Ultrahigh-temperature Conditions Research Articles

Design and Thermal–optical Evaluation of an Optical Window Module for a Near-space Remote Sensor under Ultra-high Temperature Conditions

Under hypersonic flight conditions, the optical window external surface of a near-space remote sensing system generates a large thermal load due to aerodynamic friction, resulting in serious additional contact thermal stresses and deformation of the flat window. Consequently, the imaging performance of the optical remote sensing system (ORSS) is reduced. To overcome this issue, a flexible support combination structure (FSCS) for an optical window suitable for ultra-high temperature conditions was developed in this study, which ensures the optical imaging quality requirements of the system. Based on the external thermal environment characteristics of a hypersonic aircraft, an aerothermal simulation model of the aircraft with a window component was established. More importantly, the FSCS was optimized and a thermal–structural model of the window component was established, and the opto-mechanical-thermal analysis method was proposed for the ORSS. Finally, the thermal-optical properties of the deformed window were evaluated. The results show that the optimized window component satisfies the optical imaging design requirements, which guides engineers in ultra-high temperature thermal analysis and optical imaging.

Effectiveness of Ti-in-amphibole thermometry and performance of different thermometers across lower continental crust up to UHT metamorphism

Metabasites are important constituents of deep crustal sections and are the favored rock type for studying lower crustal amphibolite to granulite transitions. However, metapelites may develop a larger number of temperature-sensitive mineral assemblages and are particular useful when extreme ultrahigh temperature (UHT) conditions are envisaged. A recent calibration of the Ti-in-amphibole thermometer by Liao et al. (2021) was supposed to make thermometry on metabasites quick and easy to apply. However, their calibration is based on experiments which were not originally designed to investigate in detail the temperature dependence of Ti in amphibole. In addition, a possible effect of aTiO2 and/or pressure on the Ti content of amphibole was not fully taken into account. This resulted in a calibration uncertainty of ± 70 °C (2σ), much higher than that of other single-mineral thermometers. In this study we firstly test the newly calibrated Ti-in-amphibole thermometer across the mid to lower crustal section of the Ivrea–Verbano Zone (IVZ; NW Italy) and compare the performance of different thermometric techniques across the sequence. Ti-in-amphibole thermometry records increasing peak temperatures from amphibolite (600–700 °C), transition (750–800 °C) and granulite (850–950 °C) zones. Titanium content of amphibole may be modified by retrograde fluid influx returning temperatures c. 200–300 °C lower than in non-altered domains. The comparison reveals that Zr-in-rutile thermometer in pelitic granulites seems to be more prone to post-peak resetting than the Ti-in-amphibole thermometry in nearby mafic rocks. This behavior is also confirmed by amphibole analyses from other UHT localities, where the performance of Ti-in-amphibole thermometry is comparable with that of Al-in-orthopyroxene in pelitic granulites. However, Ti-in-amphibole temperatures are underestimated in rutile-bearing samples and this limitation is not solely restricted to rocks containing high H2O contents as previously thought. Derived constraints on the diffusivity of Ti through amphibole demonstrate the robustness of the Ti-in-amphibole thermometer to later thermal disturbances. However, ad-hoc experiments are still necessary to improve the accuracy and precision of calibration and to extend its applicability. This advance will make mafic granulites routine targets for studies devoted to understanding the regional extent of UHT metamorphism.

Ultrahigh-temperature crustal anatexis and final cratonization in Eastern Hebei, North China Craton: Insights from ca. 2.46 Ga Taipingzhai enderbites

Charnockitic rocks are a suite of granulite-facies plutonic rocks that include dominantly granitic−tonalitic and partly dioritic rocks. The Na-rich endmembers of the charnockite series, including dioritic to tonalitic rocks, are also termed enderbites. Charnockitic rocks are the main component of the cratonic-type lower continental crust in Precambrian cratons worldwide. These rocks are generally considered to be products of the anatexis of the lower crust under high- to ultrahigh-temperature conditions and play a key role in stratification between upper and lower crustal layers as well as the cratonic stabilization (cratonization) of Precambrian continents, although further study is required to gather detailed information about these rocks. In this study, a group of igneous enderbites (dioritic−tonalitic charnockites) from Eastern Hebei, North China Craton, is investigated. Zircon U-Pb dating reveals that the enderbites formed at ca. 2.46 Ga, which is coeval with the regional granulite-facies metamorphic overprinting. The enderbites are primarily composed of clinopyroxene, orthopyroxene, plagioclase, and quartz, with minor amphibole, biotite, K-feldspar, and Fe-Ti oxides. The rocks are characterized by high Fe2O3T + MgO (9.80−15.9 wt%), Cr (71.0−292 ppm), and Ni (41.2−107 ppm) contents, as well as low Al2O3 (13.9−16.6 wt%) and K2O (1.07−2.43 wt%) contents, with high Na2O/K2O ratios (1.51−4.43) and low Sr/Y (24.5−49.5) ratios. Moreover, these rocks are enriched in light rare earth elements (LREEs), (La/Yb)N = 8.06−17.8, and yield weak Eu anomalies, (Eu/Eu* = 0.80−1.18), with negative Th, U, Ta, Nb, and Ti anomalies. Various mineral thermobarometers, oxybarometers, and hydrometers are used to constrain the crystallized P-T-ƒO2-H2O conditions of the enderbites. These rocks crystallized at high temperature (860−1000 °C), crystallization pressure (8.0 ± 1.0 kbar), and H2O-poor (1.5−2.4 wt%) conditions, with oxygen fugacities (ΔQFM) of 0.0−3.0, which suggests “hot” (high-temperature) and “dry” (water-poor) crystallization conditions. The enderbites also have heterogeneous in situ zircon Hf-O isotopic compositions: εHf(t) = 2.4−7.5; δ18O = 5.78‰−7.74‰. These new data, combined with trace element characteristics, suggest that the enderbites were derived from the partial melting of metabasites, and that assimilation and fractional crystallization controlled the compositional variation in the enderbites. Further thermodynamic and geochemical modeling suggests that the anatexis of Mg-Fe−rich metabasite under ultrahigh-temperature (>1000 °C) and H2O-poor (1.0−1.5 wt%) conditions at a low crustal depth (∼9.0 kbar) could yield a melt composition comparable to that of the observed enderbites. Postcollisional lithospheric extension and mafic magma underplating prompted the partial melting of lower crustal metabasite at ultrahigh temperatures and normal lower crustal depths, resulting in the formation of enderbites. This study demonstrates that the enderbites could be formed by ultrahigh-temperature anatexis of metabasite with amphibole dehydration melting (Pl + Amp → Opx + Cpx + melt) and offers robust evidence of the genetic links between the ultrahigh-temperature anatexis of basic rocks and the generation of enderbites. In addition, the occurrence of ca. 2.46 Ga enderbites may mark the final cratonization of the North China Craton, and the ca. 2.50−2.45 Ga tectono-thermal event was an ultrahigh-temperature metamorphic-anatexis process rather than simple regional granulite metamorphic overprinting. Therefore, the generation and emplacement of enderbites involved not only a magmatic process but also an element redistribution process in the lower crust, which has important implications for stabilization of the North China Craton at ca. 2.5 Ga.

U-Pb geochronology of rutiles from Southern granulite Terrane, India: Implications for the cooling and exhumation of East Gondwanan terranes

The Precambrian Southern Granulite Terrane of south India figures prominently in the East African collisional orogen, linked to the assembly of the East Gondwana supercontinent along with Sri Lanka, Madagascar, Antarctica, and Africa. While the timing of this collision and associated magmatic-metamorphic processes are well constrained, the mechanisms governing the cooling and exhumation of these terranes remain uncertain. This study focuses on U-Pb rutile ages derived from granulites in the Southern Granulite Terrane and attempts to extract the cooling history of the terrane. Our new U-Pb rutile ages cluster between 422 to 458 Ma, postdating regional metamorphism and indicating an extended cooling period of ∼ 35 Ma whereas trace element signatures suggest their formation during granulite facies metamorphism with temperatures reaching up to ultrahigh-temperature conditions. Calculated cooling rates using these rutile U-Pb ages range between 2–6 °C/Ma similar to the cooling rate of ≤ 7 °C/Ma from other East Gondwanan terranes. Based on these results it is proposed that the coeval exhumation of these terranes was assisted by surface erosion after the final assembly of the East Gondwana supercontinent.

Multi-stage ultrahigh temperature metamorphism in the lower crust of the Kaapvaal craton recorded by U–Pb ages of garnet

U–Pb ages were determined by split-stream LA-SF/MC-ICPMS in garnets from UHT granulite xenoliths (Star mine, South Africa; 124 Ma). They give a considerable age range of 400 million years with well-defined maximas at 3.09, 3.01 and 2.75 Ga. The oldest peak overlaps with the changeover from tonalites to K-granites at 3.14–3.04 Ga and with zircon ages of the mid-crustal granulites of the Vredefort dome (3.1 Ga) in the wake of the 3.2 Ga collision of three terrains that compose the Witwatersrand block. Subduction (or sagduction) of the uppermost crust in an ultrahot orogen setting brought shales and greenstones to the lower crust. Ultrahigh temperature (UHT) conditions are the result of high mantle potential temperatures and self- heating by the radioactive inventory of the subducted lithologies. Metamorphism, anatexis to very high degrees and melt extraction left UHT granulites as residue. Rejuvenation of UHT conditions was brought about by Dominion Group magmatism between 3.0 and 2.95 Ga. Magmatic uprise caused intense shearing in the lower crust followed by recrystallisation of the shear zones to generate the younger garnet age group. Ventersdorp flood basalt volcanism caused similar processes at around 2.72 Ga and generated the third garnet age group. Zircon gives U–Pb ages mainly around 2.72 Ga (both literature and our own data) i.e. zircon adjusted or newly crystallized at the youngest UHT event. Only few zircon grains retained older ages up to 2.94 Ga. Still unconstrained, but very high closure temperatures (≥ 1100 °C) for the U–Pb system in garnet keep the memory of the oldest ages in UHT granulites. Such ages can only be reset by recrystallization. This way, garnet records a prolonged high-temperature history of the lower crust of the Kaapvaal craton.

Electrical conductivity of copper under ultrahigh pressure and temperature conditions by both experiments and first-principles simulations

Electrical conductivity of copper under ultrahigh pressure and temperature conditions by both experiments and first-principles simulations

High powered output flexible aerogel triboelectric nanogenerator under ultrahigh temperature condition

Triboelectric nanogenerators (TENGs) have emerged as promising devices for harvesting low-frequency energy, but its application in high-temperature environments is limited. In this article, a flexible high-temperature resistant fiber substrate material was developed using needled felt and silicon aerogel. This material demonstrated exceptional resistance, withstanding exposure to a butane flame at approximately 1300 ℃ for a minimum of 10 min without experiencing burn-through. Following the application of electrodes and protective encapsulating, a high-temperature resistant silicon aerogel and fiber felts based triboelectric nanogenerator (HTFs-TENG) was successfully created. In addition, we achieved remarkable enhancements in the electrical output performance of the HTFs-TENG by precisely regulating its dielectric properties, resulting in an impressive increase in peak voltage from 17 V to 135 V. The current output increased from 1.4 μA to 6 μA. The HTFs-TENG demonstrated remarkable adaptability, operating effectively at temperatures as high as 275 ℃ and as low as approximately − 75 ℃. Moreover, it showcased an instantaneous power density output of 31.9 mW/m2 under a 100 MΩ resistance load. The HTFs-TENG displayed impressive electrical signal response capabilities at ultralow frequencies (≤1 Hz) across various temperatures and frequencies, positioning it as an ideal self-powered vibration sensor and temperature sensor for diverse generator applications.

Metamorphic evolution of high-pressure and ultrahigh-temperature granulites from the Alxa Block, North China Craton: Implications for the collision and exhumation of Paleoproterozoic orogenic belts

High-pressure (HP) and ultrahigh-temperature (UHT) granulites with a high geothermal gradient (greater than 500 °C/GPa) are prominent features of Paleoproterozoic orogenic belts and may represent paired metamorphic belts present during the early stages of plate tectonics. Understanding their pressure−temperature−time (P-T-t) paths and metamorphic evolutionary relationships could provide valuable constraints on the tectonic processes of Paleoproterozoic orogenic belts. Here, we describe garnet mafic and clinopyroxene-orthopyroxene (Cpx-Opx) granulites from the Diebusige area of the Alxa Block in the western part of the Khondalite Belt, North China Craton. Through detailed petrographic, phase equilibrium modeling, and Ti-in-amphibole thermometric studies, we obtained the preserved peak mineral assemblages of two types of mafic granulites: garnet + clinopyroxene + amphibole + plagioclase + quartz + ilmenite, and clinopyroxene + orthopyroxene + plagioclase + amphibole + garnet (rare) + ilmenite. The preserved peak P-T conditions were determined to be 850−890 °C/11.4−13.2 kbar (HP granulite-facies) and 950−970 °C/8.2−9.2 kbar (UHT conditions), with thermal gradients of ∼70 °C/kbar (moderate differential temperature/differential pressure, dT/dP) and ∼110 °C/kbar (high dT/dP), respectively. Using sensitive high-resolution ion microprobe U-Pb dating and rare earth element analysis of zircons, we found that the garnet mafic granulite recorded an HP granulite-facies metamorphic age of ca. 1.95 Ga and a retrograde cooling age of ca. 1.8 Ga, while the Cpx-Opx granulite recorded a consistent retrograde cooling age of ca. 1.8 Ga. By combining these results with the metamorphic evolution and timing (ca. 1.92−1.91 Ga) of UHT rocks from the Khondalite Belt, we suggest that the garnet (HP) mafic and Cpx-Opx (UHT) granulites may represent different stages of the same metamorphic event, shedding light on the processes involved in the collision and subsequent exhumation of Paleoproterozoic orogenic belts.

Comb polymer/layered double hydroxide (LDH) composite as an ultrahigh temperature filtration reducer for water-based drilling fluids

In deep-formation drilling, effective filter loss control in ultrahigh-temperature conditions and high-salt conditions faces challenges. Comb polymer/LDH composites (P-LDH) with partially intercalated and partially exfoliated structures were prepared by in-situ polymerization as fluid loss materials. A series of characterization results showed that the P-LDH composites were successfully synthesized. P-LDH had partially intercalated and partially exfoliated structures and excellent thermal stability. In addition, the rheological evaluation results showed that P-LDH had a low viscosity effect while maintaining the rheological properties of the drilling fluid. P-LDH can significantly reduce the filtrate loss of drilling fluids at ultrahigh temperatures and high salt concentrations. At 240 °C and 15 wt% NaCl, the filtration loss was only 6.3 mL, and the high-temperature and high-pressure filtration loss was only 29.6 mL. Through the analysis of drilling fluid particle size and filter cake microstructure, based on hydrogen, ionic bonds, and intercalation effects, P-LDH acted closely with bentonite to promote stable dispersion, improve the drilling fluid’s stability, and form a dense filter cake to reduce the filtration loss. Therefore, P-LDH has broad application prospects in ultrahigh-temperature and high-salinity formation drilling.

Ultra-high temperature suspending stabilizer and cement slurry interface interaction law and mechanism study for ultra-deep well cementing

The high temperature issue that cementing is facing is getting more and more significant as oil and gas extraction is being expanded to deep stratum. In order to increase the sedimentation stability of cement slurry under ultra-high temperature conditions, a suspension stability of cement slurry was created in the study. On the basis of previous research, its mechanism of action was examined from the perspective of interface interaction. The suspension stabilizer's low temperature adsorption behavior was investigated using the Zeta potential test and the total organic carbon (TOC) test. The findings indicate that the suspension stabilizer's apparent adsorption activation energy is 44.667 kJ/mol, which is in the range of chemical adsorption. The XRD test, infrared spectrum test, and Raman spectrum test were used to examine the cement's hydration byproducts. The findings demonstrate that hydrated calcium silicate (C-S-H) is the predominant component of the cement paste's short-term hydration products during ultra-high temperature curing. Ion concentration testing and molecular dynamics modeling were used to examine the interface interaction mechanism between the suspension stabilizer and the hydration products. The findings indicated that a network of chemical interactions, including hydrogen and ionic bonds, interacted between suspension stabilizer and C-S-H. The sedimentation stability of cement slurry is maintained by the persistence of these chemical linkages at extremely high temperatures.

Study on effects of metakaolin on the silica-cement slurry performance under ultra-high temperature conditions

In oil and gas exploration and development, the complex working conditions of high temperature and high pressure are increasing, and the strength decline of silica-cement often occurs under such conditions. In this work, the metakaolin influence on the mechanical properties and micro-structure of silica-cement at 240 ℃ and 21 MPa condition is comprehensively studied. XRD technique investigated the chemical composition of cement crystal phase, and SEM observed the micro-morphology of high temperature cement. Results showed that the loading metakaolin has reduced porosity by 12.86%, air permeability while greatly increased nanopore (＜50nm) by 36.47% and increased nanopore (＜10 nm) by 10.34%. Thus, the cement permeability reduced greatly or its anti-channelling enhanced, that is, such results improved the comprehensive performance of cement slurry. These observations, combined with the previously reported the remarkable enhancement of the MK cement compressive strength, represent a major step toward the development of strength retrogression-resistant material at high temperature.

Late Paleoproterozoic ultrahigh-temperature mafic granulite from the eastern Alxa Block, North China Craton

The timing and mechanism of ultrahigh-temperature (UHT) granulite facies metamorphism is critical to understanding the tectono-thermal evolution of granulite terranes and their relationships to supercontinent assembly. Here we document late Paleoproterozoic UHT mafic granulites from the Diebusige Complex in the eastern Alxa Block, North China Craton. These rocks occur as lens within felsic gneiss, marble, and garnet-bearing pyroxenite and contain representative granulite-facies minerals such as garnet, clinopyroxene, plagioclase, and Ti-rich amphibole. Based on phase equilibria modelling, Ti-in-amphibole (Amp) thermometer, and rare earth element (REE)-based thermometers, UHT metamorphic condition of 948 – 1048 ℃/11 – 14 kbar was obtained for the peak metamorphic stage, which was followed by retrograde metamorphism under lower amphibolite – greenschist facies (401 – 565 ℃/5.2 – 7.1 kbar). Zircon U-Pb dating and trace element systematics suggest that the protolith of the studied UHT mafic granulites emplaced at ∼ 1.97 Ga. This is followed by rapid metamorphism to UHT conditions and slow cooling in the lower crust during 1.96 – 1.86 Ga, suggesting a long-lived hot orogen in the eastern Alxa Block, possibly resulting from Andean-type subduction – accretion in the eastern Alxa Block. Combining chronological and metamorphic P-T data on UHT metamorphism from adjacent areas, our results support a long-lived late Paleoproterozoic (ca. 2.0 – 1.8 Ga) hot orogen that extends at least from the Khondalite Belt to the eastern Alxa Block.

Long‐lived high‐grade metamorphism in southern India: Constraints from charnockites and sapphirine‐bearing semipelitic granulites from the Madurai Block

AbstractThe Granulite Terrane of Southern India is a collage of Mesoarchean–Neoproterozoic crustal blocks that underwent high‐grade metamorphism associated with the final assembly of the Gondwana supercontinent during late Neoproterozoic–Cambrian. Here, we investigate the charnockites and associated sapphirine‐bearing semipelitic granulites from the eastern part of the Madurai Block (MB). We present new petrographic, mineral chemistry, and geochronological data to constrain the P–T–t evolution of the block and unravel the timescale and source of heat for the ultrahigh‐temperature metamorphism. Both the rock types contain coarse‐grained porphyroblastic garnet and orthopyroxene, yielding peak P–T conditions of 950 ± 30°C at 10.5 ± 0.8 kbar and 970 ± 40°C at 10 ± 0.5 kbar for semipelite and charnockite, respectively, using conventional thermobarometry. Peak ultrahigh temperatures are further supported by high Al content in the orthopyroxene (8.78 wt% Al2O3) coexisting with garnet (XMg: up to 0.57) and feldspar thermometry of the mesoperthites and antiperthites in the semipelite, yielding 950–980°C at 10 kbar. Subsequent decompression has led to the formation of coronal orthopyroxene3 + plagioclase3 in the charnockite and symplectic orthopyroxene3 + cordierite ± sapphirine ± plagioclase3 in the semipelite, yielding P–T range of 950–850°C and 9.5–6.8 kbar for semipelites and 950–820°C and 8–6.5 kbar for charnockite. Based on the obtained P–T estimates, preserved reaction textures, and phase equilibria modelling in the MnNCKFMASHTO system, a clockwise P–T evolution with isothermal decompression followed by cooling is inferred for both the rock types.Texturally constrained in situ monazite dating and rare earth element (REE) patterns show that the core of matrix monazite having low‐Th, Y, and extreme heavy rare earth element (HREE) depletion, yielding weighted mean ages of 582 ± 12 and 590 ± 22 Ma for semipelite and charnockite, respectively, dates the prograde evolution. The mantle of the matrix monazite in semipelite and comparable rim in charnockite, having relative Th‐enrichment compared to the core, yielding weighted mean ages of 552 ± 9 and 557 ± 13 Ma, respectively, dates extensive dissolution–reprecipitation from the melt at the peak stage. The relatively Th‐ and Y‐rich and moderately HREE‐depleted rim of matrix monazite in the semipelite, yielding weighted age of 516 ± 6 Ma, date initial garnet breakdown during post‐peak melt crystallization. By contrast, compositionally homogenous HREE + Y‐enriched monazite in the symplectite and retrograde monazites yielding weighted mean ages of 487 ± 47 Ma for semipelites and 508 ± 19 Ma for charnockites dates extensive garnet breakdown during final stages of melt crystallization and subsequent cooling. Our findings point to collision initiation at ~590 Ma, with the peak conditions attained at ~550 Ma followed by extensional collapse at ~510–490 Ma, resulting in rapid exhumation of lower crustal rocks to mid‐crustal levels under sustained ultrahigh‐temperature (UHT) conditions, followed by cooling to reach a stable geotherm. Our results suggest a long‐lived hot orogeny in the MB, where the UHT conditions were sustained for at least 40 MYr. The UHT conditions were most likely attained in the core of a long‐lived hot orogen by the combined effect of conductive heating through radioactive decay and mantle heat supply, with the former being the primary driver.

Different Cooling Histories of Ultrahigh-Temperature Granulites Revealed by Ti-in-Quartz: An Electron Microprobe Approach

The cooling history of granulite is crucial to understanding tectonic scenarios of the continental crust. Ti-in-quartz, a useful indicator of temperature, can decipher the thermal evolution of crustal rocks. Here we apply the Ti-in-quartz (TitaniQ) thermometer to ancient ultrahigh-temperature (UHT) granulites from the Khondalite Belt (KB) in the North China Craton (NCC) and young UHT granulites from the Mogok Metamorphic Belt (MMB), Myanmar. Ti content in quartz was analyzed using a highly precise method constructed in a CAMECA SXFive electron probe microanalyzer (EPMA). The granulites from the two localities show different quartz Ti contents with a constant deforced beam of 10 μm. Matrix quartz and quartz inclusions from the NCC granulites have 57–241 ppm and 65–229 ppm, respectively, corresponding to the TitaniQ temperatures of 653–810 °C and 666–807 °C. The calculated temperatures are significantly lower than the peak temperatures (850–1096 °C) obtained by other methods, due to the formation of abundant rutile exsolution rods in quartz during cooling. Thus, the low calculated temperatures for the NCC granulites reflect a cooling state near or after the exsolution of rutile from quartz, most likely caused by a slow cooling process. However, the matrix quartz from the MMB granulites is exsolution-free and records higher Ti contents of 207–260 ppm and higher metamorphic temperatures of 894–926 °C, close to the peak UHT conditions. This feature indicates that the MMB granulites underwent rapid cooling to overcome Ti loss from quartz. Therefore, determining the amount of Ti loss from quartz by diffusion can provide new insight into the cooling behavior of UHT granulites. When a large deforced beam of 50 μm was used to cover the rutile rods, the matrix quartz in the KB granulites could also yield the TitaniQ temperatures above 900 °C. Thus, our new data suggest that the TitaniQ thermometer could be useful for revealing UHT conditions.

Microfluidic investigation on asphaltene interfaces attempts to carbon sequestration and leakage: Oil-CO2 phase interaction characteristics at ultrahigh temperature and pressure

CO2 huff-n-puff is a potential approach to improve the oil displacement efficiency in the deep reservoirs, which can achieve carbon sequestration and efficient oil production, simultaneously. However, the fundamental understanding of carbon mass transport, sequestration and leakage mechanism in deep geological reservoirs at the microscopic pore scale is still ambiguous. In this work, we innovatively designed a precise CO2 huff-n-puff microfluidic experiment under ultrahigh temperature and pressure conditions (55 MPa, 115 °C) to study the microscopic mechanism of CO2 utilization, storage and leakage (CUSL) in pore scale. Moreover, we proposed the quantitative analysis method for oil-CO2 interaction behavior to explicit dissolution and extraction characteristics, pressure threshold and interface stability by introducing Pseudo-Color algorithm and relevant parameters such as dynamic oil swelling factor, contact angle and gray value. Then, the pore-scale dynamics of the fluid interaction mechanism during the soak and puff process were quantitatively characterized, corresponding to the carbon sequestration efficiency of crude oil continuously exposed to scCO2 and the leakage risk with step-down production, respectively. The experimental results indicate that during the huff process, the oil-CO2 phase behavior characteristics at 115 °C can be divided into swelling, immiscible extraction and miscible extraction regions, which are coordinately controlled by dissolution mechanism, capillary effect and vaporization mechanism. Moreover, ultrahigh temperature oil generally requires higher pressure to start extraction and miscibility (Pext = 6.38 and 15.96 MPa, MMP = 9.71 and 23.73 MPa, T = 50 and 115 °C, respectively), while the asphaltene precipitation pressure Pasp is lower. At ultrahigh temperatures, the oil-CO2 interaction also enters the contact angle fluctuation region in advance, and the morphology of asphaltene particles is single, fine and uniform. When the soaking time is 36 min, the non-extractable oil component gradually evolves into a carbon sequestration interface. During the subsequent puff process, the more stable the carbon sequestration interface in the smaller blind end, the lower the leakage risk, corresponding to the leakage pressure difference of up to 40.93 MPa. This work has important practical significance for deep resource extraction and CUSL industrial application.

Into the High to Ultrahigh Temperature Melting of Earth’s Crust: Investigation of Melt and Fluid Inclusions within Mg-Rich Metapelitic Granulites from the Mather Peninsula, East Antarctica

Abstract Precise constraints on the compositions of melts generated by anatexis under ultrahigh temperature (UHT) conditions are critical for understanding processes of partial melting and differentiation of the Earth’s crust. Here we reveal geochemical and physical signatures of anatectic melts preserved as nanogranitoids (i.e. crystalized melt inclusions) within sapphirine-bearing UHT metapelitic granulites from the Mather Peninsula, East Antarctica. Their coexistence with high−Al orthopyroxene as inclusions in garnets strongly suggests that the investigated melts were at least partially UHT in origin. The nanogranitoids are enriched in SiO2 (69.9–75.6 wt.%), strongly peraluminous (ASI values = 1.2–1.6) and potassic to ultrapotassic (Na2O + K2O = 7.1–9.5 wt.%, K/Na = 2.2–9.3). When compared to the granulitic restite, the melts are enriched in Li, Cs, Rb, Ta, Sm, Nd, Zr, U and Pb, and depleted in Ce, Th, Ba, Sr and Nb. Their geochemical characteristics are consistent with biotite−dehydration melting in the absence of plagioclase. Our calculation results indicate that these hot crustal melts have low densities of 2.47 ± 0.07 g/cm3, low viscosities of 104.9 ± 1.2 Pa·s and high heat production values of ∼2.8 μW/m3. Therefore, such melts are mobile and susceptible to be extracted from the source, and consequently their flow and removal from the deep crust may greatly affect the chemical and thermal structure of the continental crust. Secondary C − O − H fluid inclusions within garnet and orthopyroxene have also been detected. These inclusions contain magnesite, pyrophyllite, corundum, with or without residual CO2. The minerals within the fluid inclusions are interpreted as stepdaughter minerals, which were produced by the reaction of the fluid with its host. The metamorphic timing of the investigated rocks is still a matter of debate. Zircon U–Pb dating results obtained in this study suggest that the metapelitic granulites may have undergone two separated thermal events at ∼1000 and ∼530 Ma, respectively. The presence of fluid inclusions indicates that fluid infiltration and Pan–African reworking may have played an important role in obscuring chronological information of the early thermal scenario in poly-metamorphic terranes.

Fracture characteristics and in-situ damage mechanism of PIP-C/SiC composites to various temperatures and loading velocities

C/SiC composites prepared by polymer infiltration and pyrolysis (PIP) are among the most promising materials for application in ultrahigh-temperature conditions. However, the mechanical properties and damage mechanisms of PIP-C/SiC composites at different loading velocities and temperatures have not been systematically studied. In this study, in-plane compression, bending, and in-plane shear experiments were systematically performed at different loading velocities and temperatures in an inert atmosphere. The ultimate strengths of the PIP-C/SiC composite were determined under different conditions, and the failure modes were revealed. In addition, in-situ X-ray microtomography tension experiments were conducted to study the failure mechanism of the PIP-C/SiC composite. The results showed that the ultimate strengths were considerably affected by the temperature and loading velocity, and the failure modes were dependent on experimental types. The fracture location of the PIP-C/SiC composite is affected by the defect. And the direction of crack propagation is toward the existing cracks and voids.

C–O–H fluid-melt-rock interaction in graphitic granulites and problems of quantifying carbon budget in the lower continental crust

Estimates on the geological carbon cycle are subject to large uncertainties that can be reduced by thorough observation of rocks. In this contribution, we focus specifically on C–O–H fluid-melt-rock interactions in graphitic metapelitic granulites and on their bearing to the carbon budget of granulitic roots of continents. We provide robust microstructural and thermometric constraints on the coexistence of anatectic silicate melts and C–O–H fluids up to near ultrahigh temperature conditions in the archetypal crustal section of Ivrea-Verbano Zone (IVZ, Italian Alps). Fluid inclusions in garnet are investigated before and after high-temperature experiments, and contain considerable proportions of CO2, CH4, N2, but lower H2O than predicted for graphitic systems at granulite facies. When comparing and contrasting the melt compositions obtained by Perple_X and rhyolite-MELTS with natural melts from IVZ, a much better match is obtained by the former, questioning the choice of rhyolite-MELTS for modelling melting equilibria of metasedimentary rocks and for quantifying carbon budget of the lower crust. Overall, data show that assuming only a limited extent of fluid-melt immiscibility in the deep crust contradicts the evidence from natural rocks and prompts to an incomplete view of actual carbon behavior and carbonic fluids. The available experimental dataset on CO2 solubility in felsic melts cannot be used to interpret the volatile budget of melt inclusions in graphitic migmatites and granulites, as most solubility experiments were conducted under carbonate-saturated (i.e. highly oxidizing) conditions which maximize CO2 content of melt, compared to graphitic (i.e. more reducing) protoliths. As a consequence, thermodynamic models still cannot account for all the complexities related with interactions among H2O–CO2–CH4 ternary fluids, H2O- and CO2-bearing anatectic melts and graphite-bearing residues in graphitic metapelites. Targeted experimental studies are therefore crucial to boost substantial computational efforts, before any precise estimates on carbon budget and fluxes in the lower anatectic crust can be made.

Double-Wire-Based Single Distributed Optical Fiber Strain Sensing Method in High-Temperature Environment

Optical strain sensors [optical fiber strain (OFS] based on optical frequency domain reflection (OFDR) are an optical sensor with great application value and the ability to achieve distributed detection. However, both the external ambient temperature and the strain contribute to the frequency shift of the Rayleigh scattering spectrum in the optical fiber during the measurement. This means that the problem of temperature compensation (TC) must be considered when detecting strain in the environment with temperature field, especially in high-temperature environment. In this article, a method of double-wire-based single optical fiber was proposed to aim at this problem, which makes one single fiber have two functions of TC and strain sensing at the same time. The contact strain sensing experiment was carried out on the conventional standard single-mode fiber (SMF)-128 polyimide-coated (PI) distributed OFS sensor (DOFSS) under high-temperature conditions (0 °C–300 °C). The TC for the strain measurement of optical fiber sensor-based OFDR was effectively realized by performing data fusion operation on the measurement results of TC and strain sensing, and the relationship between the temperature change rate and the compensation error rate (ER) was obtained. In addition, the noncontact fiber stretching sensing experiment under ultrahigh-temperature (50 °C–600 °C) conditions was carried out for the first time, which further verified the effectiveness of the method for the compensation of the fiber strain measurement error. Feasibility especially provides a simple and effective method for the application of strain measurement technology in high-temperature environment.

Experimental investigation of heat transfer characteristics of water in a vertically–upward tube under ultra-supercritical pressure and ultrahigh-temperature conditions

Advanced ultra-supercritical (A-USC) steam power generation technology is characterized by main steam conditions of > 700 °C and > 35 MPa, enhanced cycle efficiency, and reduced environmental footprint, and is one of the important development goals of the thermal power plants today. However, scarce studies were conducted on the heat transfer characteristics of supercritical water (SCW) under A-USC operating conditions. An experimental platform to safely measure the heat transfer of SCW flowing in a vertical tube at temperature up to 760 °C and pressure up to 42 MPa was designed and built in this study. Experimental measurements of the heat transfer characteristics of SCW were performed on this platform in a wide range of temperature and pressure, up to a maximum bulk fluid temperature of 750 °C and a maximum pressure of 38 MPa. The effects of pressure, mass flux, and heat flux on the heat transfer characteristics of SCW in the ultrahigh enthalpy region (over 3200 kJ·kg−1) were then analyzed based on the experimental data. Results show that in the ultrahigh enthalpy region, the bulk fluid temperature and wall temperature increase approximately linearly with increasing bulk fluid enthalpy. The heat transfer coefficient decreases gently and then gradually stabilizes in the same range, with values in the range of 4–10 kW·m−2·K−1. In the ultrahigh enthalpy region, increasing the mass flux or decreasing the heat flux will improve the heat transfer performance. And at a pressure of > 35 MPa, increasing the pressure will improve the heat transfer performance moderately. By comparing with experimental data, the Gupta’s correlation has acceptable accuracy in predicting the heat transfer coefficient and inner wall temperature.