Ultrahigh-pressure Conditions Research Articles

Exhumation of ultra-high pressure (UHP) rocks modulated by rifted margin-subduction feedback: Implications for their preservation in old collisional orogens

In continental subduction, rifted margins can be carried to mantle depths (> 90 km) where ultra-high pressure (UHP) metamorphism above coesite stability is attained. Although different exhumation mechanisms for UHP rocks have been discussed, none of them integrate the recent understanding of rifted continental margins. Here, we perform high-resolution thermomechanical numerical experiments to demonstrate that segments of magma-poor rifted margins that reach UHP conditions can efficiently exhume back to shallower levels, while segments of magma-rich rifted margins cannot. This is because the thick layer of rocks with a basaltic composition in magma-rich margins becomes negatively buoyant during metamorphism, preventing their exhumation. This new concept might be pivotal for explaining why exhumed UHP rocks, a key feature of modern-style continental orogens, only appeared and became common late in Earth's history. We suggest that higher mantle potential temperatures and fertility in Earth's early history favored magma-rich rifted margins, making exhumation of UHP crust inefficient. Conditions for magma-poor rifted margins may have arisen during Earth's middle age (1.5–0.8 Ga) due to a colder, more refractory mantle that limited melting and magmatism. We argue that at the end of Neoproterozoic, these colder and positively buoyant magma-poor rifted margins were then subducted and efficiently exhumed to form the large collisional orogens of Gondwana where Earth's oldest coesite-bearing UHP rocks have been unequivocally found. Since then, UHP rocks have become a key and ubiquitous feature of continental orogens.

The Geodynamic Significance of Continental UHP Exhumation: New Constraints From the Tso Morari Complex, NW Himalaya

AbstractThe burial and exhumation of continental crust to and from ultrahigh‐pressure (UHP) is an important orogenic process, often interpreted with respect to the onset and/or subduction dynamics of continent‐continent collision. Here, we investigate the timing and significance of UHP metamorphism and exhumation of the Tso Morari complex, North‐West Himalaya. We present new petrochronological analyses of mafic eclogites and their host‐rock gneisses, combining U‐Pb zircon, rutile and xenotime geochronology (high‐precision CA‐ID‐TIMS and high‐spatial resolution LA‐ICP‐MS), garnet element maps, and petrographic observations. Zircon from mafic eclogite have a CA‐ID‐TIMS age of 46.91 ± 0.07 Ma, with REE profiles indicative of growth at eclogite facies conditions. Those ages overlap with zircon rim ages (48.9 ± 1.2 Ma, LA‐ICP‐MS) and xenotime ages (47.4 ± 1.4 Ma; LA‐ICP‐MS) from the hosting Puga gneiss, which grew during breakdown of UHP garnet rims. We argue that peak zircon growth at 47–46 Ma corresponds to the onset of exhumation from UHP conditions. Subsequent exhumation through the rutile closure temperature, is constrained by new dates of 40.4 ± 1.7 and 36.3 ± 3.8 Ma (LA‐ICP‐MS). Overlapping ages from Kaghan imply a coeval time‐frame for the onset of UHP exhumation across the NW Himalaya. Furthermore, our regional synthesis demonstrates a causative link between changes in the subduction dynamics of the India‐Asia collision zone at 47–46 Ma and the resulting mid‐Eocene plate network reorganization. The onset of UHP exhumation therefore provides a tightly constrained time‐stamp significant geodynamic shifts within the orogen and wider plate network.

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

Continental subduction in Paleoproterozoic: Insights from ∼ 1.9 Ga nepheline syenite in the North China craton

Subduction of continent is known as a feature of modern plate tectonics, and it is still unclear whether such a process also occurred in the early Precambrian. Despite of ultra-high pressure metamorphism of terrestrial rocks as a proxy of continental subduction, magmatism produced during continental subduction is also a potential alternative. The North China craton is well-known for the occurrence of 1.9 Ga retrograde eclogite, which was likely originated from the subducting oceanic crust along the Trans-North China Orogen (TNCO). Here a nepheline syenite (the Aohu pluton), the first of the kind from the TNCO, is discovered in Yunzhong Mts. It comprises nepheline (∼20 vol%), albite (50–55 vol%), K-feldspar (5–10 vol%), biotite (∼10 vol%), and calcite (∼5 vol%), with minor accessory minerals. No associated mafic or silicic rocks are outcropped in the pluton. SHRIMP zircon U-Pb analyses yield a crystallization age of 1893 ± 13 Ma and a metamorphic overprinting of 1871 ± 17 Ma. The rocks have medium SiO2 contents (51.9–58.9 wt%), low MgO (0.6–1.6 wt%) and Mg# (24–34), but high Al2O3 (20.0–22.9 wt%) and extremely high K2O + Na2O contents (10.0–13.6 wt%; Na2O/K2O = 1.3–2.6). They are enriched in light rare earth elements (REEs) and large ion lithophile elements, but relatively depleted in heavy REEs and high field strengthen elements. They have extremely low compatible elements (e.g., Ni and Cr). They show high (87Sr/86Sr)i ratios (0.706–0.707) but low εNd(t) values (−5.3 to −6.0; Nd T2DM = ca. 2.7 Ga). Their zircon in-situ εHf(t) values have a wide range (0 to −5.7; Hf T2DM = 2.5–2.85 Ga). The absence of mafic component and the extremely low-Mg feature, as well as their trace element patterns and initial Sr-Nd isotopes being compatible with melts derived from the Archean mafic crustal enclaves in the region, support a continental crust origin for the Aohu nepheline syenite. Based on comparison and modeling, we suggest that its generation was most likely under ultra-high pressure condition. It is thus proposed that continental subduction (into the mantle) might have occurred in the TNCO during the Paleoproterozoic.

Ultrahigh pressure filtration dewatering of municipal sludge conditioned by steel slag in combination with Fe2+/ sodium persulfate

Municipal sludge treatment in urban contexts faces significant challenges, especially when dealing with sludge characterized by exceptionally high water content and organic content. This study investigates the application of sodium persulfate oxidation activated by ferrous ions (Fe2+/SPS) in conjunction with waste steel slag as a conditioning agent for municipal sludge, capillary suction time and specific resistance filtration experiments were conducted on conditioned sewage sludge, along with dewatering tests under ultrahigh pressure conditions. Additionally, to investigate the potential underlying mechanisms, Scanning Electron Microscopy analysis, Zeta potential measurements, and comprehensive sample analyses were performed. The research reveals substantial improvements in sludge dewatering performance when steel slag is combined with Fe2+/SPS treatment. This combined treatment introduces additional ferrous ions into the sludge, generating radicals that disrupt the structure of extracellular polymeric substances and cells within the sludge. Steel slag also acts as a skeleton builder material, creating larger drainage pathways within the sludge cake under ultrahigh pressure, enhancing permeability, and accelerating moisture release. This combined treatment method holds promise for achieving deep sludge dewatering, under ultrahigh filtration pressure, with water content reduced to below 40%. The study not only highlights the advantages of using steel slag in combination with Fe2+/SPS treatment for sludge dewatering but also provides insights into the underlying mechanisms. This comprehensive treatment method reduces the excessive use of ferrous ions and costs while significantly enhancing dewatering performance, offering a promising solution for municipal sludge treatment and management.

Cold deep subduction of Indian continental crust and release of ultrahigh‐pressure fluid during initial exhumation: Insights from coesite‐bearing eclogite‐vein systems in Kaghan Valley, Pakistan

AbstractThe ultrahigh‐pressure (UHP) eclogites from the Kaghan Valley in Pakistan, which formed by the deep subduction of the Indian plate beneath the Asian plate in the Eocene, contain complex metamorphic vein systems (including both isolated veins and vein networks), with mineral assemblages of epidote + quartz + kyanite + phengite ± omphacite ± garnet. The investigations on the Kaghan UHP eclogite‐vein systems provide important insights into the mechanism and timing of metamorphic dehydration, fluid flow, and fluid–rock interaction in the deeply subducted Indian continental slab as well as the chemical characteristics of slab‐derived, aqueous fluids. Abundant lawsonite pseudomorphs, characterized by prismatic aggregates of epidote, kyanite, and quartz porphyroblasts, are first recognized in the Kaghan eclogites. This observation, in combination with the occurrence of coesite pseudomorphs in epidote porphyroblasts as well as the coexistence of epidote and coesite in the eclogite zircon, indicates the previous existence of UHP lawsonite in these eclogites. Petrological studies and phase equilibrium modelling reveal clockwise P–T trajectories for the Kaghan eclogites that are featured by prograde vectors in lawsonite‐stability regions with peak conditions of 3.0–3.4 GPa/650–690°C, followed by isothermal decompression and lawsonite breakdown under UHP conditions during the initial exhumation stage. The results of metamorphic evolution, together with in situ epidote and bulk Sr isotopic analyses, indicate that the fluids responsible for vein systems are most likely derived from the breakdown of UHP lawsonite in the eclogites. SIMS U–Pb dating of metamorphic zircons from the eclogites, integrated with the Raman analysis of inclusions in zircons, indicates that the UHP dehydration of eclogites occurred at 46.4 ± 1.2 and 46.8 ± 0.9 Ma. Analyses of hydrothermal zircons from the veins yielded slightly younger ages of 44.7 ± 1.0 and 44.9 ± 1.4 Ma, which represent the timing of fluid flow and/or vein crystallization during exhumation of the UHP rocks. Mass‐balance calculation results, in combination with the vein compositions, show that the fluid flow and fluid‐eclogite interaction led to the transfer of Si, Al, Ca, K, and incompatible trace elements from the eclogites into the fluids, from which the vein systems crystallized. This study indicates cold deep subduction of Indian continental crust along low geothermal gradients (6–7°C/km). The UHP fluid liberation and channelized fluid flow occurred during the initial exhumation of the cold Indian slab and are expected to induce the transfer of H2O and incompatible trace elements from the Indian slab to the Asian lithosphere, which potentially contributes to the formation of post‐collisional magmas. Moreover, we suggest that metamorphic vein systems in UHP lawsonite eclogites offer important constraints on the occurrence and timing of fast slab exhumation in continental subduction‐collision zones.

Similarity and normalization study of fuel spray and combustion under ultra-high injection pressure and micro-hole diameter conditions–spray characteristics

The compression-ignition engine has been widely applied in various fields due to its high efficiency, fuel economy, and adaptability. With the increasing awareness of environmental issues, emission regulations have become more stringent, leading to a growing demand for high-pressure and small-sized engines. Since developing new engines is often both costly and time-consuming, leveraging the similarity between spray and combustion processes for new engine development can significantly reduce the required resources and time. However, to date, systematic research on the similarity and normalization of sprays and combustion processes, especially under ultra-high injection pressure and micro-hole diameter conditions, remains lacking. In this study, conversion models and normalization models for spray characteristics were developed based on both time scale and multi-dimensional space scale. The spray transformation and normalization were verified for different aperture sizes, injection pressures, ambient temperatures, densities, and pressures. The results show that the models exhibit good interchangeability and normalization effects. This research outcome will provide valuable references for optimizing and designing more efficient and environmentally friendly internal combustion engines.

Heterogeneous Archean oceanic protoliths in Neoproterozoic retrogressed eclogites from Northeast Brazil: Petrological, geochemical and Sr–Nd–Pb–Hf isotopic constraints

Eclogites are reliable indicators of high to ultrahigh-pressure (HP-UHP) conditions for oceanic and continental crust and are essential rocks to understand the lithospheric convergence from subduction to post-collisional setting. Furthermore, the origin and nature of eclogite precursors may reveal crucial constraints on the crustal history before HP-UHP metamorphism. Here, we provide petrological, geochemical and Pb-Sr-Nd-Hf isotopic constraints from the Campo Grande retrogressed eclogites, Northeast Brazil, to determine the source and evolution of their Archean protoliths. Eclogites were formed under HP conditions (18 ± 1.0 kbar and 680 ± 20 °C) followed by retrogression in the amphibolite facies, which is characterized by Mg-rich garnet porphyroblasts surrounded by clinopyroxene + plagioclase + amphibole + orthopyroxene symplectites (stable at <6.0 kbar). These retrogressed eclogites have chemical compositions corresponding to enriched-type tholeiites such as E-MORB protoliths (G1 eclogitic group). A second group of retrogressed eclogites with higher amphibole content (G2 eclogitic group) shows similar chemical patterns to G1, however with higher enrichment in LILE, REE and incompatible elements. The G1 eclogite is characterized by higher modal concentration of garnet and clinopyroxene, positive εNd(t) (+2.1 to +5.8) with low 87Sr/86Sr(i) ratios (0.7024 to 0.7131), whereas G2 displays dominant coarse-grained amphibole, positive and negative εNd(t) (−7.5 to +8.5) with high radiogenic 87Sr/86Sr(i) ratios (0.7109 to 0.7255). The chemical and isotopic G1 values show typical E-MORB signatures, whereas G2 indicate an E-MORB enriched by crustal components in a supra-subduction zone setting. A LuHf isochron provided the age of 2667.9 ± 30.7 Ma, which is close to the published ∼2.65 Ga crystallization age for the G1 and G2 oceanic protoliths. Therefore, Hf isotopes in whole rock and cogenetic minerals were useful for constraining the crystallization time of metamafic protoliths. In contrast, SmNd isochron age of 606.9 ± 24.8 Ma falls within the range of 623 to 590 Ma HP metamorphism recorded in the G1 and G2 rocks. Lastly, a third type of eclogite group (G3 eclogitic group) is represented by a banded Mn-rich-garnet (spessartite) and Al-rich clinopyroxene with detrital zircon cores from 3.42 to 2.15 Ga and recrystallized rims at 607.7 ± 5.4 Ma. Mineral texture and composition, geochemistry, strongly negative εNd(t) (−4.3 to −1.5) and higher radiogenic 87Sr/86Sr(i) ratios (0.7434–0.7501) suggest a different Mn-rich protolith for the G3 eclogites. Integrated data reveal that retrogressed eclogites retain the memory of the original chemical and isotopic patterns of Archean oceanic protoliths and its diachronous reworking processes at deep crustal levels.

Mantle metasomatism induced by water-fluxed melting of subducted continental crust at ultrahigh pressures

Abstract Mantle metasomatism under ultrahigh-pressure (UHP) conditions is widely recognized in orogenic peridotites and pyroxenites from UHP terranes. However, the processes by which the deeply subducted continental crust reacts with the mantle remain obscure. To investigate the metasomatic regime under UHP conditions, we conducted layered reaction experiments between gneiss and peridotite at 5 GPa and 800–1100 °C, with free water added in some of the experiments. At temperatures below the gneiss solidus, the major metasomatic agent is aqueous fluid, with the main reaction products being orthopyroxene + phlogopite + K-richterite. At temperatures above the gneiss solidus, hydrous melt becomes the major metasomatic agent, and the major reaction products vary from orthopyroxene + phlogopite to orthopyroxene + garnet with increasing degree of melting. The transformation from phlogopite to garnet occurred between 1000 °C and 1100 °C for runs without water added and between 800 °C and 900 °C for runs with water added. Pyroxenites in UHP terranes are mainly characterized by the metasomatic growth of orthopyroxene and garnet at 4–6 GPa and 750–1000 °C. Only experiments with water added reproduced the metasomatic assemblage at similar pressure-temperature conditions, indicating that mantle metasomatism in UHP terranes is probably mainly induced by water-fluxed melting of the continental crust under UHP conditions.

Exhumation of ultrahigh-pressure eclogite and metarodingite within UHP serpentinites from the Chinese southwestern Tianshan

Extensive research over the past two decades suggests that serpentinite loses its ability to effectively facilitate the exhumation of high-density high-pressure (HP) eclogites at depths of 60–80 km under average subduction zone geotherms. However, at Changawuzi, the western termination of Chinese southwestern Tianshan, eclogite and eclogitic metarodingite are commonly enclosed within ultrahigh-pressure Ti-chondrodite serpentinites (510–530 °C, 37 ± 7 kbar). This metamorphic mafic–ultramafic association, which has undergone a complex evolution from oceanic alteration to deep subduction and subsequent exhumation, presents a unique opportunity to study the incompletely understood mechanisms leading to the exhumation of ultrahigh-pressure (UHP) eclogite in UHP serpentinite.The Changawuzi serpentinite wraps three different rock types: retrograded eclogite, Rodingite I and Rodingite II. Field observations and petrological analyses indicate that the precursor of Rodingite I intruded as vein into the serpentinite protolith prior to subduction, sharing the evolution towards ultrahigh-pressure conditions. According to its composition, the serpentinite originated from a depleted oceanic mantle peridotite, with only minor enrichment in fluid-mobile elements (FME) during oceanic serpentinization. The eclogites have N-MORB like bulk compositions, with lower Si but higher Mg content compared to other eclogites in the Tianshan area, and appear to have been relatively unaffected by oceanic alteration processes. The Changawuzi serpentinite and eclogites likely evolved within a slab setting with limited interaction with seawater. Petrological studies and phase equilibria modeling suggest that the eclogites experienced peak UHP metamorphism at 28–34 kbar and around 460–465 °C. Density measurements yielded relatively low densities of 2.66–2.97 g/cm3 for the host serpentinites, but 3.27–3.63 g/cm3 for Rodingite I. The similarity in the low temperature/ultrahigh pressure conditions, as well as the geochemical characteristics shared by the serpentinite and eclogites, further support the connection between the Changawuzi serpentinites and the interior of the subducting slab. According to our data, two types of UHP eclogitic mafic rocks exhumated with UHP serpentinite. (1) High density Rodingite I veins are embedded within serpentinite and share a common evolution and exhumation history with the host serpentinite. (2) The eclogite and serpentinite tectonically detached from the interior of the subducting slab at different depths and ascended to the plate interface above the slab (subduction channel). These two rock types experienced separate exhumation processes within the subduction channel during the early stages of exhumation. Subsequently, the buoyant serpentinite captured the denser retrograded eclogite at a depth of approximately 80 km, and together they underwent further retrograde metamorphism as they ascended towards the surface. During a later exhumation stage, external fluid induced a second serpentinization process, leading to the formation of Rodingite II within the subduction channel. This study presents a novel exhumation mechanism specific to the Tianshan eclogites and highlights the significant role of deeply subducted serpentinite in the exhumation of eclogites and eclogitic metarodingites from sub-arc depths within an oceanic subduction zone.

Mantle refertilization at high-pressure conditions of continental subduction channel: Evidence from orogenic peridotites in the Sulu UHP terrane, eastern China

Refertilization of depleted peridotites widely occurs in lithospheric mantle but is poorly understood in a continental subduction channel. The Sulu orogenic belt is a typical ultra-high pressure (UHP) terrane formed by continental subduction and collision. To understand the complex metasomatic processes on peridotites during continental subduction, we combined detailed petrographic and geochemical studies for fertile garnet lherzolites (Chijiadian) from the Sulu UHP terrane, as well as refractory peridotites (Xugou and Lijiatun) for comparison. The fertile garnet lherzolites (Chijiadian) are not residues of low-degree partial melting, but they formed from refertilization processes during peak-UHP metamorphic stages (garnet-facies) in a continental subduction channel, as reflected by abundant clinopyroxene (12 vol%) and garnet (12 vol%), low bulk-rock Mg# of 91 and high Al2O3 of 2.4–3.3 wt%. Garnet, clinopyroxene, and orthopyroxene display secondary poikilitic textures and often contain early phases of olivine, spinel, and garnet inclusions, indicating later precipitation of these minerals into depleted peridotite protoliths. The clinopyroxenes show enrichment of large ion lithophile elements (LILE) and high 87Sr/86Sr of 0.7061–0.7084. The estimated pressure-temperature are 720–770 °C at 4.4–4.8 GPa, consistent with previous constraints on UHP conditions. These features suggest strong refertilization processes at UP-UHP conditions (garnet-facies) in continental subduction channels. The metasomatic agents for refertilization would be basaltic-intermediate melts which incorporated continental materials. Similarly, Xugou harzburgites and Lijiatun dunites also record the subducted continental signatures with enrichment of LILE and high Sr isotopes on clinopyroxenes (87Sr/86Sr: 0.7050 to 0.7065). However, Xugou harzburgites and Lijiatun dunites overall do not display the same typical refertilization features as for Chijiadian, as reflected by low abundances of clinopyroxene and high Mg# of 92–93. Consequently, continental subduction could lead to diverse types of metasomatism of refractory peridotites, including refertilization at UP-UHP metamorphic stages in subduction channels, as in other tectonic settings.

Investigations on the Diesel Spray Characteristic and Tip Penetration Model of Multi-Hole Injector with Micro-Hole under Ultra-High Injection Pressure

Increasing the injection pressure has a significant impact on atomization and combustion characteristics. Spray tip penetration serves as a vital parameter for fuel injection control and engine structure design. However, a reliable spray tip penetration model for ultra-high-pressure injection is currently lacking. To address this gap, this study establishes a theoretical 0-dimensional model for spray tip penetration under ultra-high pressure (300 MPa) conditions. The model is based on the conservation of momentum and phenomenological models. The new model divides spray tip penetration into two stages: Pre-breakup and post-breakup, with fuel injection rate and spray cone angle used as model inputs. To validate the model, high-speed camera observations and constant-volume chamber experiments are conducted to investigate the spray characteristics. The results indicate that the new spray tip penetration model demonstrates improved predictive accuracy across all experimental conditions.

Detrital garnet petrology challenges Paleoproterozoic ultrahigh-pressure metamorphism in western Greenland

Abstract. Modern-style plate tectonics is characterised by the global operation of cold and deep subduction involving blueschist facies and ultrahigh-pressure metamorphism. This has been a common process since the Neoproterozoic, but a couple of studies indicate similar processes were active in the Paleoproterozoic, at least on the local scale. Particularly conspicuous are extreme ultrahigh-pressure conditions of ∼ 7 GPa at thermal gradients &lt; 150 ∘C GPa−1 proposed for metamorphic rocks of the Nordre Strømfjord shear zone in the western part of the Paleoproterozoic Nagssugtoqidian Orogen of Greenland. By acquiring a large dataset of heavy minerals (n = 52 130) and garnet major-element composition integrated with mineral inclusion analysis (n=2669) from modern sands representing fresh and naturally mixed erosional material from the metamorphic rocks, we here intensely screened the area for potential occurrences of ultrahigh-pressure rocks and put constraints on the metamorphic evolution. Apart from the absence of any indications pointing to ultrahigh-pressure and low-temperature–high-pressure metamorphism, the results are well in accordance with a common Paleoproterozoic subduction–collision metamorphic evolution along a Barrovian-type intermediate temperature and pressure gradient with a pressure peak at the amphibolite–granulite–eclogite-facies transition and a temperature peak at medium- to high-pressure granulite-facies conditions. In addition, we discuss that all “evidence” for ultrahigh-pressure metamorphism proposed in the literature for rocks of this area is equivocal. Accordingly, the Nordre Strømfjord shear zone is not an example of modern-style plate tectonics in the Paleoproterozoic or of very low thermal gradients and extreme pressure conditions in general.

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.

Effect of Zr/Al binder ratio on properties of PCBN composites

Polycrystalline cubic boron nitride composites (PCBN) were synthesized by mixing cBN micro-powder, Zr powder and Al powder in different mass ratios under high temperature and ultra-high pressure conditions. The phase composition and microstructure of the composites were analyzed by X-ray diffraction and scanning electron microscopy. The effects of different Zr/Al mass ratios to the sintering behavior and related properties of PCBN composites were studied in order to obtain a binder ratio scheme with excellent performance. The research shows that when the Zr/Al ratio is 16 wt%:8 wt% (2:1), the hardness of the sample is the highest, which is 33.4 GPa, and the fracture toughness is the best 6.6 MPa·m1/2. Crack bifurcation, deflection and particle reinforcement have significant reinforcement and toughening effects on PCBN composites. When the Zr/Al ratio is 12 wt%:12 wt% (1:1), the PCBN composite with the best density is obtained, the porosity is as low as 0.7%, and the strength of the sample is the highest, which is 864.2 MPa.

Development of an In-Situ Simulation Device for Testing Deep Pressure-Preserving Coring Tools under High-Temperature and Ultrahigh-Pressure Conditions

With the increasing mining depth of deep mineral resources, the underground temperature and pressure also increase, which requires more advanced mining equipment. Therefore, to adapt to the special application scenario of the research and development of pressure-preserving coring tools under the extreme environmental conditions of deep strata, in this study, an in-situ simulation device under high-temperature and ultrahigh-pressure conditions is developed. The principles and methods of applying temperature and pressure to the device are expounded. Furthermore, the two main modules of the device are analyzed and studied experimentally. On the one hand, a segmented simulated coring test cabin is constructed, and pressure testing of the test cabin is carried out. The results show that the test cabin with inner diameters of 150 mm and 500 mm runs stably under the working condition of a pressure up to 190 MPa (considering the influence of temperature of 150 °C), and the cabin remains in the stage of elastic deformation. There is no leakage of pressure or fluid in the whole test process. On the other hand, the performance of the driving module is tested. The results show that the driving module can provide a stable rotation speed of up to 150 r/min when the sealing pressure is 140 MPa. Therefore, the device can be applied to carry out simulated coring test and is suitable for the research and development of pressure-preserving coring tools in deep extreme environments, which may promote the development of deep mining engineering.

Repeated Caledonian burial and ultrafast cooling and exhumation of high‐pressure granulite facies rocks from the Blåhø Nappe on the island of Fjørtoft, Western Gneiss Region, Norway

AbstractThe allochthonous Blåhø Nappe in the Nordøyane ultra high pressure (UHP) domain, Western Gneiss Region in Norway, acts as a window to examine geological processes occurring in continent–continent collisional zones, but many aspects regarding its tectonometamorphic evolution remain debated and elusive. In this contribution, an integrated study including major‐ and trace‐element zoning in garnet, phase equilibrium modelling and the simulation of cation diffusion in garnet was conducted on two high‐pressure (HP) granulite facies rocks from the Blåhø Nappe on the island of Fjørtoft. The results shed new light on the complex geodynamic processes that act in continent–continent collisional zones and finally shape collisional orogens. Phengite, biotite, amphibole, zoisite‐allanite and low‐Zr rutile enclosed in garnet likely attest to a prograde eclogite facies metamorphism for the studied rocks. Pressure–temperature (P–T) conditions of ~1.5–1.6 GPa and 615–670°C were retrieved for this stage. An extensive re‐equilibration under peak HP granulite facies conditions of ~1.5 GPa and 925 ± 50°C followed. Subsequently, the rocks were cooled and reburied to eclogite facies conditions of ~1.8–1.9 GPa and 805–825°C. This was followed by a final stage of decompression and cooling to amphibolite facies conditions of ~650–780°C and 0.5–1.0 GPa. Cooling and exhumation rates of &gt;400°C/Ma and &gt;75 km/Ma, respectively, indicating an ultrafast temperature and pressure decrease are estimated for this stage from simulations of cation diffusion in garnet. The anticlockwise P–T path obtained here is relatively complete and compatible with a repeated burial history during the Caledonian orogeny but not with UHP conditions proposed for the Blåhø Nappe. Our model proposes that the rocks later forming the Blåhø Nappe were buried to lower crustal depths of approximately 55 km equating to a geothermal gradient of ~13°C/km during the early Caledonian orogeny. Subsequent heating of these rocks to HP granulite facies conditions was likely driven by slab break‐off and hot mantle upwelling. Baltica underthrusting during the Scandian continent–continent collision cooled and transported the Blåhø Nappe to greater depths. The obtained cooling and exhumation rates indicate ultrafast exhumation, presumably in an exhumation channel.

Fabrication of polycrystalline cubic boron nitride composites under high pressure

The PCBN (polycrystalline cubic boron nitride) composites were synthesized by mixing cubic boron nitride micropowders with Ti and Al micropowders at a certain mass ratio under high temperature and ultra-high pressure conditions. Phase composition and microstructure of the samples were analysed by X-ray diffraction and scanning electron microscopy. The effects of sintering temperature on the mechanical properties and microstructure of the PCBN ceramics were investigated. It was shown that BN, AlN, TiN and TiB2 phases coexist in the PCBN ceramics fabricated at ultra-high pressure (5.5GPa) and high temperature (1400-1500?C). With the increase of sintering temperature, pores and gaps inside the PCBN composites gradually disappeared and densified structure was formed. The best comprehensive mechanical properties of the PCBN composites were obtained at 1500 ?C with a flexural strength of 1009MPa and microhardness of 35.8GPa.

In situ synthesis of PcBN composites by Sialon combined with cBN-TiB2-AlN and their properties

In this paper, the Sialon phase was synthesized under the conditions of ultra-high pressure (5.5 GPa) and high temperature (1550 °C), and the polycrystalline cubic boron nitride (PcBN) composite was in situ synthesized with TiB2, AlN, Sialon as the binder of cubic boron nitride (cBN). X-ray diffractometry (XRD), universal testing machine, field emission scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM) were used to study the effects of Sialon rod crystal on the phase composition, microstructure and mechanical properties of PcBN composites. The results show that when TiB2 rod crystal is formed in the system, the irregular long rod-like new phase Sialon grows along the [0001] face appears. The mechanics properties and machinery properties of the sintered body were significantly improved due to the formation of Sialon. When the generation amount of Sialon is 30 %, the aspect ratio of Sialon is 3/1– 4/1 at most, with high hardness and strength of 27.49 GPa and 903.741 MPa, respectively, as well as the fracture toughness and wear are relatively favorable, separately 7.387 MPa·m1/2 and 1602, the interface is well bonded and the density is the highest. At this time, the comprehensive performance of the PcBN composite material is most superior.

Influence of the high-pressure ω - Zr phase on selected properties of sintered zirconium powder materials

Most commercial zirconium alloys are obtained by melting methods and consist of α-Zr. The sintering of zirconium powders is carried out mainly by pressure methods, which is the reason for the appearance of higher stresses in the materials and the presence of the high-pressure ω-Zr phase. Sintered zirconium materials containing α-Zr, α-Zr + β–Zr + Nb and ω-Zr + α-Zr phases, with a relative density of approximately 98%, using the Spark Plasma Sintering method and the ultra-high pressure method were obtained. X-ray diffraction methods were used to determine the content of individual zirconium phases in the materials. Stresses were measured in alpha and omega zirconium phases by the sin2 ψ diffraction method for all investigated materials. Hardness, tensile strength and elongation of materials were measured. The greatest elongation of 7.1% was found for sintered materials containing ω–Zr. The presence of the ω - Zr obtained under ultra-high pressure conditions does not significantly affect the stress level in ω Zr and in the α-Zr phase of the High Pressure – High Temperature sintered material. Tribological tests were carried out using the ball-on-disk method, with alumina as counter-samples. The research showed an adverse effect on the abrasive wear of the high-pressure omega Zr phase. The zirconium oxidation process and the separation of the oxide from the wear surface plays an important role in the abrasion of all sintered zirconium materials.