xiejiagou gold deposit located in the Zhaoyuan-Laizhou gold belt is composed of altered-rock-type gold mineralization and superposed auriferous quartz veins, showing unique two-stage gold mineralization. Oxygen and hydrogen isotopic analyses yielded the following results: δ18OH2O = 0.8‰ to 4.4‰ and δD = −106‰ to −85‰ for altered-rock-type mineralization, and δ18OH2O = 3.6‰ to 5.6‰ and δD = −98‰ to −89‰ for auriferous quartz-veins. Combined studies on Co/Ni, Sb/Bi and As/Ag ratios of pyrites, it can be inferred that the ore-forming fluids were dominated by magmatic water mixed with very little meteoric water. The fractured altered rocks in the ore-hosting fault zones are characterized by mylonitization, cataclastic lithification, and structural lenses, reflecting a compressional (closed) ore-forming system. In contrast, the occurrence of auriferous quartz veins in fissures of altered-rock-type orebodies and the fact that altered-rock-type ores commonly occur as breccias cemented by auriferous quartz veins that reflect an extensional (open) ore-forming system for the vein mineralization. The increase in δ34S values from stage I (5.8‰–7.2‰) to stage II (6.6‰–9.0‰) indicate that the altered-rock-type mineralization was the result of intense water–rock interaction, while the occurrence of immiscible inclusions in auriferous quartz veins demonstrates that fluid immiscibility contributes significantly to gold deposition in the vein-type mineralization. Fluid-inclusion microthermometric data indicate that the fluids for the altered-rock-type mineralization are characterized by moderate-to-high temperature (262–368 °C), and low-to-moderate salinity (4.3–10.8 wt.% NaCl equivalent). In contrast, halite-bearing inclusions are found in auriferous quartz veins, and its fluids are characterized by moderate-to-high temperature (290–376 °C) and moderate-to-high salinity (5.1–41.9 wt.% NaCl equivalent). From early stages (I and II) to the late stage (III), homogenization temperature and high temperature element (W, Sn, and Mo) concentrations in pyrite first decrease and then increase, δ34S values and metallization-related element (Au, Ag, and Bi) concentrations in pyrite first increase and then decrease. Therefore, it can be inferred that the two distinct types of gold mineralization in the Xiejiagou gold deposit may be two separate mineralization events. The presence of magnetite in the auriferous veins suggests an increase in oxidation state during the vein mineralization. Importantly, the Xiejiagou gold deposit preserves two types of mineralization in a single deposit and uniquely records a metallogenic transition from a compressional, reduced environment to an extensional, oxidized environment, as a result of a regional stress field transition that occurred in the Zhaoyuan-Laizhou gold belt at ca. 120 Ma.

Ore Genesis of the Lower Urgen Porphyry Molybdenum Deposit in the Northern Great Xing’an Range, Northeast China: Constraints from Molybdenite Re-Os Dating, Fluid Inclusions, and H-O-S-Pb Isotopes

The Lower Urgen molybdenum deposit (44,856 t Mo @ 0.141%), situated in the northern Great Xing’an Range, is a newly discovered porphyry molybdenum deposit. Mineralization is characterized by veinlet-disseminated- and vein-type quartz–sulfide orebodies primarily occurring in the cupola of the Early Cretaceous granite porphyry stock. In this study, we present a detailed description of the ore geology, molybdenite Re-Os dating, H-O-S-Pb isotopic compositions, and fluid inclusion (FI) analyses including petrography, laser Raman, and microthermometry to precisely constrain the timing of ore formation, the origin of ore-forming fluids and materials, as well as the metal precipitation mechanism. Molybdenite Re-Os dating yielded two model ages of 141.2 ± 1.5 and 147.7 ± 1.7 Ma, coeval with the regional Late Jurassic–Early Cretaceous molybdenum metallogenesis. The hydrothermal process can be divided into three stages: the quartz–molybdenite(–pyrite) stage, quartz–polymetallic sulfide stage, and quartz–carbonate stage. Four types of FIs were distinguished for quartz, including two-phase liquid-rich (L-type), saline (S-type), CO2-rich (C1-type), and CO2-bearing (C2-type) FIs. Microthermometric data showed that the homogenization temperatures and salinities from the early to late stages were 240–430 °C, 5.0–11.9, and 30.1–50.8 wt% NaCl equiv.; 180–280 °C and 3.0–9.1 wt% NaCl equiv.; and 120–220 °C and 0.2–7.9 wt% NaCl equiv., respectively, suggesting a decreasing trend. H-O isotopic compositions indicate that the ore-forming fluids were initially of magmatic origin with the increasing incorporation of meteoric water. S-Pb isotopic compositions indicate that the ore-forming materials originated from granitic magmas, and the mineralization is genetically related to the ore-bearing granite porphyry stock in the deposit. Fluid immiscibility and fluid–rock interaction are collectively responsible for the massive deposition of molybdenite in stage 1, whereas fluid mixing and immiscibility played a critical role in the deposition of polymetallic sulfide in stage 2.

Estimation of Temperature Homogeneity in MEMS‐Based Heating Nanochips via Quantitative HAADF‐STEM Tomography

AbstractSample holders for transmission electron microscopy (TEM) based on micro‐electro‐mechanical systems (MEMS) have recently become popular for investigating the behavior of nanomaterials under in situ or environmental conditions. The accuracy and reproducibility of these in situ holders are essential to ensure the reliability of experimental results. In addition, the uniformity of an applied temperature trigger across the MEMS chip is a crucial parameter. In this work, it is measured the temperature homogeneity of MEMS‐based heating sample supports by locally analyzing the dynamics of heat‐induced alloying of Au@Ag nanoparticles located in different regions of the support through quantitative fast high‐angle annular dark‐field scanning TEM tomography. These results demonstrate the superior temperature homogeneity of a microheater design based on a heating element shaped as a circular spiral with a width decreasing outwards compared to a double spiral‐shaped designed microheater. The proposed approach to measure the local temperature homogeneity based on the thermal properties of bimetallic nanoparticles will support the future development of MEMS‐based heating supports with improved thermal properties and in situ studies where high precision in the temperature at a certain position is required.

Origin of Ag-Pb-Zn mineralization at Huanaote, Inner Mongolia, NE China: Evidence from fluid inclusion, H-O-S-Pb and noble gas isotope studies

The newly-discovered Huanaote Ag-Pb-Zn deposit, containing 1173 tons Ag with a grade of 154 g/t, is situated in the western part of the Great Xing’an Range metallogenic belt. The source of metals and the fluid evolution for this large metallogenic system are still ambiguous. Mineralized Ag-Pb-Zn veins are primarily hosted in Late Carboniferous monzogranite and Devonian slate. Three paragenetic stages of mineralization were recognized at Huanaote, including (stage I) early pyrite + arsenopyrite + quartz ± K-feldspar; (stage II) the main ore stage sulfide (sphalerite, galena, chalcopyrite and pyrite) + sulfosalt (freibergite, bournonite, wittichenite and tetrahedrite) + quartz + sericite + chlorite ± epidote ± fluorite; and (stage III) late pyrite + quartz + calcite. The homogenization temperatures of fluid inclusion assemblage for stages I and II range from 254 to 337 ℃ and 143 to 270 ℃, respectively, while the fluid salinity varied from 2.3 to 14.2 and 0.9 to 11.8 wt% NaCl equiv. for stages I and II, respectively. The fluid δ18OH2O and δDH2O values range from −0.4 to +6.2‰ and −116.8 to −104.8‰, respectively, indicating that the source of the fluids was primarily derived from a magma with less contribution from meteoric waters. Sulfur isotope analyses of sulfides exhibit δ34S values from −4.3 to +8.0‰, consistent with those observed in other Ag-Pb-Zn deposits in this region, suggesting the sulfur was mainly magmatic origin with minor sedimentary sulfur addition. Similarly, the Pb isotope compositions of sulfides resemble those of local Mesozoic magmatism, implying a Mesozoic magmatic source for the metals. Additionally, the noble gas isotope compositions, specifically the 3He/4He ratios (ranging from 4.41 to 7.18 Ra, mean of 5.56 Ra) for fluid inclusions,strongly support a deep magmatic fluid responsible for the formation of Huanaote deposit. Fluid cooling, mixing with meteoric waters and dilution are suggested to be important processes for Ag-Pb-Zn deposition at Huanaote.