Subduction of carbon rich sediments and crust at convergent plate boundaries exerts a crucial control on Earth's mantle chemistry and surface habitability. Recent attention has focused on exposures of fully-carbonated mantle rocks as these may attest to an overlooked sink for subducted carbon not sampled by arc volcanism. However, even in the best-studied example, the Semail Ophiolite, Oman, the setting for carbonation remains highly contentious, with conflicting inferences from geochemistry and geochronology. We approach this problem by combining microanalysis of halogens and detailed petrography to fingerprint the origins of carbonating fluids. Fluids were derived from both sedimentary pore fluid expulsion and deep slab decarbonation reactions in a subduction zone setting. Through mass balance modelling we show that CO2 fluxes into the forearc from deep decarbonation (1.7-3.4 ×1013 gyr-1 C) could represent up to 90% of the global flux entering subduction zones, indicating that carbonated mantle peridotites likely represent a major sink for subducted CO2 which may have varied through geological time.

Interstitial fluid flow within the osteonal lacunar-canalicular system (LCS) is crucial for osteocyte mechanotransduction and bone remodeling. This study aims to develop a three-dimensional finite element model of an osteon with gradient-varying boundary conditions to systematically investigate how mechanical loading, outer wall constraints, and pulsatile blood pressure modulate intra-osteonal fluid flow. This study constructs a three-dimensional finite element model to systematically analyze the dynamic responses of fluid flow behavior under gradient boundary conditions. Gradient parametric analyses were performed by varying: (1) axial strain amplitudes (250-5000 με) to simulate different activity levels; (2) radial displacement constraints at the outer wall (0- 0.042 μm) to represent confinement by surrounding tissues; and (3) pulsatile blood pressure amplitudes (A = 0-2.5) at the inner wall to mimic physiological to hypertensive conditions. The resulting pore pressure, fluid velocity, and fluid shear stress (FSS) distributions were analyzed. All parameters exhibited axisymmetric distributions. Peak pore pressure, fluid velocity, and FSS increased nearly linearly with strain magnitude, ranging from 1.7×104 to 1.4×105 Pa, 1.69×10-8 to 3.50×10-8 m/s, and 0.34 to 6.5 Pa, respectively. Relaxation of outer wall constraints from fully constrained (0 μm) to fully elastic (0.042 μm) significantly reduced all three parameters. Elevated pulsatile blood pressure markedly increased intra-osteonal pore pressure (from 2.7×104 to 6.5×104 Pa) but had minimal effect on velocity and FSS. A subsequent multiscale validation using an explicit LCS model showed that the macro-scale poroelastic model accurately captures global trends, while local FSS within canaliculi is amplified by a factor of 1.5-2.5. The gradient boundary condition approach effectively quantifies the differential and synergistic effects of mechanical load, structural constraint, and vascular pressure on the osteonal fluid environment. These findings provide a quantitative framework for understanding mechanotransduction in bone and may inform clinical strategies for managing bone adaptation and disease.

Abstract Calcite is prone to chemical and microstructural modifications, especially after having been strained at high stresses and strain rates, as during hypervelocity impact events. These modifications include precipitation from pore fluid as well as replacement of strained volumes by recrystallization. In calcite aggregates of a metagranite breccia of the Ries Bunte Breccia, shocked calcite is partly replaced by new, undeformed grains. This breccia indicates shock conditions of 10–20 GPa by the presence of planar deformation features in quartz of the metagranite. Shocked calcite shows grain orientation spread (GOS) angles of 3–10° and contains e ‐, f ‐, and r ‐ twins, as well as a ‐ and f ‐type lamellae. In contrast, the new coarse calcite grains, which are hundreds of μm in diameter, have low GOS angles (<1°), and do not contain twins. Calcite aggregates have a chemical zonation (varying Mn n+ content), which is independent of new grains, suggestive of fast transformation. We propose that the new grains originate from sites of high crystal‐plastic strain and grew by grain boundary migration driven by the reduction in strain energy, replacing previously strained grains at low stresses, that is, static recrystallization. Heating experiments on shocked calcite confirm the strain control on static recrystallization.

Marine gas hydrates are commonly found in sediments rich in fines or in mixtures of fine and coarse-grained sediments; consequently, the macroscopic properties of these reservoirs are controlled by fines dynamics, which in turn are governed by pore fluid chemistry. However, the impact of pore fluid chemistry changes on the migration and sedimentation of fine-grained sediments has not been extensively considered to date. Therefore, this study employed a high-pressure, low-temperature hydrate reactor to observe the dynamic sedimentation behavior of fines (montmorillonite and mica) during pore fluid chemical changes in the presence of hydrates. It was found that montmorillonite with a high electrical sensitivity index (SE characterizing their responsiveness to pore fluid chemical changes) exhibits increased sedimentation rates in brine solutions, while low-SE mica demonstrates the slowest sedimentation in brine conditions. Furthermore, low-field nuclear magnetic resonance (LNMR) coupled with dynamic fines. Migration experiments investigated sedimentation behavior and pore structure response mechanisms under varying pore fluid chemistry. Results indicate that higher SE of fines correlates with more pronounced migration behavior and porosity variations in fine-grained sediments under flowing pore fluids. This study reveals the influence of pore fluid chemistry on fines dynamic behavior, establishing an intrinsic relationship between fines dynamic behavior and SE .

Chitosan-based photothermal synergistic antibacterial composite sponge achieves acute hemostasis and repair of infected wounds.

Abstract Carbon dioxide‐rich brine formation during geological carbon sequestration induces calcite dissolution, governed by the physicochemical coupling of fluid flow, reactive transport, and pore structure evolution. Unveiling the mechanisms that control this dissolution, particularly under varying flow and structural conditions, is essential for predicting CO 2 plume migration and ensuring long‐term storage stability. While previous studies have explored these coupled processes, they often lack explicit resolution of fracture‐matrix interactions and are limited by computational scalability. In this study, we present a novel pore‐scale numerical framework that integrates the volumetric lattice Boltzmann method with a GPU‐CUDA parallel computing architecture, enabling efficient simulations of reactive flow in both fracture‐free system and fracture‐matrix system. Results reveal that injection velocity governs dissolution morphology and efficiency, with higher velocities reducing reactivity due to preferential flow, while temperature moderately enhances front heterogeneity but has limited impact on overall dissolution behavior. Based on the dissolution profiles observed in two types of 3D carbonate rock cores, three distinct calcite dissolution regimes (uniform, channel widening, and face dissolution) are identified. Moreover, the normalized permeability‐porosity relationship exhibits a negative correlation with temperature across all cases, except at higher injection velocities in the fracture‐matrix system, where a mixed correlation emerges under the influence of the fracture.

Influence of pore fluid on the elasto-plastic property of shales

The consolidation behavior of soft soil foundations subjected to cyclic loading presents a complex Multiphysics problem critical to the stability of transportation infrastructure and offshore structures. Traditionacontinuum mechanics approaches often struggle to capture the granular rearrangements and micro-structural evolution inherent in soft clays and silts under repeated stress applications. This study employs the Discrete Element Method (DEM) coupled with a coarse-grid fluid dynamics scheme to simulate the hydro-mechanical response of soft soil assemblies. By modeling the soil skeleton as a collection of bonded particles and the pore fluid as a continuum interacting through drag forces, we investigate the generation and dissipation of excess pore water pressure and the resulting cumulative settlement. The simulation results reveal that cyclic loading frequency and amplitude significantly influence the breakdown of inter-particle bonds and the reorganization of the force chain network, leading to non-linear consolidation rates that deviate from classical Terzaghi theory. The study further elucidates the mechanism of strain accumulation, showing that particle reorientation acts as the primary driver for permanent deformation after the initial breakdown of soil structure. These findings provide micro-scale insights that enhance the predictive capability for long-term foundation settlement.

The consolidation behavior of soft soil foundations subjected to cyclic loading presents a complex multiphysics problem critical to the stability of transportation infrastructure and offshore structures. Traditional continuum mechanics approaches often struggle to capture the granular rearrangements and micro-structural evolution inherent in soft clays and silts under repeated stress applications. This study employs the Discrete Element Method (DEM) coupled with a coarse-grid fluid dynamics scheme to simulate the hydro-mechanical response of soft soil assemblies. By modeling the soil skeleton as a collection of bonded particles and the pore fluid as a continuum interacting through drag forces, we investigate the generation and dissipation of excess pore water pressure and the resulting cumulative settlement. The simulation results reveal that cyclic loading frequency and amplitude significantly influence the breakdown of inter-particle bonds and the reorganization of the force chain network, leading to non-linear consolidation rates that deviate from classical Terzaghi theory. The study further elucidates the mechanism of strain accumulation, showing that particle reorientation acts as the primary driver for permanent deformation after the initial breakdown of soil structure. These findings provide micro-scale insights that enhance the predictive capability for long-term foundation settlement.

ABSTRACT The weathered transition zone in rock slopes is a geological interface characterised by heterogeneous development of joints and fractures within the rock mass. This structural heterogeneity can lead to the accumulation of pore fluids at the weathering interface under extreme rainfall, resulting in considerable hydro-mechanical damage. Therefore, monitoring the stability of this interface is crucial for assessing the overall stability of rock slopes. To address the monitoring challenges posed by extreme rainfall-induced instability at rock slope weathering interfaces, this study conducted seepage failure modelling experiments and developed an anchored monitoring model. Temporal relationships among slope displacement, pore water pressure and rock bolt axial force were analysed using the monitoring principles of intelligent terminal structure sensors integrated within slope anchoring systems. This analysis enabled the establishment of monitoring and early warning criteria based on the pore pressure gradient and rock bolt axial force at the weathered interface. Thereafter, the proposed early warning model for the weathered transition zone was validated through numerical simulations. This study provided quantitative criteria for the stability monitoring and early warning of rock slope weathering interfaces under extreme rainfall conditions.

Antarctic water tracks are shallow groundwater flow networks that route summer season meltwater downslope over the ice table. Water track pore fluids are highly concentrated in solutes, including silica, and water track sediments are enriched in sediment fines. However, given the extreme cold and aridity of the McMurdo Dry Valleys, it has not been clear whether aluminosilicate weathering is occurring in Dry Valleys water tracks, or whether high solute concentrations merely reflect evaporative concentration of marine or eolian-derived salts, rather than aluminosilicate weathering. Based on geochemical and isotopic analysis of water track pore fluids and freshwater snow and ice melt samples from the McMurdo Dry Valleys, coupled with flow path modeling and measurements of soil aluminum concentration, we show that silica enrichment in water tracks is not due only to silicic waters being evaporatively concentrated, but, instead, that water track composition is consistent with active and ongoing aluminosilicate weathering of water track soils. We show that water tracks connect the landscape at the hillslope scale, draining areas up to 105 m2 to 106 m2 each, and concentrating silica and other solutes from across the watershed. We find that water tracks are sites where chemical weathering products like clays and amorphous aluminum−bearing aggregates are being generated in situ, and solute concentrations are consistent with fluids in equilibrium with weathering product mineral phases. This suggests that expansion of water tracks due to regional warming, greater snowmelt, or permafrost thaw could increase the area of exposed soils in which chemical weathering can occur, altering Antarctica’s role in globally relevant soil biogeochemical processes.

Influence of Lithofacies and Diagenetic Evolution on Pore Structure and Fluid Mobility of Tight Sandstone Reservoirs: The Fourth Member of Xujiahe Formation in Tianfu Area, Sichuan Basin, China

Abstract The morphology of fault zones formed by slow faulting is markedly different from that of brittle faulting. In this study, we quantify the three‐dimensional (3D) pore distribution and permeability structures of two rock samples that have been deformed to failure by slow and brittle faulting, respectively. Our results show that the permeability structure of fault zones varies greatly depending on the faulting mechanism. Fault cores formed by slow faulting exhibit much higher porosity and permeability compared to the surrounding damage zone and wall rocks, unlike those formed through brittle faulting. Since slow slip events associated with high pore fluid pressures are common in active tectonic regions, we propose that slow slip events can serve as a mechanism to maintain the permeable pathways beneath the seismogenic zone, facilitating the movement of mantle‐derived fluids from deep reservoirs toward the surface.

This study provides high-resolution pore-fluid profiles of surficial sediments (down to 40 cm) from four submarine mud volcanoes (MVs) of the Olimpi Mud Volcano Field (OMVF) in the Eastern Mediterranean, including the Gelendzhik, Heraklion, Moscow and Milano MVs. Here, we present major ions (Na + , K + , Mg² + , SO 4 ² - , Cl - ), sulfide, methane, dissolved inorganic carbon (DIC), δ¹³C DIC , ammonium, phosphate and silicate concentrations. These results were evaluated in relation to both early and deep diagenetic processes shaping pore-fluid chemistry. The four MVs can be classified into two geochemical groups: Gelendzhik and Heraklion, dominated by deep-sourced hypersaline fluids from Messinian salt dissolution and Moscow and Milano MVs, characterized by pore fluids largely reflecting seawater-derived compositions. In the hypersaline group, signatures of deep processes persist such as smectite–illite conversion at Heraklion and ammonium and methane upward migration, demonstrating that near-surface pore fluids retain the imprint of deep diagenesis. Organic matter oxidation via sulfate reduction (OSR) and anaerobic oxidation of methane coupled to sulfate reduction (AOM-SR) were also active, even within the hypersaline environments of the Gelendzhik and Heraklion MVs, as evidenced from stoichiometric ratios of ΔDIC and ΔSO 4 2- and δ 13 C DIC isotopic data. In the hypersaline Gelendzhik MV, the diagenetically added DIC, representing the isotopic signature of mineralized organic matter, is estimated at −53.1‰, further indicating active AOM-SR under extreme salinity. Overall, our findings demonstrate that deep-sourced fluids shape near-surface pore-fluid chemistry, generating pronounced heterogeneity among MVs and provide rare geochemical evidence of microbial resilience in hypersaline submarine environments.

The contraction of sands subject to cyclic increases and reductions in temperature is of great practical importance; however, the effect of the initial packing condition and the mechanism underlying the behaviour are not completely understood. In this study, a thermal discrete-element method was developed by considering thermal expansion of particles and heat conduction through particles and interstitial pore fluids. Cyclic changes in temperature were simulated on samples with a variety of initial densities and degrees of anisotropy. The contraction of the soil skeleton was isolated from the thermal expansion of the particles using the ‘mechanical strain’ concept. Looser samples showed a larger mechanical strain accumulation, in line with observations in previous laboratory work. Highly anisotropic samples had a significant cyclic thermal contraction even in the case of samples with a high density. Over the duration of the thermal cycles, a continuous decrease in fabric anisotropy was observed for the anisotropic samples, which may be associated with the fundamental mechanism underlying the cyclic thermal contraction of the sands.

The abnormal pore pressure is possibly generated through a comprehensive process including geological, physical, geochemical, or hydrodynamic factors. Generally, all mechanisms are abstracted as four typical categories, namely skeleton deformation, pore fluid mass increase, temperature change, and other mechanisms. Traditional methods for evaluating reservoir overpressure often only consider the influence of a single factor and lack mathematical methods for a comprehensive explanation of reservoir overpressure. Therefore, this article is dedicated to proposing a comprehensive mathematical model, incorporating effective mean stress, shear stress, temperature, pore collapse-induced plastic deformation, time-dependent skeleton deformation, and pore fluid mass increase, to account for pore pressure generation in sedimentary basins. The effects of various factors on pore pressure generation are analyzed, and case studies are conducted. Main conclusions are drawn that both the compressibility of sediments and the porosity at the surface control the pore pressure generation rate and vertical gradient. The pore pressure generation rate and vertical gradient in deep formation are larger than those in shallow formation. The higher compressibility and lower porosity at the surface lead to a greater pore pressure generation rate and vertical gradient during the skeleton deformation. The lower compressibility and a lower porosity at the surface can cause a higher pore pressure change rate and vertical gradient during the pore pressure mass increase and temperature change. By comparison, mechanical loading plays a more important role in pore pressure generation rate and vertical gradient than aquathermal pressuring.

The moldic pore-vuggy reservoirs of the Ma54-Ma51 sub-member in the Majiagou Formation, central Ordos Basin, are key targets for deep natural gas exploration, yet the alteration mechanisms and controlling factors of burial-stage pressure-released water karstification remain unclear. Herein, an integrated methodology encompassing core observation, thin-section analysis, and geochemical testing was adopted to systematically clarify the development characteristics and multi-factor coupling control mechanisms of this karst process. Results show that burial-stage pressure-released water karst is dominated by overprinting on pre-existing syndepositional and supergene pore networks, forming complex reservoir spaces via synergistic selective dissolution. The development of preferential dissolution zones is jointly controlled by differential compaction of the weathering crust, permeability heterogeneity of the overlying strata and weathered crust, and diagenetic fluid properties. After the supergene diagenetic stage, differential tectonic deformation and burial compaction induced overpressure in pore fluids, which drove acidic pressure-released water to migrate along high-permeability pathways such as the “sandstone windows” overlying the Ordovician weathering crust. These fluids preferentially dissolved high-permeability moldic pore-vuggy dolomites in paleo-karst platforms and steep slope zones, whereas tight micritic dolomites served as effective barriers. The acidic environment sustained by organic acids and H2S in pressure-released water promoted carbonate dissolution, and carbon-oxygen isotopes as well as pyrite δ34S values verify that the fluids were derived from mudstone compaction. This study reveals that the distribution of high-quality reservoirs is jointly determined by the synergistic preservation of moldic pore-vuggy systems in paleo-karst platforms and steep slopes and directional alteration of pressure-released water along preferential pathways, providing crucial geological guidance for the evaluation of deep carbonate reservoirs.

The shale oil reservoir is characterized by ultra-low porosity and permeability and multi-scale strong heterogeneity. During the sampling process of downhole cores, the rocks can easily be affected by drilling fluid contamination, mechanical stress damage, and other factors, altering the original distribution of oil–water and the characteristics of pore structures. Oil removal and oil saturation are critical steps in core pre-treatment, yet the mechanism of its impact on cores has not been systematically studied. This research focuses on oil removal in six cores from the Jimsar shale oil reservoir with different oil saturations. The necessity and effectiveness of the oil removal saturation and its impact on the microstructure of the cores were systematically evaluated by employing nuclear magnetic resonance (NMR), CT scanning, and permeability testing methods. The results indicate that there are significant differences in fluid composition, pore structure, and wettability among downhole cores, making oil removal saturation treatment a necessary prerequisite for subsequent experiments. High-temperature and high-pressure oil removal shows significant effectiveness, with an average core weight reduction of 2.46% and average reduction in T2 peak area of 73.75%. The efficacy of oil saturation is influenced by the initial pore-throat distribution in the cores. The oil removal process significantly alters petrophysical parameters, with an average increase in porosity of 3.21 times and permeability rising by an average of 2.16 times, although individual variations exist. Microstructural analysis demonstrates that the oil removal process preferentially removes crude oil from larger pores, while residual oil is mainly distributed in smaller pores, indicated by a left shift in T2 peak values. Meanwhile, high-temperature and high-pressure conditions induce microfracture development, promoting the migration of crude oil into smaller pores. This research reveals the complex impact mechanism of the oil removal saturation process on shale cores, providing a theoretical basis for accurately evaluating shale reservoir characteristics and optimizing experimental design.

ABSTRACT Marine organic-rich shales in southern China maintained overpressure conditions caused by hydrocarbon thermal cracking during the deep-burial stage and gas leakage during the period of tectonic uplift, accompanied by organic pore development and preservation. Presently, there is no comprehensive framework for revealing the preservation of organic pores in shale reservoirs. In this study, multiple approaches, including CO2 and N2 adsorption, scanning electron microscopy, fluid inclusion microthermometry, laser Raman spectroscopy, and thermodynamic modeling, were used to quantitatively evaluate organic pores and investigate pore fluid pressure evolution in the Wufeng Formation and Longmaxi Formation shale reservoir in the eastern Sichuan Basin. Measured results show that organic micropores in shale samples from three wells at different structural units have similar values of volume and specific surface area. Organic mesopore volume accounts for 40% to 70% of the organic pore volume. The degree of organic mesopores development in wells JYA, JYB, and JYC is proportional to the pressure coefficients (Pc) with shale reservoirs. Pore fluid pressure evolution within shale reservoirs can be divided into two stages: 160–85 Ma and 85 Ma to present day. Overpressure was generated in shale pores during the first stage, with Pc increasing from 1.57 to 2.2, and the overpressure protected most of the organic pores from compaction. The second stage was characterized as the reduction and dissipation of overpressure during the Yanshanian and Himalayan Orogenies. By comparing the closed-system modeling of overpressure and pore fluid evolution across different structural zones, this study demonstrates the possible increase in overpressure and decrease in organic pore volume during the Yanshanian Orogeny. In intensely tectonically active zones, the development of faults and fractures can lead to overpressure dissipation within shale reservoirs, resulting in poor organic mesopore preservation and low hydraulic fracturing productivity during the Himalayan Orogeny. Conversely, in weakly tectonically active zones, the shale reservoir maintained an overpressured state during the Himalayan uplift, with large-diameter and high-roundness organic mesopores preservation, indicating that overpressure during uplift can provide important preservation for organic mesopores. This contribution provides greater insight into organic pore preservation and shale gas enrichment in other tectonic settings around the world.

Dry–wet cyclic-dependent hysteretic soil-water retention and deformation behavior of a soft clay under varying pore fluid concentrations